Principles of Guided Missiles and Nuclear Weapons. INSTITUTION Bureau of Naval Personnel, Washington, D

Home , AT4, Beam riding, Command guidance, Enzian, Glide bomb, Guidance system

DOCUMENT RESUME ED 070 581 SE 014 139 TITLE Principles of Guided Missiles and Nuclear Weapons. INSTITUTION Bureau of Naval Personnel, Washington, D. C.; Naval Personnel Program support Activity, Washington, D. C. REPORT NO NAVPERS-10784-A PUB DATE 66 NOTE 370p.; Revised 1966

EDRS PRICE MF-80.65 HC- $13.16 DESCRIPTORS Instructional Materials; Mechanical Equipment; *Military Schools; *Military Science; Military Training; Nuclear Physics; *Nuclear Warfare; *Post Secondary Education; *Supplementary Textbooks; Textbooks ABSTRACT Fundamentals of missile and nuclear weapons systems are presented in this book which is primarily prepared as the second text of a three-volume series for students of the Navy Reserve Officers' Training Corps and the Officer Candidate School. Following an introduction to guided missiles and nuclear physics, basic principles and theories are discussed with .a background of the factors affecting missile flight, airframes, missile propulsion systems, contro3 components and systems, missile guidance, guided missile ships and systems, nuclear weapons, and atomic warfare defense. In the area of missile guidance, further explanations are made of command guidance, beam -rider methods, homing systems, preset guidance, and navigational guidance systems. Effects of nuclear weapons are also described in categories of air, surface, subsurface, underwater, underground, and high-altitude bursts as well as various kinds of damages and injuries. Besides illustrations for explanation purposely a table of atomic weights and a glossary of general terms are provided in the appendices. (CC) IF

U S DEPARTMENT OF HEALTH. EDUCATION & WELFARE OFFICE OF EDUCATION D THIS DOCUMENT HAS BEEN REPRO DUCED EXACTLY AS RECEIVED FROM THE PERSON OR ORGANIZATION ORIG INATING IT POINTS OF VIEW OR OPIN IONS STATED DO NOT NECESSARILY REPRESENT OFFICIAL OFFICE OF EDU CATION POSITION OR POLICY

0-r e ';111 KL,L 041,

S I PREFACE

This book is intended primarilyas aclassroom training text for NROTC and OCS students. Other principalusers will be officers enrolling in the correspondence course based on this text, and NROSstudents. This is the second volume of a three-volumeseries dealing with naval weapons. The first volume, Principles of Naval Ordnanceand Gunnery, NavPers 10783-A, deals with shipboard navalweapons systems, including guns, rockets, bombs, torpedoes, mines, and depthcharges, but not guided missiles and nuclearweapons. The basic sciences as applied to naval weapons, including fire control,are explained. The present volume deals withmany basic principles and theories needed for understanding guided missile flightand control, and basic nuclear weapons information. The fundamentalsof the different types of missile guidance are discussed. Because its distribution is not limited by securityregulation, it is necessarily general in nature with minimumreference to actual weapons in current use. Considerable detail is givenon the effects of nuclear weapons but not on the construction or operation ofthe weapons. The user should bear in mind that this text isnot designed for maintenance or for operating personnel, nor for useas a manual on operations or tactics. The third volume, Navy Missile Systems, NavPers10785-A, describes specific Navy missile systems, illustratingthe application of the principles explained here. The text and illustrations of this bookwere prepared by the Train- ing Publications Division, Naval PersonnelProgram Support Activity, Washington, D. C. 20390, for the Bureauof Naval Personnel.Credit for technical assistance is given to the Bureauof Naval Weapons, Officer Candidate School, Newport, R. I., NROTC Unit, University of Texas, Austin, Texas, and NROTC Unit, Universityof Oklahoma, Norman, Oklahoma.

Original Edition 1959 Revised 1968 THE UNITED STATES NAVY

GUARDIAN OF OUR COUNTRY The United States- Navy is responsible for maintainingcontrol of the sea and is a ready force on watch at home and overseas,capable of strong action to preserve the peace or of instant offensive action to winin war. It is upon the maintenance of this control that our country'sglorious future depends; the United States Navy exists to make it so.

WE SERVE WITH HONOR Tradition, valor, and victory are.the Navy's heritage from the past.To these may be added dedication, discipline, and vigilance as thewatchwords of the present and the future. At home or on distant stations we serve with pride, confident in the respect of our country, our shipmates, and our families. Our responsibilities sober us; our adversities strengthen us. Service to God and Cciuntry is our special privilege. We servewith honor.

THE FUTURE OF THE NAVY The Navy will always employ new weapons, newtechniques, and greater power to protect and defend the United States onthe sea, under the sea, and in the air. Now and in the future, control of the sea gives the UnitedStates her greatest advantage for the maintenance of peace and forvictory in war. Mobility, surprise, dispersal, and offensive power are the keynotesof the new Navy.The roots of the Navy lie in a strong belief in the future. in continued dedication to our tasks, and inreflection on our heritage from the past. Never have our opportunities and our responsibilitiesbeen greater.

3 CONTENTS

CHAPTER

PART I. GUIDED MISSILES

1. Introduction to guided missiles 1

2. Factors affecting missile flight 24

3. Components of guided missiles 51

4. Missile propulsion systems 69

5. Missile control components and systems 97

6. Principles of missile guidance 145

7. Command guidance 189

8. Beam-rider guidance 181

9. Homing guidance 205

10. Other guidance systems 225

11. Guided missile ships and systems 249

PART II. NUCLEAR WEAPONS

12. Fundamentals of nuclear physics 268 13. Principles of nuclear weapons andtheir handling. ..290

14. Effects of nuclear weapons 302 APPENDIX

A. Table of atomic weights andbibliography 345

B. Glossary 347

INDEX 359

iii d

PART 1.-GUIDED MISSILES.

CHAPTER 1

INTRODUCTION TO GUIDED MISSILES

GENERAL SCOPE OF THE TEXT DEFINITION Part I of this book is a brief introductionto A GUIDED MISSILE isan unmanned vehiclethe basic principles that govern the design, that travels above the earth's surface; it carriesconstruction, and use of guided mistAles. Part an explosive warhead or other useful payload;II deals with nuclear weapons. Many of the and it contains within itself somemeans for con-principles we will discuss apply to all missiles; trolling its own trajectory or flight path. Aglidemost of them apply to more thanme. The treat- bomb is propelled only by gravity. But itcon- ment will necessarily be general. Securityre- tains a device for controlling its flight path,and quire'', --Its prevent any detailed descriptionof is therefore a guided missile. specific missiles in an unclassified text. This The Navy's guided missiles, includingTer-text will therefore contain very littleinforma- rier, Tartar, Taboo, Sidewinder, Sparrow,Bull-tion about specific missiles; they will bede- pup, and Polaris, meet all the requirements ofscribed in some detail in a supplementaryvol- the above definition. ume, Navy Missile Systems, NavPers 10785-A. The Army's Honest John (now obsolete)is a 3-ton rocket that is capable of carryinga nuclear The reader will find some repetitionin this warhead. Because it contains no guidancesys-text; this is intentional. The subject iscom- tem, Honest John is not a guided missile.Theplex; it deals with many different phasesof Navy's homing torpedoesare self-propelledscience and technology. The begihningstudent weapons with elaborate guidance systems. Theof guided missiles faces a paradox. Wemight homing torpedo can hunt for a target and, whensay that you can't thoroughly understandany it finds one steer toward it ona collision course.part of a guided missile unlessyou understand Because it does not travel above the earth'ssur-all the other parts first.We will deal with face, the homing torpedo is nota guided missile. this problem by first discussing the guided A MISSILE is any object thatcan be pro-missile as a whole, with a brief consideration jected or thrown at a target.This definitionof its propulsion, control, guidance, andlaunch- includes stones and arrows as wellas guning systems. Each of these subjects willthen projectiles, bombs, torpedoes, and rockets. Inbe treated at some length inone or more later current military usage, the word MISSILE ischapters. gradually becoming synonymous with GUIDED All guided missiles contain electronicde- MISSILE. It will be so used inthis text;we willvices; some of these devices arevery complex. use the terms MISSILE and GUIDED MISSILE A sound understanding of the operatingprin- interchangeably. This permits inclusion of theciples of missile guidance isvery difficult with- Asroc, which is not a guided missile, buttsaout some background in basic electricityand missile,an important one in ship missile weapon electronics.Students who have no background syhtems.Another missile is Subroc, which isin electronics should use Introduction to Elec- fired underwater from a torpedo tube, is guidedtronics, NavPers 10084; it should, if possible, during its air flight, returns to the water,andbiiimpPlementedby further reading in basic acts as a depth charge. texts on electricity and electronics. 5 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

WEAPONS SYSTEMS power, aircraft became the primary weapon of the Navy. The battle of the Coral Sea, in 1942, The missiles alone are useless for defensewas the first major naval engagement in which or offense without the remainder of the weaponssurface ships did not exchange a single shot. system. A weapons System is vitally dependent When a navy so controls the seas that it can on search radar inputs, command and controlsafely approach the enemy coast, it can extend devices, and power supplied from other equip-its striking power inland to the distance its ments. A missile weapons system consists of aweapons can reach. A heavy cruiser can bom- weapon direction system, one or more fire con-bard enemy installations about 15 miles inland. trol systems, the launching system, and theCarrier-based aircraft extend the Navy's force intosiles.The missiles may be all of one typefor hundreds of miles over enemy territory. or mere may be two or more types in the systemThus, during the Korean War, the whole of North on a ship. Korea was subject to attack by carrier-based A mere listing of the components of a weaponsaircraft of the U. S. Navy. system would be rather lengthy. Many trained The Navies-Regulus guided missile had a men are ,needed to operate the various parts.range comparable to that of a carrier-based The coordination and cooperation required toaircraft.It was designed so it could also be make all components and personnel work to-launched from a submarine, even where we did gether properly is not a i1 1Wple task. It requiresnot control the surface of the sea. Although a thorough knowledge of the interrelationshipRegulus is being phased out,it gave valiant and interactions involved.Intensive technicalservice as a forerunner of Polaris. Some of the training is necessary for the technicians whomissiles will be used as drones for training operate and maintain the equipment, each in hispurposes. own specialty.A network of communication The Polaris missile, called the FleetBallis- facilities is necessary for communication be-tic Missile (FBM), also submarine-launched, tvieen the men operating the different units. extends the Navy's striking power far inland. Officers must have agoodbackgroundknowl-Early models of the Polaris had a rangeof 1500 edge of how a weapons system operates, and themiles; advanced Polaris has a range of about interaction and dependence of the various parts.2500 miles.With such a range, even the most This book will not describe the components of aremote place on earth can be reachedby its fire weapons system, other than the missiles, norpower, while the submarine that fires it remains their functioning. Officer texts and correspond-submerged, undetected by the enemy. ence courses are available for specialty study, One of the strongest elements in our national such as Combat Information Center Officer,defense is the Strategic Air Command (SAC), NavPers 10823-B. which can launch a devastating nuclear attack against any enemy within a few minutes after PURPOSES AND USES OF notice. But SAC bases are large, and expensive GUIDED MISSILES to build and maintain. Their position is known to The primary mission of our Navy is controlour possible enemies. At the outbreak of war, of the seas. We propose to keep the sea lanesthey would probably be the first objective in a open for our own and for friendly commerce; insurprise attack. time of war, we propose to deny use of the sea The intercontinental ballistic missile (ICBM) to our enemy.Historically, this mission hascarries a nuclear or thermonuclear warhead. been accomplished by the use of warships armedIt can reach its target o: 'another continent within with the most advanced weapons of their time.minutes after launching.It can approach the When John Paul Jones challenged the Britishtarget at such a speed that any countermeasures control of the seas, his warships carried gunsmay be very difficult. Its shore-based launching having an effective range of a fewhundredyards.sites are small, relatively cheap to build and In the Civil War, the Union Navy maintained amaintain, and relatively easy to conceal. Be- successful blockade of southern ports with the,cause they can be widely dispersed, they are help of guns that could shoot a little more than' difficult to attack even if their location is known. a mile. The battleships of World War I carriedICBMs Paunched from shipboard would have a rifled guns with an effective range in the order ofmobile base, of course, which could be maneu- 15 miles. When aircraft became more effectivevered as necessary to evade the enemy or to weapons than guns, in both range and strikingcome within range of the target. Chapter 1INTRODUCTION TO GUIDED MISSILES

The ICBM does not face the problem of re-the AA guns if not brought down by missiles. turning safely to friendly territory aftercom-High-speed aircraft flying at low altitudes (pos- pleting its mission, for. guided missilesaresibly to avoid radar detection and tracking) are expendable by design, while our strategicbomb-susceptible to AA guns and conventional gunfire. ers and their crews are not. SAC has been Guided missiles are becoming increasingly supplemented by the ICBM. - important in aircraft armament. When two jet An Intercontinental Ballistic Missile (ICBM)aircraft are approaching each other head-on, the has a range of over 3000 nautical miles. In thisrange closes at a speed between one-half and one class are the Atlas (5500 to 9000 nautical miles),mile per second. Under these conditions it is Minuteman (over 5000 nautical miles), and Titandifficult even to see an enemy aircraft, and hitting (about .5000 nautical ,plies).These missilesit with conventional aircraft weapons is largely were developed by the Air Force, and are shore-a matter of luck. But the air-to-air missile can launched. "lock on the hostile aircraft while it is still An Intermediate Range Ballistic Missilemiles away, and can pursue and hit the target in (IRBM) has a range up to 1500 nautical miles.spite of its evasive maneuvers. This term is now applicable only to Thor and The defense of a naval task force against air Jupiter both of them Air Force Missiles, andattack is somewhat similar to that of defending both being phased out. an American city or industrial area against air Some missiles have a range in the intervalattack.The enemy attack will be detected by 500 to 3000 nautical miles. The Navy's Reguluslong-range search radar while the attacking Iis in this range group.Its successor, theplanes are hundreds of miles from the target. Polaris, has a greater range, but is still in thisAshore, the early warning radars, calledBallis- group. Hound Dog, Mace, and Matador are Airtic Missile Early Warning System (BMEWS), are Force missiles in this range. located at distant outposts inCanada and-Alaska. Each of the services has several short-rangeAt sea, they are aboard picket ships at some dis- missiles that are operational. The Navy mis-tance from the main body of the task force. The siles in this group include Bullpup, Sidewinder,first line of defense will probably be interceptor Sparrow III, Taloa, Tartar and Terrier. Othersaircraft, which will attack the enemy planes with are under development. dne of the aims in theair-to-air missiles. A second line of defense development of advanced types of missiles is tomay consist of moderate range surface-to-air increase their range as well as their accuracymissiles, which will intercept the attacking and dependability. planes at rangesfrom about 20 to more than 65 Modern military aircraft can fly so high andmiles.A third line would consist of shorter so fast that conventional antiaircraft guns arerange missiles, designed to intercept at ranges ineffectual against them during high flights. Asbetween about 5 and 20 or 30 miles, and anti- you know, a gun is not aimed directly at a movingaircraft guns with ranges up to 10 miles. target; it must be so aimed that both the pro- Protection against underwater attack is af- jectile and the target will reach a predicted pointforded by missiles, such as Asroc, homing at the same time. During the flight time of thetorpedoes, and depth bombs, all of which are in- projectile, a high-speed aircraft will travel cludedin the antisubmarine warfare (ASW) several miles. The projectile cannot change itsarsenal. A study of the statistics of submarine trajectory after it is fired; the aircraft can, anddevastation in past wars might convince you ASW a slight change of course can take it beyond theis more important than anti-air warfare. Al- lethal range of the projectile burst. though there is a difference of opinion as to the The surface-to-air guided missilecan inter- relative importance of these two types of de- cept attacking aircraft at greater heights andfenses, the Navy has not neglected either ore. greater ranges than any projectile. If the air-We have antisubmarine weapons to be dropped craft changes its course or takes evasive actionfrom airplanes, to be fired from surface ships, to escape the missile the guidance system of theand to be fired from submarines. missile will change its course accordingly to Because the defense system outlined above follow the aircraft up to the instant of intercep- is formidable, it is improbable that enemy airtion. craft will try to bomb our cities, or attack a task Aircraft attacking a ship headon, or low-flyingforce with bombs or torpedoes. Enemy attacks slower speed aircraft and helicopters used forare more likely to be with air-to-surface mis- strafing and spotting, could come within range ofsiles, launched at a range of perhaps a hundred PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS miles or more, and submarine or surface-firedused car.It resembles an ordinary aircraft missiles. rocket; it differs, of course, in having a guidance The question remains: how do we defend our- system, and movable control surfaces by which selves against enemy intercontinental ballisticthe guidance system can control its flight path. missiles,air-to-ground missiles, andAt the other extreme, the ICBM has a range of submarine-launched missiles? We must assumethousands of miles, with size and weight in that the enemy has weapons as swift and lethalproportion; its proportional cost is even higher. at ours.The early mods of Nike and TerrierThe ICBM, like most missiles, has the familar missiles were designed to shoot down jet air-rocketshape.. Some of the earlier missiles craft. They were swift enough for that, but with resembled conventional aircraft; they differed the development of ICBMs, which can be launchedfrom aircraft in having a guidance system rather from foreign shores, or possibly from hiddenthan a pilot.They were designed to dive into submarines, defense requires shooting downthetheir targets rather than release abomb load and missiles launched by our enemies. The answerreturn. is antimissile missiles. They must be capable Guided missiles are classified in a number of launch, or very short notice, extremely fast,of different ways, perhaps most often by function, and extremely maneuverable. They can be rela- such as air-to-air, surface-to-air, or air-to- tively small, jusibig enough to explode the enemysurface. The new designation symbols for mis- missile high in the air (or inthe water) before itsiles and rockets classify them according to the can reach its target. Such antiballistic missileslaunch environment (R for ships), mission (0 for (ABMs) are being developed and means are beingsurface attack; U for underwater attack), and explored for rendering enemy missiles ineffec- vehicle type (M for missile). tive within range of our shores or ships. A nonballistic missile is propelled during all When the antimissile missile becomes oper-or the major part of its flight time; the propul- ational, it will probably lead to further develop-sion system of a ballistic missile operates for ments. Our aircraft carry air-to-air missilesa relatively short time at the beginning of flight; for defense against enemy aircraft; an inter-thereafter, the missile follows a free ballistic continental ballistic missile might carry air-to-trajectory like a bullet (except that this trajec- air missiles for defense against other missiles.tory may be subject to correction, if necessary, These might be called anti-antimissile missiles by the guidance system).Some missiles are though if we have the ingenuity to develop suchdesigned to travel beyond the earth's atmos- weapons we may be able to think of a shorterphere, and reenter as they near the target. Others name for them. depend on the presence of air for proper opera- Such speculations about the future are nottion of the control surfaces, the propulsion sys- very instructive. But this prediction is safe:tem, or both. the effort to develop faster and better missiles, Missiles may be further classified by type and the race between missiles and missileof propulsion system, such as turbojet, ramjet, countermeasures, will continue as long as theor rocket; or by type of guidance, such as com- threat of warexists or until some new andmand, beam-riding, or homing. unforeseen weaponmakes guided missiles obsolete. INTRODUCTION TO MISSILE GUIDANCE INTRODUCTION TO MISSILE TYPES The missile guidance system keeps the To perform the various functions outlinedmissile on the course that will cause it to above, missiles of many different types mustbe intercept the target.It does this in spite of developed.A list, later in this chapter, will.initial launching errors, in spite of wind or show the number of missile types now opera-other forces acting on the missile, and in spite tional or in various stages of develoPment. of any evasive actions that the target may take. can be assumed that other missiles, not yetThe guidance system may be provided with announced, are being developed. . certain information about the target before The Navy's Sidewinder is a relatively smalllaunching.During flight it may receive addi- air-to-air missile with a range of a few- miles.tional information, either by radio from the A Sidewinder costs about as much as a goodlaunching site or other control point, or from

ab. Chapter 1INTRODUCTION TO GUIDED MISSILES the target itself.On the basis of this infor- The German V-2 used a combination of pre- mation, the guidance system will calculateset and COMMAND guidance. Before launching, the course required to intercept the target,it was set to climb vertically for a certain dis- and it will order the missile control systemtanceand then turn onto the desired course. to bring the missile onto that course. Speed andposition of the V-2 were determined From the paragraph above, it might be in-by a radar at the launching site. This informa- ferred that the guidance system is an intelli-tion was analyzed by a computer, which deter- gent mechanism that can think. This, of course mined when the missile had reached a position is untrue. The missile guidance system isbaseciand speed that would carry it, along a ballistic on a relatively simple electronic computer. Buttrajectory, to its target.At that instant, the even the most complex computers, such as Uni-missile propulsion system was shut down by vac and other "giant brains," cannot think.radio command. Thinking is a conscious process, confined to man The Army's Nike surface-to-air missile is and few of the hie r animals. No matter howa more modern example of command guidance. complex it may be, a computer is simply a ma-Throughout the missile flight, radars at the chine built so that when certain things happen,launching site track both the missile and its certain other things will result. The design oftarget. A computer continuously calculates a computer is nothing more than an advancedthe course that the missile must follow to exercise in the logic of cause and effect. A com-reach the point of intercept.Throughout its puter can take no action that isn't built into itflight, Nike is steered along the desired course by its designer (except, of course, the erraticby radio commands from the ground. action that might result from a bad connection Sidewinder has a HOMING guidance system, or a faulty component). sensitive to infrared (heat) radiation.It will steer itself toward any strong source of in- In the later chapters of this text you will findfrareds- The exhaust of a jet aircraft is such a statements such as this: "When Terrier detectssource, and Sidewinder can steer itself "right an AM signal, it 'mows it is off the beam center,up thetailnipe* ofan enemy jet. but it does not know, from the AM signal, whist: Infrared is not the only basis for homing way to go to get back to beam center." We makeguidance. A missile can be designed to home such statements without further apology, but it ison light, radio, or radar energy given off by, essential that the students understand what weor reflectediromthe target.It could also, are doing. We are using a convention becauselike a homing torpedo,' be designed to home on it saves time and space. Remember that a mis-a source of sound waves; but because a guided sile doesn't "know,* or "see," or "think," ormissile travels at from one to a dozen times "decide." the speed of sound, such a system would not Several distinct types of guidance are pos-be practical. However, sound waves are used sible; a given missile may use one type, or afor detecting underwater targets.The word combination of two or more.These types"Sonar* means Sound Navigation and Ranging include preset, homing, command,beam-riding,systems, and includes all types of underwater and inertial guidance, besides some less-knownsound detection devices.The Asroc torpedo onessuchascelestial,celestial-inertial,uses sonar detection in its underwater phase. terrestrial-reference, and stellar guidance sys- Because its source of information is energy tems. given off by the target itself, Sidewinder guid- Although it cannot be called a guided missile,ance is an example of PASSIVE homing., Other the air-steam torpedo has a simple guidancemissiles carry a radar transmitter, "illumi- system. Before launching, its gyro is set for anate* the target with a radar beam and home predetermined course; the gyro holds the torpedoon the radar energy reflected from Ihe target. on that course throughout its run to the target.This is an ACTIVE homing guidance system. The torpedo is capable of steering itself, but itA SEMI-ACTIVE system is also possible; the receives no information after the instant oftarget is illuminated by a radar beam from the launching. This is PRESET guidande: Thelaunching site or other control point, and the German V-1 is another example. Before launch-missile homes on energy reflected from the ing, it was set to follow a given course, and totarget. dive on its target after traveling a preset dis- The Navy's Terrier is similar to Nike in tance. both function and performance; but its guidance PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS systemis entirely different.Terrier uses HISTORY OF GUIDED MISSILES BEAM-RIDER guidance. A radar transmitter at the launching site keeps a narrow beam ofINTRODUCTION radar energy continuously trained on the target. Terrier simply rides up the beam. The brief sketch that follows will enable Intermediate-range (around 1500 miles) andthe student to view the present day guided long-range (3000 miles or more) missiles maymissilein a historical perspective, and to use a NAVIGATIONAL guidance system. Theconsider the most recent developments in their missile determines its own position in relationrelation to early experiments. It serves no other to the target, calculates the course required topurpose; it is not necessary to memorize the reach the target position, and steers itself alongdates listed here. that course.A missile may be designed to Guided missiles, as defined at tho beginning navigate with the help of radio or radar beacons,of this chapter, were first used in World War just as a ship may navigate with the help ofII.But they could net have been built at that Loran. A missile may navigate by dead reckon-time without previous experiments in both ing, through the use of an INERTIAL guidancepropulsion systems and guidance.We will system.It may navigate by taking star fixeslook briefly, at early developments in both of through a telescope (celestial navigation), or bythose fields.Our latest missiles, of course, examining the ground with radar and comparingare based also on developments in many other what it sees with a map. Or it may use a com-fields, including mass production techniques, bination of two or more ol these methods. metallurgy, aerodynamics, radar, and elec- As previously stated, a missile may havetronic computers; but we cannot describe the more than one type of guidance system, andevolution of those developments here. switch from one to another during its flight. For example, a long-range missile may climb PROPULSION SYSTEMS to a preset height and turn onto a preset course shortly after launching, then navigate Weapon propulsion systems are usually clas- to the target vicinity, and finally home on thesified as gun type, reaction type, and gravity infrared or other energy given off by the tar- type. Gun type propulsion systems are also get. Or a surface-to-air missile may ride acalled impulse propulsion systems and include radar beam until it gets near the target, thenall weapons in which a projectile is ejected from switch over to homing guidance. a container, such as a gun barrel or a launching tube.The only application of this type of pro- COMPONENTS OF GUIDED MISSILES pulsion in missiles is for the "ship-clearing" portion of the journey of some missiles and In the course of thediscussionthus far, sometorpedoes.' of the components of guided missiles have been Older type glide bombs and other gravity- mentioned.Every missile has a framework, poweredmissilesareobsolete.Although called the airframe, to contain the components. propeller-driven aircraft, under radio control, In the airframe is the warhead, the propulsionhave been used as target drones, a propeller- system (including the fuel), guidance system,driven guided missile would be too slow to be control system, and an auxiliary power system.effective. Most current missiles depend on some Chapter 3 defines each component; fuller de-form of jet or rocket propulsion (reaction type scriptions are given in other chapters. Eachpropulsion system). An exception is the Walleye, system has many parts, some of them intricatea glide bomb type under development. and delicate, with a network of electrical, hy- The development of present day tra..4ed mis- draulic, and mechanical connections linking allsiles was dependent on the deveiopk:.ent of jet parts. The next section describes the develop-propulsion, although the experimental work was ment of some of the components and ways indone for the purpose of developing .a jet engine which the changes affected the missiles. .Thefor planes. improvement of missiles is a continuing process In France, in 1909, Guillaume. outlined the to increase the reliability, simplicity, range, andbasic theory of turbojet propulsion. In 1927, lethality of the weapons. As significant improve the Italian Air Ministry built and tested a plane meats are achieved, older missiles are phaseddriven by a form of mechanical jet propulsion. out and new ones are installed. The fuselage of this plane was shaped like a Is 10 Chapter 1INTRODUCTION TO GUIDED MIOILES OIMMIII111141

tube, with flaring ends. A conveutionalpro-other hand, carry their own sourcfl ofoxygen for peller was mounted in the throat of thetube, combustion, and they operate even more effi- forming a "ducted propeller" installation. This ciently in a vacuum than they do in air. craft had good maneuverability and good sta- The principle of rocket propulsion hasbeen bility, but in other respects itsperformanceknown for nearly 2000 years. In the Far East, was poet .In 1932, Campini, an Italian, designed rockets were used in warfare as earlyas the and later flew the first plane powered bya 13th century.Several western armies used thermal jet;it differed from modern jets inrocketprojectiles in the early part of the using a piston engine, rather thana turbine, 19th century, but not very effectively. Theyseem as a compressor. to have been of more value in frightening the After Campini's successful flight, develop- enemy than in doing physical damage. The Brit- ment of improved jet engineswas undertakenish used rockets in their attack on Washington in in several countries.In England, in 1930,1812; and in the Star Spangled Banner, Francis Frank Whittle patenteda jet engine based onScott Key referred to the "rocket's red glare" the principles used in modern jet aircraft.during the bombardment of Fort McHenry. (Some After combustion, the exhaustgases of the jethistorians believe that the British *CI.* using were used to spin a turbine; the turbine, inrockets as signals, rather than weapons.) Mili- turn, drove theth compressor.The first suc-tary interest in rockets lapsed after the middle of cessfulul flight of a turbojet powered aircraft the 19th century, because developments inguti- was made in England in May 1941.In the nery made gun projectiles '01.?.perior to rockets in U. S., development of jet engineswas turnedrange, and far superior in accuracy. over to General Electric Company because of Among rocket engineers, Robert H. Goddard itsexperiencewithturbine - drivensuper- is known as the "Father of Rocketry." Goddard chargers.At present, nearly every matuifac- was born in Massachusetts in 1882. By the time turer of aircraft engines is developing andhe earned his Bachelor of Science degree is building turbojet engines. 1908, he was obsessed by thoughts of rocketsand The pulsejet engine uses the forward motion rocket propulsion. He believed, quite correctly, of the missile or. aircraft, rather thana tur- that rocket propulsion would be the most suitable bine, to compress the air and fuelvapor before means for sending measuring instrumentstathe combustion. The pulsejet principle was patentedtop of the earth'!" atmosp!. ,re, and eveitivallyt3 ti by a German engineer in 1930, and furtherde- the moon. Ur. tfi t3W. iirne noone had investigated veloped by Bleeker, an American in 1933. Thethe physics of rocket propulsion, andno one had pulsejet engine was much improved by the Ger- worked out the necessary mathematics. Goddard mans during World War II, and was used to powerdecided to do both. their V-1 guided missile. Before Goddard's experiments, rocketscon- The ramjet also depends on forward motionsided of a quantity of propellant packed ina for compression, but it differs from the pulse-cylindrical tube.Goddard discovered that by jet in having no moving parts. Thebasic ideaforming the after end of the tube intoa smooth, of a ramjet was patented by Rene Lorin,atapered nozzle, he could increase the ejection French engineer, in 1913.This was followedvelocity of the combustion gases eight times by a Hungarian patent in 1928, and another without increasing the weight of the fuel. Accord- French patent, by Leduc, in 1933.None of ing to Goddard's calculations this would, fora these patent& resulted in a workable ramjetgiven weight of fuel, drive the rocket eight times engine. The basic ideas were sound; butsuc-as fast and sixty-four times as far. cessful development of a ramjet engine had Goddard was given a Navy commission in to wait for extensive dataon the behavior of1917, and assigned to the job of improvingthe fluids at extremely high speeds. The firstsuc- Navy's signal rockets. This assignmenten- cessful ranitat flight was made in June of 1945abled him to continue his development of rocket at the Applici Physics Laboratory of the Johnstheory. After the war he summarized his Hopkins University in the course of developingatheories and experience in a paper called power plantfor the Navy's Talo4 missile.A Method of Reaching Extreme Altitudes.This Turbojets, pulsejets, and ramjetil all dependreport, published by the Smithsonian Institution on the presence of air for the combustion of theirin 1920, consisted almost entirely of equations, fuel.CNosequently, none of them can operateformulas, and tables, but it containedone state- beyond ti,, earth's atmosphere. Rockets, onthement of general interest.It proposed the idea

11.10k.d PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS of multi-stage or step rocketsthat is, onement of space ships. Oberth's book discussed rocket carrying anotherand said that by thisthe possibility of putting an artificial satellite means .a rocket could be sentto the moon, whereinto orbit around the earth. (Except for a it could explode a charge of flash powder to makescience-fiction story published in 1870, that a light visible from the earth. was the first time this idea had beenexpressed During the twenties and early thirties, God-inprint.)Oberth believed that passengers dard continued his experiments with the help could travel to and from the satellite in smaller of a small salary (as professor of physics"landing rockets." In this. way, the satellite at Clark University) and grants from the Gug-could be transformed into a manned space genheim and Carnegie Foundations. His liststation, which could ultimately serve as a of accomplishments is impressive. We havelaunching pointforspaceships. Neither mentioned his idea of multi-stage rockets,Goddard nor Oberth mentioned the possible and his design of the tapered nozzle. He wasuse of rockets as military_weapons. the first to suggest that a liquid-fueled rocket The German "Society for Space Travel, could provide the sustained thrust necessaryInc." was organized in 1927, with Oberth as for sending a vehicle into space.He waspresident and Willy Ley as vice president. the first to actually launch a successful liquid-(Willy Ley is still probably the world's most fueled rocket.(That was on 16 March, 1926;popular author on the subjects of rockets, mis- the rocket reached an altitude of 184 feet.)siles, and space travel.) The society began at He proved, first by calculation and later by ex- once to experiment with liquid-fueled rocket en- periment, that rocket propulsion canbe used in agines. The rockets carried two tanksone gaso- vacuum. He was the first to fire a rocket thatline and one of liquid oxygen. These two liquids traveled faster than sound; he was the first tohad to be fed simultaneously and in the right develop a gyroscopic steertng mechanism forproportions to the combustion chamber, where rockets; and he was the.first to usevanes in thethey were mixed and burned. Most of the at- jet exhaust stream to stabilize the rocket duringtempted launchings ended in failure, for one of the first phase of its flight. two reasons. First, liquid oxygen is extremely But Goddard was forced to end his experi-cold; it froze the valves, so that they refused to ments in1935, for lack of funds. Duringopen or close at the proper time. Second, the World War II he again worked for the Navy,combustion temperature was so high that the this time to develop rockets to aid the takeoffrocket burned up after a few seconds. In later of the Navy's flying boats. He died in 1945.experiments, the combustion chamber was sur- NASA's (National Aeronautics and Space Admini- rounded by a cooling jacket filled with water. stration) Goddard Space Flight Center atGreen- With this model, the society launched a number belt, Md. is just one of many activities namedof rockets that burned for about thirty seconds, in his honor. and reached an altitude of half a mile or more. A group of rocket enthusiasts, inspired byThe next step was to omit the water from the Goddard's experiments, formed the Americancooling jacket, and circulate the fuel throughthe Rocket Societ:in 1930.During the thirtiesjacket before burning it. When the society tried this group performed a number of importantto launch such a rocket, using gasoline as fuel, experiments with rocket motors, but theirit immediately exploded.Ley suggested using work was limited in scope by lack of money.ethyl alcohol, slightly diluted with water, in Hermaun Oberth isa German counterpartplace of gasoline.This system worked very of Goddard.Like Goddard, he worked on thewell.The same system and the same fuel physics and mathematics of rocket propulsioncombination were later used in the German during the first World War.There is goodV-2 missiles, the American Viking rockets, evidence that he independently conceived theand the rocket-propelled experimental planes idea of multiple -stage liquid fuel rockets. HeX-1 and X-1A. read Goddard's report shortly after it was The Versailles peace treaty (1919) limited the ptAlithed, and in 1923 published a book of hisGerman army to 100,000 men; it was forbidden own, called The Rocket into Inte to have aircraft or antiaircraft guns, or field artillery of more than 3-inch caliber. This Mae exploration of the upper atmoephere may explain why the German army took an but toberth, every improvement in rocketryearly interest in rocket development; the treaty was limply a step toward the eventual develop- of Versailles didn't mention rockets at all. In Chapter 1INTRODUCTION TO GUIDED MISSILES

1932, the army established a small researchwhile under complete radio control from the project under the direction of Captain (later Gen-ground. One of the problems that plagued the eral) Walter Dornberger to develop liquid-fueledarmed forces was stabilizationkeeping the rockets for use as weapons. No one in Germanyaircraft on an even keel so that it couldre- had any experience with rocket propulsion, ex- spond properly to radio commands. Because cept the members of the Society for Space Travel. a well-built model airplane is inherently stable, Dornberger visited the society and hireda veryGood didn't have to worry about this problem. young member named Werner von Braun. His contribution was to design and builda mini- The team of Dornberger and von Braun,ature radio receiver coupled to the control sur- with a small staff of assistants, began to testfaces through a miniature servo-system. rocket motors on an artillery testing range The Army and Navy resumed their experi- .near Berlin.In December of 1934, they sue-ments with radio command during the late ceeded in firing two rockets to a height of aboutthirties, and by 1940 both had developed radio- 6,500 feet. This news eventually filteredup controlledplanes for use as target drones. to the high command. In 1936, General von Missiles with elementary preset and command Fritsch went to the test range for a demonstra- guidance were used during World War II, but tion. The general was impressed. The resultsuccessful beam-riding, radar and infrared was a new and much bigger research institutehoming, and inertial guidance systems are all the Peenemunde Project, which became thepostwar developments. center for German research, development, and Although the Germans had the most spec- manufacture of robot bombs. After the war,tacular tactical success with guided missiles, von Braun came to the United States, where he our own Government made considerable prog- has become a leader in this field. ress in research on radar homing, aerodynamics, control of glide bombs and pilotless air- GUIDANCE SYSTEMS crait.The first homing guided missiles to be used successfully by any nation were flying BAT The history of guidance systems is short.bombs, launched from Navy planes (fig. 1-1). AU of the significant developments are recent, The code name BAT suggests the principleon principally because the state of electronics be- which it operated.Like bats, which give out fore the nineteen forties was relatively primi-short sound pulses and guide themselves by tive. Many of the pioneers in the fields of mis-reflected echoes, the BAT missile was directed sile guidance and propulsion are still actively atby radar echoes from the target. The missile work on guided missile development. was equipped with a radar transmitter and The Americans developed a flying bombreceiver which enabled it to home on the target. called the Bug, during the first World War. It Figure 1-1A shows the BAT mounted ina glider was simply a pilotless aircraft, with a rangetype of airframe. of about 400 miles.The Bug was ready for The Awn missile (fig. 1-1B) was controlled production by the middle of 1918, but by thatin AZimuth ONly. It was a standard 1000-lb time it was apparent that the war would bebomb fitted with an extended tail that carried a over in a few months, and the Bug was neverflare, a radio receiver, a gyro stabilizer to produced.Its accuracy would have been poor; preventroll, and rudders for steering right and it had no guidance system. But the Bug led toleft.This air-launched missile was used with the suggestion that pilotless aircraft could begreat. success in destroying bridges, canal locks, controlled by radio.Beginning in 1924, bothand similar targets. the Army and Navy experimented with radio- The Felix bomb (fig. 1-1C) was automatically controlled planes.Several moderately suc-guided by means of an infrared homing device cessful flights were made, with the pilotlesslocated in its nose. WW II ended before itwas plane controlled by radio from a parent plane used in combat. that flew nearby. This project was dropped in The Roc missile (fig. 1-1D) combined tele- 1932 for lack of money. vision equipment for transmitting a picture of In 1935, an American high- school studentthe target to the launchthg plane and a radio- named Walter Good built and flew a radio-.control system for guiding the missile. This was controlled model airplane.This was the firstthe first use of television as a method of time on record that a plane of any kind hadguidance. The TDN, a Navy missileusedagainst been successfully launched, flown, and landedthe Japanese sea targets and some shoreline PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

targets in the South Pacific, also used television- radio command guidance. The Navy's air -to- surface guided bomb, Walleye, uses TV contrast homing guidance. GUIDED MISSILES IN WORLD WAR II Ilk During World War II, theJapanesedeveloped and used two devices of interest in the history of guided missiles.One of these was an air- launched,radio-controlled,rocket-assisted glide bomb.Its performance was limited.It had to be launched from a plane at low altitude, within two and a half miles of the target. This made the launching planes highly vulnerable to antiaircraft fire, especially after we began to use the proximity fuze. The Japanese dropped this project before the end of the war. The second Japanese missile was the Baka bomb. This was a rocket-propelled glide bomb designed for use against shipping.It carried a human suicide pilot; for this reason we can't call it a true guided missile. The Baka bomb had poor maneuverability, and because of this we were able to shoot down a great many of them with antiaircraft fire. Of the guided missiles used during World War II, those made by the Germans were the 4. most advanced, and the most effective.The V-1 was developed early in the war, and was successfully flight tested at Peenemunde as early as the spring of 1942. By 1943, the Peene- munde center was working on 48 different antiaircraft missiles. The work was later con- solidated into 12 projects in an effort to get the missiles into production in time to influence the outcome of the war. The V-1 was a robot bomba pulsejet midwing monoplane with a conventional airframe and tail construction. It used gyro stabilization and preset compass guidance. It was launched from a ramp with the help of boosters, and had to reach a speed of about 200 mph before its developed enough Uu4st to keep it air-airborne. Their 1-ton warhead did serious damage, but the V-1 missiles were slow.After proximity fuzes were rushed to Englandto combat them, about 95% of them were brought down .. by antiaircraft fire. 33.2-.5. The V-2 was a large missile, propelled by Figure 1-1.Early types of guided missiles:liquid-fuel rockets.Its total weight at launch- A. Bat, radar guided; B. Aran radio commanding was over '14 tons, including a 1650 -pound guidance; C. Felix bomb, infrared homingwarhead. It was launched vertically, andpreset guidance; D. Roc missile, radio-control andto tilt over to a 41- to 47-degree angle a short television guidance. time after launching. When it reached a speed

d .14 Chapter 1INTRODUCTION TO GUIDED MISSILES

calculated to take it to the target, its propulsion Several missiles developed in the United system was shut down by radio command, and itStates were mentioned above with regard to then traveled a ballistic trajectory. Its accuracytheir guidance systems. The Army Air Corps was not high, and its maximum range was onlybegan the development of guided glide bombs about 200 miles.But it descended almostin 1941.These included Azon, Razon, Tarzon, vertically on its target, at speeds of fromand Roc. Roc and Tarzon, controlled in azi- 1800 to about 3300 mph. No V-2 missilewas muth and range, were developed during WW II ever intercepted, or shot down by antiaircraftbut were not used in combat. Tarzon was used fire.Because it was supersonic, it would hitsuccessfully during the Korean war. the target before it was heard approaching. In 1944, we carried out a glide-bomb mis- Five other German missiles which were insion against Cologne, Germany, and a majority various stages of final testing when the warof the bombs reached the target area. In this ended, are worth a brief mention: same year, aircraft were used to control Rheinbote was a surface-to-surface missilet el evision-sighted,explosive-laden bombers propelled by a three-stage rocket, withbooster-(called "Weary Willies") unfit for further assisted take-off.It reached a speed of overservice.These radio-controlled bombers saw 3200 mph about 25 seconds after launching, andsome service over Germany. had a range of about 135 miles. Wasserfall was a supersonic surface-to- Our first jet-propelled missile was a radio- air missile, propelled by a liquid-fuel rocketcontrolled flying wing of the GORGON series guided by radio command; speed:560 mph;of missiles; a later version was a copy of the range: 30 miles. German V-1, with a few improvements. Schmefterling was a smaller version of By the end of WWII, the Navy had a number Wasserfall, intended for use against low-altitudeof guided missile projects in various stages targets at ranges up to 10 miles. It carriedaof development.The Gargoyle was an air- 55-pound warhead. launched, liquid-rocket engine powered, radio- Enzian was another surface-to-air missile,controlled glide bomb with a flare for visual designed for use against large bomber forma-tracking. Another Navy glide bomb the Glomb, tions.It was propelled by a liquid-fuel rocket,carried a television monitor through which the and was launched with four solid-fuel boosterpilot of the launching aircraft could observe its rockets. approach to the target; it was guided by radio The X-4 was an air-to-air missile designedcommand. The Loon was a U. S. Navy version for launching from fighter aircraft as shownof the German V-1, intended for shore bombard- in figure 1-2.It was propelled by liquid-fuelment. The Gorgon IIC was propelled by a ram- rockets and stabilized by four fins placed sym-jet engine, tracked by radar, and guidedby radio metrically.Its range was 1-1/2 miles; speedcommand. In 1944, the Navy assigned develop- 560 mph at an altitude of 21,000ft. The X-4wasment of the Bumblebee project to the Applied guided by commands from the launching aircraft,Physics Laboratory of the Johns Hopkins Uni- through a pair of fine wires that unrolled fromversity.This project has produced Terrier, two coils mounted on the tips of the missile fins.Tabs, and Tartar.

UNREELS WIRE

83.20 Figure 1- 2. LaunchingX-4 missile with wire guidance. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Missile developments after three letters indicated the intended use of the World War II missile: AAMair-to-air missile As we have shown, the principal guided ASMair-to-surface missile developments during World War II AUMair-to-underwater were German; the United States laggedfar be- SAMsurface-to-air hind.Japanese and British missile develop- SSMsurface-to-surface ments were insignificant, and as far as we UAMunderwater-to-air know, the Russians had none at all.In 1945, USMunderwater-to-surface the Russians captured most of the production These designations will not disappear from engineers and technicians of the V-2 project,use in the immediate future.Publications will as well as several tons of missiledata andnot be revised merely to change missile des- perhaps a few V-2 missiles. The design staffignations, but the new, uniform designations of the Peenemunde project, including von Braunwill be used in new and in revised publications. and his principal assistants, surrendered to theThe new designation indicates the launch en- Americans rather than to the Russians. Wevironment (where launched and from what type captured and shipped to the proving ground atof launching device), mission, delivery vehicle White Sands, New Mexico, enough intact V- 2s andtype, design number, and series symbol of the spare parts to make, eventually, about70 com-missile.Attachment 6 to the BUWEPSINST plete missiles. lists the current designation, former designation, popular name, and service of missiles, During the first few years after the war,rockets, and probes in all the United States 1othsAirerican and Russian missile effort wasservices at the time of publication. New mis- partially devoted to assimilating the Germansiles and rockets are assigned the next con- developments. Our own experitnents with thesecutive design number within the appropriate captured V- 2s provided valuable training forbasic mission. lamching crews, and valuable knowledge of missile engineering. Our "V-2 Program" ran NEW DESIGNATIONS FOR MISSILES from March 1948 to June 1951.One of its principal successes was a high-altitude record The following table explains the new des- of 250 miles, achieved by a WAC-Corporalign:Mona and lists the Navy missiles and rockets missile boosted by -a V-2.This record stoodwith their current and former designations. for many years. The design number is a number assigned Postwar missile developmenthasbeen rapid.to each type of missile with the number "1" Many missiles are nowoperational; many othersassigned to the first missile developed. For have been abandoned at various stages of de-example, all five modifications of the Terrier velopment, or rendered obsolete by more ad-missile (BW-0, BW-1, BT-3, BT-3A and HT-3) vanced weapons. We Will not try to cover thesehave the design number "2". Tartar missile developments here; a list of obsolete missilesmodifications (Basic and Improved Tartar)have would be longer than a list of those now cur-the design number "24". rent. To distinguish between modifications of a missile type, series symbol letters beginning with "A" are assigned. Therefore, rthe Terrier CLASSIFICATION OF BW-0 has been assigned the symbol letter UNITED STATES MEWL= "A" and the Terrier BW- I has been assigned the symbol letter "B".The series symbol GENERAL letter fellows the design number. Incidentally, to avoid confusion between letters and numbers, Although missiles are popularly known bythe letters "I" and "0" will not be used. their names, such as Sidewinder or Terrier, If neoessary, a prefix letter is included be- every missile is assigned a desigaation cos.!,foie the military designation. A list of ap- misting of letters and numerals. In the designs-plicable prefix letters is down at the bottom tion system used meta the recent changeof the bible on the following page. (required by DOD Directive 4000.20 and imple- All Navy missiles are assigned mark (Mk) mented bystivaparist8800.2), the firstand modification (fled) numbers. These numbers

$41 Chapter 1INTRODUCTION TO GUIDED MISSILES

Navy Missile and Rocket Designations (Reprinted from Naval Aviation News, September 1963)

LAUNCH ENVIRONMENT SYMBOLS Popular Name Currezt DesignationFormer Designation Letter Title Description Missile Series

A Air Air launched. Terrier 13W-0 RIM -4A SAM-N-7 B Multiple Capable of being launched from more than Terrier BW-1 R111-2B SAM-N-7 one environment. Terrier BT-3 RIM-2C SAM-N-7 C Coffin Horizontally stored in a protective en- Terrier HT-3A RIM -4D SAM-N-7 closure and ground - launched. Terrier HT-3 RIM-211 SAM-N-7 H Silo Vertically stored below ground level and Sparrow ADM -7A AAM-N-2 Stored launched from the ground. Sparrow II AIM-7B AAM-N-3 L Silo Vertically stored and launched from be- SparrowIII AIM-7C AAM-N-6 Launched low ground level. SparrcwIII AIM-1'D AAM-N-6A AAM -N -6B 11 Mobile Launched from a ground vehicle or 'mov- Sparrow HI AIM-7E able platform. Tans (6B) R111-8A SAM-N-613 P Soft Pad Partially or nonprotected in storage and Tabs (613W) RD1-8B SAM-N-6I3W . launched from the ground. Tales (6131) RIM-8C SAM-N-6131 R Ship launched frau a surface vessel, such as Tales (611W1) RIM-8D SAM- N -6BWI ship, barge, etc. Tales (11C) RIM-8E SAM-N-6C1 U Underwater Launched from a submarine or other Sidewinder I AIM-9A AAM-N-7 underwater device. Sidewinder IA AIM-9B AAM-N-7 Sidewinder AIM-9C AAM-N-7 ICBSION SYMBOLS IC -BAR Sidewinder AIM-9D AAM-N-7 D Decoy Vehicles designed or modified to confuse, IC-111 deceive, Cr divert enemy defenses by BnlWP AGM-12A ASM -N -7 simulating an attack vehicle. Bullpup A011-1213 ASM -N -7A E Special Vehicles designed or modified with elec. Bel** AOM -12C ASM-N-7B Electronic ironic equipment for communica- Bullpup Trainer ATM -12A ASM-N-7 tions, countermeasures, electronic (Martin-Marietta) radiation sounding, or other elec- Bullpup Trainer ATM -12B ASM-N-7A Ilduson) tronic recording or relay 1111811101111. Hawk 11111-23A M-3 G Surface Vehicles *wiped to destroy land or sea Tartar Basic 1113144A SAM-N-7 Attack targets. Tartar Improved 111314413 SAM-N-7 I Intercept-Vehicles designed to intercept aerial Polaris Al UGM-27A Aerial targets, defensive or offensive. Polaris A2 11121-27B Q Drone Veddcles designed for target, recon- Polaris.A3 UGIM-27C naissance, ar enradllence purposes. Mabee BQM-34A QIC T Training Vehicles designed ar permanently mod- Firebee AQM-34B KDA-1 ified for training purposes. Mete* AQM -34C XDA-4 U Underwater Vehicles designed to destroy enemy sub- 11QM-36A EDIR-5 Attack marines or other underwater targets AQM47A =213-1 or to detonate underwater. AC/11-38B RP-78 W Weather..Vahicles designed to observe, record, 11(111-311A ILDB-1 or relay meteorological data. . ZQM-4M ED60-2 Petrel AQM-41A AUM-N-2 VIDUCLE TYPE SYMBOLS Redeye XIIIM-411A Gelded Unmanned, seN-propelled vehicles de- MIHROC UUM-44A lidssile signed to move in a trajectory or Shrike AGM-45A ABM -N -10 flight path all or Ply above the Condor AGM-53A AS11-N-11 earth's surface and whore trajectory Phoenix AIM-MA AAMX-11 can be controlled remotely or by hom- PQM-56A CT-41 ing systems, or by inertial and/or Rocket Series programmed *dance from This term amine iodide ewe ve- Weapon Alpha RUR-4A hicles, space boosters, or liked tor- MIROC R1111-11A pedoes, bit doss triode target and reconnoissance drones. STATOR PREFIX SYMBOLS N Probe 110n-orblftl instrinested vehicles ed in- Solved n *ace nahisionsiliet creased JSpend Test Vehicles especiallyconfigered shnply to to penetrate The serespsoe =drat- (Temporary) accommodate test. meat and report dots. . X Special Test, Vehicles sonoodifted they will not be re- R Ito -hat Selt-prepillsd velkelet Itlesst (Penaseent) turned to original mos. or rends enitrol gekbace X RepsrimentalVellielee =kw development. miens, wham trajectory atemot, be. Y Prototype Preproduction vehicles for test. altered after II nosh* Vehicles in Anode, stage. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS and the name of the missile constitute the officialThe missile and booster together weigh mire nomenclature approved by BuWeps. Missilesthan a ton. There are 12 launchers in each Nike having two-stage propulsion systems (separatebattery, which is operated by about 100 officers boosters), for instance, the Terrier and Talos,and men. have one Mk and Mod number for the complete Continued developmental work with the Nike round.However, the individual missile andmissile has resulted in improvements in the booster sections have their own mark andoriginal missile; Two mods of the Nike- modification numbers. Hercules, the MIM-14A and MIM-14B, are All missiles in service, an well as mostoperational.Batteries of Nike-Hercules (re- of those still under development, have beer.placing the Nike-Ajax) are deployed in the given popular names.Some of these namesUnited States and in Europe (NATO countries follow this pattern: only).The Nike-Hercules has a range of about AGM, AIMWinged creatures. Example:75 miles and a weight of 10,000 pounds. It is Sparrow, Bat. capable of carrying a nuclear warhead; it is de- RIMMythological terms. Example: Taloa.signed for use against either single aircraft or UGM, RGMAstronomicalterms.Ex-whole formations of aircraft.The missile is amples: Polaris, Regulus. 27 ft. long; the booster 14-1/2 ft. long. Both At the present time, most missiles appearuse solid propellant. The warhead is provided to be exceptions to the above "rules."Forwith a safety feature, so that it can detonate example, Sidewinder and Bullpup are not wingedonly at altitudes sufficiently high to prevent creatures; Terrier is not a mythological term;damage to friendly surrounding terrain. Asroc and Alfa are not astronomical terms. Nike-Zeus (SLIM) is an antimissile missile Many of the air launched missiles areequipped with a nuclear warhead, and designed named after birds: Falcon, Quail, Hawk, Petrel,to defend the United States against attack by Redhead Roadrunner, Shrike, and Condor. Noteenemy intercontinental ballistic missiles.It that all of these except one (Quail, used as ahas a 200-mile range and weighs 22,800pounds. decoy) are birds of prey marked by character-It is more than twice as long and three times istics of swift, aggressive action, and thereforegreater in diameter than the Nike-Ajax. The appropriate for missile names. "X" in its designation indicates that it is experimental and not yet deployed (at time of this writing). CURRENT U.S. szRvrcE MISSILES The Nike-X is under development; it is planned to intercept submarine-launched mis- GENERAL siles. The most advanced portions of the Nike- Zeus are used in it. Because of the rapid developments in the Hawk ammo is designed to supplement the guided missile field, the lists given below willNike missile system by destroying attacking be out of date before you can read them. Someaircraft at low altitudes.The launching fa- of the missiles listed may have become ob-cilities are sufficiently portable to be used by solete.Others, now under development, willfast-moving combat troops. Hawk is propelled probably be announced. by a solid-fuel rocket. The missile is about 17 ft. long, and about 14 inches in diameter. ARMY MISSILES It has a 22-mile range and weighs about 1275 pounds. Operational mods are deployed in Nike -Ajax (MEM) is the Army's first super-Europe, Panama, Okinawa, and the U.S.; ad- sonic antiaircraft guided missile. It is designedvanced mods are being produced and tested. to intercept and destroy attacking enemy aircraftHawk has intercepted Corporal, Honest John, regardless of evasive action. Nike guided mis-and Little Join rockets in flight. sileunits are now deployed around vital in- Corporal (WM) may be equipped with either dustrial, highly populated, and strategic Itemsa unclear oraa conventional warhead. It was the of the United Oates. Nike-Ajax is about 20 ft.first guided missile capable of carrying a low and 1 ft. in disaster, with two sets of finsnuclear warhead. It can engage tactical targets for guidance and steering.It is boosted toat ranges of 75 miles or more. Corporal gives supersonic speed by a solid-propellant booster,the Army field commander great firepower on and maintained by a liquid-ibel sustainer motor?the battlefield, and ambles him to strike selected Chapter IINTRODUCTION TO GUIDED MISSILES

targets deep in enemy rear areas.Corporal Lance (XMGM) was formerly designated follows a ballistic trajectory during most of itsMissile B.It will replace the Honest John flight; weather and visibility conditions place noand Lacrosse. Its range is 3 to 30 miles, and restriction on its use. The propulsion systemit carries either a nuclear or a conventional uses a liquid-fuel rocket motor. The missilewarhead.Its high mobility makes it a valuable travels through space at several times theaid to troops. speed of sound.Corporal battalions are now Davy Crockett (MGM) may be mounted on a deployed in Europe, but are being replaced byjeep, mechanical mule, or armored personnel the more potent Sergeant. carrier, and one version may be carried by two Sergeant (XMGM) is a single-stage, solid-men.It has a sub-kiloton nuclear warhead and propellant, ballistic guided missile intended tois meant as a defensive rather than an offensive replace Corporal, with improvements In power,weapon. range, and accuracy.It has entirely replaced Redeye is a new development in hand- the first atomic artillery, the 280-mm "Atomiccarried weapons. It is a shoulder-fired, solid- Annie," with 8-inch howitzers firing an atomicpropulsion, heat-seeking missile to be used shell. against low-flying aircraft and helicopters. It Redstone (PGM) is a supersonic single-stageis not operational at this time.One model is ballistic missile with a range of about 200 miles,designed for Marine Corps use.- designed to extend and supplement the range and Honest John (MGR) is an unguided rocket fire power of Army artillery. It is deployed intype with a 12- to 20-mile range. R has a Europe but is being replaced by Pershing. nuclear warhead.The Army is replacing it The Pershing (XMGM) is a two-stage with the Lance.The Marine Corps also for- 10,000-lb solid-propellant missile. It is trans-merly used it. ported on a tracked vehicle or helicopter. The Little John (MGR) has a 10-mile range. Pershing has a 400-mile range, compared toIt supplements the heavy artillery in airborne divisions and air-transportable commands. It the 200-mile range of the Redstone. Its war-may be replaced by Lance.It may have a head is nuclear; its trajectory is like that of annuclear or a high explosive nonnuclear warhead. intercontinental ballistic missile. The Army has several missiles to be used Jupiter (PGM) was theArmy's intermediate-as drones for target, reconnaissance, or sur- range ballistic missile (no longer in serviceveillancepurposes.RedheadRoadrunner as a missile).Its range is in the order of(MQM), Kingfisher (AQM), and Cardinal (MQM) 1500 miles, and it is propelled by a liquid-are so used. fuel rocket. In 1958-57 the Navy tried to make Two missiles acquired from the French are it a submarine-launched missile, then decidedthe SS-10 (MGM) and the SS-11 (XAGM). Both that the liquid propellant system made it =-are wire-guided missiles, principally for anti- suitable for submarine use, and dropped thetank use. project to begin development of the Polaris. Other antitank missiles are the Entac (MGM), The Jupiter-C (without the warhead, of course),Shillelagh (CMGM), TOW, and M-72 (LAW). was used for the Vanguard earth satellite pro-The Shillelagh is the first guided missile to gram by providing a back-up satellite launch-be fired from a gun tube from which conven- ing capability. tional ammunition can also be fired.It is to Lacrosse (MGM) is used in close tacticalbe installed on the General Sheridan assault support Of ground troops.It is an all-weathervehicle, and on assault helicopters. missile, propelled by a solid-foel rocket motor, with a maximum range of 20 miles, and capableAIR FORCE MIESILES of carrying warheads Wily effective In area- type bOmbing (rather than pinpoint bombing). It Matador (MGM) is a tactical missile driven was designed to supplement, and perhaps even-by a turbojet engine at a speed of 850 mph. It tudly to replace, cOnventional antipery. Thehas a length of about 40 It and a wing span of Lacrf system includes Qat 4Vie,aabout 29 ft.It can carry a nuclear warhead, 12r012 muented on a shandard Army truck,and may be guided by radio command or by a and Mier ground equipment.It is operationalnavigational system.Its range Is more than inatm"but is being phased Out of inventory,650 miles. 'radical missile groups armed with to be rupileed by lanes. Matador are now deployed in Europe and on PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Formosa, but no more Matador missiles are A second liquid- fueled giant is the two-stage being procured; it is being replaced by Mace.Titan.Titan I (HGM) and Titan II (LGM) are Falcon (AIM) comes in several versions;intercontinental ballistic missiles. In general, one has radar guidance; another hes infraredTitan is similar to Atlas, except that Titan has homing;still another has a hybrid infrareda second-stage motor. It has the greatest pay- radar guidance. Falcon is a supersonic missile,load and range of any of our ICBMs. Titan II propelled by a solid-fuel rocket. It weighs aboutis being used for the Gemini spacecraft, which 100 pounds; and is about 6 ft long. One modelis a three-ton, two-man vehicle planned to carries a nuclear warhead.At last count,rendezvous equipment in space and assemble thirteen models were in operational or ex-it, and to test the effect of prolonged weight- perimental stages. Its range is about 5 nauticallessness in man. miles. One of the most publicized missiles is the Genie (AIR) is a rocket-propelled air de- Minuteman (LGM). As the name implies, fenSe missile that may be armed with a nuclearreadiness for prompt firing is an important warhead with proximity fuzing. Note that it isfeature. It is called a second generation ICBM, classified as a rocket, and is unguided. It waswhich means that it incorporates many im- formerly called Ding -Doug. provements over the first ICBMs, the Atlas Bomarc (C128) is a long-range air defenseand Titan.It is a 5500-mile range, inertially missile that can destroy attacking aircraftguided, solid-propellant ballistic missile with at ranges of more than 100 miles and altitudesthree stages. Numbers of Minuteman missiles above 60,000 ft.The missile is about 47 ftare deployed in hardened and dispersed silos. long, has a wing span of about 18 ft, and weighsOnce set up and checked out, the missile is about 15,000 pounds.It is launched verticallyready to fire at a moment's notice, requires by solid-fuel boosters, and is sustained in flightvery little supporting equipment, and is able by twin ramjet engines. Bomarc B attains ato stand by, ready to fire, for long periods of speed of Mach 2.7 and has a range of more thantime with very little maintenance. Minuteman 400 nautical miles and carries a nuclear war-II has an improved guidance and control system head. and an improved reentry vehicle. Thor (PGM) is the Air Force's intermediate- Two types of the Mace are used by the Air range ballistic missile (IRBM). It is propelledForce, one launched from a mobile base (MGM) by a liquid-fUel rocket at a speed of Mach 10;and one from hard sites (CGM). Both types are range is over 1500 miles. Thor is provideddeployed at sites. It is an air-breathing surface- with an inertial guidance system. to-surface missile with inertial guidance. It is Thor has been phased out as a missile and isturbojet powered and may have either a con- being converted for space boosters. Thor Able,ventional or a nuclear warhead. The B model a series of multistage rockets using the Thorhas a 1200-mile range.Its predecessor was missile, has been used for a series of lunarthe Matador.The recoverability of training probes and for carrying a recoverable datamissiles was demonstrated with the Mace. capsule (containing a mouse) over its 6000 - Quail (ADM) is an air-launched decoy de- mile flight range. signed to confuse enemy defenses.It is de- Atlas (POM) is an intercontinental ballisticployed at SAC bases, tobecarriedbyB -52s. Its missQe with a range of more than 5000 miles.range is about 200 miles; the turbojet powered It th launched by rocket engines that developadvanced version has a range of about400miles. many tons of thrust, andmillions ofhorsepower, Hound Dog (AGM) is launched by inter- within a few seconds. Atlas reaches a top speedcontinental bombers.It is an air-breathing, of about Mach 15 more than 10,000 miles anair-to-surface standoff missile with a range hour. It will descend on itstuget at that speed,of over 500 nautical miles. The B version has from a height of about 800 miles.This hugea nuclear warhead, and isturbojetpowered. liquid-propellant missile is launched vertically Missiles that are used by the Air Force and from a fixed base.It carries a nuclear war-the Navy are Bullpup, Sidewinder, Sparrow III, head. ft is be phased out for missile: use andand Shrike.These are described In the nut being developed' as a launchvehicleforthe spacesection. program. The first Mercury spaceeraftto orbit In the process of developing and perfecting the earth, welt Colonel JohnH.GlennJr.aboard, are dropped from the program. was boosted tub orbit by an Atlas booster. Two examples are the Spark, begun about the Chapter 1INTRODUCTION TO GUIDED MISSILES same time as the Matador, and the Rascal. The Snark was actually a pilotless aircraft and the Rascal was a rocket-powered missile.

NAVY MISSILES Sidewinder (AIM) (fig. 1-3) is probably the simplest and cheapest of all guided missiles. It is about 9 ft long, and weighs about 155 pounds. It has only about 24 moving parts, and no more electronic parts than a table radio. It attains a speed of Mach 2 relative to the launcher, and a range of several miles; itis. designed to destroy high-performance aircraft from sea level to altitudes above 50,000 ft.It has an infrared homing system. Sidewinder was named after a desert rattlesnake.(The Sidewinder snake, like all of the pit vipers, has infrared receptors on its head that enable it to detect the presence of prey by its body heat.) Side- winder is now the primary airborne missile used by squadrons in the Sixth Fleet in the Mediterranean, and the Seventh Fleet in the Western Pacific. The Sidewinder-1C version has an improved rocket motor and has switch- able guidance, infrared or radar-guided. The physical appearance of the improved Side- winder is very similar to that of its predeces- sors but its performance is quite different. The Air Force also uses the Sidewinder missile. Sparrow I (AIM) is 12 ft long and weighs 300 pounds; it reaches a speed of Mach 2.5 relative to the launcher, within a few seconds after launching.It is provided with beam- rider guidance, and is propelled by a solid-fuel rocket.Navy planes can carry two to four of the missiles, and can fire them singly or in salvos. Sparrow II (AIM) was developed as an experimental missile, and not intended to become operational.It has, however, been adopted for operational use by the Royal Canadian Air Force. Sparrow III (AIM) is very similar to Spar- row I, but with a much more sophisticated semi-active CW homing guidance system. It is slightly heavier than Sparrow I, a little faster, 144.1 and has a longer range. It will first supplement,Figure 1-3.Pilot in high- altitude flight suit and then replace Sparrow I in the fleet. stands beside the Sidewinder missile. Sparrow III (AM) is also used by the Air Force. Several versions of Sparrow III are insistance to countermeasures, and longer electri- use, and research is continuing to improve thecal power burn time are improvements include& missile fUrther.Temperature - resistant ex-in the Sparrow M. plosives, greater seeker sensitivity, greater Petrel (AQM) is newly obsolete; although a range, higher maxim= altitude, increased re-few of these missiles may still be found in the PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS. fleet, they are no longer in production. PetrelProvidence, and Springfteld the attack airis a subsonic missile with radar homing,craft carriers Kit:t,1±,merica and Con- powered by a turbojet engine.Its payload isstellation; the nuclear -power cruiser Long not a warhead, but a homing torpedo. As itsBeach; on frigates, plus several destroyers of designation indicates,itis now used as aall DLG classes. drone. Advanced Terrier is quite different from the Bul 1pup (ASM) is 11 ft long and weighsearly Terrier. A nuclear warhead is available about 540 pounds. It is relatively inexpensive,for it, and improvements have been made in simple b design, and extremely accurate.the conventional explosive warheads. Important Bullpup is a tactical missile with a conventionalchanges have been made in the control system, warhead, designed for use by carrier-basedwhich, although not a part of the missile, is aircraft against small targets such as pillboxes indispensable for its operational use. tanks, and truck convoys, in support ofground Although considerably smaller, the Tartar troops. It is powered bye solid-fuel rocket, and(RIM) is similar in function to Terrier, except has a range of 15,000 ft at a speed of Mach 2.that it is propelled by a dual-thrust rocket, and Bullpup B is a big brother version of theis launched without a separate booster. The original missile.It is longer, heavier, fasterTartar system, designed for DD's, is installed (with a consequently greater range) and carriesaboard the guided missile destroyers numbers a 1000-lb warhead instead of a 250-lb warhead. 2 through 24, and aboard the cruisers Chicago, It is not intended to replace Bullpup A, but toColumbus, and Albany. At present writing, six complement it.Many of the components aredestroyer escorts (DrGs) also are to be armed interchangeable.The Bullpup B has an all-with Tartar missiles. On cruisers, it supple- weather capability which the A did not have; itments the Talos missile. Its launching system can locate and destroy its target in foul weather, is compact and rapid firing, which makes it at night, or in poor visibility. adaptable to destroyers, and even smaller ships.Figure 1-5 shows a Tartar missile One version of Bullpup has a prepackagedleaving the launcher, which holds two missiles. liquid motor and a nuclear warhead.SeveralA smaller model launcher holds only one years of research were needed to produce a fuelTartar missile at a time. combination with good storage properties, and Talos. (RIM) (fig. 1-6) is a two-stage mis- reliability, that could be handledwithsafety. Notsile designed to bring down enemy aircraft all problems with the liquid propellant engineand missiles at ranges of 65 miles or more. have been solved. It is 20 feet long, and weighs 1-1/2 tons. It is Bullpup is also used by the Air Force. launched with solid-fuel boosters, and is sus- The Navy's3 Ts Terrier, Talos, andtained in flight by a ramjet; it reaches a speed Tartarhave undergone many Changes sincein excess of Mach 2 within about 10 seconds of their inception.The Typhon program, which was to incorporate all three missiles into launching.It can be used with either a nuclear one system, has been set back for further re-warhead or a conventional warhead. During the search. New research is going on to developfirst part of its flight, Talon is a beam rider. a system in which the 3 Ts can be used as partAs it approaches its target, it switches over of a system, possibly using the same launchingto homing guidance. Talos systems are installed system. on the cruisers Galveston, Little Rocky Okla- Our first missile ship, the U.S.B. Glatthoma Eft, Albany, Columbus, Chicago, and (DDG-1), was equipped with Terrier mis Beach. (tTGM)(fig.1-7) is the Navy's Terrier (RIM) (fig. 1-4) is a supersonicintermediate-range ballistic missile, with a beam-riding antiaircraft missile with a rangerange up to 2500 miles.It is designed for of more than 10 miles.(The HT-3 Terrierlaunching either from surface ships or from uses semi-active homing guidance.) It issubmerged submarines, for bombardment of launched by a solid-fuel booster rocket, andshore targets. It is propelled by solid fuel. At is propelled by a solid-fuel sustainer ;oast.present, nineteen submarines capable of launch- Terrier is about 15 feet long without itsing Polaris are operational.Each submarine booster, and weighs 1-1/2 tons.Terriercarries 16 missiles.At this time, develop- batteries have been installed on the guidedmental work on the Polaris is centered on im- missile cruisers Boston, Canberra, Topeka;provement of the submarine-launched missile.

.4 Chapter 1 INTRODUCTION TO GUIDED MISSILES

K. aal r

33.262 Figure 1-4.Terrier missiles and launchers.

Three versions of Polaris have been de- The emphasis currently is on antisubmarine veloped:A-1, A-2, and A-3. The A-1 and A-2warfare (ASW), and several weapons are being are operational; the A-3 has been successfullydeveloped or improved. tested and soon will be aboard submarines, Although Asroc (RUR) is rota guided missile, replacing the older mods. ThePoseidon missilebut a rocket-propelled torpedo or a depth is being developed from the Polaris technology.charge, it is one of the important missiles of The increase in range, from 1500 miles forthe Navy.It is part of the missile armament the A-1 to over 2500 miles for the A-3, isoneof many destroyers, including destroyer escorts, of the most striking improvementse With theirand of four cruisers. One form of the Asroc nuclear warheads, Polaris submatines can de-is a surface-ship launched, rocket-propelled live a blow on the enemy which can eliminatehoming torpedo and the other is a nuclear depth several large industrial areas within minutescharge, also rocket propelled. Both forms can after an attack on the United States. be fired from the same deck-emplacedlauncher. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

rid.

'k js,

33.284 Figure 1-5.Tartar missile leaving launcher.

Some destroyers have the DASH (Destroyerto our Weapon Alfa (formerly called Weapon Anti-Submarine Helicopter) system, which de-Able), which is being phased out. livers the Asroc to the target by means of a Other missiles of the Navy in various stages remote-controlled helicopter. An Advancedof development and use are: Asroc is under development. Shrike (AGM), an antiradiation missile with Two other antisubmarine weapons are thepassive radar homing, which was formerly called Astor and Subroc (UUM).Astor is a wire-ARM. The Air Force also plans to use it. guided torpedo and Subroc is a submarine Walleye (AGM), an air-to-surface glidebomb rocket fired from a torpedo tube. Subroc waswith TV guidance controlled by a pilot in the installed on the ill-fated submarine Thresher,mother plane, no propulsion, but a powerful and is being installed on other submarines of theconventional warhead.It has shown amazing Thresher class. accuracy at a range of several miles. Anantisubmarine surface-to-underwater Zuni, a Navy and Marine Corps rocket, missile developed and built in Norway, the Terne,air-to-surface, has a 5-mile range. It can be is being purchased by the Navy to installarmed with various heads, including flares, on two destroyer escorts.It is comparablefragmentation, and armor piercing.

20 Chapter 1INTRODUCTION TO GUIDED MISSILES

C:At; , 4

3.143 Figure 1 -8. Talcs missiles on launcher aboard ship.

Condor (AGM) is a long-range missile de- Phoenix (AIM) is a long-range air-to-air signed to enable aircraft to destroy tacticalmissile designed to be carried by the TFX targets chile outside the range of .enemy de-.Navy plane. fenses.A gyro-stabilized tzlevision camera Figure 1-8 shows the configurations of is the target seeker. . some Navy missiles and rockets. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

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4- .,1=1;4'..k 44i '- 11+' 3 ';4' . , :1,0,,

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3.78 Figure 1-7.Polaris. Chapter 1INTRODUCTION TO GUIDED MISSILES

POLARIS

SUBROC

TARTAR

ASROC =233MME1 SPARROW III ZUNI

11201,3 4astaitanti BULLPUP ALFA

SIDEWINDER

REGULUS I

144.2 Figure-1- 8.Navy missiles and rockets; comparative sizes and silhouettes.

. .1 CHAPTER 2

FACTORS AFFECTING MISSILE FLIGHT

A. INTRODUCTION briefly summarized. A detailed study of air in motion, and the mathematical analysis of the GENERAL various forces present, are beyond the scope of this text.The discussion will be general A guided missile, by definition, flies above and qualitative, and no mathematical develop- the surface of the earth. Aerodynamic long- ment will be attempted. range missiles, as well as all missiles of short In general, missile aerodynamics are the and medium range, are subject throughout their same for both subsonic and supersonic flight. flight to the forces imposed by the earth's at-The basic requirement is common to all craft mosphere. Ballisticmissiles, though theyintended to fly:in order to fly successfully, follow a trajectory that takes them into space,.the craft must be aerodynamically sound. But must climb through the atmosphere after launch- the high speeds and high altitudes attained by ing, and must descend through it before strik- current guided missiles give rise to new prob- ing the target.All missiles are subject tolems not encountered by most conventional air- gravitational and inertial forces. This chaptercraft.An example is the shock wave that is will briefly discuss the principal forces that produced when a flying object attains the speed act on a guided missile during its flight.Itof sound. Problems of oxygen supply for air will show how the missile trajectory may bebreathing missiles arise at high altitudes, and controlled by designing the missile airframeproblems of skin heating by friction with the air and control surfaces to utilize or overcomearise at high speeds, and upon reentry into the the forces acting on them. earth's atmosphere. Before proceeding further, some brief definitions may be helpful. Aerodynamics may be defined as the science THE ATMOSPHERE that deals with the motion of air and other gases, and with the forces acting onbodies mov- As mentioned above, the earth's atmosphere ing through these gases. An aerodynamic mis- extends upward about 250 miles. Although there sile is one that uses aerodynamic forces toare some differences of opinion as to where the maintain its flight path. A ballistic nliadleatmosphere ends and space begins, the limit does not depend upon aerodynamic surfaces todefined,is generally accepted. The atmosphere produce lift;it follows a ballistic trajectoryis quite definitely divided into three layers, after thrust (from its booster) is terminated. troposphere, stratosphere, and ionosphere (fig. A guided missile can alter its flight path by- 24), eachwith its distinct characteristics. means of internal or external mechanisms. The earth's atmosphere is a gaseous en- CHARACTERISTICS OF THE ATMOSPHERE velope surrounding the earth to a height of roughly 250 miles.The characteristics and One of the most important characteristics properties of the atmosphere change with al-of the atmosphere is the change in air density titude, and therefore missile flight is affectedwith a change in altitude. differently. With increasing altitudes the density of the An understanding of missile aerodynamicsair decreases significantly.At sea level, the requires a familiarity with several of thedeneity of air is about .076 pound per cubic basic laws of physics.These laws will befoot. '.At 20,000 feet, air density is only about Chapter 2-FACTORS AFFECTING MISSILE FLIGHT

The procedure then repeats itself-that is, a second temperature minimum is reached, and xt ER SPA ctL. then, after a short constant-temperature zone, 0 1j,. "- C it starts rising again. These temperature mini- .\ mums mark the boundaries between the three // \ regions of the atmosphere: thetroposphere, the // \\ stratosphere, and theionosphere, shown in / . \ figure 2-1. / TRANSMITTE \ \ i \ LAYERS OF THE ATMOSPHERE ii tot I Troposphere I t c \ The troposphere is the lowest layer of the :-- atmosphere and extends from the surface of the \ ,- __. - TROPOSPHERE APPROX. earth to a height of 10 miles. It is made up of \ . // O-io mi. 99% nitrogen and oxygen by volume, and accounts \ for three-fourths of the weight of the atmos- .. ./ phere. Within this layer temperature decreases -.,----1___ STRATOSPHERE with altitude, andftis in this layer that clouds, IONOSPHERE APPROX. APPROX. snow, rain, and the seasonal changes exist. 50-250M1.'' 10-50 MI. Because of the high density of the troposphere, aerodynamic surfaces can be used ef- 33.21 ficiently to control missiles in this region, and Figure 2-1.-Atmospheric regions. propellers are practical for low. speed power plants.However, this high density causes a .0405 pound per cubic foot.Because of the gradual decrease in air density with altitude, a missile flying at 35,000 feet encounters less air resistance-that is, has less DRAG-than 100 does a missile flying close to sea level. NoYY )1 e The absolute pressure existing at any point 90 in the atmosphere also varies with altitude. The pressure acting-on each square inch of the 80 ly0oooY. earth's surface atsea level is actually the 0)(0yoxe weight of a column of air one inch square, ex- 400,000 1 tending from sea' level to the outer limits of the YO atmosphere. On a mountain top, this column of oVoio air would be shorter, and-thus the weight (pres- 60 YeSeZefti sure) acting on each square inch would beless. 5° Therefore, absolute pressure decreases with a )coYo0 increased altitudes. 40 Another' characteristic of the atmosphere 30 Y YvAvP)( which varies with altitude is temperature (see figure 2-2). However, unlike 'density and pres- 20 ooy Vpit sure, temperature does not vary directly with 100,000 altitude. From sea level to about 10 miles,. the 10 AYYoNloV temperature drOps steadily. at .a rate of approximately 3.1/2° F per thousand -feet( It then re- >at4 steady rate TEMPERATURE IN DEGREES FAHRENHEIT until -another. -Constant-teMperature zone is 33.20 reached. Thia.zone -lasts for several miles at Figure 2-2.-Temperature varies indirectly which point the temperature starts decreasing. with altitude. . , 1r-

PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS large amount of drag. The dense lower atmos-information about them is conjecture. The phere slowed down the German V-2 from 3300sphere or layer immediately above the ionos- to 1800 mph. At extremely high speeds the fric-phere has been named the mesophere and is tion caused by this dense air produces such highbelieved to contain many mesons and other skin temperatures that ordinary metals melt. cosmic particles.A meson is an unstable particle, between electron and proton in mass, Stratosphere firstobserved in cosmic rays. Two types have been identified as mesons, 1r mesons and At The stratosphere is the layer of air abovemesons.Some are positively charged, and the troposphere. Its upper limits are around 40evidence indicates that some are neutral. An- to 50 miles above sea level.In this regionother theory is that mesons are the binding temperature no longer decreases with altitudeenergy between protons and neutrons. but stays nearly constant and actually begins to Space beyond 600 miles is called the exos- increase in the upper levels. Higher tempera-phere. It is approximately 1/3000 of the earth's tures in the upper levels are caused by ozone,atmosphere in terms of mass.Air particles which is heated by ultraviolet radiation from theare few and far apart in this area. sun.(Ozone is a gas which is produced when Much information about the upper air has electricity is discharged through oxygen.) Thebeen transmitted to earth from orbiting satel- composition of the stratosphere is similar tolites, which carried instruments to measure that of the troposphere; however, there is prac-radiation, temperature, meteorites and micro- tically no moistureinthe stratosphere. Propeller-driven vehicles cannot penetrate thismeteorites, and weather information. region because of the low air density, and aerodynamic surfaces have greatly reduced PHYSICS OF FLIGHT effect in controlling missiles. FORCES ACTING ON A MISSILE Ionosphere IN FLIGHT Above the stratosphere and ranging up to The flight path of a missile is determined about 250 miles above sea level is the iono-by the forces acting upon it.Some of these sphere. This is a region rich in ozone andforces are due to nature; others are man consists of a series of electrified layers. Themade.The natural forces are not fully con- ionosphere is extremely importint because oftrollable but their action on the missile can be its ability to refract (bend) radio waves. Thismodified by causing the missile to fly slower property enables a radio transmitter to sendor faster, higher or lower, adding (or remov- waves to the opposite side of the world by aing) control surfaces such as wings and fins, seriesof refractions and reflections takingincreasing the propelling force, and similar place in the ionosphere and at the surface ofcontrol.Although natural forces are not fully the earth. controllable, they are to a considerable extent The characteristics of the ionosphere varypredictable.Various combinations of natural with daylight and darkness, and also with theforces and manmade forces produce different four seasons.Until recent years we haveeffects on the missile flight path. known very little about the physical character- Gravity, friction, air resistance, and other istics of this region. During thr, past few yearsfactors produce forces that act on all parts of many' instrument-carrying rockets have beena missile moving through the air.One such sent into the ;ionosphere to obtain informationforce is that which the missile exerts on the about the temperatures, the pressures, theair as it moves through it.In opposition to composition of the air, and the electrical char-this is the force that the air delivers to the acteristics of the various layers. missile.The force of gravity constantly at- The lower part of the ionotipheie (20 to 60tracts the, missile toward the earth, and the miles up) is sometimes calledthechemosphere.'missile must exert 'a corresponding upward force to remain in flight. Higher Atmospheres FigUre 2-3A illustrates the forces acting on The reaches of space beyond the ionospherea, body in level flight through the air, at a have not been fully 'explored and .much of theuniform speed.Note that the force tending to Chapter 2FACTORS AFFECTING MISSILE FLIGHT

FORCE OF A GRAVITY

FORCE OPPOSING FORCE DUE MOTION TO MOTION

RESULTING DIRECTION OF MOTION FORCE OPPOSING GRAVITY 144.3 Figure 2-3.Forces acting on a body moving through air: A.Equal forces; B. Unequal forces. produce motion (toward the left) exactly bal- ing force exerted by the air is entirely the ances that resisting the motion. The force ofresult of the missile motion through it. But if gravity is exactly opposed by the lifting force. it were possible for an observer to ride the In accordance with Newton's first law (dis-missile itself, it would appear that the missile cussed below), a moving body on which allis standing still, and that the air is moving forces are balanced will continue to move inpast the missile at high speed. the same direction and at the same speed. This illustrates the basic concept of rela- Figure 2-3B illustrates the effect of unbal-tivity of motion. The forces that the air exerts anced forces acting on a body. The length ofon the missile are the same, regardless of the arrows is proportional to the respectivewhich is considered to be in motion. The force magnitude of the forces, and the arrowheadsexerted by the air on an object does not depend point in the direction in which these forceson the absolute velocity of either but only on are applied. The illustration shows that forcesthe relative velocities between them.This A and B are equal and opposite, and that C andprinciple can be put to good use in the study of D are equal and opposite. But force F is opposite missile aerodynamics, and in the design of to and greater than force E. As a result, themissile airframes and control surfaces.In a body shown will accelerate in the direction ofwind tunnel,the missile or model remains j force F.This figure is an example of vectorstationary, while air moves past it at high representation of the forces acting on a body. speed.The measured forces are the same as Any number of forces may be shown by vectorthose that would result if the missile, or model, representation. They can be resolved, orwere moving at the same relative speed through simplified, into resultant force that is the neta stationary mass of air. effect of all the forces applied. Note that in the illustration, forces are acting NEWTON'S LAWS OF MOTION on a spherical body. By changing the share of the body acted upon, the action of the forcescan Although Newton lived long before the missile be modified. These effects are discussed laterand space age (1842-1727), the laws of motion in the chapter. which he discovered and formulated are valid for missiles and other objects passing through RELATIVITY OF MOTION ..1(4 the atmosphere. Newton's first law states: "A body ina To an observer standing on the ground and state of rest remains at rest, and a body in watching the flight of a missile through the air,motion remains in uniform motion, unless it appears that the missile is moving and theacted upon by some outside force." Thismeans air standing still. It would seem that the oppos-that if an object is in motion, it will continue rp 27' PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS in the same direction and at the same speed Force = Mass times Acceleration, until some unbalanced force is applied.And, whenever there are unbalanced forces acting Or on an object, that object must change itsstate of motion. For example, if you were to push F= ma against a book lying on a table, you would have to supply sufficient force to overcome frictionThus any object in motion is capable of exert- in order to set the book in motion.If youing a force. Whenever a force is applied through would eliminate all of the restraining forcesa distance, it does work. We can expressthis acting on the book once it is in motion, it wouldas: continue to move uniformly until acted upon by some outside force.It is these restraining Work = Force times Distance forces with which we are mainly concerned in the study of aerodynamics. Or Newton's second law states: "The rate of W = Fd change in momentum of an object is proportional to the force acting on the object, and in Any mass that is in motion is capable of the direction of the force.' The momentum ofapplying a force over a distance, and there- an object may be defined as theforce thatfore of doing work.Whenever the motion of a object would exert to resist any change of itsmass is changed, there is, in accordancewith motion. Newton's second law, a change in momentum. Newton's third law states: "To every actionLIFT AND DRAG there is an equal and opposite reaction.' This law means that when a force is applied to any Figure 2-4 represents a flat surface mov- object, there must be a reaction opposite toing through an airstream.In accordance with and equal to the applied force.If an object isthe principle of relativity, the forces acting on in motion, and we try to change either thethe surface are the same, zegardlessof whether direction or rate of that motion, the objectwe think of the surface as movingto the left, or of will exert an equal and opposite force.Thatthe airstream as moving to the right. One of force is directly proportional to the mass ofthe forces acting on the surface is thatproduced the object, and to the change in its velocity.by friction with the air.This force acts in a This can be stated as: direction parallel to the surface, as indicatedby

144.4 Figure '2-4Forces acting on a flat surface in an airstream. Chapter 2FACTORS AFFECTINGMISSILE FLIGHT the small white arrow at thelower right. As thethe top than on the bottom air strikes the surface,the air will be deflected of the wing. This downward. Because the air hasmass, this changepressure differential tends to force thewing in its motion will result in upward, and gives it lift. a force applied to the Figure 2-5 represents thegeneral shape surface. This force acts ata right angle to theof a section of the wing of surface, as indicated by thelong black arrow in a conventional air- figure 2-4. The resultant craft.In such an aircraft, themajor part of of the frictional andthe necessary lift is provideckby deflection forces, indicating thenet effect of the the Bernoulli two, is represented by the long effect. As we will explain later,a wing of this white arrow. Theshape is not suitableibruse on missiles flying horizontal component of this forceoperating inat or above the sp-eed of a direction opposite to the motion of thesurface, sound.None of the Navy missiles listed in chapter1 depends on is drag. The vertical force,operating upward,a wing of this shape for lift. is lift. The angle that the movingsurface makes All of them get with the airstream is the the necessary lift entirelyfrom the angle of angle of attack. Thisattack, as illustrated in figure 2-4. angle affects both the frictionaland the deflection force, and therefore affects Air tends to cling to the surfaceof the plane. both lift and drag.This thin region of nearly static Another scientist, Daniel Bernoulli(1700- air is called a 1782), discovered that boundary layer.Within the boundary layerthe the total energy in anyfluid velocity ranges fromzero at body surface system remains constant.That is, if one ele-to free-stream velocity ment in any energy system isdecreased, another a short distance away. increases to counterbalance it. Sudden changes in velocity,density, and pres- This is called Bernoulli's sure cause disturbance waves in theflow in the theorem.Airboundary layer. If the flow flowing past the fuselageor over the wing of a is smooth, it is said guided missile forms to be "laminar;" if it isdisturbed it is called a system to which this"turbulent," and skin friction theorem can be applied. Theenergy in a given is greater than in laminar flow. If the surfaceis rough, the turbu- air mass is the product of itspressure and itslent layer is increased and velocity.If the energy is to remainconstant, skin friction is it follows that a decrease in greater.Even a comparativelyinsignificant velocity will produceproturbance on the surface, such an increase in pressure, and thatan increase in as rivet heads, velocity will producea decrease in pressure.can produce turbulent flow. The term"stream- Figure 2-5 represents the lining" has come to describethe technique of flow of air overdesigning shapes to give low a wing. section.Note that the air thatpasses resistance or drag and prevent or delay boundary-layerturbulence. over the wing must travel a greaterdistanceIn supersonic conditions than air passing under it.Since the two parts the formation of shock waves causes the boundary layerto thicken at of the airstream reach thetrailing edge of thethe point of contact with wing at the same time, theair that flows over the shock wave and the wing must move fasterthan the air thataerodynamic pressurecan be transmitted for- flows under.In accordance with Bernoulli'sward through the boundarylayer. Boundary layer theorem, this results ina lower pressure on

LIFT PRESSURE DECREASED

AIR PI ES UP AIR FLOW VELOCITY INCREASED BOUNDARY THRUST LAYER DRAG NORMAL NORMAL AIR AIR FLOW FLOW

Xi*/ VELOCITY PRESSURE INCREASED DECREASED SLIGHTLY WEIGHT OF MISSILE

33.38 33.23 Figure 2-5.Air flowover a wing section. Figure 2-6.Forces actingon a movingmissile. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS effects and shock waves are presentsideby side ATTITUDE. This term refers tothe orien- in supersonic flow and their effectscontributetation of a missile with respectto a selected to each other.A very small shock wave isreference. sufficient to disturb the flow over anentire wing surface behind it. Since lift depends on the flow STABILITY. A stable body is one that of air past the surface, reduction inflow produc-returns to its initial position after ithas been es a reduction in lift. The boundary layer effectdisturbed by some outside force.If outside has been reduced by using highly polished sur-forces disturb a stable missile fromits normal faces, asfree as possible from any irregularities.flight attitude, the missile tends toreturn to A complete and precise theoretical explanationits original attitude 1when the outsideforces of the processeswhich cause a lamimuy boundaryare removed.If a body, when disturbed from to become turbulent has not been formulated. its original position, assumes a newposition and neither returns to its origin nor moves AERODYNAMIC FORC ES any farther from it, thebody is said to be atneutrally stable.If the attitude of a neutrally All present day guided missiles have stable missile is changed by anoutside force least part of their flight paths within the earth'sor by a change in itscontrols, the missile atmosphere; therefore it is important that youremains in the new position until otherforces understand the principles of aerodynamics. influence it. The principal forces acting on a missile in stability, level flight are THRUST, DRAG, WEIGHT,and A third type of stability is negative or instability.In this case a body displaced LIFT. Like any force, each of these is a vectorfrom its original position tends to move even quantity which has magnitude (length)and direc- air- tion. These forces are illustrated infigure 2-6.farther away. For example, if an unstable When the missile is not flying in a straightcraft is put into a climb, ittends to climb more line, an inertial force, termed centrifugal force,and more steeply until it stalls. acts on the missile.In a turn maneuver, this MISSILE MOTIONS. Like any moving body, causes an acceleration greater than gravity, andthe guided missile executes two basickinds of the missile weight and centrifugal force combinemotions: ROTATION and TRANSLATION.In to form the resultant force. pure rotation all parts of thebody pivot about an imaginary axis passingthrough the center of gravity (fig. 2-7), describing concentriccircles around the axis.In movements of translation TERMINOLOGY (linear motions), the center of gravity moves A discussion of the problems of aerody-along a line and all the separateparts follow namic forces involves the use of several flightlines parallel to the path of the centerof gravity. terms that require explanation. The following definitions are intended to be as simple and basic as possible. They are not necessarily the definitions an aeronautical engineer would use. YAW ,AIRFOIL. An air;o4 is any structure around ROTATES ON which air flows in a manner that is useful in VERTICAL AXIS controlling flight.The airfoils of a guided missile are its wings or fins, its tail surfaces, PITCH and its fuselage. ROTATES ON LATERAL AXIS DRAG is the resistance of an object to the ROLL ROTATE! ON flow of air around itIt is due in part to the LONGITUDINAL boundary layer, and in part to the piling up of AXIS air in front of the object. One of the problems of missile design is, to reduce drag while CENTER OF GRAVITY maintaining the required lift and stability. STREAMLINES are lines representing the 39.22 path of air particles as they flow past an object, Figure 2-7.Missileaxes;,flight attitude of as show in figure 2-5. a guided missile. 30 04 Ls 1

Chapter 2FACTORS AFFECTING MISSILEFLIGHT All the partshave the same velocity andthe same direction of movement, less than the pressure on the underside.The as in forward movement.amount of lifting force provided isdependent to Any possible motion of the bodyis composed ofa large extent on the shape of the wing. Addi- one or the other of these motions,or is a com-tional factors which determine bination of the two. the amount of lift are the wing area, the angle at which thewing The three axes of rotationalmovement aresurface is inclined to the airstream, represented in figure 2-7as pitch, yaw, and and the roll. density and speed of the air passingaround it. The missile ROLLS, or twists, abouttheThe airfoil that gives the greatestlift with the longitudinal axis, the referenceline runningleast drag in subsonic flight hasa shape similar through the nose and tail. It YAWS,or turns toto the one illustrated in figure 2-8. right of left, about the vertical axis.PITCH, or Some of the standard terms appliedto air- turning up or down, is a rotation aboutthe lateralfoils are included in the sketch.The foremost axis the reference line in thehorizontal planeedge of the wing is called the leading runningperpendicular to edge, and the line of flight.that at the rear the trailing edge (fig. 2-8A).A Rotary motions aboutany of these three axes arestraight line between the leading andthetrailing governed by the steering devicesof the missile, such as the aerodynamic control edges is called the chord.The distance from surfaces. Aone wingtip to the other (not shown) is knownas fourth motion is necessary forcontrol as well asthe SPAN. The ratio of thespan to the average for flight. This is the motion of translation,thechord is the ASPECT RATIO. The forward movement resultingfrom the thrust angle of provided by the propulsion system. incidence (fig. 2-8B) is the angle betweenthe wing chord and the longitudinal axisof the fuse- AXES.. A missile in normal levelflight can be considered to move about lage. In figure 2-8C, the largearrow indicates three axes, asthe relative wind, the direction of theairflow shown in figure 2-7. Whenever thereis a dis-with reference to the moving airfoil. placement of a missile about The angle any of these threeof attack is the angle between the chordand the axes, the missile may do any one of thefollowing: direction of the relative wind. 1. It may oscillate about theaxis (oscilla-Center of Pressure tion). 2. It may increase its displacementand get out of control. The relative wind strikes the tiltedsurface, and as the aiy flows around the wing,different 3. It may return to its originalpositionamounts of rating force are exerted readily, without oscillation (damping). on various points of the airfoil. The sum (resultant)of all The last possibility, whichindicates a stablethese forces is equivalent toa single force missile, is the one desired. We willshow later how this problem of stability ismet in missile design.

LEADING TRAILING EDGE EFFECTS OF AERODYNAMIC FORCES (A) EDGE The aerodynamic forceslift,drag, weight, and thrustmust all be consideredin missile design in order to take advantageof the forces ANGLE OFINCIDENCE and make the missile flyas intended. (B) LONGITUDINAL AXIS OF FUSEL AGE Lift 4 ANGLE OF ATTACK Lift is produced bymeans of pressure dif- 4ANGLE OF INCIDENCE CENTER OF PRESSURE ferences. There are dynamic pressures, or the '- pressure of air in motion, ahil. differencesin RELATIVE LONGITUDINAL AXIS the static pressure of the atmosphere; OFFUSELAGE which is WIND exerted-by the weight of the coldmnof airlbove the missile. DYnando Pressure is the primary factor contributing to, lift. :The air 33.24 pressure on figure 2-8.Standard nomenclatureapplied the upper surface of an airfoil (wing)must be to airfoils. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS acting at a single point and in a particular C EN T_E_R_ OF_ direction.This point is called the center of ....ZREGGURE pressure. From it, lift can beconsidered to LOW ANGLE be directed perpendicular to the directionof OF ATTACK the relative wind. The dynamic or impact force of the wind also against the lower surface of the airfoil MEDIUM contributes to lift, but no more than one-third B ANGLE OF of the total lift effect is provided by thisimpact ATTACK force. As we have shown, the resultant force on a wing can be resolved into forces perpendicular HIGH ANGLE and parallel to the relative wind; these com- C OF ATTACK, ponents are lift and drag. If a missile is to NEAR BURBLE continue in level flight, its total lift must equal POINT its weight. As the angle of aftackincreases,the lift increases until it reaches a maximumvalue. HIGH ANGLE At the-angle of maximum lift, the air no longer nOF ATTACK, flows evenly over the wing, but tends to break 11 BEYOND away from it.This breaking away (the burble BURBLE point) occurs at the stalling angle.If the POINT angle of attack is increased further, both lifting force and airspeed decrease rapidly. 33.24 Figure 2-9.Effect of angle of attack oncenter Angle of Attack of pressure and air flow. In actual flight, a change in the angle of attack will change the airspeed.But if forhas an upward and backward direction(fig. test purposes we maintain a constantvelocity 2-9)).At a positive angle of attack of about3° of the airstream while changing the angleofor 4°, the resultant has itsmost near* vertical attack, the results on a nonsymmetrical wingdirection (fig. 2-9A). Either increasing orde- will be as shown in figure 2-9. The sketchescreasing the angle causes the directionof the show a wing section at various anglesofresultant to move farther from the vertical. attack, and the effect of these different angles on the resultant force and theposition of theDrag center of pressure. The burble point referred to in the lower Drag is the resistance of air to motion through theit. The drag component of the resultantforce on sketch is the point at which airflow over to the direction uppersurfacebecomes rough,causing ana wing is the component parallel uneven distribution of pressure.The burbleof motion. This force resists the forwardmotion point is generally reached when the angle ofof the missile. If the missile is to fly, dragmust attack is increased to about 18° or20°. At thisbe overcome by thrustthe force tendingto push angle of attack the separation point is placed sothe missile forward. Drag depends on the missile near the leading edge that the upperairflow isarea, the air density, and the squareof the disrupted and the wing is in a stall (fig.2-9D).velocity. Air resists the motion of all parts of At moderately high angles of attack, the flowingthe missile, including the wings, fuselage,tail air can follow the initial turn of the leadingedgeairfoils, and other surfaces. The resistance to but it cannot follow the wing contour completely;those parts that contribute lift to the missileis then,the stream separates fromthe surfade nearcalled induced drag. The resistance to all parts the trailing edge (fig. 2-9C). At small angles ofthat donot contribute lift is parasitic drag. attack, the resultant is comparativelysmall. Its From ,Newton's laws, we know two things: direction is upward and back from the vertical,First,. if all the forces applied to a missile are and its center of pressure is well back from thein balance, then if the missile isstationary leading edge.Note that the center 'of pressureit will remain so; if it is moving, it will con- changes with the angle of attack, and the resultanttinue to move in the same direction atthe 32t1". Chapter 2FACTORS AFFECTINGMISSILE FLIGHT same speed until an outside force to it. is appliedsecond. The horsepower expendedby a missile Second, if an unbalancedforceone notin uniform forward motion counteracted by an equal andopposite force is then is applied to the missile, it will accelerate DV in the direction of the unbalanced = force. hp

where D is the drag in pounds,and V the speed Thrust in feet per second.

At the instant of launching,missile speedAcceleration is zero, and there isno drag.(We will, for the moment, disregardair-launched missiles.) The force of thrust developed This term has been freelyused in the chapter by the propulsionwithout positivedefinition. system will be unbalanced,and as a result the Acceleration is missile change either in speed or in directionof motion. will accelerate in thedirection ofA missile accelerates ina positive or negative thrust. (A solid-fuel rocketdevelops full thrust almost instantly. sense as it increases or decreases speedalong When a long-rangethe line of flight. A missilealso accelerates liquid-fuelrocketislaunched,it may bein a positive or negative physically held down untilits engines have sense if it changes developed sufficient thrust.) direction in turns, dives, pullouts,or as a result Whenthrust-weightof gusts of wind. buringaccelerationsa missile ratio reaches its maximumvalue, accelerationis subjected to large forces of the missile is ata maximum.maximum. Hut, during the which tend to keep launching phase, missile it flying along its original lineof flight. This is speed quickly in-in accordance with Newton'sfirst law of motion: creases. Because drag is proportionalto the square of the speed, drag increases A particle remains atrest or in a state of very rapidly.uniform motion in a straightline unless acted The force of thrust is thusopposed by a progres-upon by an external force. sively increasing force of drag. The missile will Acceleration is measured interms of the continue to increase in speed, butits accelerationstandard unit of gravity, (rate of increase of speed)will steadily decline. abbreviated by the This decline will continue until letter "g." A freely fallingbody is attracted thrust and dragto the earth by a force equalto its weight, with are exactly in balance; the missilewill then flythe result that it accelerates at a uniform speed as longas itsthrust remains at a constant rate constant. of approximately 32 feetper second per second. Its acceleration while infree fall is said to be one "g." If the propulsive thrust is Missiles making rapid turnsor re- decreased for anysponding to large changes in thrustwill experi- reason (such as a command from theguidance system, or incipient fuel exhaustion) ence accelerations many times thatof gravity, the forcethe ratio being expressedas a number of "g's." of drag will exceed the thiust.The missileThe number of "g's" which will slow down until the twoare again in balance. a missile can with- When the missile fuel is stand is one the factors which determinesits exhausted, or 'themaximum turning rate and the typeof launcher propulsion system is shut downby the guidancesuitable, for the weapon. The system there is no more thrust.The force of delicate instru- drag will then be unbalanced, ments contained in a missilemay be damaged and will cause aif subjected to accelerationsin excess of design negative acceleration, resultingin a decreasevalues. in speed. But, as the speeddecreases, drag will also decrease. Thus therate of decrease in speed also decreases. Amissile will maintainPROBLEMS OF MISSILE CONTROL a uniform forward motion when are equal. thrust and drag The power required to maintain A missile must be uniform forward motion is equalto the product so designed and construc- of the drag and the speed. If ted that it will flya specified course without drag is expressedcontinual changes in direction.The degree of in pounds, and speed in feetper second, thestability of a missile has product is power in foot-poundsper second. a direct effect on the By definition, one horsepower behavior of its controls; andfor this reason a is 550 ft-lb perhigh degree of stabilitymust be maintained. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS missile in flight by reactingagainst the medium As the speed of a missile increases,its sta- They are Nifty is changed by shifts in the center of pres-through which the missile is passing. changes in theobviously not useful for missiles thattravel in a sure. A pressure shift causes where the air is very airflow acting on the missile surfaces.Evenvacuum (or in high altitudes in &peedrarefied).In high-speed missiles, thecontrol in pure supersonic flow, variations surfaces can be made smaller;under certain will cause shifts in center of pressure. altogether. The use of fixed fins, and spinningof theconditions they can r a eliminated missile, are the simplest means ofstabilizing a missile in flight.Movable control surfaces react with air according to the lawsof aerodynamics to control the missile in flight.FigureStability in Subsonic Flight 2-10 shows examples of controlsurtacedesigns missile in flight; Fins may be used to stabilize a Figure 2-11 represents a and locations. it is longitudinally stable aboutits lateral axis through the center of gravity.Airflow over the wing is deflected downward. Thisangle of deflection is called the downwashangle. When lift decreases as a result ofreduced speed, this dovmwash angle decreases, andproduces pressure changes. At certainspeeds, unstable conditions are set up as a result ofsuch pressure shifts. When an unstable condition occurs,the BULLPUP control system must quicklycompensate by FIXED moving the control surfaces orchanging the get out STABILIZING MOVABLE CONTROL SURFACES missile speed; otherwise the missile may SURFACES of control, Unstable conditions aremost serious at transonic speeds.Most missiles have dive control and roll recovery devicesto overcome TARTAR unstable conditions.For example, the horizontal tail surfaces may beplaced high on the A fin to minimize the effects ofdownwash.(At supersonic speeds, the downwashproblem disappears.) Unstable airflow over the wings of amissile may cause the ailerons tooscillate, creating a condition known as"buzz." A similar condition called "snaking" may exist aboutthe yaw axis as a result of rudderoscillation. The troubles

DIRECTION OF MOTION

WING SECTION

DOWNWASH 144.5 144.6 Figure 2-11.Dovmwash (indicatingthe closing Figure 2-10.Control surfaces:. A. Fixedand the .wing and the movable surfaces; B. Control surfacedesigns of the streamlines under and locations. subsequent dovmwash). qt3. (1;11' Chapter 2FACTORS AFFECTING MISSILEFLIGHT may be partially compensated forby nonrevers-when the missile changes its angle ofattack. ible control systems, or byvariable-incidenceFor example, if the missilenose begins to control surfaces. pitch downward, the force of the In a stable aerodynamic body, airstream an oscillationagainst the upper surface of the stabilizerwill caused by an outside disturbingforce tends toincrease. This will tend to push the tail down- be damped and to disappear instead of becomingward, and thus return the missile to itsoriginal greater. The missile must be stabilizedaboutattitude. three axes of flight to maintaina steady flight Since most modern missilesare supersonic, condition, so the missile neither increasesnorwith only a few seconds of flight at decreases its angle of attack. subsonic speeds, the forces that affect missile flightat Stability about the vertical axis is usuallysupersonic speeds are of more importanceto provided for by vertical fins. Ifa missile beginsyou.They are discussed in the next section. to yaw to the right, air pressureon the left side of the vertical fins is increased. Thisincreased pressure resists the yaw and tends to force the AERODYNAMICS OF SUPERSONIC tail in the opposite direction. Insome missiles MISSILE FLIGHT the vertical fin may be dividedand have a movable part, called the rudder, that isusedfor So far we have discussed the directional control. principles of In addition to the rudder,producing lift by using cambered(curved) wings. there may be trim tabs thatcan be set for aCambered wings are still usedon conventional particular direction of flight relativeto theaircraft but are not used on most prevailing wind. present day The vertical sides of theguided missiles. Most operational missilesuse fuselage also act as stabilizing-surfaces.Thestreamlined fins to provide stability andsome same action takes place here as on the-fin, butlift. with a lesser correcting force. Before discussing aerodynamics ofsuper- Another means for obtainingyaw stabilitysonic missile flight, let us definesome of the is by sweepback of wings. Sweepbackis theterms used. angle between the leading edge ofa wing and a line at right angles to the longitudinalaxis ofREYNOLDS NUMBER the missile.If a missile yaws to the right, the leading edge of the left sweptbackwingbecomes During the development ofa new missile more perpendicular to the relative wind, whiledesign, scale models of the proposedmissile the right wing becomes lessso.This putsare tested in wind tunnels. But the performance more drag on the left wing, and lesson the right. of the, model does not necessarily indicatethe The unbalanced drag at the twosidesperformance of the actual missile,even when all of the missile tends to force it back toits orig-known variables are scaled down. In inal, attitude. some cases the effect of a given variable on the modelmay STABILITY ABOUT THE LONGITUDINALbe opposite to its effect on the full-sizemissile. AXIS may be provided by dihedralanupwardReynolds number is a mathematical ratio involv- angle of the wings. As the missilestarts to roll, the lift force is ing relative wind speeds, air viscoscityand no longer vertical, butdensity, relative sizes of the modeland missile, moves toward the side to which the missileand other factors. The use of this ratiomakes is rolling. As a result, the missilebegins toit possible to predict missile behaviorunder sideslip.This increases the angle ofattackactual flight conditions from the behavior of the lower wing, and decreasesthat of the of upper. the model in the wind tunnel.The Reynolds Lift on the lower wing will thereforenumber is also applicable inhydrodynamic increase, while lift on theupper wing decreases.testing. This unbalanced lift tends to rollthe missile back to its original attitude. MACH NUMBERS AND SPEED REGIONS STABILITY ABOUT THE LATERALAXIS is accomplished by horizontalsurfaces at the Missile speeds are expressed in terms of tail of the missile..The stationary part ofMACH NUMBERS rather than in milesper hour these surfaces is the stabilizer; the movableor knots. part is the elevator. The Mach number is -the. ratioof Pitch stability' resultsmissile speed to the local speed of sound..For from the change in forceson the stabilizerexample, if a missile is flying ata speed equal

35 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS to one-half the local speed of sound, it is saidvelocity. This region extends from about Mach to be flying at Mach 0.5.If it moves at twice1.2 upward. In supersonic flow, little turbulence the local speed of sound, its speed is thenis present. Mach 2.(The term "Mach number" is derived HYPERSONIC FLIGHT. When any object from the name of an Austrian physicist, Ernstmoves through the air, the molecules ofair re- Mach, who was a pioneer in the field of aero-quire a finite time to adjust themselves to its dynamics: It is pronounced "mock.") presence, and to readjust themselves afterit has passed. This period of adjustment and re- Local Speed of Sound adjustment is called the relaxation time. If the time required for a missile topass agiven point The speed expressed by the Mach number isis equal to or less than the relaxation time, the not a fixed quantity because the speed of soundmissile is moving at hypersonic speed. Relaxa- in air varies directly with the square root of airtion time is longer at high altitudes, and the temperature.For example, it decreases frombeginning of the hypersonic speed zone is cor- 780 miles per hour (mph) at sea level (for anrespondingly lower.Velocities that are not average day when the air is 59°F) to 661 mphathypersonic at sea level may become so at high the top of the troposphere. The speed of soundaltitudes. Under most conditions, the hypersonic remains constant between 55,000feet and 105,000speed zone begins somewhere between Mach 5 feet, then rises to 838 mph, reverses, and fallsand Mach 10. to 693 mph at the top of the stratosphere. Thus you can see that the speed of sound will varyHEAT BARRIER with locality. The range of aircraft and missile speed is This is not a barrier in a physical sense, but divided into four regions which are defined withits effect tends to limit the maximum speed of respect to the local speed of sound. Thesea missile through the atmosphere.Heat results regions are as follows. not only from friction, but from the fact that at SUBSONIC FLIGHT-, in which the airflow overhigh speeds the air is compressed by a ram all missile surfaCes is less than the speed ofeffect. The temperature rise caused by the ram sound.The subsonic division starts at Mach 0effect is proportional to the square of the Mach and extends to about Mich 0.75.(The uppernumber. The average temperature at sea level is limit varies with different aircraft, depending onconsidered to be 59°F; temperature decreases the design of the airfoils.) steadily with altitude to about 46,000 feet, above At subsonic speeds sustained flight is de-which it is assumed tobe constant. At sea level, pendent on forces produced by the motion of theram temperature is about 88°F at Mach1-29° aerodynamic surfaces through the air. Whenthehigher than the standard temperature. At surfaces of airfoils are well designed, the streamMach 2, ram temperature at sea level is about of air flOwe' smoothly over, under, and around260°F, and at Mach 4 about 1000°F. Missiles them, and the air Stream conforms to the shapecapable of flying at these speeds mustbe capable of the airfoil. In addition, When the airfoils areof withstanding these temperatures. This prob- set to ifie proper angle; and motion is fast enough,lem is particularly serious with ballistic mis- the airflow will support the weight, of the air-siles intended to plunge down into the atmos- craft or. Missile. phere at speeds in the order of Mach 12. A TRANSONIC FLIGHT, in which the airflowsignificant part of the development effort for over the-surfaces is mixed, being lessthanlong-range ballistic missiles has been devoted sonic epeed in 'Some areas and greater thanto development of nose cones capable of with- sonic 'peed in others. The limits of this regionstanding extreme temperatures. are not sharply defined, but areapproximately Mach 0.75 to Mach 1.2. Under these conditions,SHOCK WAVE shock waves are present; the airfloW is turbulent, and the missile may be severely buffeted. A The term "shock wave" is often used in high - speed shOuld be made to acceleratedescribing effects of nuclear explosions but it through the transonic zone in the least possible!is not a phenomenon occurring only in tremen- time to prevent theeedisturbanCea. dous explosions. The same interaction of forces SUPERSONIC FLIGHT, in which the airflowproducea a shock' wave in less overpowering over all eurfaCes is at speedigreaterthan soundsituations.

38 Chapter 2-FACTORS AFFECTINGMISSILE FLIGHT

. As a missile moves through the air, the airmeans that the greater the speed of themoving tends to be compressed, and topile up in frontbody, the fewer the numberof air particles of the missile.Because compressed aircan flow at speeds up to the speed that will be able to movefrom its path, with of sound, it canthe result that the air beginsto pile up in front flow smoothly around a low-speedmissile. Butof the body. as the missile approaches the speed of sound, When the object reaches thespeed of sound, the air can no longer get outof the way fastthe condition represented in enough.The missile surfaces split theair- figure 2-12D oc- stream, producing shock curs. The pressure wave can no longeroutrun waves. A shock wavethe object and prepare the airparticles in the is a sharp boundary betweentwo masses of airpath ahead. at different pressures. The particles then remainundis- Shock waves can seriously alter turbed until they collide withthe air that has the forcespiled up in the airstreamjust ahead of the acting on a missile, requiring radicalchangesobject. in trim.The missile tail surfaces As a result of the collision,the air- may bestream just ahead of the object is ;educedin seriously buffeted and wing dragrises.Anyspeed very rapidly; at the sametime deflection of the control surfaceiin an attempt its density, to overcome these conditions pressure, and temperature increase. may cause new As the speed of the object isincreased beyond shock waves, which interact withthose alreadythe speed of sound, the present. For this reason theremay be certain pressure, density, and speeds at which the controls temperature of theb air just aheadof it are in- become entirelycreased accordingly; anda region of highly useless.In some cases the controlsbecome reversed, and the action which compressed air extends some distanceout in usually resultsfront of the body.Thus a situation occurs in in a turn to port may result inone to starboardwhich the air particles forward instead. These effects andmany others may be of the com- the result of compressibility, pressed region atone moment are completely a property of theundisturbed, and at the nextmoment are com- airstream which is not prominentat low speeds but which cannot be ignored at high pelled to undergo drasticchanges in velocity, speeds.density, temperature, andpressure.Because THE NATURE OF COMPRESSIBILITY.-of the sudden nature of When an object moves throughthe air, it con- the transition, the tinuously produces small boundary between the undisturbedair and the pressure disturbancescompressed region is calleda shock wave. in the airstream as itcollides with the air You cannot see these particles in its path. Each suchdisturbance-4 changes taking place in small variation in the air but you can see thesame type of action oc- pressure of the air-iscurring in water. Usinga boat on a lake in out transmitted outward in the forin ofa weak pres-analogy, the changes mightbe described as sure wave.Each expandingpressure wavefollows. travels at the speed of sound.Although each For the purposes of the illustration, pressure wave expands equally in all directions, we'll the important direction is assume that the waves or ripples formedon the that in which thelake will move at 10 mph, andthe Mach number object generating-it is moving. is the ratio of boat speed to As long as theobject, wave speed. is moving at low sub- With the boat at rest, thewaves made by the sonic speed, its positionwith respect to theboat bobbing up and down will pressure wave. it produces -is similar tothat spread out in con- shoWn in figuie 2-12A. The centric circles at the rate of 10mph (fig.2-13A). pressure wave ex-Now if the boatmoves at the rate of 5 mph pands in all directiOns.. Sinceits speed is high(representing a speed of Mach compared -vki:h that of the body, 0.5), the ripples the variation inwill still spread out at therate of 10 mph but pressuie travels .well aheacl.andagitatesthe airthey will no longer be concentric (fig. particles in the path .of motion..Hence, when 2-13B). the body arrives at In figure 243C, the boat ismoving at the same any given point, the. airspeed as the speed ofwave propagation, repre- particles there are .already inmotion and cansenting Mach 1, and all the easily and smoothly flow around waves are tangent to it. . each other at the bow of theboat. In figure In figure 2-12B, and C, the-objectis repre-*2-13D, the boat is moving at sented as increasing .,inspeed but as still twice the wave traveling below ionic speed-Mach 2-and it leaves theripplesbehind. velocity.As speed in-The wave patternnow becomes a wedge on the creases, the object at any moment isnearer thesurface of the water. undisturbed air particles in its In the air, with three- path.Thisdimensional flow, the patternwould be a cone. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

FORMATION OF FORMATION OF AIR FLOW AIR FLOW DISTRIBUTION PRESSURE WAVE DISTRIBUTION PRESSURE WAVE

KEY

MI: INMAL POSITION OR A MOVING OBJECT. r =RADIUS OF PRESSURE WAVE CIRCLE: (SPEED OF SOUND) X (TIME FOR OBJECT r.IA: POSITION OF OBJECT A SHORT TIME LATER. TO GET FROM CENTER OF CIRCLE TO )=POSITION OF PRESSURE WAVE CREATED BY POINT VI THE TIME MOVING OBJECT IS AT "A". = MACH NUMBER OF MOVING OBJECT. B g AREA IN PATH OF MOVING OBJECT, JUST "..2FLOW OF AIR STREAM. AHEAD OF PRESSURE WAVE. 33.26 Figure 2-12.Compressibility of air at various speeds.

The semivertex angle is the MACH ANGLE.Thethe wavefront is perpendicular to the line of greater the speed above Mach 1, the smaller theflow (fig. 2-14A).The normal shock wave is angle.The shock waves form at the point ofusually very strong; that is, the changes in pres- greatest density, where ripples meet. The bowsure, density, and temperaturewithin it are wave of the boat is closelyanalogous to thegreat. The air passing through the normal shock conical shock wave that spreads from the nosewave always changes from supersonicto sub- of a supersonic missile. Both have the same sonic velocity. cause: the fact that an object ismoving through OBLIQUE shock waves are 'those in which the a fluid faster than the fluid itself canflow. airstream changes in direction upon passing through the transition marked by the wavefront (fig. 2-14B). These waves are produced Ty Pea of Shock Waves. in supersonic airstreams at the point ofentry of wedge-shaped and other sharply pointed bodies. There are several types of shock waves, theThe resulting wavefronts make angles of less principal classes being 'the NORMAL and thethan 90° with the line of flight. Like the normal shokk wave, the oblique wave occurs at a point OBLIQUE. .These differ primarily in the way in.! which the airstream passes through- them.of change in velocity from a higher to a lower In the normal (or perpendidular) wave, theairvalue.The driange in speed is usually from passesthrough without changingdirection; andsupersonic to subsonic but not always so.In Chapter 2FACTORS AFFECTINGMISSILE FLIGHT

NORMAL SHOCK WAVE RATE OF WAVE PROPAGATIONI0AWN SUPERSONIC FLOW NIC

M0.0 a ..5 A SUBSONIC MAY

_ - SUPERSONIC BOAT MOVING AT SPEED OF 551PN -- -SHOCK WAVES

N.2.0

alba&ACM ANGLE IVOR. 20 MPH 33.27:.28 Figure2-14.Fqrmation ofshockwaves: A. Normal shock waves; B. Oblique shock waves.

C BOAT MOVING AT SPEED OF IOMPH BOAT MOVING AT SPEED OF 20 MPH

144.72-15 shows the manner in whichshock waves Figure 2-13.Mach angle analogy. behave at increasing airfoil speeds.In figure 2-15A, the airfoil is traveling at Mach 0.75.The airflow over the upper surface is fast some cases the airflow is supersonic both enough to up-cause the formation of a shock vraveontheupper stream and downstream of theoblique wave. In general, the variations in surface. As the airfoil speed increasestoMach density, pressure,0.90 (fig. 2-15B ), the airflowbecomesfast enough and temperature are lesssevere in the obliqueto cause an additional shock wave than in the normal wave to form on the wave. As we havelower surface. Figure 2-15C shows thewaves said, a shock wave is a sharp boundarybetween two masses of air at different moving toward the tra:.1g edge as the airfoil pressure. Airspeed is increased to Mach 0.95. Finally,when behind the oblique shockwave has a lowerthe airfoil reaches supersonic speed relative speed than that in front,and there- (fig: 2-15D fore has a higher and E), the upper and lower shockwaves move pressure. all the way back to the trailingedge and, at the NORMAL shock wavescan occur over thesame time, a new shock wave is produced in wing surfaces of a subsonic aircraftthat ex-front of the leading edge. ceeds its maximum safe operatingspeed (fig. 2-15A).The high speed (but still subsonic)CONTROL OF SUPERSONIC MISSILES airstream flows up over the leadingedge of the wing, increasing in velocity as it does so, and Aerodynamic control is the connectinglink passes the speed of sound. At a pointon thebetween the guidance system and themissile wing slightly rearward of the leadingedge, theflight path.Effective control of the flight path velocity of the flow decreases, changingfrom arequires smooth and exact operationof the supersonic to a subsonic value. At thepoint ofmissile control surfaces. transition a normal shock The control sur- wave is formed. Thisfaces must have the best possibledesign con- process illustrates the following rule whichfiguration for the intended speed ofthe mis- always holds true: The transiitionof air fromsile.They must be-moved with enough force subsonic to supersonic flow. 4s smoothand ,un-to produce thenecessary change of direction. accompanied by shock waves, but thechange from supersonic to subsonic Methods must be found for balancingthe vari- flow is 'alwaysous controls, and for changing them tomeet sudden and is accompanied by largeVariationsthe variations of in pressure, density, and temperature. lift and drag at different FigureMach speeds so as to maintain missilestability.

39 43 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

EXPANSION WAVES OBLIQUE SUPERSONIC REGION SHOCK WAVE f SUBSONIC (TRAILING EDGE) >c/ REGION OPINITIAL e M. Q75 FLOW OP

SUPERSONIC REGION FINAL FLOW (FASTER) M0.90

SUPERSONIC REGION OBLIQUE SHOCK WAVE (COMPRESSION WAVE) EXPANSION WAVES 33.30 Figure 2-16.Airflow about a supersonicfin.

low pressure area above the fin. Beneaththe fin, M0.95 the force of the airstream(dynamic pressure) 33.28and the formation of oblique shock wavesresult Figure 2-15.Shock waves at various in a high pressure area. Thedifferences in speeds of airfoils. pressure above and below thefin produce lift. Fixed fins are usually called verticalstabilizers or horizontal stabilizers,depending on their In some modern missiles lift is achievedposition and function. entirely by the thrust of the main propulsion Guided missiles may also be provided with system. The Polaris missile, for example,hasmovable control surfaces, sincestationary fins no fins.It is important that you realize thatcannot provide the precise controlneeded to keep fins cannot control a missile outside theearth'sthe missile on a desired course.Movable con- atmosphere. The methods of achieving controltrol surfaces can be divided into twotypes: in space will be discussed later in the course.primary and secondary. The primarycontrols include ailerons, elevators, and rudders(fig. External Control Surfaces 2-17). Secondary control surfaces include tabs, spoilers, and slots.Primary control devices The simplest control surfaces are fixedfins.are responsible for maintainingmissiles along The flight of an arrow is an example ofthedesired trajectories. If no unstabilizingcondi- stability provided by fixed fins. The featheredtions were present, primary controlcould func- fins on an arrow present streamlinedairflowtion satisfactorily. A missile can becontrolled surfaces which ensure accurate /light.Since more accurately and moreefficiently, however, supersonic missile fins are not cambered, aby the use of secondary controls,in various slightly different lift principle is involved than combinations, working in conjunction withpri- with the conventional wing. At subsonicspeedsmarycontrols. a positive angle of attack willresult in impact pressure on the lower fin, surfacewhich will Ailerons, elevators, and rudders are attached produce lift just as with the conventional wing,to fixed wings and tails as in a conventional At supersonic speeds, the formation of expan-aircraft. sion waves and oblique shock waves also con- In figure 2-17, ailerons areattached to the tributes to lift. Figure 2-18 shows a cross sec-trailing edges of the wings. When one aileron it.is lowered, the other is raised.Movement of tion of a supersonic fin and airflow about andbrings Due to the fin shape, the air isspeeded,up throughthe ailerons changes the wing camber a series of expansion waves.This results in aabout roll control.The wing with the raised Chapter 2FACTORS AFFECTINGMISSILE FLIGHT

of attack the slot can be openedto allow air to RUDDER spill through and thus prevent RUDDER TAB a stall. AILERON Dual Purpose Control

AILERON The primary and secondary controldevices TAB discussed above are used on older typemissiles, although the Bullpup missileuses a type of tab. For high-speed missiles,new control surface SPOILER designs have been developed.Examples of such surfaces are eleyons, rollerons,ruddervators, and ailevators. As thenames indicate, these are multipurpose control devices. For example,an ELEVATOR TAB elevon replaces an elevator andan aileron, ELEVATOR allowing control of pitch andyaw by a single control mechanism. The Regulusmissile used 33.39this device. If operated together,they serve as Figure2-17.Control devices onconventionalelevators; if operated differentially, type missiles. they serve as ailerons.If the missile tail surfaceswere inclined upward, to foima V with the missile axis, controls on the trailing edgesof these sur- aileron moves down and the otherwing moves up. faces could be used as ruddervators.By suitable combinations of movements,they could Elevators attached to the horizontaltailcontrol the missilein both pitch and yaw. stabilizers may be used for pitchcontrol. The elevators are raised or lowered Figure 2-10A shows the fixed andmovable stabi- together. lizing surfaces on Tartar andBullpup missiles. Rudders attached to the verticalstabilizers (fig. 2-17) may be used for The Tartar has four fixed trapezoidaldorsal yaw control. fins the length of the rocketsection, and four If the rudder moves to the right thetail movesindependently movable tail fins.The tail fins to the left, and the missileyaws to the right. are folded during handling and stowage. Tabs are hinged to primary controlsurfaces, The Terrier BT-3 has fixeddorsal fins and the force exerted by these devicesis directedand folding tail surfaces. Fourbooster fins to act against a primarycontrol and not theare mounted 90° apart aroundthe after end of missile itself.For example, considera tab the (fig. 2-17) on an elevator. If booster, and are in line with themissile tails the tab moves up-and the dorsal fins.The Terrier BW-1 has ward, the deflected air will exerta downwardfixed tails. force on the elevator.The elevator will then The Taboo missile has four movable move down.Note that it is still the elevator, wings not the tab, that directly controls in a cruciform arrangement atapproximately the missile.the missile longitudinal center ofgravity. Four A fixed tab is preset fora given condition offixed fins near the after section stability; a trim tab is controllableand its are mounted in setting can be varied over line with the four wings. The boosteralso has a wide range of con-four fins, which are attached to theexit nozzle. ditions.A booster tab is used to assistin applying force to move control After the booster propellant has burnedout, the areas. surfaces of largebooster airframe drops off. A spoiler can be any of seferaldevices- -Control at Starting Speeds for example, a hinged flapon the upper surface of the wing. Suppose that a gust of air causes the Surface-launched missiles start outwith zero left wing to lose lift. The spoileron the rightvelocity, and accelerate to flying wing can be raised to "spoil" the smoptthflow of speeds. For air over it, and thus decrease its Mt a short time after launching, airspeedover the to equalcontrol surfaces is slow, and thesesurfaces are that of the other wing. unable to stabilize the missile A slot is basically a high-lift device or control its locatedcourse. With small, booster-launchedmissiles, at the leading edge of the wing.At a normalthis problem is not serious. angle of attack, it has no effect. At high Terrier, for ex- anglesample, builds up enough speed foraerodynamic PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS stability in a fraction of a second. But heavy powerful.Another method of jet control con- intercontinental ballistic missiles rise slowlysists in mounting several auxiliary jetsat from their launching pads, and may requirevarious points (fig. 2-18A) on the missile sur- auxiliary control devices for a number of secondsface. By turning on one or more of theauxiliary after launching. Two types of auxiliary controljets, it is possible for the guidance and control have been used. systems to change the missile course as required. Heat shields are necessary to protect EXHAUST VANES are surfaces mounted di-the main body of the missile from exhaust heat rectly in the exhaust path of a jet or rocketgenerated by the jets.The use of auxiliary engine (fig. 2-18B).When the exhaust vanesjets makes it possible to eliminate the outside are moved, they deflect the direction ofexhaust,control surfaces entirely. This is the steering and thus produce a lateral component of thrustmethod most likely to be used for control of that can be used to keep the missile pointed inmissiles after they leave the atmosphere (and the desired direction. This is possible becauseeventually, for the control of space ships). the exhaust velocity is very high, even when the missile has just begun to move. Because of .the VECTOR CONTROL. Man-made forces may tremendous heat in the exhaust, the life of ex- exert velocity vector control of missiles in haust vanes is short.The German V-2 usedflight. A ballistic missile before rocket burn- exhaust vanes made of carbon. The meltingout, when it is receiving rocket thrust with point of carbon is far above the exhaust tem-gyro control of the direction of motion(fig. 2- perature. But because carbon burns, the vanes19), is receiving velocity vector controlthe were eroded rapidly.Bythe time the V-2missile path is being shaped as desired, at each reached a speed at which the vanes were noinstant. On the other hand, a rocket under pure longer needed, they were burned away com-thrust, uncontrolled in magnitude and with no pletely.Exhaust vanes are also used to stabi-direction control, is not considered as receiving lize missiles In travel outside the atmosphere.velocity vector control. A missile experiencing JET CONTROL (fig. 2-18) is similar tothrust may have its velocity vector controlled by exhaust vane control in that both deflect thethe use of auxiliary devices to control the speed exhaust to produce a lateral component of thrust.and direction of missile flight.The thrust One method of jet control consists in mountingitself may be controllable in magnitude and the engine itself in gimbals, and turning thedirection.Both of these types are directional whole engine to deflect the exhaust stream (fig. controls, achieved by the following general steps: 2-18C).This system requires that the enginetracking the target; predicting its future posi- be fed by flexible fuel lines, and the controltion; and converting target data to directional system that turns the engine must be veryorders, either inside or outside the missile. In the case of guided missiles or ballistic missiles before burnout, the directional orders are im- plemented in the missile so as to produce directional control forces. This may be achieved GIMBALLED ENGINE CHANGES by the use of fins or rudders, by controlling DIRECTION OF THRUST the direction or magnitude of the main thrust, or by auxiliary side thrusts(rockets).In the ss last example there is a slight overlap between thrust and directional control; here directional controlis achieved by means of the thrust itself (fig. 2-19B). A guided missile is usually under the combined influence of natural and manmade forces during its entire flight. Man-made forces include thrust and directional control. AUXILIARYDIRECTIONALFq".0 The vector :sum of all the forces, natural and THRUST JET CONTROL man-made, acting on a missile at any instant, maybe called the total force vector (fig. 2-19C ). A B It is this vector, considered as a function of 33.177-.181 time, in magnitude and direction, which provides Figure 2-18.Jet control of flight attitude. velocity vector control. Chapter 2FACTORS AFFECTINGMISSILE FLIGHT

THRUST (MANMADE/

a. BEFORE BURNOUT

GRAVITY AERODYNAMIC FORCES (NATURE) (NATURE)

gf,C10ft 10(4.1S1 b. AFTER BURNOUT SOS AERODYNAMIC FORCES (NATURE) B

GRAVITY (NATURE)

GRAVITY AERODYNAMIC

144.9 Figure 2-19.Vector control:A. Before and after burnout;B. Threat vectors; C. Total force vector. Vector control as achieved in some mods ofburning propellantare exhausted through four the Polaris missile will bedescribed briefly. The Polaris has no controllable nozzles, and each nozzle hasa jetevator which aerodynamiccan be moved to deflect thegases as ordered surfaces, and must therefore be stitbilizedand controlled by other by the flight control subsystem.Figure 2-20 means.Its flight controlillustrates the action of the-jetevatorsin stabi- subsystem provides control andstabilization of the missile during lizing and steering the missile.For convenient its:powered flight: Thereference, the nozzlesare numbered clock- propulsion subsystem providesthrust and thrust vector control. The combustion wise as seen from therear.The jetevators, gases from theone on each nozzle, are. pivotedon the top and PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS bottom on nozzles 2 and 4, and at eitheiside onBoth lift and drag are directly proportional to nozzles 1 and 3. The jetevators normally func-the square of missile speed. tion in pairs.Those on nozzles 2 and 4 can DRAG REDUCTION. It is essential that deflect the gas stream either to the right or thesupersonic missiles be designed for minimum left, and those on 1 and 3 can deflect it eitherdrag. A low drag configuration makes it pos- upward or downward. Figure 2- 20 shows how the sible to use a smaller power plant, with a 'jetevators function in the missile to producelower rate of fuel consumption. The resulting pitch up, yaw to the right, and missile clock-saving in bulk and weight can be used to extend wise roll.Positioning jetevators 1 and 3 asthe range of the missile, add to its warhead shown in figure 2-20A, deflects the gaff streampayload, reduce its overall size, or any combina- upward, which causes the Missile to pitch up-tion of these three. ward. In part B of the figure, jetevators 2 and The effects of thickness distribution, Rey- 4 deflect the gas stream to the right and causenolds number, surface imperfection, and Mach the missile's nose to yawtothe right. In part C,number all influence missile drag. Wing drag each jetevator pair is set differentially (No. 1is influenced by thickness ratio, sweepback, deflects the gas stream downward, No. 3 deflectsaspect ratio, and section of airfoil. Total drag it upward; No. 2 deflects it to the right, No. 4 toof the missile is made up of fuselage drag, wing the left); this drives the missile into a clock-and fin drag, and another factor not present in wise roll. The jetevators are moved by signalssubsonic flight:mutual interference between from the flight control subsystem of the missile.the drags of the individual parts. For example, the drag of a wing may be strongly affected, EFFECTS OF MISSILE CONFIGURATION for better or worse, by the shape of the body on which it is mounted.Since drag is directly The configuration of a guided missile isproportional to velocity squared, minimum drag the principal factor controlling the drag anddesign becomes of paramount importance as lift forces that act on it. And these two forcesmissile velocity increases. largely determine the overall efficiency Of the LIFT EFFECTIVENESS. A steady liftforce, missile.Missile configuration and strengthequal to the weight of the Vssile, must be main- are dependent on the required missile maneuver-tained to keep the missile in level flight. Addi- ability, stability, speed, and operating altitude.tional lift must be available for maneuvering.

144.10 Figure 2-20.Jetevator action for missile control: A: Jetevators positioned to cause missileto pitch up;B. Jetevators positioned for yaw to the right; C.Jetevators positioned for clockwise roll. Chapter 2FACTORS AFFECTINGMISSILE FLIGHT

A missile must beso designed that the necessary lift is provided with minimum drag.And, for satisfactory controlresponse, lift must vary TAIL UNITS smoothly with the angle of attack. The conditions of flight associatedwith subsonic airflow are well known.Airflow phenomena at supersonic speeds are orderly, and CONVENTIONAL Ve TYPE OR can be analyzed mathematically.But in the DOUBLE RUDDER transonic speed range, majordesign problems arise. A great deal remainstobe learned about airflow in thisrange. Airflow over an ideal wing wouldbe sub- )1-1 sonic until the missile reachesa velocity of Mach 1, and it would thenimmediately become VERTICAL TAIL 120° FINS CRUCIFORM supersonic.In other words, an ideal wing,if it were possible to makeone, would eliminate WING ARRANGEMENTS the transonic range.Actually, the transonic range begins when the flowover any part of the missile becomes supersonic,and continues MIDWING HIGH WING PARASOLo WING until the flow over all parts ofthe missile becomes supersonic.The free-stream Mach SIIOE number at which transonic flowbegins on any given missile is called the criticalMach number for that missile. Every missile is designed fora cruising speed either below the transonicregion or LOW WING CRUCIFORM aboveit; no missileis intended to cruise CRUCIFORM RELATIONSHIP within this region. Forsupersonic missiles, the effects of the transoniczone can be minimized in two ways. First, therange of speeds included within the transoniczone can be nar- rowed by suitable design of themissile. Second, by maintaining maximum powerplantthrust until INUNE INTERDIGITAL after supersonic velocity is reached,the missile can pass through the 33.35 transonic region in Figure 2-21.Arrangementsof minimum time.Supersonic missiles are often control surfaces. launched with the help ofboosters. A booster may be considered as an auxiliarypowerplant. It consumes fuel at a rapid rate, and developsas "tail units" may be used at themid-section a high thrust.After the missile has passedor even at the nose of the missile; in through the transonic region its others, booster fallssome of the "wing arrangements" shownin the away.The missile is then propelled atsuper-figure may be used as tail units. sonic speed by its own powerplant,which has a The CONVENTIONAL and lower rate of fuel consumption anda smaller CRUCIFORM are thrust than the booster. the most popular tail arrangements.The HIGH WING and cruciform wing arrangementsare used Figure 2-10B represents locationsand de for most missiles. The INLINE signs of control surfaces ofcurrent guided cruciform ar- missiles. rangement is widely used, especiallyfor super- The optimum arrangement ofair-sonic missiles. The INTERDIGITALform is foils on a missile is governed bymany factors,used on older mods of Terrier. such as speed, rate of acceleration during the In some supersonic missiles,body lift may launching phase, range, and whetheror not thebe the only lifting force. missile is to be recovered.. The sketches In such high-speed inapplications,controlsurfaces can be made figure 2-21: show some of 'themore commonsmaller or eliminated altogether, arrangements of missile airfoils. In some as inPolaris, mis-,thus counteracting the increaseddrag at high sale designs, arrangements shownin the figurespeeds. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

At supersonic speeds, the advantages of camber (curve) of the airfoils no longer exist, and wing designs must be modified. The wing '011111111111111. DOUBLE WEDGE receives its lift as a result of the angle of attack rather than of any increase in velocity MODIFIED DOUBLE of the air stream over the upper surface as 4111111.111111 compared with the lower surface. A smooth WEDGE flow of air over the wing (or fin) surface keeps down the drag; anything that increases turbulence. 41111111111111111111 BICONVEX of the airflow increases drag. A FIN DESIGNS. Supersonic fins are symmetrical in thickness cross section and have a smallthickness ratiothe ratio of the maximum thickness to the chord length. The DOUBLE WEDGE, shown in figure 2-22A, has the least drag for a given thickness ratio, but in certain applicationsitis inferior because it lacks strength. The MODIFIED DOUBLE WEDGE has relatively low drag (although its drag is usually higher than a double wedge of the same thickness ratio) and is stronger than the double wedge. /-\ The BICONVEX, also shovm in the figure, has CLIPPED TIP DELTA DELTA OR TRIANGULAR about one-third more drag than a double wedge of the same thiclmess ratio. It is the strongest of the three but is difficult to manufacture. RECTANGULAR RECTANGULAR WITH RAKE The planform of the fins- -the outline when B viewed from aboveis usually either of the CATHEDRAL ANGLEC. DELTA-MODIFIED DELTA(rakedtip)or "DROOP" USED WITH SWEEP RECTANGULAR types shown in figure 2-22B. BACK FOR These shapes considerably reduce unwanted BETTER CONTRO shock wave effects. The combination of a raked tip and cathedral droop (fig. 2-22C) of the wings permits better control as the swept-back wings delay air compressibility. Most missile bodies are slender cylindrical structures similar to those shown in figure 2-22B. Several types of nose sectionsare used. If the missile is intended for supersonic speeds, the forward section usually has a pointed arch profile in which the sides taper in lines called OGIVE curves (fig. 2-22D(a).Missiles which OGIVE SHAPE BLUNT NOSE fly at lesser speeds may have blunt noses as shown in figure 2-22D(b). The Sidewinder is an example of a missile with such a nose.. An air- breathing missile nose which includes the duct for the ramjet propulsion system is also shown (fig. 2-22D(d). ROUND NOSE BLUNT NOSE WITH AIR DUCT Hydrodynamics 0 Since surface-fired missiles for underwater' 33.33-.41 attack are part of the missile armamentOf Figure 2-22.High speed configuration char- many ships, you need to !mow something about acteristics: A. Supersonic fin cross-sectional the'.: effect of water. . on missile shape, speed, shapes; B. Supersonic fin platforms; C. Wing trajectory, and other aspects. The development angle; D. Missile noses. Chapter 2FACTORS AFFECTINGMISSILE FLIGHT of lift on a surface moving inwater differs The greater the lift required substantially from the samephenomenon in air of the hydro- because water is almost incompressible foil, the greater must be theeffective angle of air is highly compressible. while attack at which it moves, withinthe normal range When a missileof angle of attack. As speedincreases, water, moves through air, a change in the densityof the air occurs at various points of like air, cannot get out of theway of the moving the missile and foil fast enough. Discontinuitiesof flow occur, its airfoils.The same motion throughwater produces a different effect. The causing cavitation (formation ofareas of vac- flow of wateruum), and lift decreases,drag increases, and past an inclined plane (the hydrofoils)can be treated as two separate motions. buffeting and other undesirablephenomena may The first is occur.This is called the stalling point,com- the streamline flow (fig. 2-23A),just as is en- parable to the burble point inair. countered in air, and the secondis a circulation (fig. 2-23B). The circulationcomponent is due Designers of missiles whosetrajectory is directly to the incompressibilityof water. Thepartly through air and partlythrough water must net flow (resultant) is thesum of the two com- consider, both aerodynamic andhydrodynamic ponents (fig. 2-23C). The resultantvelocity iseffects on the missile shapeand its wings and greater above the plate than belowit, and therefins. This requires compromisesin design. For is therefore a powerfuluplift force. The dragexample, an airfoil should bethin to achieve force is parallel to the directionof motion.the smoothest flow of airover the surfaces, but a hydrofoil must have thick sections,or at least the leading edge must berelatively thickbecause of the extremely widerange of attack angles to which it may be subjected. Therefore,some lift has to be sacrificed in order tohave a foil able to withstand water forces.Water has greater buoyancy than air, so less liftingforce is needed, but at the same time thedrag force is greater, so a greater propulsive force is needed.Rico- chetting or skipping at water entrymust be prevented.All these factors must beconsidered in the missile configuration. ASTREAMLINE FLOW VELOCITY

GUIDED MISSILE TRAJECTORIES

The trajectory of a missile is itspath from launch to impact or destruct.There are two basic types of missiletrajectories: ballistic andaerodynamic(includingthe"gravity- VELOCITY biased" aerodynamicallysupported trajectory). BCIRCULAR FLOW A number of other trajectoriesare named according to the path traveled.Some of these trajectories are: aeroballistic,glide, powered flight, terminal, zero lift, skip,and standard or ideal. The chapterson guidance illustrate some of the trajectories. In a BALLISTICtrajectory, the missile is acted upon only by gravityand aerodynamic VELOCITY drag after the propulsiveforce is terminated. C RESULTANT FLOW Gun projectiles havea purely ballistic trajectory; ballistic missileshave at least the major 144.11 pArt of the trajectorya ballistic one. Figure 2-23.Flow of waterabout an inclined, An AERODYNAMIC missile plane: A. Streamline flow; B.Circular flow; is one which uses C. Resultant flow. aerodynamic forces to maintainits flight path; it usually has a wingedconfiguration. r: PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

of intercept will be calculated, and the missile TRAJECTORY CURVES course will be turned toward the newpoint of Missile trajectories include many types ofintercept. curves. The exact nature of the curve is BEAM-RIDER TRAJECTORY.As we will determined by the type of guidance and theexplain in a later chapter, abeam-ridermissile nature of the control system used. For somemay follow either a pursuit curve or alead-angle missiles, the desired trajectory is chosen be-course, depending on the type ofsystem used. fore the missile is designed, and the missile is FLAT TRAJECTORY.An intermediate- closely limited to that trajectory. Missiles mayrange or long-range air-breathingmissile is offer a choice of trajectories. usually made to climb as quickly as possible HYPERBOLIC TRAJECTORY.A missileto the altitude at which its propulsionplant using a hyperbolic guidance system will firstoperates most efficientlysomewhere between climb to the desired altitude, then follow an arc30,000 and 90,000 feet.After reaching this of a hyperbola before living on its target. If thealtitude the missile flies a flat trajectory to the control stations are ideally located with respecttarget area.The missile is made to climb to the target, the hyperbolic course is a closesteeply to a desired altitude, level off, fly aflat approach to a straight line. This system is nottrajectory to the target area, then divestraight used with any of our guided missile systems atdown. present.It operates on the Loran principle, BALLISTIC TRAJECTORY.Polarisis with a "master" and a "slave" station sendinglaunched vertically, so that it can get through radio signals to fix the location of the target.the densest part of the atmosphere as soon as possible.At a certain altitude, which may be PURSUIT CURVE.Some homing missiles,controlled by either preset or command guid- and some beam riders, follow a pursuit curve.ance, the missile turns to a moregradual At any given instant, the course of the mis-climb.After burnout, or shutdown of the pro- sile is directly toward the target.If missilepulsion system by radio command, the missile and target are approaching head-on, or if the"coasts" along a ballistic trajectory to the missile is engaged in a tail chase, the pursuittarget. curve may be a straight line unless thetarget From launch to warhead detonation, long changes course. But a missile that pursues arange ballisticmissiles follow a trajectory crossing target must follow a curved trajec-approximating that shown in figure 2-24, sepa- tory.As the missile approaches a crossingrating into three flight stages. Missiles that are target, the target bearing rate increases, andlaunched vertically travel only a comparatively the curvature of the missile course increasesshort distance before turning to a slant angle. correspondingly.In some cases the extremeIf launched from under water as the Polaris, curvature of the pursuit course may be toomost of the vertical part ofits flight path is sharp for the missile to follow. Underwater. Powered flight continues until the LEAD ANGLE COURSE.Some homing mis- end of the second stage, when ballisticflight siles follow a modified pursuit course. Thebegins.The distance to the target determines deflection of the missile control surfaces isthe point at which it is necessary for the misFile made proportional to the target bearing rate.to go into the ballistic curve that will bringit The missile flies not toward the target, butdown on the target. Computations are made by toward a point in front of it. The missile thusmissile system computers before missile firing. develops a lead angle, and the curvature of its COMBINATION TRAJECTORY.A special course is decreased. case is the trajectory of the Asroc weapon(fig. A further refinement is possible if a com- 2-25).It is fired from a launcher on a surface puter, either in the missile or at a controlship and is boosted into the air by rocket thrust station, can use known information about the(phase 1).After burnout of the rocket it goes missile and target to calculate a point of inter-through the air in a ballistic trajectory(phase cept which missile and target will reach at the2) until it strikes the water surface.It falls same instant. Because the missile isguided,straight down through the water fora short time. directly toward the pointof intercept, its tra-Then it begins hunting for the target (phase3), jectory is a straight line. If the target changesand homes on it (phase 4) when it has been course during the missile flight, a newpoint located.

48 t7 Chapter 2FACTORS AFFECTINGMISSILE FLIGHT

POWERED (GUIDED) ( FREE-FALL) PHASE, 0 PHASE roo"... SECOND STAGE VA SEPARATION APOGEE 090NinsfAIRIVEPARATION JETTISONING RE-ENTRY BODY

FIRST STAGE SEPARATION AND SECOND STAGE IGNITION

egmIa

ATMOSPHERE r, FIRST STAGE IGNITION LAUNCH PHASE REENTRY EJECriON PHASE

EA TARGET t- 5500 NAUTICAL MILES

33.269 Figure 2-24.Typical trajectoryof an ICBM (Polaris).

The Subroc missile also followsa combina-beginning and end of it. tion trajectory 'throughair and water, but it is They are therefore launched from submerged liable to be pushed off thedesired course by submarines. the force of the wind.The magnitude and 1 PROPORTIONAL NAVIGATIONCOURSE.direction of the prevailing PropPrtional navigation is winds at various a homing guidancepoints on the earthare well known. But the techl:Aque in which the missileturn rate is di- +zetl prevailing winds are much modifiedby a num- proportional to the turn rate inspace ofberoffactorssuchas local topography, fine of sight. The seeker tracksthe targetthermal updrafts due to local semi-independently from the missile heating of the maneu- earth'sSurface,thedistributionof high- vers. Lead angles and navigationratios (N) canpressure and low-pressure air usually be chosen so that themissile acceleration masses, and will exceed the target storms and their associatedturbulence.All 1 acceleration only slightly.-of these factors can be predictedto some extent, FACTORS AFFECTING but the Tenabilityof the prediction MISSILE TRAJECTORY decreases with both time anddistance.For that reason, air-breathingmissiles must be provided with means for correctingany devia- The principal factors affectinga missile'stion in course that might trajectory are, ofcourse, the design of the result from un- missile and its guidince system, predicted winds.A ballistic missilemay be which are mansubject to correctionas it rises through the made. Natural external forcesaffecting theatmosphere. But it descends trajectoryinCludewind, on its target at gravity,magnetic such a speed that the effect ofwind is unlikely forces, and the corioliseffect.In the. use ofto produce a seriouserror. any long-range missile, all of thesemufiti.be taken into account. GRAVITY.A long-range WIND. All missiles flythrough the atmos- missile using a phere, either during their entire navigational guidance systemmay use the direc- flight or at thetion of the center of theearth as a reference. 49 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

15.115 Figure 2-25.Trajectory of an Asroc missile.

It does so by using a pendulum, plumb bob, or The CORIOLIS FORCE must also be com- some similar device, to measure the directionof pensatedfor. It is caused by the earth's the gravitational force. The measuring devicerotation, and tends to deflect a missile to the is acted on by two forces: gravity, which tendsright in the northern hemisphere, and to the to pull it toward the center of the earth; andleft in the southern hemisphere. As the earth centrifugal force, caused by the earth's rota-turns on its axis, its surface moves toward the tion, acting at a right angle to the earth's axis.east at a rate determined by latitude.At the The direction indicated by the measuring device equatorthe earth's surface is moving to the is that of apparent gravitythe resultant of theeastwitha speed of more than 1000 mph;at two forces.The motion of the missile itself .the poles, its speed is zero. will create additional forces that tend to disturb Assume that a missile is launched directly the gravity-measuring device.Any missilenorthward in the northern hemisphere. At the guidance System that uses a gravitational refer-instant of launching, it will be moving to the ence must compensate for these disturbingeast at the same rate as the Surface from which .4 forces. it is launched.But as it moves northward, it MAGNETIC FORCES.Some missiles mayflies over points whose eastward velocity is use the strength or the direction of theearth'sless than its own. As a result it will be deflec- magnetic field as a reference for navigation.ted eastward, or toward the right. Now imagine Both strength and direction of the field varya missile fired southward in thenorthern from point to polet on the earth.In general,hemisphere. It will fly over points whose these variations have been measured and plotted.eastward velocity is greaterthan its own.It But at any given point On the earth, the magneticwill therefore be deflected westward(still field is subject to annual, monthly, and evento theright) with respect to the surface. daily variations.It is subject to honperiodic . The amount of deviation produced by the variations in "magnetic Storing" that resultcortolis force depends on the latitude, length, from bursts of ions or electrons radiated fromand direction of _the missile flight.Since it the sun.Meet of these variations are piedict-can be accurately predicted, suitable correc- able With.teaionable accuracy, and can betakentions can be made by the missile guidance into account in the missile guidance systeni.system. 6 CHAPTER 3

COMPONENTS OF GUIDEDMISSILES

INTRODUCTION Figure 3-1 shows some typicallocations of components.The arrangement of thecom- GENERAL ponents is not the same for allmissiles. Most modern missiles are madeup of a missile assembly (with all its components), andabooster, This chapter is intended to providean overall view of a guided missile and the whole being called a completeround. Tartar its variousmissile is an exception--it doesnot have a components. Most of the materialin thisseparate booster. chapter is covered inmore detail elsewhere in this text. AUXILIARY POWER SUPPLY. Allmissiles Airframes and control surfaces,must contain auxiliary power supply (APS)sys- for example, were treated inchapter 2. Pro-tems in addition to the main engine pulsion systems, control systems, required for and guidancethrust.The APS systems providea source of systems are each givenone or more separatepower for the many devices needed for chapters. Their principal features will success- be brieflyful missile flight.Some APS systems relyon summarized here. Warheads, (except nuclear)the main combustion chamberas the initial which are not covered elsewhere in thistext, source of energy; others have theirown energy will be treated in some detail. sources completely separate from the main The principal components ofa guided missile are: propulsion unit. WARHEAD. The warheadmay be designed to inflict any of several possiblekinds of dam- AIRFRAME age on. the enemy. The warhead is thereason that the missile exists; theother componentsGENERAL are intended merely to ensure that thewarhead will reach its destination. The term AIRFRAME has thesame meaning AIRFRAME.The airframe is thephysicalfor guided missiles as ithasfortheconventional structure that carries the warheadtothetarget,airplane.It serves as a vehicle tocarry all and contains the propulsion, guidance,and control systems. the other parts of the missile,and it provides the aerodynamic characteristicsrequired for PROPULSION SYSTEM.Thissystem pro-successful flight.Research on airframes is a vides the energy required toMove.the missile from the launeher to thetaitet. major part of our missile developmenteffort. Since the guided missile isessentially a CONTROL SYSTEM,The 'Contioolsystemone-shot weapon, its structure has two. functions. can be simpler It keeps'. the missile inthan that Of a conventional aircraft.Missile stable flight, and it translatetthe commandsbodies are designed so that inner components Of the guidande sgstent .inte.MOtiOnefthe control surfaces; or into is:Oa-Other are readily available for testing, removal,and means forrepair.. The major componentsare mounted to mOdifying the missile ttejectofY:!.' form independent units. GUIDANCE,. 'SYSTEM:4thia**Or deter- Most modern trtistilles Whether the are made up of several fmissile` ih bn the 'oriktredsections (fig. 3-2). (Oldermods do not have this trajectorq Of the Ordered velocity.U the missileconstruction.) Is off course, the guid nce sy ten 'Sandi; etriii, 'Each section is a cylindrical signals to the &Agra sgetem shell machined from metal tubingrather than a built-up structure with internalbracing. Each PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

AIRFRAME

PROPU CO ROL GUIDANCE WARHEAD

GUIDANCE WING SECTION WARHEAD

RADAR ACCUMULATOR B 144.12 Figure 3-1.Location of components inguided missiles: A. Taloa missile; B. Active homingmissile.

tri AFT ) )HYDRAULIC ELECTRONIC ELECT ENGINE COMPARTMENT COMPARTMENT MRI.COP L-J 144.13 Figure 3-2.Sectionalization of amissile.

made prior to launching.Covers and access shell contain& one of the essentialunits or com- and dirt ponents of the missile, such as thepropulsiondoors are sealed to prevent moisture system, the .electronic controlequipment, thefrom entering the missile. Basically, the.missile is designed to carry warhead, or the fuze assembly. . the warhead to thetarget.. The size and weight .Sectionalized construction has.the advantage accommodated by the of etrefigth With simplicity,and also providesof the Warhead must be and rePair of the corano-missile structure. The missile mustbe Relight ease in rePlaeenient strong enough to nents, since the shells areremovable as separateand compact as possible, yet carry the warhead.(and other components), and Units. The sections are jOined byvarious.types subjected, Of cOnniations. deilined forsiMpliciti'of Opera-viith4and the forces to which it willbe tion. ;'Aceeeil ports aresometimes priiVided innsuch as gravity, air (or water) pressure, winds, which idjustments can beheat, stresses of acceleration anddeceleration, the shells, through '' 1"- Chapter 3 COMPONENTS OFGUIDED MISSILES and other forces. For every pound of weight The nose of Taloacontains the air intake saved in the missile structure,lees propulsionfor the ramjet engine. energy is required.The weight and balance Talcs is, in effect, relationships must be given careful a double-walled tube. Its considera-central part is takenup by the ramjet engine. tion. The initial location ofthe center of gravityAll of its other components is of extreme importance.The center of gravity warhead, fuel tanks, can change during missile flight guidance and controlsystemsare crowded because of thewithin the space betweenthe inner and outer burning of the propellant, andseparation of thewalls.(In one model, booster after burnout. Thesefactors and others one of these components is carried inside thecentral diffuser in the nose.) must be carefully included inthe calculations ofThe middle part of the missile designers toproduce a structure Terrier is takenup by a that will performas expected. chamber filled with solidrocket propellant. The warhead, fuze, and the majorpart of the guidance and control systems,are located forward of the BODY CONFIGURATION fuel chamber. Buta part of the guidance and control system is locatedin the double-walled cylinder that surrounds the The Navy missiles describedand illustrated exhaust duct at the after end of the missile.Electric cables and in chapter 1 show therange of body configurationpneumatic lines to maintain found in operational missiles.In general, the communication design of the airframe is between the two parts ofthe guidance system 1 determined by per-pass through covered channels along formance requirements. Earlytypes of missiles the out- were strikingly similar in side of the missile. appearance to a jet Polaris, pictured in chapter1, represents fighter of similar performance,in the high sub-still a third type of missile sonic speed range.The wings, like those of body configuration. carrier aircraft, could be folded. Note that there areno external control sur- Before launch-faces; any necessarychanges in trajectory ing, the wings were extendedand locked in place. are Most modern missiles accomplished by jet deflection.Note also that have wings that arethe nose is bluntly rounded.Its trajectory (fig. folded (Tartar) or removed(Terrier, Taloa)2 -24) takes it far beyond the when stowed, but the size,shape, and location earth's atmosphere; of the wings and fins halm it descends on its targetat a steep angle, and at undergone extensivetremendous speed. As itre-enters the atmos- changes for use at supersonicspeeds. Newestphere, friction with the mods of Tartar (fig. 2-10)and Terrier have air 'generates a great dorsal fins, deal of heat. The polarisnose cone shape and construction have been determined Terrier, Sidewinder,and Talcs are typical by the requirements of this problem.The materials for of present day airframes.In general, the air-the outer surface have frame is a long, slendercylinder without wings. been especially developed Its tail fins provide to resist high temperature.Suitable insulation weathercock stability. Ais provided between theouter skin of the nose second set of fins, mountednear the center ofcone and the internal components, the missile or forwardof the center, provide to prevent additional stability. damage to the warhead.Advances intechnology Control of the missile ishave permitted changing from accomplished by pivotingone or more pairs of the blunt nose of earlier mods to the pointednose of the AS. fins, rather than by theuse of conventional The two configurations ailerons, rudders, andelevators. Note that, as of Asroc (antisubmarine rocket; is notaguidedmissile)differ in Terrier, the forwardfins may be mounted atin size but each has four 45° angles to the horizontaland vertical. major assemblies: payload (warhead), airframe,ignition and separation assembly, and rocket motor.During theballis- The note shape is'determinedby other re-tic flight (fig. 2-25) of requirements. The Terrier noSit (not allmods) the missile, the rocket is long and slender,becluiSe motor drops away when therequired velocity is that Shape has beenreached, and the airframe found highly efficient at supersOnicspeeds. Side- drops away near the end of ballistic flight, freeingthe warhead to Winder, although it tkavelSat a comparablecontinue to target intercept. speed, has a hemispherial irget.This. is The torpedo configuration has a parachutewhich opens after the necessar beCause of theinfrarediiitekbpgrocket motor and the airframe device located immediatelybehind the nose have dropped away surface. and carries it to waterentry. Both torpedo and depth charge configurationshave a nose cone PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS flight but whichneeds no outside air supply,since it carries its streamlined for aerodynamic own source of oxygen.But this is a rather arbi- shatters upon water entry.The depth charge has of engines operate by fin extension tips on the failfins. The extensiontrary distinction. Both types water entry. The finexpelling a stream of gas athigh speed from a tips are sheared off upon nozzle at the after end of thevehicle. For our extension tips provideaerodynamic stability to considered as a type of the depth charge from the timeof airframe sep-purposes, a rocket canbe Two of the fins arejet engine. aration until water entry. The pulsejet, which propelledthe German plain fins and two are teefins. V-1, was used by the Navyto propel an early Because of theunderwater-to-air-to-wat& No current mis- operational cycle of Subroc,its design had tomissile that is now obsolete. qualities of a torpedosiles are driven by pulsejets.Taloa is propelled include the hydrodynamic by a ramjet.The Navy used turbojets forits and aerodynamiccharacteristics of a missile. the now obsolete In size and shape ithad to be made to fit aRegulus I and II, and for tube, from which itPetrel.Terrier, Sidewinder, andPolaris are standard submarine torpedo propelled by solid-fuelrockets. Tartar, too, is fired. has a solid-propellant rocketmotor, though it is different from the othersitis a dual-thrust rocket motor (DTRM),which develops both PROPULSION SYSTEMS booster and sustainerthrust, eliminating the need for a separate boosterand sustainer for GENERAL the missile. indicate that, Because chapter 4 is devotedto propulsion Current developments appear to until the advent of nuclearpropulsion, most if systems, they will be coveredverybrieflyhere. will be powered missiles have beennot all of our future missiles The powerplants of guided by solid-fuel rockets.Research on nuclear referred to as "reaction engines."But strictly conducted for use in to propel a vehiclepropulsion engines is being speaking, any engine designed spacecraft as well as in missiles. is a reaction engine.All of them operate in has been con- law, which states Although liquid-fuel propulsion accordance with Newton' s third sidered too complicated for usein missiles, a that for every action there is anequal and op- engine de- the forcethattheprepackaged and sealed liquid-fuel posite reaction. For example, veloped for the Bullpupair-to-surface missile tires of a car apply to theroad is opposed by an For this and it is this reactionhas been highly successfulin tests. equal and opposite force application, liquid-fuel propellantand a propel- that drives the car forward.A propeller-driven pressurizing medium arepermanently aircraft operates by increasingthe momentum lant reaction is applied to sealed in a tank which isintegral with the rocket of the air; the resulting thrust chamber. An outstandingfeature of this the propeller and its shaft,and, through athrust shipboard tests or wehavepointed outengine is that it requires no bearing, to the airframe. As checkoff prior to mounting onthe aircraft nor earlier, speed requirementsmake it impossible missiles. Because thebefore launching. to use propeller-driven The liquid-fuel rocket isused in the Air speed of the propeller tipexceeds the speed of tip enters the tran- Force Titan, and in thatapplication it has certain the airframe, the propeller advantages.Liquid fuel provides more energy sonic zone while theaircraft speed is copsider- solid fuel, and can In the transonicthan an equivalent weight of ably below the speed of sound. maintain a' high thrust for arelatively long time. zone, the thrustdevelopedby the propeller drops increase in aircraftA liquid-fuel propulsion systemcanbe shutdown off rapidly, and a further by radio command at anydesired instant, speed becomes impracticable.Therefore, all some form ofwhereas a solid-fuel systempresents complica- current guided missiles depend on tions, although shut-down andrestart have been jet propulsion. accomplished in experimentalmodels.The rather complex SYSTEMS liquid-fuel rocket must have a TYPES OF JET PROPULSION system of fuel and oxidizer linesand pumps, and elaborate equipment atthe Popular terminology makes adiatectionit requires relatively jet takes in airlaunching Bite.At present, a large missile between jets and roekets: a propelled by a liquid-fuelrocket requires a from the atmosphere, andpropels itself forward firing. The last two by increasing the momentum ofthe air; a rocketlengthy "c01Mtdown" before Chapter 3COMPONENTS OFGUIDED MISSILES factors make the liquid-fuel rocket impracticablemissiles present a somewhatdifferent problem. for ship-launched missiles. The effective radius of The liquid-fueled Atlas,developed by theAir damage from a high- Force as an ICBM, is explosive warhead in the airdepends on the being phased out fortype, shape, and size of thecharge, and on the missile use and is being changedfor spacecraftnature of the target itself. use.It, too, requires a longcountdown, which reduces its value as a deterrent The designer of the payloadfor any type of missile. military weapon is facedwith a number of variables, some of whichare unpredictable. For example, in the design WARHEADS of an antiaircraft missile, he must consider thefollowing factors: GENERAL 1. Altitude affects thelethal radius of a The warhead is the fragmentation warhead; thefragments main- reason-for-being of anytain a lethal velocity througha greater distance service guided missile; itmay contain any ofat high altitudes. a large number of destructiveagents.This versatility must not be confused 2. The relative velocityof target and mis- with inter-sile has a direct bearingon the optimum angle changeability, because the designof the mis-of ejection of fragments. sile and warhead must bethoroughly integrated. The designer must The guided missile fuze determine the angle at whichthe greatest mass may be defined asof fragments should beejected. that device which causes thewarhead to detonate The timing in such a position that sequence of fuze operationas well as the maximum damage willbeguidance system of the missile,must function inflicted on an average target.A fuze may bewith great precision if any of several types, suchas impact, time, or the target is to be proximity. destroyed.The fuze must be bothsensitive and fast to ensuresuccess against high-speed Guided missiles areprecision-built weapons;aircraft or supersonic missiles. they are expensive inmanpower, materials, and 3. The armor of the money. The most accurate control and guidance target, if any, influ- systems will be of little value ences the design specificationsfor fragment if the warheadsize and velocity. Fragmentsthat are effective cannot produce enough lethaleffect at the rightagainst conventional aircraft time to destroy or at leastcripple the target. of today may The warhead problem be too light or too slow topenetrate the protec- must be solved for eachtive covering of the airplanesor missiles of the type of missile, to perm[t finalcrystalizationoffuture. any integrated missile plan. The multiplicity of types of The ultimate aims and.desires of weapon- ground targets Makers have always been to has led to the development ofnumerous types "arm" of the user. strengthen theof lethal devicesfrom handgrenades to hydro- The rock in the hand ofgen bombs. A 500-pound bombmay be armor- primitive man added strengthand distance topiercing, semi-armor-piercing, the blows that he coulddeliver; the bow and or general- arrow greatly multiplied man's purpose. R may be equipped withan impact fuze, effective strikinga time fuze, a proximity fuze,or a combination distance; and the rifle andcannonhave progres-of these types. sively increased the strengthand range of his striking power. The type of target is themost influential Guided missiles area newfactor in warhead design. A means for lengthening the arni of the fragmentation-type user. Butwarhead might be effective againstconventional the striking effect dependson the nature of theaircraft, or against missiles warhead and on how accuratelyit can be delivered of moderate speed. to the intended target. The But a missile intendedfor use against a whole warhead of a guidedfleet of attacking bombers,a city, or against a missile is its payload, andjustification forhigh-speed ballistic missile, employment of the missilelies in its ability to would require an entirely different type ofwarhead. Because of deliver its payload tothetarget. the wide variety in types A guided missilemay carry one of thevar- of surface targets, it ious types of warheads, andone or more ans.is necessary to have missilesthat can use sev- Missile warheads ititendedfor eral types of warheadsinterchangeably, or to use against ships develop a whole family of or land targets present: design,problems similar missiles. to those of older The third component ofthe warhead, the weapons. Surface. u-airsafety and arming device (S&A),is of critical PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

The S&A The damage produced by afragmentation importance with nuclear warheads. warhead depends (in part) on theamount of metal device must prevent accidentaldetonation and the amount must initiate detonation at the momentdesired.available to form fragments, and on of explosive available forbreaking the casing In nuclear warheads there areseveral devices Aerial targets to prevent accidental or prematuredetonationsand propelling the fragments. are more susceptibleto damage by fragments if the warhead explodes a shortdistance away, TYPES OF WARHEADS rather than in contact with thetarget. Against a partially protectedsurface target, a frag- when ex- The types of warheads that mightbe used withmentation warhead is most effective blast, frag-ploded in the air above the target,rather than guided missiles include: external Figure 3-4 shows this effect. mentation,shaped-charge,explosive-pellet,on the ground. rod,Fragments from the air burst strikethe partially chemical, biological, nuclear, continuous personnel. clustered, thermal,illuminating, psychological,protected target and the entrenched exercise, and dummy. Those that areintended A fragmentation warhead can have agreater true warheadsmiss distance than a blastwarhead and still for use against an enemy are not remain effective. The pattern offragmentation within the definition of warhead, and areusually effectiveness, as referred to as heads, such as exercise heads.also makes a difference in Some types of warheads will bediscussed in a classified course, Navy MissileSystems, Nay- Pers 10785-A. BLAST-EFFECT WARHEAD. The blast NITALtIC FRAGMENTS effect warhead consists of a quantityof high- explosive material in a metallic case.The force of the explosion sets up a pressure wave in the air or other surroundingmedium; the pressure wave causesdamage to the target. This type of warhead is mosteffective against underwater targets, because water isincom- FUSS TIMER pressible, and relatively dense.Torpedo war MAIN EXPLOSIVE MARGE IIINttING CHARGE heads are of this type. Blast-effectwarheads against small 33.8 have been used successfully Figure 3-3.Basic construction of a ground targets.They are considerably less effective against aerial targetsbecause the fragmentation warhead. density of the air, and therefore theseverity of the shock wave, decreaseswith altitude. . FRAGMENTATION WARHEAD. The fragmentation warhead uses the force of ahigh- explosive charge to break upthe warhead casing into a number of fragments,and to to destroy or propel them with enough velocity MACRON AWL! ITITN PRANIGNTATION RAMA. damage the target. The size andvelocity of DETONATION OP MARINO the fragments, and the patternin which they are dispersed, can be-controlled by variation MITALLK 'RAIMENT' the warhead. in the design and construction of I i SAMEGAS 'ARAM The velocity of the fragmentsdepends on the and on the ,Ila TARGET type and amount of explosive used, t 4 The ' ratio of explosive-to-fragmentweight. INTEMICNIO EMITrummy. average size of fragmentsdepends on the shape, size, and brittleness ofthe warhead casing, and on the quantity and type of etyllo- siVe. Greater uniformity infragment size can 144.14 be achieved by scoring orotherwise weakening the casing in: a regularpattern, as shown in Figure 3-4.Effect of fragmentationwarhead figure 3.3. on surface target. Chapter 3COMPONENTS OFGUIDED MISSILES does the velocity. Thepayload can be designed to "propagate" itsenergy and material in all directions.This is called isotropicpropaga- OUTER tion (fig. 3-5B).When the payload is designed SHELL so that more fragmentsor energy are released in one direction than another,the propagation pattern is called nonisotropic (fig.3-5A). It is more effective than an isotropicpayload of the same size and weight if you knowwhere to aiin it.This directing of theexplosion is the basis of the shaped chargeeffectiveness. A large part of the warhead's explosiveenergy is directed to the target in anarrow beam. SCORING OF Advanced Types of Fragmentation WARHEAD BODY Warheads 144.16 Figure 3-6.Controlled A knowledge of fragmentationpropagation is fragmentation warhead. a basic requisite in designingmany types of warheads.Theories are checked outwith the use of scaled models, using different the charge-to-mass ratioof the missile, the type types ofof explosive used, and theshape of the fragments. explosives, and varied missileshapes and casingTest firings have thicknesses. These studies have substantiated the value of the resulted inthecontrolled designs. One typeof controlled frag- development of warheads withcontrolled Size, mentation warhead is shown shape, number, and initialvelocity of fragments. in figure 3-6. Var- The initial velocity of the ious shapes and sizes offragments have been fragments depends ontested for different typesof targets. The most effective types have beenadapted for some missile warheads. Shaped-Charge Warhead

A shaped charge consistsof a casing and a _17441. quantity of high explosive.The explosive is so shaped that the force ofthe blast it produces is largely concentrated ina single direction. Asa result, a shaped chargehas high penetrating power.It is widely used againstarmored surface targets. For example,the antitank bazooka used during World War IIand in Korea useda shaped charge. Figure 3-7 shows howthe shape of the charge affects the penetratingability of the blast.All three of the chargesshown in the figure have the same weightand type of explosive.The flat charge at the leftproduces an explosive force rather evenlydistributed over a given area of the target;this charge produces little penetration. Theshallow-cone shape of the middle charge producesa greater concentration of the explosive force,and penetration of the target is deeper.The deep-cone shape atthe right has concentrated theexplosive force so as 144.1.5 to penetrate the targetarmor. Metallic frag- Figure 3-5.Payloadpropagation: meats of the armor A. Nonigotropic; B. can now reach the interior Isotropic. of the target, and doadditional damage. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

EXPLOSIVE DEEP CHARGE CONE SHALLOW CONE METALLIC CAVITY LINING

FRAGMENTS OF CAVITY LINING AND ARMOR ----41 4, ARMOR THICKNESS

Figure 3-7.Penetration effectiveness ofvarious shaped charges. 33.9

In the explosion of a shaped charge, abeamindividuul charges that can withstand theinitial of very hot gas (called the jet) isejected at anblast of the principal warhead while still ensur- extremely high velocity.If the cavity is lineding explosion at or within the target. with some material that canbebrokeninto small pieces or can be melted by the explosion,theChemical Warheads efficiency of the charge is greatly increased. A chemical warhead is designed toeject The small particles of the liner arecarried bypoisonous or corrosive substances andthus the jet, which is thus increased in weight.As aproduce personnel casualties, or todestroy result it can penetrate`a thick target. combustible targets by the use of incendiary When used in guided missilewarheads, materials.Warheads containing gases may shaped-charge explosives have possibilitiesofliberate any of the well -known typessuch as great effectiveness against both aircraftandmustard gas, lewisite, or some newlydeveloped heavily armored surface targets. chemical. The effects produced are either denial of the use of the target area orpersonnel Explosive-Pellet Warhead casualties within the area.Missiles equipped with chemical warheads also serve aspossible An explosive-pellet warhead consists of acounterthreats to initiation of gas warfareby group of separately fusedexplosive pelletsthe enemy. It is likely that quantities of housed in a casing.The easing contains an poisonous war gases are included in thearsenal additional quantity of explosive to eject theof every major power, and the possibilityof pellets from the math warhead casing.Thetheir use remains a threat. However,the cer pellets themselves de not explode until theytainty of retaliation in kind has served as a contact or penetrate the target. If the target is deterrent since World War I. an aircraft or. missile,maximum destruction A variety of disabling gases have been devel- can be accomplished when thepelletti areoped. These gases temporarily inactivate mili- detonated after penetrating the outer skin oftary and/or civilian personnel by a variety of the target. pellet contributeS both bJsteffects, without death or permanent disability. effect and igh-velocity metallic fragments. when The possibilities of these agents have been ex- ploredin research and tests and some have been detonation occurs. . The aitplosive-pellet is an ideal weapon forused in riot situations. Use avant* aerial targets. Its fulldevelopment The incendiary warhead contains a material is dependent upon perfecting a fuse for the that burns violently and is difficulttoextinguish. Chapter 3COMPONENTSOF GUIDED MISSILES Chemical weapons are useful principally against warheads. Decoy warheads ground targets, but mayalsobe effective against may carry "window," aerial targets that contain which causes false radarechoes, or noise- combustible mate- makers to confuse rials.Incendiary materials suitablefor use in sonar operators of antisub- warheads include magnesium, marine ships. jellied oil or A DUMMY warhead has gasoline, and phosphorous.Incendiary warheads only the outward are also referred to as thermalor fire war- appearance, the size, shape, andweight of a heads. real warhead. It is usedintraining and practice operations. Biological Warheads EXERCISE or trainingwarheads do not A biological warhead containsbacteria orcontain any explosivematerial but otherwise other living organisms cirkble ofcausing sick- contain the parts ofa real warhead, so theycan ness . or death.The biological agentcan bebe assembled, disassembled,tested for elec- specifically chosen for use againstpersonnel, trical continuity, and otherwiseused for training livestock, or crops. Antipersonnelagents might exercises. be chosen to cause eithertemporary disability The ASROC (Rocket Thrown Torpedo)uses a or death, depending on the objectivesof thetorpedo for its warhead. attacker.An explosive charge placedin a biological warhead wouldensure ejection and Nuclear and ThermonuclearWarheads initial dispersion of the biologicalagents. Spe- cial attention must be given to thedesign and A number of presentday guided missiles construction of biological warheadsin orderare equipped with nuclearor thermonuclear that the bacteria or other agent willremainwarheads. The blast effects andradiation alive, and be carried to the targetunder theeffects which result from thedetonation of these most favorable conditions. warheads cause immediatephysical damage to Probably every major nationhas an arsenala large target area, andsickness and death to of biological material touse in "germ warfare"personnel a considerabledistance from the in such a variety ofways that it would tax the explosion. The blast effectsare, of course, imagination of the averageperson. Use of "germ many times greater than thoseeffected by the warfare" has been restrained,as in the case ofdetonation of conventionalexplosives.After chemical warfare, for fear ofretaliation in kind. effects caused by the settlingor fallout or radioactive material Other Special Purpose Warheads can result in sickness and death of personnel atgreat distances from the Several other special types ofwarheads mayexplosion, dependingon wind and other atmos- be used. These include:radiation, illumination,pheric conditions. psychological, exercise, and dummywarheads. The development oftactical nuclear weapons RADIATION warheadsmay use radiologicalwith varied methods ofdelivery makes obsolete material in the samemanner as chemical orthe concept that nuclearweapons are used only biological agents, scatteringthe radioactiveto devastate whole citiesor metropolitan areas. material according to plan.The possibilitiesWe still have the largebombs and missiles to and ramifications of thistype of warfare willdo the strategic job, butwe also have the much not be explored further here. smaller weapons to gaintactical objectives. ILLUMINATING warheads havelong been used in projectiles during nightattacks to point FUZES out or silhouetteenemy fortifications. This has A fuze is a device thatinitiates the explosion been especially useful duringShore bombard-of-the warhead. Ina guided ment.Illuminating warheadsare also used in missile the fuze may aircraft bombs and rockets or may not be a physicalpart of the warhead. to assist in theIn any case, it isessential to proper warhead attack of ground targets, andsubmarines. Nooperation. application has been made in guidtd A large variety of fuzetypes is missiles.available. The fuze typefor a given application PSYCHOLOGICAL warheadsdo not carrydepends on characteristics lethal or destructive agents,but carry material of the target, the missile, and the warhead.To ensure the highest designed to create a psychologicaleffect on theprobability of lethal enemy rather than actual physical damage.Pay- damage to the target, fuze loads may be propaganda design must be basedon the location, vulner- 1 leaflets, mysteriousability, speed, size,and physical structure of objects that appear dangerous,inert or dummythe target. PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS the missile approaches thetarget (fig. 3-9C), Impact Fuze the impact fuze will stillfunction on contact. Impact fuzes are actuated by theinertialThis combination of fuzes has beenused chiefly force that occurs when a missilestrikes aon air-dropped bombs.The Sidewinder and target.Figure 3-8 is a schematic representa-Sparrow also use such a combination. tion of an impact fuze and theexplosives it sets off in the warhead. As shownin the left-handTime-Delay Fuze diagram (fig. 3-8A), a chargeof sensitive ex- end of the plosive is contained in the forward Time delay fuzes are used in some typesof fuze; a movable plunger is mountedin the after end, where it is held in placeby a spring orgun projectiles. Thisfuze is designed to detonate the warhead when apredetermined time other suitable device.(The booster and main launching. One type fuze.) has elapsed after firing or charge are not part of the of time-delay element consistsof a burning During the flight of the missile, theplungerpowder train; another uses a clocklikemechan- remains in the after end of thefuze. When theism. In either type, the timeinterval cannot be missile strikes the target, itdecelerates sud-changed afterlaunching. For that reason, preset denly, and the inertia of theplunger carries ittime-delay fuzes are unlikely to be usedin guided forward. As shown in the right-handdiagram,missile warheads. Presettime-delay fuzes can figure 3-8B, the plunger strikesthe shock-be used for stationary targets.With a moving sensitive priming mixture anddetonatesit. Thistarget, especially a fast moving onelike a mis- charge in turn detonates thebooster chargesile or aircraft, the timedelay would be in which detonates the main burstingcharge of theerror most of the time.If the delay problem warhead (fig. 3 -9A). A time delayelement isis considered one of distancerather than time, sometimes used in conjunction with animpactthe fuze can be placed at the rearof the war- fuze, so that the warhead can penetratethe tar-head, and the desired result couldbe obtained get before detonation (fig.3-9B). as the warhead wouldpenetrate the target before the fuze could function.Such fuzes are An impact fuze may be usedin conjunction projectiles, with a fuze of another type, such as aproximityusually used for armor-piercing fuze.If the proximity fuze fails to operate asand antitank missiles.

MAIN MAIN CHARGE CHARGE

BOOSTER BOOSTER CHARGE CHARGE

PRIMING PRIMING MIXTURE MIXTURE

PLUNGER DIRECTION OP FLIGHT

PLUNGER TUBE TUBE

33.10 Figure 3-8.Impactfuze action: A. Before impact; B. After impact. Chapter 3COMPONENTS OFGUIDED MISSILES

Proximity Fuzes

Proximity fuzes are oftencalled VT (variable time) fuzes. Theyare actuated by some characteristic feature of the targetor the target area (fig. 3-9C). Severaltypes of proximity fuzesare possible; for example;photoelectric, acoustic, A pressure, radio, radar, or electrostatic.Each of these types could bepreset to function when the intensity of thetarget characteristic to which it is sensitive reachesa certain magnitude. Proximity fuzesare designed so that the warhead burst pattern willoccur at the most IMPACT FUZE effective time and locationrelative to the target. Designing the fuze to producean optimum burst pattern is not easy, sincethe most desirable pattern depends largelyon the relative speed of missile and target. If targetswith *idely varying speeds are to be attacked,it might be possible to adjust the fuzesensitivity for t.ite ag,eed of the individual target,as predicted bycom- puter. Proximity fuzes activate thewarhead detonating system after integrating'two factors: the distance to the target,and the rate at which the range is closing.

IMPACT FUZE WITH Since a proximity fuzeoperates on the basis TIME DELAY ELEMENT of information receivedfrom the target, it is subject to jamming by falseinformation. This is one of the importantproblems in proximity fuze design.The fuzes are designed forthe Maximum resistance tocountermeasures con- sistent with other requirements.If the fuze is made inoperative by jamming,the missile cannot damage the target unless itscores a direct hit. A more serious possibilityis that jamming, instead of making the fuzeinoperable, might cause premature detonation ofthe warhead before the missilecame within lethal range of the target. Some counter-countermeasures (CCM) have been devisedto counteract or by- pass the effects of enemycountermeasures. Although any of the effectslisted above photoelectric, acoustic,pressure, electromagnetic (radio, radar),or electrostaticcan be used as the basis for proximity Y. T. OR fuze action, and PROXIMITY FUZE although all of them havebeen used at least experimentally, it has been foundin practice that the radio proximityfuze is more effective 144.17 than tiny of the others.This fuze transmits Figure 34.-rInfluence of.fuze type on point ofhigh-frequency radio waves, whichare reflected warhead detonation: A. Impactfuze; Time7 from the targetas the missile.approaches it. delay impact fuze; C.Proximity fuze. BecaUse of the relative motionof missile and target, the reflected signal,as received at the PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS missile, is of a higher frequency than thetrans-also be called an AMBIENT fuze, that is, a fuze mated signal.The two signals, when mixed,acted upon by the environment of thetarget, will generate a Doppler frequency, theamplituderather than by the target itself. of which is a function of targetdistance. When AMBIENT type. fuzes might be used against this e:nplitude reaches a predeterminedlevel,stationary ground targets but they could not re- the fuze functions and detonates thewarhead.act swiftly enough to follow the almostin- A rAilio fuze uses signals of a lowerfrequencystantaneous changes of altitude that a missile thln 2 radar fuze. or modern aircraft couldundergo.Also, a ..krOUSTIC systemti ('actuated by sound wavestarget could be thousands of miles from the iron, the target) are obsolete becauseof thelaunching point of the missile and it wouldbe speed of present day missiles, whichoutrunextremely difficult to know the best air pressure sound.Acoustical sensors are still used tovalue to set into the fuze for detonation. A diaphragm PHOTOELECTRIC fuzes react to external activate mines and torpedoes. in 1..7pi)mechanism vibrates when sound. waveslight sources and ordinarily are inoperable lz:k",der water strike it, exerting pressure on anconditions of low visibility. in crystal that sets off the mine.The acoustic fuze must react only to specific sounds Ground-Controllsd Fuzes not o all sounds. The need ter sensitivebut In gi'ou:ad- oz. ship-controlled fuzes, some selw,tive acoustic fuzes is one 0 the rearmsdevice is employed to measure thedistance for the 14.'0 studies on amide madeby f: 41; and from missile to target.The control device is sea mammals. not 'mounted in the fuze, but at someremote MAGNETIC inclueilon mines can be set offcontrol point. When the proper distance exists by the magnetie field of an a; iproaching ship,butbetween missile and target, a signal is Ben'.from this system is not used in gu±ded missiles.the control point to pause detonation of the war- Magnetostatic fuzing is also ursd for subsurfacehead.".'11:e method is most often used vith targets, but. its use in air systems is still inthe in:clear warheads. Our missiles in silos(Min- developmental stage.The mavetic field thatuteman, for example) are ground controlled. surrounds the oarth, and the Itvtation in theStudies are underway to make possible control earth's magneileni waled ati magnetism,from the air. are the forces used in magnetostaticfuzing. ELHOTROMAGNETIC fuzva may operateDesign Considerations with radio, radar (microwave), infrared, or ultraviolet waves.The basic proximity fuze A fuze must be reliable, accurate, and safe. must have a transmitter - receiver, amplifyingIt must he safe for the men who musthandle it circuitry to amplify the returnsignalso it willand also safe against countermeasuresby the activate the detonator, eleidrical safety devicesenemy. At the same time, itmust be sensitive to prevent premature detonation, and a powerenough to detonate upon signal. To increasethe supply to generate and provide electrical powerprobability of an optimum detonation, the weapon to the fuze. designer may put in duplicate ,ysiems(re- ELECTROSTATIC fuzing has application overdundancy), or he may have two types of fuzes, short distances. It may use active, sezniactive,so that if one fails there isanother. The many passive, or . semipassive modeS ofoperation.variades that must be considered in designing Air targets become electrostatically charged asa fuze for a guided missile make it a difficult they pass through the atmosphere, butwaterand complicated problem repiringconstant vapor or rain dissipates much ofthe charge,study and expez.zaentatton to make improve- which poses a problem for the fuze. ments. HYDROSTATIC fuzes are operated by the SAFETY AND AP.MING.Each fuze has a pressure variations in the ocean as causedby safety and arming (S&A) device to controlthe the passing of a 'ship or submarine. Toavoid detonation of the payload, so there will not be a prematurefiring by natural'mite action;premature detonation nor a dud. While this is pressure-firing mechanisMs aredesigned .soimportant MT' all weapons, it is especially so they: will not be affected by. midimotion ed.*,for nuclear warheads.Redundancy is used to water. Pressure- firing mechanismsare, seldomemanre arming at the proper instant and safety alone,,but are generally comb?? ed with otherat all other times.The safety device shown influencerfired devices, A hydroziatic ftize mayht firtre 9-10 is a physical barrier between Chapter 3COMPONENTS OFGUIDED MISSILES

SENSITIVE EXPLOSIVES INSENSITIVE EXPLOSIVES

.visor.wets,:ivvittisi ta,tikfrv' DETONATORa TARGET FUZE 4 b" AU ILIAI INITIATING FIRST SIGNAL EQUIPMENT BOOSTER

1. RADIO SIGNAL SMALL SENSITIVE BARRIER 2. RADAR WAVE AMPLIFIES CONTAINS MORE SENSITIVE EXPLOSIVE 3. ACOLJST:' '14PUL- BETWEEN DETONATION EXPLOSIVE EXPLOSIVE CAPABLE OF SES SENSITIVE WAVE COMPONENT INITIATING MATERIAL TO 4. ELECTROMAGNETIC AND TO ENERGY AMPLIFY CONVERTS HIGHER IMPULSES INSENSITIVE PLATEAU ELECTRICAL ORDER DETONATION EXPLOSIVES NECESSARY S. ELECTRONIC OR WAVE TO DETONATION TO TO IMPULSES MECHANICAL SUFFICIENT PREVENT DETONATE 6. PHOTOELECTRIC ENERGY MAGNITUDE TO INTERACTION 2ND SIGNALS INTO INITIATE EXCEPT BY BOOSTER 7. HYDROSTATIC EXPLOSIVE WARHEAD SIGNAL PRESSURES ENERGY ENERGY INITIATION RELEASE

144.18 Figure 3-10.Schematic oftypical explosive train withsafety device.

the sensitive and insensitivesegments of the explosive train. cases. This is too costly. Instead,redundancy This physical barrier is notis used in both safety andin arming devices to removed until armed statusis required. It isachieve a high reliability. usually of metal and actsas a fuze might. The purpose of this barrier is to preventdetonation FUZE POSITION INWARHEAD.In gen- of the large segments ofinsensitive explosive eral, fuzes may be classifiedas NOSE FUZES, if the fuze is unintentionallyactivated. located in the nose of thewarhead, or BASE FUZES, located at itssfter The safety devices includedin the S&A are end. The fuze or com- designed to prevent accidental bination of fuzes to be used, andtheir location activation. Thein the warhead, dependon the mission at hand purpose of the primary safetymechanism isand the effect desired. for safe fUnctioning of the missile;the secondary Proximity fuzes are safety device is mainly for always in the nose of the missile. the purpose of over- SIGNAL AMPLIFICATION.Thesignal re- coming countermeasures.This is becomingceived from the target increasingly complex. may need to be amplified to, be of sufficient strengthto be read by the Since the arming deviceis actuated by afuze. The type of amplifierused depends on the specific signal; such as the radarwaves from signals received by the targetdetection device a target, the countermeasuremay. supply a false (TDD), whether theyare infrared rays from the target signal. Bylaunchinga decoy, orby sometarget, radar waves, or audiosignals. other method the enemymay deceive the arming The fuze booster amplifies device. The safety devicemustprevent arming the detonation by the false signal. As meationedbefore, signal sent by the fuze. The amountof explosive this isin the fuze itself isvery small but very sensitive. a complex problem which requires.-ebnitaatThe fuze booster is study. A further complicationis the fact that larger and less sensitive' the S&A' device Cannotbe it multiplies the strength ofthe fuze signal and given a complete test,initiates the detonation in the .nextportion of the for to do No would destroythe .S&A in mostexplosive train. PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

urement from a distance."In actual TELEMETERING SYSTEMS telemetering practice, the measurements are done by various equipments in themissile while THE NEED FOR TELEMETERING it is in flight.These measurements are then is undertransmitted to a ground station byelectronic When any complex device or system during the flight and development, it must be given anexhaustive se- means and analyzed partly ries of tests which will revealits operatingpartly after theflight. This telemetering for itspermits the measurement and study ofmissile characteristics and serve as a basis point. tactical evaluation. With mostdevices and sys- component performance from a remote tems, conditions are such.that humanobservers canetudy these characteristics close athand and PHOTOGRAPHIC RECORDS measure numerous quantitieswhile the device operation. For example Photographic or other recordingsmade in or system is in actual considered telemeter- a new airplane isrepeatedlyflovm undervaryingthe missile itself are not conditions by a skilled test pilot.Each flighting, because there is nogreat distance between provides first hand information tothe pilot, asthe measuring and the recordinginstruments. well as information derived fromspecialized recording instruments carried inthe plane. One basic exception is visualmeasuring of the (sometimes referred to as external telemeter- Should the plane crash, with the loss than pilot and . recording equipment,the cause ofing) that is done at remote stations rather failure may never be determined. in the missile. An example is the use of cameras The problems encountered in missilede- (at the launch site or other points) which are velopment are greater than those metin airplaneused to photograph the missile's flight.One such flight- camera, the THEODOLITE camera,takes pic- development since the missile cannot be the same tested by a human pilot. Inmost cases amissiletures of the missile in flight, and, at is lost forever shortly afterlaunchingbeingtime, continuously records theazimuth and Surface of the elevation of the camera, as well asthe time at reduced to junk on striking the By using two or earth; or falling into the sea. which each frame is exposed. The test versions of Reguluswere designed more of these camerasand a triangulation for intact 'recovery after testflights, and re-process, a missile's range,bearing, altitude, second-by-and velocity can becomputed for any instant of cording. equipment to indicate the to show the second performance of missilecomponents could flight. This data can then be plotted be carried within the missile itself.But most missile's flight path. Other information,such as missiles are nonrecoverable. Telemeteringmissile flight attitude, control surface move- evalua- ments, target intercepts, and any breaking upof equipment is therefore essential to an also be ob- tion of component and systemperformance,the missile due to malfunction, can failure.tained from the pictures. Theinformation ob- and to indicate the cause of component of course As you know, guided missiles are subjectedtotained from visual recordings is, a series of rigid systemstests on the groundlimited by the quality of the camera(resolving during and after "their development.However, power, etc.), theweather, and the range of the the results obtained on the groundmay be verymissile. Although visual recording data is different 'from those obtained-froth amissile invery valuable inmissiledevelopment and flight flight. Temperatures; pressure's, andaccelera-testing, it is limited tooverall missile perform- tions encountered in flight maysignifiCantlyance and thereforecannot show the internal operation of the missile components. change the operation of the missile.:Electrcinic through a and other types of control systemequipment may An instrument panel observed react verY.differently under the stressof flighttelevision camera constitutes a form of tele- conditions than, they do on 'the ground: 'Formetering with a large number ofchannels, in these Treasons, certain Plight -testmethods havewhich quantitative information is madeimme- been developed to providegroUnd personnel diately available for observation andrecording. with an accurate basis for determiningin-tlight performance. RADIO TELEMETERING Theie flight-teating methods rely on a pro- Telemetering of data relating to the mis- ,- cesscalled.TELEMETERING, The word °telemeter° is of Greek originand means' ameas- sile's internal operation is accomplished by_the Chapter 3COMPONENTS OFGUIDE? MISSILES use of a radio link. Radiotelemetering has been A great deal of informationis needed dur- in use since the mid- thirties,especially foring the various stages ofa missile test or transmitting weather data gatheredby balloon-development program, supported instruments. This data on such subjects as is emitted tolaunching performance, flight data,and oper- remote stations by radio transmitters.The principal element of this kind of ation of the control and guidancesystems. equipment isData measured by the telemeteringsystems called RADIOSONDE, andis still one of theof guided missiles include (1) aerographer's most changes of atti- importantweather-tude in roll, pitch, andyaw; (2) flight data such predicting devices.Suspended from weatheras air speed and altitude; (3) missile accelera- balloons, radiosondes provideweather information by sampling the readings tion during launching or maneuvering;(4) am- of variousbient conditions of temperature,humidity, and meteorological instruments insequence.Re-pressure; (5) structural information suchas sistance values are caused tovary with humidity,vibration and strain;(6) control functions, temperature, etc. This variation inturn causessuch as operation of the control receiver, modulation of the transmittercarrier frequency. auto- A simple telemetering pilot operation, servo operation,displacements system might meas-of control surfaces, and operation ofthe homing ure only "yes-non information suchas whether or not the fuze is armed at or other target-seeking equipment;(7) pro- any given instant.pulsion information,including fuel flow and This type of system tellsan observer when an event has taken place. A usual thrust, temperatures andpressures in the method is torocket assembly; (8) ordnancefunctions such as change an audio modulation frequencyeach time an event takes place. fuze arming time* (9) upper-airresearch data, The frequency changesuch as sampling for cosmic radiation*radiation; (10) *gives evidence that .the transmitterwas working the both before and after each performance of the electric, hydraulic, pneu- successive event.matic systems; and (11) informationon the per- In such a transmitterno rigid demands areformance of the telemetering made on the stability of the audio equipment itself, frequency,including reference voltages forcalibration and or upon its waveform. time marks, to permit synchronizing Missile radio telemetering recordings systems (includ-as received by several different receiverslo- ing ground equipment)are usually designed tocated along the flight path. carry out the following majorprocesses: Many of these measurementsare inter- 1. Observation of missilefunctions. related. 2. Conversion of the measured Some of them requirea high order quantitiesof time resolution, especiallyas the speed of into electrical signals. themissile 3. Transmission of the signalsfrom the increases. For others, a few missile to a receiving station. samplings per second are adequate.A telemetering system must be capable of The receiving station performsthe following transmitting functions: large amounts of varied dataeach second. With so much information to behandled, a 1. Receives the transmittedsignals. multi-channel 2. Decodes the signals. systemisplainly indicated, because a single commutated channelwould not 3. Displays various data invisual form. give sufficient time resolution. 4. Records informationpermanently for fu- . ture use. The missile-borne telemeteringequipment must meet certain designspecifications which The requirement that thetelemetering sys-include: tem accurately transmita large amount of data in a short period of time has 1. Being sufficiently light .inweight so the resulted in theflight characteristics ,of themissile will not be development of very reliableradio telemeteringaffected. systems which employ MULTIPLEXING to pro- 2. Being rugged enough to withstandthe vide the necessary number ofdata channels..severe forces, pressures, and temperatures encountered during missile flight. TELEMETERING REQUIREMENTS . 3. Being small enough to permitease of installation. Guided missiles present theirown peculiar., 4. Being expendable. problems, caused by limited space, high launch- 5. Being reliable enough toensure that the ing acceleration, high speed, andthe varied andquantities being measured numerous measurements required. are faithfully transmitted to the receiving station.Because most PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS missiles are fired only once, the telemeteringalso result in a saving in the time required must be reliable or a sizable expenditure offor missile instrumentation. time and money will be wasted. Accuracy, sta- Missile telemetering systems in general bility, and simplicity are imperative. Becauseconsist of the components shown in figure 3-11. of these requirements, telemetering personnelThe END INSTRUMENTS located in the missile check their calibration work just prior tomeasure the desired quantities, andproduce launching. Launching subjects the missile-corresponding data signal voltages which are led borne telemetering equipment to severe con-to a bank of subcarrier oscillators. Here the ditions of acceleration, vibration, and some-data signals frequency-modulate the oscillators. times condensation. For example, a mis-The resulting signals are combined to produce a sile is launched at high altitude from a parentsingle complex signal which is then impressed plane, its parts may be cold. When the missileon a v-h-f carrier signal andtransmitted by the reaches a lower altitude, the condensationmissile telemetering antenna.At the remote that takes place may impair operation of thereceivingstation,the transmitted signal is telemetering equipment. received and eventually broken down into its The missile may roll, or it may be throwncomponents, permanently recorded,and into a climb or dive, and through all theseanalyzed. gyrations the telemetering equipment must continue to function. A directional antenna mayEnd Instruments cause thesignal to be lost entirely, long with valuable information, at a critical time; such an antenna requires a number of data- The end instruments are the sensing devices receiving stations to ensure continuous recep-which are carried in the missile to observe the tion.The pattern of the antenna on the missilecomponents on which information is to be tele- should be such that reception is not impaired m etered. by changes in missile attitude.The antenna End instruments that are common toall should be designed for minimum aerodynamicsystems fall into two classes: PICKOFFS and drag; with supersonic missiles, this require-TRANSDUCERS. (Transducers are sometimes ment is particularly important. Nose probesreferred to as pickups.) In telemetering par- or an insulated section of the missile nose arelance, the term"pickoff"is usually reserved sometimes used as radiating surfaces.In fordevices which collect data in electrical form some missiles, a part of the airframeitselfand relay that data in electrical form. is excited by a feedline and serves as a trans- The term "transducer" generally is re- mitting antenna. served for the devices that convert nonelectrical As in any system of measurement, the te-indicationsfor example, mechanical motionto lemetering system should neither impair thevoltages which can beused for telemetry trans- operation of the equipment it monitors, normission purposes. exert an undue influence on the quantities it (Because of the necessity for compact mis- measures.In small missiles, the distributionsile equipment, telemetering end instruments of telemetering instruments must be so ar- are very often built into the missile as integral ranged that the center of gravity remains un- parts of the overall system.) disturbed. The exercise head is the location of the major components of the missile telemetering equipment. When the exercise head's installed, COMPONENTS OF A connections are made to the missile components TELEMETERING SYSTEM that are to be tested. The most common type of telemetering sys- The nature of the telemetering installationtem Used for guided missiles is thef-m/f-m, is determined by the requirements of the par- or DOD (Department of Defense) system.Pulse ticular test, and the exact functions to be te-telemetering systems are also used to a limited lemetered for each flight must be car fully extent. chosen. For example, a small number of The f-m/f-m telemetering system usesthe functions may be studied with great precision, basic techniques of frequency modulation and can rather than a larger number of functions on abe used to transmit large quantities of missile time - sharing' basis.Such' a selection' might data very rapidly. Chapter 2COMPONENTS OFGUIDED MISSILES

ALTITUDE - SENSOR AND END INSTRUMENT

ACCELERATION SENSOR AND END INSTRUMENT ' SUSCARRIER OSCILLATOR

VHF TRANSMITTER

SUSCARRIER OSCILLATOR R4 TRANSMISSION LINE

VHF ANTENNA

MOW

TRANSDUCERUCER SURCARRIER OR PICKOFF . OSCILLATOR MISSILE ANTENNA END INSTRUMENTS SUICARRIER FREQUENCY OSCILLATOR MODULATED VHF TRANSMITTER

TRANSDUCER SUSCARRIER OR PICKOFF OSCLLATOR 11) IN THE MISSILE

RECEIVING STATION ANTENNA

DEMULTIPLEXER UNIT

SUSCARRIER DISCRIMINATOR DATA SUICARRIER VISUAL DISCRIMINATOR RECORDING EQUIPMENT SUSCARRIER (2) ON SHIPBOARD OR GROUND4STATION DISCRIMINATOR

33.209:.213 Figure 3-11. Basic telemetering system.A. Location of components in missile; B. Simple block diagram ofa 3.hhannelr- f-m/f-m telemetering system. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

Pulse telemetering systems operate on aing those intervals.This process is often re- time-sharing basis; that is; they transmit sepa- ferred to as TIME- DIVISION MULTIPLEXING. rate items of information one at a timeand in a Data transmitted from the missile may be regular sequence. The missile data suppliedbyobserved on instruments as the flight pro- all the channels are transmitted on the samegresses, and simultaneously recorded onfilm carrier wave; but each channel is sampled foror magnetic tape.Suitable decoding and com- comparatively short intervals of time and isputing equipment are used to facilitate the work permitted to modulate the transmitter only dur-of data reduction and analysis. CHAPTER 4

MISSILE PROPULSIONSYSTEMS

INTRODUCTION increasing efficiency of countermeasurestends to make all subsonic missiles obsolete. A brief history of the evolution Missiles of missileintended for use against high-speedenemy mis- propulsion systems was presented inchapter 1. siles and manned aircraft must becapable of Chapter 3 gavean overview of the types ofhigh speeds. propulsion used in present-day missiles, All air-to-air and surface-to-air and ofmissiles now operational fly at supersonicveloc- possible future developments. Thischapter willities and depend on some form of jet engine for present the principles of operationof the differ- propulsion. ent propulsion systems and theapplication of basic laws of science to them. Jet propulsion is a means of locomotion The differentbrought about by the momentum ofmatter types of propellants used and themethods of using them are discussed. Advantages expelled from the after end of the propelled and dis-vehicle. This momentum is gained by thecom- advantaged of each typeare recounted. Newbustion of either a solid ora liquid fuel. Com- combinations and experimentalpropellants are touched upon. pared to reciprocating engines, jet propulsion systems are simple in construction. Thebasic GENERAL components of a jet engine are a combustion chamber and an exhaust nozzle. Somesystems require accessory componentssuch as pumps, in- The propulsion system ofa missile is thejectors, turbines, diffusers entire system required to propelthe missile, and ignition systems. including the engine, accessories suchas pumps CLASSIFICATION OF and turbines, pressurization system,tankage and JET SYSTEMS all related equipment. -- Until the start of. World War II,the recip- Jet propulsion systems used in guidedmis- rocating engine-propeller: combinationwas con-siles may be divided into two types:ductedpro- sidered satisfactory for the propulsionof air-pulsion systems (also called atmosphericjets) craft. We have alread explained thespeedand rockets. limitations of propeller-driven craft. .As the Missiles using a ducted propulsion system speed of the propeller approachesthe speed ofare air -breathing missiles; they are incapable of sound, shock waves form and limitthe devel-operating in a vacuum.The missile takes in opment of thrust.This .condition requires thta quantity of air at its forward end, increases use of extremely large engines to productanyits momentum by heatingit, and produces further increase in speed.Research in the design of propellers thrust by permitting the heated airand fuel may make it possible tocombustion. products to expand throughan ex- overcome some of their limitations.But athaust nozzle. This process may be broken present, some form of_ jetpropulsion is re-down into the following steps: airis taken in 1 quired for high subsonic and supersonicspeeds:and compressed; liquid fuel is injectedinto GUided missiles must travel at highspeedsthe compressed air; the mixtureis burned; to lessen the probability of interceptionand de.f.t.and the resulting hot gases are expelled struction by enemy countermeasures. through Although'a nozzle.The air may be. compressed inany a few highLsubsonic missiles are stillopera-of several ways. tional for use against surface targets, In a turbojet engine, air is most ofcompressed by a rotary compressor, whichin those on hand are used for target,practice. Theturn is operated by a turbine locatedin the PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS path of the exhaust gases and mounted on the PRINCIPLES OF JET PROPULSION same shaft as the compressor.(A turboprop engine, now used in some manned aircraft but BASIC LAWS AND FORMULAS not in guided missiles, makes use of a propeller mounted at the forward end of the com- Before taking up propulsion systems, let us pressor turbine shaft.) In a pure ductsystem,review the way gases are affected by variations such as. the ramjet, air is compressed by thein pressure and temperature.Gases at high forward motion of the missile through it.Thetemperatures and pressures are used in the now obsolete pulsejet also depends onfor-main propulsion systems of missiles, aswell ward motion for compression. It differs from the as for driving various mechanismswithin many ramjet in that combustion is intermittent, rathermissiles.These gases may be in the form of high pressure air (or other inert gases) stored than continuous. in flasks, or in the form of fuel combustion Rockets do not depend on air intake forproducts. The use of stored compressed gas their operation, and are therefore capable ofhas been limited to small vernier rockets in traveling beyond the atmosphere.A rocketballistic missile reentry bodies, but flasks of engine carries with it all the materiels re-compressed gas are used to operate parts of quiredforitsoperation. These materialsmissiles, for launching Polaris, and fordud- usually consist of a fuel and an oxidizer. Thejettisoning some missiles. oxidizer is a substance capable of releasing alltheoxygen required for burning theAbsolute Pressure fuel. Figure 4-1 charts the types of jetpropulsion Although we live at the bottom of an ocean systems.Both types, rockets and atmosphericof air, we do not feel the pressure whichthe jets, receive their thrust as reaction to theatmosphere exerts on us because it is nearly exhaust of combustion gases. Jet engines fre-equal in all directions. quently are called reaction motors, since the In all problems involving the laws of gases, exhaust gases produce the action while thepressure should be figured inpounds per square opposite motion of the missile or aircraft rep-inchabsolute, which is the gauge pressure resents the reaction.Both types can be calledplus 14.7 psi at sea level. thermal jets because they are dependent on the action of heat.The reaction which propels theAbsolute Temperature jet engine occurs WITHIN the engine, and does not occur as a result of the exhaust gases The temperature of a gas can be measured pushing against the air. with respect to an absolute zero value.This

JIIT-ROPULUON POWIM PLANTSI

.r---1- IIICHAIIICAL JOTSII 1:111111111AL JOTS) L - I

33.12 Figure 4-1.Classification of missile jet powerplants. Chapter 4MISSILE PROPULSIONSYSTEMS value, which is usually expressedin terms of the and volume together. Thesame ratios of change centigrade scale, representsone of theof volume and pressurewere found tobe present fundamental constants of physics. Itwas estab-in all gases, and theywere found to be constant lished experimentally duringa series of testsover a wide range of temperatures. made in the study of the kinetictheory of gases. The first law of gases is Boyle's According to this view,a gas, like other law: forms of matter is composed of The volume of any drygas, the tem- molecules made perature remaining constant, variesin- up of combinations of atoms.Normally, the molecules of any substance versely with the pressureon it; that is, are in constant the greater the pressure, thesmaller motion.In the gaseous state, the motionsare assumed to be entirely random. the volume becomes. That is, the This is true only if the temperaturehas molecules move freely inany direction and are in constant collision, both remained the same. among themselves In general, when the pressure is keptcon- and with the walls of ihe container.The moving particles possess energy of stant, the volume of a gas is proportionalto its motion, or kineticabsolute temperature. This isknown as Charles' energy, the total of which is equivalentto thelaw: quantity of heat contained inthe gas.When All gases expand and contract to heatisadded;the total kinetic energy is the increased. When the gas is cooled, same extent under the same change of the thermal temperature, provided there isno change agitation is diminished and themolecular velocities are lowered. in pressure. Finally, since the volume ofa gas increases The molecules do not allhave the same velocity, but display as the temperature rises, it is reasonable to a wide range of individualexpect that if a confined sample ofgas were velocities. The temperature ofthe gas, according to the kinetic theory, heated, its pressure would increase.Experi- is determined by thements have shown that thepressure of any average energy of the molecular motions.Pres-gas kept at a constant volume increases for sure is accounted for by consideringit as resulting from the bombardment each degree centigrade risevery nearly 1/273 of the wallsof its pressure at 0° C. Becauseof this finding of the container by the rapidlyflying molecules. The particles are considered it is convenient to state thisrelationship in to have perfectterms ofabsolutetemperatures.For all elasticity, so that they reboundfrom the wallsgases atconstant volume, thepressure is with the same velocities withwhich they strikeproportional to the absolute temperature. them. The general gas equation In accordance with thekinetic theory, if the comes from a heat energy of a given combination of Boyle's law and Charles'law, gas sample could beand it is expressed by combining theirequations reduced progressively;a temperature wouldinto one. That is: be reached at which themotions of the molecules would cease entirely.'If known with PI VI P2 V2 accuracy, this temperature could thenbe taken as the absolute zero value. Itwas assumed from TI T2 the experiments that -273°Crepresents the theoretical absolutezero point at which allwhere P1. and Ti are the original molecular motion ceases, and pressure and no more heat re-temperature and P2 and T2 refer tothe new mains in the substance. Allgases are convertedpressure and temperature; and V1 refers to to the liquid state before thistemperature is reached. the original volume and V2refersto the new volume. In using this formula besure that Gas Laws pressure and temperature are in absolute units. In the experiments to All real gases depart somewhatfrom the determine absoluteBoyle-Charles law (idealgas law). pressure and absolutetemperature, the behavior Missile of gases under different designers must apply the laws, with thevariation pressures ande,tem-for the gas to be used, in theirdesign of the peratures revealed the lawsof 'gases.Any change in the temperature of Jet propulsion systems. The gasesare produced a gas causes aby the burning of the propellant (liquidor solid); corresponding change in thepressure, makhigit necessary to consider temperature, the missile design must channelthe gases to pressure,produce the most thrust availablefrom them. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

APPLICATION OF BASIC LAWS where v1 is the initial velocity of a mass, v2 TO MISSILE PROPULSION its final velocity, and t the time during which this change of velocity occurs. If we substitute The two moat common methods by which wethe above value of acceleration in the original produce thrust are by mechanical means (pumpsformula, F = Ma, we get or fans), and by thermal means(chemical reac- Mv- Mv tion). The squid is an example of the mechanical 2 1 jet found in nature. It draws water into its body F t and then by muscle contraction forces this water rearward through a small opening at an incr easedSince My is momentum, the above formula velocity, thus propelling itself forward. shows that the thrust produced by a jet engine In our study of guided missiles we areis equal to the rate of change of momentum of concerned with thermal jetsthose that operateits working fluid. We can write the above by reaction to the exhaust of combustion gases. formula as follows: With the help of some elementary mathematics, we will show how a jet-propulsion sys- F = m (v2 - v1) tem develops the thrust required to propel a guided missile. All jet-propulsion systems arewhere m represents MA, and is called the mass based on the principles expressed in Newton'srate of flow of the working fluid in slugs per second and third laws of motion, discussed in second. chapter 2.According to Newton's second law, In the original equation, F = Ma, we can the acceleration of a body acted on by an un-substitute the equivalent weight for mass, and balanced force is in the direction of the appliedget force, directly proportional to the magnitude of Wa the force, and inversely proportional to the F = mass of the body.This relation can be expressed as a formula: When we apply this formula to a jet propul- F = Ma sion system, F is the unbalanced force that accelerates the working fluid through the ex- or, force equals mass timesacceleration, withhaust nozzle, and a is the acceleration of the force expressed in pounds, acceleration in feetfluid in feet per second per second. In accord- per second per second, and mass inSLUGS. ance with Newton's third law ofmotion, the (A slug is a unit of mass; the mass of a body inforward thrust developed by the jet propulsion slugs is equal to its weight, in pounds, dividedsystem is equal and opposite to the unbalanced by the acceleration due to gravity in feet perforce applied to its working fluid. second per second.) The weight of any given Now, let W equal the total weight of working mass varies, depending on the force of gravity, fluidthatflows through a missile propulsion which varies with the distance from the earth'ssystem during the time the system is producing center.The relation between weight and mass thrust, and let t equal the total time during can be expressed in the formula: which the system develops thrust. ThenWA is the weight rate of flow of working fluid, in pounds per second.Letting w = WA, we can now write a formula for the thrustdeveloped by a jet propulsion system: w in which M is the mass in slugs, .W the weight T = (v- v) in pounds, and g the acceleration due to gravity 2 1 in feet per second per second (approximately 32.2 ft /sect at sea evel). where T is the thrust in pounds; w is the weight Acceleration is the rate of change of veloc-ratepof flow of the working fluid, in pounds per ity. This is expressed in the formula second; v1 is the initial (intake) velocity of the -vi workingAdd; v9 is the final (exhaust) velocity v2 of .the fluid; we g is the acceleration due to a = gravity.This equation gives the thrust applied Chapter 4MISSILE PROPULSIONSYSTEMS to expel the working fluid from the exhaustper hour. For example,assume that a missile nozzle of the engine.And, in accordance withtraveling at 3750 mph has Newton's third law of motion,the same equation 56,000 pounds of thrust. The above equation showsthat the also expresses the forwardthrust developedengine is developing 560,000 by the propulsion systemto propel the missile. horsepower: Figure 4-2 representsa jet engine which is taking in air at its 3750 x 56,000 forward end at a speed 375 = 560,000 hp of 1000 feet per second. The burning fuel within the engine heats theair and increases itsAlthough it is possible to speed to 2000 feetper second.If we assume calculate the horsepower developed by the propulsionsystem of that the working fluid flowsthrough the enginea missile in flight, the student at the rate of 64.4 poundsper second, application should remem- of the thrust formula ber that jet-propulsionengines are always shows that this engine israted in terms of pounds developing a thrust of 2000pounds. of thrust, rather than Note that the thrust developed in horsepower. by an engine A.rocket engine takes in is always expressed inpounds of force, not in no air from the terms of workor horsepower. A jet engineatmosphere; its working fluidconsists of the combustion gases resultingfrom burning fuel. that is fired in a teststand does not move. ItSince the rocket carries therefore does no work,and consequently de- its own supply of velops no horsepower, oxygen as well as its fuel supply,the initial although it may exert itsvelocity of the working fluid, maximum thrust.At a velocity of 375 miles relative to the missile, is zero.Thus, the formula for the per hour, one pound of thrustwill develop one thrust developed by horsepower. For a missile inactual flight, it is a rocket engine reduces to possible to calculate the horsepower developed EW by the propulsion system veV from the formula: T= e VT Horsepower =375 where w is the rate of fueland oxidizer consumption in poundsper second, and ve is the where V is the missile exhaust velocity of thegases.But the above velocity in milesperformula expresses only the hour, T is thrust inpounds, and 375 isa con thrust due to mo- stant having the dimensions mentum of theworking fluid.If the pres- of mile-poundssure of the working fluid, afterit leaves the

--,...."I = COMBUSTION AIR .. CHAMBER -. EXHAUST; EXHAUST NOZZLE ' GAS If:INJECTORS

FUEL Via 1000 FT/SEC 1 Ws84.4 LB/SEC V232000 FT/SEC THRUST at ) 84.1 LB/SEC THRUST"32.2 FT /3E0(2000 FT/SEC-1000 FT/SEC) THRUST32000 LBS.

144.19 Figure 4-2.Developmentof thrust in a propulsionsystem as an example of Newton's second and thirdlaws of motion. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS exhaust nozzle, is greater than the pressuretakes place. Combustion is necessary toprovide outside the missile, the actual thrust is lessthrust.Useful thrust cannot be attained in an than that given by the above formula.It isatmospheric jet unless the combustionproducts obvious that if the gases that have left theare exhausted at avelocity greater than that of missile are at a higher pressure than the sur-the intake gases. rounding atmosphere or space, these gases In all thermal jets, the heat energyreleased are capable of doing work.That work, whichby the combustion process is convertedto kinetic might have been used to propel the missile,energy through expansion of the gasesof combus- will be wasted. A more accurate formula fortion as they pass through the exhaustnozzle. rocket thrust is: The chamber is usually a cylinder, although it may sometimes be a sphere. Itslength and T=v +(Pa - Pe) Ae diameter must be such as to produce a chamber g e volume most suitable for complete andstable combustion. The chamber length and thenozzle in which Pa is the pressure of the surroundingexit diameter are determined by thepropellants atmosphere (or space), Pe is the pressure ofto be used. Both mustbe designed toproduce the the exhaust jet, and A. is the cross-sectionaloptimum gas velocity and pressure atthenozzle area of the exhaustjet.If the exhaust nozzleexit. can be so designed that it decreasesthe pressure of the exhaust jet to that of thesurround-EXHAUST NOZZLE ing space,the pressure term in the above equation becomes zero. This condition repre- An exhaust nozzle is a nonuniformchamber sents the maximum thrust available for anythrough which the gases generated in the com- given propellant and chamber pressure.Al-bustion chamber flow to the outside. Itsmost though this condition cannot be fully attainedimportant areas are the mouth, throat, andexit, in actual practice, well-designed nozzles makeidentified in figure 4-3. The function ofthe noz- it possible to approach it closely. zle is to increase the velocity of the gases.The It is a common misconception that jet en-principle involved was announced many years gines operated by pushing against the surround-ago by a Swiss physicist,Daniel Bernoulli. Ber- ing air.Ducted jets depend on air as a work-noulli's principle applies to any fluid(gas or ing fluid,but they do not need air for theliquid). It may be stated as follows:"Pro- exhaust to push against.Rockets require novided the weight rate of flow of afluid is air.Air acts only to impede the motion of aconstant, the speed of the fluid willincrease 'rocket, first by drag, and secondby hinderingwhere there is convergence in the line.It will the high-speed ejection of the exhaust gases.decrease where there is a divergencein the Thus rockets operate more efficiently in aline."Figure 4-4 illustrates this principle. total vacuum than they do in the atmosphere.The velocity of the fluid will increaseat point #1. At the point of divergence, point#2, the COMPONENTS OF JET PROPULSION speed of the fluid will decrease. The increase SYSTEMS in speed between points #1 and #2 iscaused by a conversion of potential energy(fluid pressure) To achieve high thrust, it is necessary to produce large quantities of exhaust gases at high temperatures and pressures. To produce these exhaust gases, jet propulsion systems consist THROAT of a combustion chamber, an exhaust nozzle, and a fuel supply. Liquid -fuel systems require additional parts,such as injectors, pumps, and ignition systems. Air breathing engines require diffusers at the air intake. .9 COMBUSTION CHAMBER The combustion chamber is that part of the 33.13 system in which the chemical action(combustion) Figure 4-3.Location of nozzle areas. Chapter 4-11113SII:EPROPULSION SYSTEMS to kineticenergy. Thus the pressure drop of the fluid through therestriction is proportional to the velocity gained.When the fluid reaches point #2, the kineticenergy is again converted to potentialenergy. At point #2, the fluid velocity decreases, and thepressure of the fluid increases. VELOCITY INCREASES This relationship holds truefor subsonic flow GASES AT SUBSONIC NEVER EXCEEDING of gases. In the convergentnozzle in figure 4-5 A VELOCITY SPEED OP SOUND AT A, the speed willincrease up to the speed of EXIT sound, depending on the degreeof convergence. Such nozzles are often usedon subsonic turbojets.It has been found that,with a nozzle of this type, if the internalpressure of the combustion Chamber ismore than about 1.7 times the external presSure,an excess pressure re- SUBSONIC GAS mains in the gases after theyleave the nozzle. VELOCITY DECREASES This excesspressure represents wastedenergy. The performance ofcombustion systems using this type of nozzle is thereforelimited. SUPERSONIC GAS In the divergent nozzlein figure 4 -5B, VELOCITY INCREASES gases at subsonic speeds will slowdown, depending on the degree of divergence. Gases at supersonic(faster than sound) speed behave differently. Asthese gases pass through the divergent nozzle,their velocity is INCREASED because of their high state. of CONVERGENT DIVERGENT SECTION compression. The drop inpressure at the point THROAT SECTION of divergence causesan instantaneous release of kinetic energy, whichimparts, additional speed to the gases. To obtainsupersonic exhaust velocity, the DeLaval nozzle,figure 4-5C, is commonly used.This nozzle firstconverges to bring the subsonic flowup to the speed of "1.'"""14 REGION OP sound. SUBSONIC:: REGIONFOLFOWSUPERSONIC Then the nozzle diverges,allowing PLOW the gases to expand and producesupersonic flow. The Prandtl nozzle (fig. 4-5D)is more ef- SONIC VELOCITY ficient than the straight-conedDeLaval nozzle but is more difficult toengineer and produce. It increases the .rateof flow at a higher rate

MOUTH THROAT

EXIT

33.15 RESTRICTION Figure 4-5.Gas flow throughnozzles: A. Sub- sonic flow through a convergentnozzle; B. Flow 33.14 through a divergent nozzle; Figure 4-4.Fluid flowthrough a restriction. C. Convergent- divergent nozzle (DeLaval);D.Prandtlnozzle. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS than the normal convergent-divergenttype. With regard to their physicalstate, pro- The shape of the nozzle determines thecha.-pellants may be either solids, liquids, gases, or acteristic of gas flow, which must be smooth.various combinations of these. However, gases Other nozzles ofincreasing importance nreai e rarely used as missilepropellants, for two the adjustable area type in which the nozzle areareasons. First, liquids or solidshave a higher environ-density than most gases, even when thelatter are is varied to suit varying combustion of mental conditions. highty compressed; thus a larger quantity The best size for the nozzle throat is dif-solid or liquid propellant can be carriedin a ferent for different propellants. In each case,given space.Socond, a greater energy trans- the best size has to be determined byexperi-fc,pmation ,results when a substance goesfrom ment and calculation.The nozzle must besad or liquid to gas than results when a gas designed for a specific set of propellant andis merely accelerated to a highervelocity. combustion characteristics to obtain higher velocity and increased thrust.The area ofRating or Comparing Propellants the throat section is determined by theweight rate of flow.The area at the exit of the di- Several means have been worked out for vergent cone is determined by the desiredratiorating,or comparing, various rocketfuels of expansion of the gases between throatand(propellants).Comparison is made by determining total impulse.Total impulse is the exit. product of the thrust in painds timesburning FUEL SUPPLY time in seconds. Or, The fuels and oxidizers used to power a jet engine are called propellants. The chemical IT (Total Impulse in lb-sec)= reaction between fuel and oxidizer in the com- T (Thrust in lbs) x t (Duration insecs). bustion chamber of a jet engine produces large quantities of high-pressure high-temperature Solid propellants are rated, or compared, gases. When these gases arechanneledthroughon the basis of SPECIFICIMPULSE, the amount an exhaust nozzle, a largepart of the heatof impulse produced by one poundof the pro. energy they contain is convertedinto kineticpellant. energy to propel the missile.When you read In pound-seconds per pound, this isequal of an engine that can travel faster than a gunto the total impulse divided by theweight of projectile, operate in a vacuum, deliver athe propellant. Stated as a formula,it is: great deal more energy than a reciprocating engine, and do so with a fewor no moving parts, I(Specific Impulse in lb- sec /lb) you may get the idea that some verycomplex chemical mixture is used as the propellant. IT (Total Impulse in lb-sec) This is not so.Jet-propulsion engines can W (Weight of Solid Fuel in lbs) operate on such fuels as kerosene,gasoline, alcohol, gunpowder, and coal dust. However, in the search for an ideal propel- A common method of comparing liquid pro- lant, many complex fuels have been tried.Apellants is on the basis of specific thrust. mere listing takes up a whole pagein the en-Specific thrust is equivalent to specific impulse cyclopedia. The search goes on for more power-for solid propellants but is derived in aslightly ful propellants, particularly for boosting.spacedifferent way. Specific thrust is defined asthe vehicles. For example, liquid hydrogen(whichthrust in pounds divided by the weightrate of becomes liquid at 423° F below zero or-252° C flow of fuel in pounds per second. Or, When mixed with liquid oxygen in a rocket engine, produces about 35.percent more thrust Tap (Specific Thrust in lbs/lb/sec ) = than the kerosene type fuels now used. It will be used to propel Centaur and other un- T (Thrust in lbs) manned earth orbital and interplanetary flights W (Weight Rate of Flow in lb. persec) as well as upper-stagerockets now being developed for manned lunar landings. rine is being. studied as an oxidizerto help Specific thrust is frequently expressed in produce more thrust. seconds.

80 Chapter 4MISSILE PROPULSION SYSTEMS

Specific propellant consumption is the re-asphalt-potassium perchlorates,black powder ciprocal of specific thrust; itis the rate ofwith ammonium nitrate,and other recently propellant flow, in poundsper second, requireddeveloped combinations. to produce one pound of thrust. Or, Perfluoro-type propellants, and aluminum or magnesiummetal components combined with an oxidant Specific Propellant Consumption have given = higher specific impulse than othercombinations. The finished product takes the Weight Rate of Flow (lbs/sec) shape of a grain, or stick.A charge may be madeup of one Thrust (lbs) or more grains.Combustion of solid propellants will be discussed later in thischapter. Other terms you should knoware mixture An ideal solid propellant would: ratio and exhaust velocity. 1. Have a high specific impulse. Mixture ratio designates the ralativequan- 2. Be easy to manufacture fromavailable tities of oxidizer and fuel used in thepropellant raw materials. combination.It is numerically equal to the 3. Be safe and easy to handle. weight of oxidizer flow divided byweight of 4. Be easily stored. fuelflow. Exhaust velocity is determined 5. Be resistant to shock andtemperature theoretically on the basis of theenergy content changes. of the propellant combination.The actual ve- 6. Ignite and burn evenly. locity of the exhaust gases is ofcourse less than 7. Be non-water-absorbent (nonhygro- this theoretical value sinceno jet engine can scopic ). completely convert the energy contentof the 8. Be smokeless and flashiest!. propellant into exhaust velocity.Thus, effec- 9. Have an indefinite service live. tive exhaust velocity is sometimes usedand is It is doubtful if a single propellanthaving determined on the basis of thrust andpropellantall of these qualities willever be developed. flow: Some of these characteristicsare obtained at the expense of others, dependingon the per- Effective Exhaust Velocity= formance desired. Thrust (lbs) Liquid. Propellants Mass Rate of Flow (lbs/sec) The liquid propellantsare classified as Solid Propellants monopropellants or as bipropellants. Monopropellants are those whichcontain within themselves both the fuel and oxidizerand Solid propellants are of two types.One are capable of combustion as they exist. Bi- of these consists of a fuel, suchas .a hydro- carbon propellants are those in which thefuel and mixed with a chemical capable ofoxidizer are kept physically separateduntil they releasinglarge quantities of oxygen (a chlorateare injected into the combustion chamber. An or a nitrate).A second type consists ofaexample of a monopropellant compound, would be the nitrocellulose, for example, that mixture of hydrogen peroxide and ethylalcohol; releases large quantities ofgases andheat whenan example of a bipropellant would be liquid it decomposes. When mixed withadditives (inoxygen and kerosene. small quantity as stabilizers), this type is called When oxygen or an oxygen-rich chemicalis a double-base propellant.It is used most forused as an oxidizer, the best liquid fuels small rockets. appear to be those rich in both carbonand hydrogen. Of course it is possible to combine thetwo In addition to the fuel and oxidizera liquid types in a single propellant mixturecalled apropellant may also contain a catalyst toincrease composite propellant.This is the type mostthe speed of the reaction. A catalyst used for missile propellants. is a substance used to promote a chemicalreaction The ingredlapts of a solid propellant..arebetween two or more other substances. mixed so as tr produce a solid of specified chemical and physical characteristics. Inert additives which do not take partin the Somechemical reaction are sometimes combinedwith examples of materials used in making solidliquid fuels.An example is water, which is propellanuare asphalt-oils,nitroglycerin,often added when alcohol is usedas a fuel. 77 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

chemicalthe missile and cause erraticbehavior. Some Although it does not take part in the if reaction,the water does provide additionalliquid propellants will react spontaneously particles which contribute to a higherthrustsubjected to pressures above their limit.Solid throughpropellants also have pressure limits butthey by increasing the rate of mass flow liquid propellants. the system. are much higher than for Most liquid-fuel rockets use the bipropellant type liquid fuel, as itis less likely toSPECIAL PARTS react to shock and heat than monopropellants. When separated, as they are beforeentrance In addition to the combustion chamber, into the combustion chamber, the.fuel andexhaust nozzle, and fuel supply, which all re- oxidizer are generally incapable of chemicalaction type engines must have, liquid-fuel en- reaction. Bipropellants which ignite spontane-gines also use injectors and igniters,and nusly upon contact with eachother are calledair-breathing missiles must have a diffuser or hypergolic. An exampleis Diinazina (un-intake duct, where the high-speed air is con- symmetrical dimethylhydrazine (UDMII)), orverted into low-speed, high-pressure, gasfor Aerozine 50, .used in Titan II and III with nitro-entry into thecombustionichaitier-lai an oxi- gen tetroxide as oxiditer.Those which re-dizing element. quire the addition of energy(electric spark, igniter, or: other) to cause chemical reactionInjectors are said to be diergolic.Thixotropic propellants are jellied substances with metallic The injector is similar in function tothe anbstanc ea (alumininn) suspended in them, whichcatVthietor in a reciprocating engine. It vapor- greatly increases the propellant densityandizes and mixes the fuel and oxidizerin the the specific impulse of the liquid engine.Thereproper: proportions for efficient burning. are a large number of liquidfuels but there Figure . 4-6 shows schematic sketches of are few knownpractical oxidizers. Some highlythree types of injectors.In the multiple-hole effective oxidants are too dangerous' to storeimpingement type (fig. 4-6A), oxidizer and fuel arrangement of separate and handle,. are injected through an While solid propellants are stored withinholes in such a way that the jet-like streams the coMbustion chamber, liquid propellantsareintersect each other at some predetermined stored in tanks and injected. into the combustionpoint; where the fuel and oxidizer mixand chamber 'In. general, liquid propellants providebreak up into vapor-like droplets.A spray .barning,41Me: than solid propellante.injector (fig. 4-6B) has oxidizer and fuel holes a longer arranged in circles, so as to produce conical They -have . a, further adTantage inihat combustion din. be easily stOPped and started at willor cylindrical spray patternsthat intersect by contiollinithe: proPellant flow. within the chamber. The nonimpinging injector, An ideal liquid propellantwould: shown in the lower sketch in figure 4-6, is 'one' 1. Be easy to Manufacture fromavailablein which' the oxidizer and fuel do' not impingeat raw materials: any specific, Point, but aremixed by the tur- 2. Yield a high..heat,of conibUstion perunitbulence- within the chamber weight of miXture...- 3. Have a 'low freezing Ignition Systems 4. Haye a high '.specific gravity. S. lovi:,.tintiCitt! and :corrosive effects, Unless- the fuel and oxidizer form a com- S, Have stability in, storage. bination that ignites spontaneously; aseparate 7. 'Have_.low, molecular weight of thereactionignition must be, provided to initiate the reaction. The igniter must be locatedwithin we a low vapors pressure. the pimbUstion chanibei (fig. 4-2) at a point it is where it. Will receive satisfaCtory starting the solid If either fuel or can.be .9-41;t., mixture that ignites readily. e. oxidizer accumulates excessively in the chamber of;liquid propellants ..hefOre tionAegine,: animCentrolled explosion some s)iiiefile;.ignition 113 br ought ts'rof 'some 00ratir.re the PlUC(f similar to thOse e,-,03UtET2, of `gravity1 used`.:in'reciprocating:engines.An electric

ggeek:sn,.goa'b. Chapter 4MISSILE PROPULSIONSYSTEMS

igniter squib type is shownin figure 4-7. A powder-charge ignition system (fig.4-7)is often used for solid-fuel rockets.It consists ofa powder squib whichcan be ignited electrically from a safe distance; itburns for a short time, with a flame hot enoughto ignite the main propellant charge. A catalyticignition system uses a solid orliquid catalytic agent that brings about chemicaldecomposition of the propellant. OXIDIZER F Diffusers A The purpose of the airintake and diffusion system is to decelerate the CONVERGENT CONE velocity of the air OXIDIZER from its free streamspeed (fig. 4-2) to the DIVERGENT-CONE desired speed at the entranceof the combustion chamber with a minimum ofpressure loss. As mentioned above, only air-breathingengines need diffusers:Diffusers are of two general types: subsonic, and FUEL supersonic. Diffusersare illustrated in the sectionon ramjet engines.

CHAMBER WALL OXIDIZER ELECTRIC IGNITER SQUIB ' PROPELLANT PROTECTIVE DIAPHRAGM

.FILAMENT OR PLATINUM WIRE BRIDGE

IGNITES BLACK PONDER, BLACK p,OWDER IGNITER

144.21 .Types of igniterd:A. Electric ter squib type; B. Blackpowder Charge PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

SUBSONIC DIFFUSERS.Subsonic diffusers ATMOSPHERIC JETS may be internal compressiondiffusers or external compressiondiffusers..Although theGENERAL principles are known, no completely successful external compression diffuser has beende- Any jet-propelled system that obtains oxygen support veloped.Velocity decrease at a point externalfrom the surrounding atmosphere to to the air inlet would permit simplificationofthe combustion of its fuel is an atmospheric the .air diffuser design. jet engine.Pulsejets, ramjets, turbojets, and An internal compression diffuser is aductturboprops are all of thistype, although the located at the forward end of the engine betweenlatter are not used in guided missiles. Ob- the air intake and the injector. Between these . viously, the operation of these engines is two points, the diameter of the duct increaseslimited by the amount of oxygen available, and (fig. 4-11A), and as.a result, the velocity of thethey can operate only at altitudes where the air decreases and the pressure increases.Ifoxygen content of the air is adequate.The the pressure change is to be kept small, theupper limit of operation depends onthe type of diffuser length must be increased. Too greatdesign of thearticular engine. a length could result in pressurelosses due to The first successful application of atmos- skin friction, so a compromise value usuallypheric jets to missile propulsion was the has to be used. pulsejet engine used in the German V -1 missile. SUPERSONIC DIFFUSERS.At supersonicPULSEJET speeds the intake air must be reduced to subsonic speed with a minimum loss of pressure.A PUlsejet engines are so called because of problem of diffusion at supersonic speedslathethe intermittent or pulsating combustion proc- production of shock waves at the inlet. Super-ess. Although pulsejet engines wereusedby the sonic diffusers may be clasiffiedas:(1) NormalU.S. Navy to propel an early missile, they are shock (fig. 4-1IB); (2) converging-diverging;now considered obsolete, and wewillgiventhem and (3) conical or "spike" diffusers, alsoonly brief treatment here, to explain the princi- called "center body" diffuser (fig. 4-11C). Inples of their operation. a normal shock diffuser adiverging duct is Figure 4-8 illustrates the fundamental con- used, which reduces thediffusionprocess totwostruction of the pulsejet. The principal parts of steps.The normal shock wave at the inputa pulsejet are the diffuser, grillassembly (con- section reduces the velocity to approximately thetaining air valves, airinjectors, add fuel inspeed of sound; then the air is diffusedto jectors), the combustion chamber, and the tail subsonic speeds in the diverging duct. pipe (exhaust nozzle). The DIFFUSER is aduct . . of varying cross section at the forwardend of The converging-diverging diffuSer principlethe engine, between the air intake and the grill. is similar to that of the EieLaval nozzle(fig. Between these two points the diameter increases; 4 - 5C ) except that the process is in reverse,as a result, the velocity of airentering the also in two steps.While the supersonic airdiffuser decreases and its pressure increases. stream is passhigthrough the converging portion The grill assembly carries the fuel injectors of the thict, its velocity is deoreasedto the speedinjectors for starting air, and the-.air-intake of sound (Bernoulli's theoreni). Its velocity is'snappers' valves. The latter are spring loaded, further .decreased, to the . desired velocity,and are normally closed, so as tocompletely while it is passing through the'diifergent portionblock off the diffuser from the combustion cham- ollthe diffuser. ber.Air and -' fuel :Aired in the combustion In the "center...,body":':ciiifiiserAfig. 4-IIC),chamber are, ignited initially by a spark plug; a conical nose spike,Lis ',PlaCed"- inside.thethereafter,lhe mixture is ignited spontaneously. diffuser',apieMblY.' i';Whenjthe supersonic flowThe tailpipe is of uniform' cross section and, for of air approachesthe":cone;-...a.,,cohical shock a given engine diameter, has a specificoptimum wave is formedand:the,Supersonic flOiv thrOugh length. this shock Held &Owedto.Subsonic.: velocity. The Aiffuiion. 'is _completed in theSubsonic Operating Cycle portion the diffuter: Thiel-tYpe of :.diffnier . is usedipn.':':,rinijeta':#8,4eling., it As the engine Moves through the air, ram-air Mach 2:or greater:', pressure builda up in the diffuser.When this pressure exceeds that of the combustionchamber and the valve spring, than that of the inlet air. Theresultingpressure the valves open anddifferential createsa thrust in the direction of air enters the combustionchamber. Fuel isflight. then injected, and the air-fuelmixture is ignited by a spark plug. The fuel and Because of the speed withwhich the com- air pass throughbustion gases rush down thetailpipe, they over- venturis (fig. 4-8), which atomizethe fuel andexpand and produce mix it thoroughly withthe air, so it ignites a partial vacuum within the readily. combustion chamber. Therain pressure in the diffuser then exceeds thepressure in the cham- The burning fuel rapidlyproduces combus-ber; the flapper valvesopen (fig. 4-9B), and a tion gases that createa pressure of 25 to 35fresh supply of air enters thechamber. Because psi in the combustion chamber.The spring-of the decrease inpressure, the pressurized loaded air intake valves (fig. 4-9)in the grillfuel system is able to injecta fresh supply of assembly prevent thesegases from escapingfuel.As a result of the partialvacuum, a por- forward. tion of the hot exhaustgas is drawn back into the chamber; the temperature of As the pressure in thecombustion chamber this gas is high rises, it exceeds the enough to ignite the air-fuelmixture, and a new pressure in the fuel sys-cycle begins. Note that thespark plug ignition tem, Ind automatically shutsoff the flow of fuel:*is required only to start the The flaming gases rushdown the tailpipe and engine; after starting,its combustion cycle isself-sustaining exhaust to the atmosphere ata speed greater(similar to a diesel engine).

Figure 4-8.Cross sectionof a pulsejet engine.

CLOSED

COMBUSTION CHAMBER ' PRESSURE

-4-9.Air -intake Valve usedin pulsejet-engine cross- sectional view: A. ppen;14.B: PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

The frequency of the combustion cycle lathefuel and oil systems, and for the front engine resonant frequency of the combustion chamberbalancing support. and tailpipe. A formula for resonant frequency The primary function of the compressor of a closed pipe is: sectionis to receive and compress large masses of air, and to distribute this airto the Velocity of sound combustion chambers.The centrifugal com- Frequency= 4 x length pressor consists of a stator, oftenreferred to as a diffuser vane assembly, and arotor or The frequency of variouspulsejet' enginesimpeller (see fig. 4-10A). The rotor consists that have been used in the past ranges fromof a series of blades which extendradially from about 50 to over 200 cycles per second. It wasthe axis of rotation. As the rotor revolves, this intermittent cycle which gave the nameair is drawn in, whirled around by the blades, "buzz bomb" to the German V-1 rocket. and ejected by centrifugal force at high velocity. The stator consists of diffuser vanes that Limitations of Pulsejets compress the air and direct it into thevarious firing chambers: Air leaves the impeller One of the disadvantages of pulsejets is that,wheel at high velocity.As it passes through at the instant of launching, there is no ramthe diffuser vanes it enters a larger space; its pressure in the diffuser. For that reason,mostvelocity therefore decreases, and its pressure pulsejets are incapable of developing enoughincreases. static thrust to take off under their own power. The axial compressor is similar to a pro- They are therefore launched with the help ofpeller. The rotor consists of a series of compressed air injected into the chamber alongblades set at an angle, extending radially from with the fuel, or from a catapult, or with boosterthe central axis.As the rotor of the axial rockets, or by a combination of these means.compressor turns, the bladesimpart energy The speed of a pulsejet is limited to the lowof motion in both a tangential and axial direc- subsonic range because at higher speeds the ramtion to the ram air entering through the front pressure developed in the diffuser exceedstheof the engine.The stator does not rotate. Its chamber pressure at all times throughout theblades are set at an angle so as to turn the air combustion cycle; the flapper valves thereforethrown off the trailing edge of the first-stage cannot close, and the cycle cannot maintain it-rotor blades, and redirect it into the path of self. Also, this type of engine has slow efficiencythe second- stage, rotor blades. One rotor and index because its fuel consumption rate is high.one stator comprise a single-stage compressor. A number of rotors andstators assem- TURBOJETS bled alternately make up a multistage compressor, as in figure 4-10. A turbojet engine is an air - dependent thermal In a multistage compressor, air from the jet-propulsion device. It derives its name fromfirst row of compressor blades is accelerated the fact. that its compressor is driven by a tur-and forced into a smaller space.The added bine wheel, which is itself driven by the exhaustvelocity gives the air greater impact force. gases. Turbojets may be divided into twotypes,This compresses the air into a smaller space, depending. on the type of compressor.Thesecausing its density to increase. The increase are centrifugal-flow turbojets(fig. 4-10A) andin density results in a corresponding increase axial-flow turbojets (fig. 4-10B). Both typesin static pressure.This cycle of events is are the sane in.operating principles. repeated in each successive stage of the compressor. Therefore, by increasing thenumber ComponentO of Turbojets of stages, the final pressure can be increased to almost: desired value. The axial -flow turbojet is longer than the .The major components of bothtypes of turbojets are an accessory section Compressor sec-centrifugal, flow type, but has a smaller frontal tion, combustion section, and exhaust settion..area, - and therefore is more streamlined. The The.acceesory section serves as a mountingcentrifugal compressor is simpler than the axial pad lor accessories,. includingthe generator',and has a higher pressure ratio per stage. The hydraulic .. pumpstarter,:. and: tachometer, foraxial-flow compressor, however, has a higher various. engine components, .. Such as units' of theper stage efficiency. Chapter 4MISSILE PROPULSIONSYSTEMS

burners are convergentto increase the velocity of the gases just beforethey pass through the FUEL nozzle diaphragm. SPARK PLUG The flame crossover tube AIR connects one chamber IN to the next, allowing ig- common atAillifil nition to occur in all chambersafter the two TAIL CONE chambers containingsparkplugs have fired. The exhaust sectionconsists primarily of .0.P OP a 101.1%:P 1 ' SO nozzle and an inner Plr sX'....: ....' ..;;...... cone.This assembly 'I.'.'.1=-PMiEr.h.lipmoma. ....'''''''''' P'', ."4 Ir-,.,..,,., . 0 straightens out the turbulentflow of the ex- ), haust gases caused byrotation of the turbine (/ ' \ r. wheel, and conveys these gases to the.nozzle outlet in a more perfect andconcentrated gas- flow pattern. The exhaust-nozzlediaphragm is composed AO:ESSORY COMPNESSOI COMBUSTION EXHAUST of a large number ofcurved blades standing A perpendicular to the flow ofcombustion gases and arranged ina circle in front of the turbine wheel. By acting as . both a restrictor anda director,this diaphragm increasesthe gas velocity.Its primary function is tochange the direction of the gasesso that they strike the turbine-wheel vanes at,or nearly at, a 90° angle. The impact of thehigh-velocity gases FUEL against the buckets of theturbine wheel causes If the wheel 'to rotate. COMMOTION GNAWER The turbine-wheel shaft is coupled to the compressor-rotorassembly COMBUSTION shaft.Thus, part of the =13°- "If cc.APRusic21 , EXHAUST energy of the exhaust gases is transformed and transmittedthrough El the. shaft to operate the compressor and the engine-driven accessories. 12.28A Figure 4-10.Cross-sectionalviews of turbojets: A. Centrifugal; B.Axial -flow turbojet. Operating Cycle The combustion section includes combustion The operation ofa turbojet may be sum- chambers, .spark plugs,a nozzlidiaplumgm, andmarized as follows: a turbine wheel and shaft. Thecombustion cham- The rotor unit of the bers, or burners, inboth types of turbojetcompressor is brought up to maximumallow- engines, have the same function able speed by the starterunit, which is geared and prodUce theto the compressor shaftfor, starting. same results. They differ in sizeand number, Air is depending on the type of drawn in from the outside,compressed, and engine. Each combus-directed to the combustionchambers. Fuel is tion chamber has the followingparts: outer com-injected through the fuel bustion chamber, innerliner, inner liner dome, manifold under pressure, and mixes with the air inthe combustion flame crossover tube, andfuel-injector nozzle.chambers. The outer combUstionchamber retains the Ignition occurs first in thecham- air BO that a high-pressure.supply bers containing the sparkplugs, and then in is availablethe other 'chambersan instant later by way of to the inner liner atall likes.This air alsothe .flime 'crossover serves as a. cooler . jacket., The inner liner tubes.High-pressure houses the,,niea in which combustion. and coolant air pass through fuel and air, arethe exhaust ',Iiozzle diaphragmand strike the mixed .and burned. Many roundholes in theturbine blade is inner liner allow the airto enter and mix with at the most effectiveangle. the fuel indhigh-temperiiturecombiationgaseet_i,Part of. the energy of the exhaust stream is The forward endof- the inner liner iialloivedabsorbed bY the turbfine,resulting in a high to slide over the dome rotational 'speed.The remainderis thrust. to aCcOmmodate expan-The tUrldne.wheel transmits sion, contraction. . energy through The after.end-of thethe coupled turbineand cOmpressor-rOtorithafts PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS to operate the compressor. Once started, com-In addition, the turbojet is capable ofproviding bustion is continuous. sufficient static thrust to permit an aircraft or The afterburner is an important part of jetmissile to take off under its own power.The fighter aircraft, but has limited application indisadvantages of turbojets (compared with other guided missile propulsion. It was developed totypes of jet engines) include the following: give additional thrust when needed forshort 1. They are large and bulky in comparison periods of time, as in launching or during ato other types of jet engines. steep programmed climb. 2. They are delicate and complex mechan- The additional thrust is obtained by burningisms with many moving parts. additional fuel in the tailpipe section.That 3. Their maximum speed is in the low super- portion of the air which served only as asonic range. . coolant for the main combustion chambers is sufficient to support combustion of the addi-RAMJET tional fuel.The added thrust is large, but the. overall efficiency of the turbojet decreases A ramjet engine derives its name from the because the specific fuel consumption is greatlyram action that makes itsoperation possible. increased. During a missile launching, an(This engine is sometimes referred to as the afterburner could provide approximately30%athodyd, meaning aerothermodynamicduct.)' It increase in thrust; when the missile reaches ais the,:aiMplest of the air-breathingpropulsion speed of 600 mph, an afterburner can increaseengines, anthem no mowing parts. its thrust by from 70% to 120%. Ramjet operation is limited to altitudes below The thrust augmentation by afterburningabout 90,000 feet because atmospheric oxygen increases substantially with increase in flightis necessary for combustion. The velocitythat speed.At about Mach 2 speed, the thrust iscan be attained by a ramjet engineis theoreti- 2.5 times as great as that without afterburning.cally unlimited. The faster a ramjettravels However,thespecificfuel consumption isthe more effectively it operates, andthe more roughly three times as great as without the after-thrust it:develops. But its upper speed islim- burner. This disadvantage decreases with speed,ited, in practice, to about Mach 5.0, because so that at Mach 3 or 4 and higher,the after-of frictional heating of the missile sldn.The burner engine is more efficient than the simplemajor; disadVantage . of a ramjet is that the higher turbojet engine. An afterburning engine must be speed, at !hick it is designed:. to.. operate, provided with a. variable area dischargenozzlethe higherihtlipeediO vihich it mustbe boosted and for supersonic speeds it should also have anbefore automatic operation can begin. adjustable inlet diffuser. Turbojets with an afterburner are called turboram jets. They are not used in any of ourComponents of Ramjets elided missiles, but supersonic missiles also take advantage of the ram air pressure at high :ramjet, consists ore-cylindrical speeds. The thrust of the turbojet decreasesthbe'::open: 'midi, with a' hiel-injection with increasing altitude but it is nearly constant444emtineide:From thisthe term "flying over a speed range offrem 0 to 650 mph for a originated. Even 'though all ramjets given altitude.There is .a slight increase incontain the same basic parts, the structureof thrust as speeds in excess of about 300mph arethese parts must be modifiedeto produce satis- obtained because of the beneficial effects of ramfactory operation in the various speed ranges. air compression. The specific fuel consumptionThe,Iprinalpal ,parts, ramjet engine:: are a of a turbojet decreases with increases in altitude.difftleeiYieetiontit484MinatiOnc:bhanthee that This, plus the fact that the thrustincreasescontains; tnet filjeCtiki3OPirk:plugs`and flame- slightly at high "speeds," places the optimum trate' (fig 4-11 ). operatihgpoht of the. turbojet inthehigh-speed, The diffiieferliiiaten serves the same Pur- high-altitude region:" pose in the ramjet as it doesin the pulsejet. Three 'Wailes `"Of the- Air Force turbo!. ItdeelfeaSeszthlk,,,,:vLelonit*,.anC4ncreases-the, jets-rMatader, *tee, and Hound Dog. The Navy's".=6:iiiiiiiiiiii3OfftWiffetiiiiiiittaitittSince there is Regulus; imitieing.Phased, out, is a turbojet.no wall or 'Closed grill inthe frOnt section Turbojets are well ',suited:AO aircraft andOf'-Z ramjet,` the pressure increase of the ram Missiles because of their'10 fuel 'eOnsuniption.air At*. be gieat enough to preventthe escape Chapter 4MISSILE PROPULSIONSYSTEMS of the combustion gases out the front of the en- its own power.If fired at rest, high - gine. Diffusers must beespecially designed for pressure a specific entrance velocity, combustion gases wouldescape out the front as or predetermined well as the rear.For satisfactory operation, missile speed.In other words, thedesired pressure barrier is developed Only the engine must be boostedto a suitable sub- when air sonic speed so that theram air entering the is entering the diffuserat the speed for which diffuser section develops that particular diffuserwas designed. a pressure barrier high enough to confine theescape of combustion The combustion: chamberis; of oourse thegases to the rear only. Figure 4-11A area in ,whiChlxueiiing occursandhigh-pressure is a dia- gasps:, are generated. The fuel gram of a subsonic ramjet engine.Note the injectors are simple tubular construction,and the openings connected to a continuous-flowfuel supply sys- at front and rear. tem, adequately pressurizedto permit fuel to flow against the highpressures that exist in the As ram air passes forward section of thecombustion chamber. through the diffuser CombuistiOnlio started by section (fig. 4-11A) the velocityof the air de- a spark plug; oncecreases while the pressureincreases. This staxtedAe. iscontinuous and selt-supporting. is brought about by the The flameholder preventsthe flame front from increase in cross sec- being swept too far toward tion of the diffuser, inaccordance with Ber- the rear of the engine noulli's theorem for incompressibleflow. Fuel thus stabilizing and restrictingthe actual burning is sprayed into the combustion to a limited area. Theflameholder also ensures chamber through that the combustion-chamber the fuel injectors.The atomized fuel mixes temperature willwith the incoming air, andthe mixture is ignited remain high enough to supportcombustion. by the spark plug. As A. ,ffaiiieholder-;: a metal grid. :'Or shield previously stated, burning is continuous after initialignition, and no further punctureti-mithof variety. of sharp edged. holes spark plug action is needed. (usually''riotround);designed:: tci itabilizea flame.:;-; Burning propellants tendto linger in these holes and this The gases that result -fromthe combustion ensures continuous ignitionprocess expand in all directions,as shown by of the injected fuel throughoutthe operatingthe arrows in the central cycle. ThinteholderSiirenecessary part of the combus- prevent tion chamber (fig. 4-11A).Astheyexpandinthe ablOrilW4ittlieliiiiiihigt Amt.* theyair :.rushing forviiird 41* gasea are stopped by, thrq*:itlietombustion.:chamber.: Thecordig- barrier the midi& and loration- of air and,the internal -the 'ffaineholders isa;sloping 'sides ;the,::diffuser. sectionas indi, crucial development. problemin the ramjet. cateci.411:;. the diagram by the shortil, Wide The flame speed varieswith different fuels black but in general the flame 'speed arrows.The ',OnlYiliVenue:::ofescape remaining is slower thanfeetheitOMbustion gases iithrough the 'air. speed through thecombustion chamber. exhaust The flameholders reduCethe local air speed nozzlei32andc-here..-,,another::;Jimportailtenergy to accommodate the slowerflame speed. cOnVersil*:Otaiiii::::;_,TherpretiSureenergYof the cOn*MtiOngaSesialiiiiireitedto:velocity. The The design and locationof the fuel injectiongases enter the exhaust nozzles and the controlsystem for fuel injection nozzle atless than the local speed of sound.But, while theypass are important to' get the correctproportionthrough the convergent nozzle, of air and fuel 'mixturein the combustion the pressure en- chamber. erey of the gaiesdecreases and the Velocity increases up to the local- speedof sound at the The exhaust nozzle performs-thesame func- exhaust .nozzle .exit. tion as in any. jet- propulsionengine. Types of Ramjets liiiiiiitOiWdeVelotiedMik:',ithc, et ;k as the ifOrmirgaiierelirWard;.:directiens:The born- Rangetscntax-belsubsonicror Supersonic.'The . latter inefbe low oupersonic bailment :(Jf ''cointlustion :gasesagainst the slo- or high supersonic.ping sides of the diffuserand,the ram-air bar- Subsonic:Ramjets rier. exert. a force -sin theforviard direction. Thiti forivard; force. not balanced :by: the coMbUstion gases .that --escape. through:the ex- Zefinti00.740Yel9P haUst nozzle. The unbalancedforce constitutes

. the:thrustthat propets the missile: PRINCIPLES OF GUIDED MISSILES.AND NUCLEAR WEAPONS progressing from diffuser inlet tocombustion- Supersonic Ramjet chamber entrance, the obliqueness ofthe shock The operation of a supersonicramjet is thewave successivelydecreases until a normal same as that of asubsonic ramjet, with theshock wave followed by subsonicflow is pro- following exceptions. First, thesupersonic jetduced. speed. Second, This energy transformation isachieved by must be boosted to a supersonic using a diffuser of the typeshown in figure a higher. pressUre 'barrierexists in the super- decreases the sonic engine,. resulting in greaterthrust. 4-11C. The diffuser centerbody In order to operate, a low-supersonic ram-obliqueness of the shock waves, allowing super- jet must be boosted to asupersonic speed, sonic air to flow inside thediffuser inlet. speed, be- As supersonic flow passes throughthe con- approximately equal to its operating the velocity is fore ignition. When the forwardspeed of thevergent section of the diffuser, ramjet becomes supersonic, anormal shocksteadily decreased and the pressure corre- entrance to the diffuserspondingly increased.' At somepredetermined wave forms at the point in the diffuser, air velocityapproaches section.The location of this shock wave is waveforms. shown in figure 4-11B. On theupstream sidethe sonic value and a normal shock free-stream air .As previously stated, whenlow-supersonic air of the normal Shock wave, the abrupt is moving at a low supersonicvelocity.' As theflows through a normal shock wave, an supersonic air passes through the shock wave,decrease in velocity and increase in pressure value,results.The subsonic air produced by the its velocity drops abruptly to a subsonic the divergent with a corresponding increase in pressure.Thusnormal shock wave flows through section of the diffuser, whereit undergoes an the shock wave produces a suddenincrease in inair pressure at the diffuserentrance. As theadditional velocity decrease and pressure compressed subsonic air flowsthrough thecrease.Here again the diffuser has achieved diverging diffuser section, an additionalincreasea pressure barrierat the entrance to the com- in pressure and decrease invelocity occurs.bustion chamber. The exhaustnozzle shown in mixed withthe diagram is of the convergent-divergenttype As in a subsonic ramjet, fuel is flow at the exit. the highly compressed air, themixture is igniteddesigned to produce supersonic initially by a spark plug, and burningis con- A ramjet is designed to operate best at some The potential energy pos-given speed and altitude. The pressurerecovery tinuous thereafter. designed for oblique shock sessed by the combustion gases isconverted intoprocess in a diffuser waves is more efficientthan that in diffusers kinetic energy by the exhaust nozzle. single normal The convergent-divergent nozzleshown indesigned for subsonic flow or figure 4-11B allows the gases toexceed theshock waves. For that reason theramjet engine Therefore, with properoperates best at high supersonicspeeds. To local speed of sound. attain this speed, a rocket orother type of design modificationS, the ramjet engine can generally larger and travel efficiently at supersonic speed.. booster is used, and it is Now, assume that we want to design aramjetheavier than the ramjet itself. that Will travel.; at. higher 'supersonicspeeds. nil engine{ tdeit11::--editeCtO. long.-range At speeds of. around Math 2.0,shock waveshightspeed[Mitsilekiincethethrust increases formed at the diffusev inlet areoblique (fig.SiithSpeek inclAhe rati if Friel consumption per 4 -11C) rather than normal. Air velocityin front.unit: of thruSt,clecreases with speed. of an 'oblique shock Wave ishigh supersonic. When Supersonic free- stream air passesthrough an oblique shock waVe. anincrease in pressure ROCKET MOTORS and 'a decrease inVsloUitYoCeur, but the velocity is, still, supersonic:' For example; airwith aGENERAL freestieam'veloCity of ..4500`: mph maypass Unlike a jet engine, a rocket carrieswithin through ;an'. oblique shock waveand:Still have a required for its veloCity of900 mph. Also when,supersonic airitself all the mass and energy diirergent-t;vpe.:: diffuser sections,operation.It is independent of the surrounding flows ! through, In .a rocket, the chemical reaction . as shoWninfigureS 4-1IA and; 4-118:Ihe ?velocitiv medium. PressuredeCreeseS.takes place at a very rapid rate.This results of hat'. air increases and the in:higher temperatures higher operating pres- .Therefore,thediffUser.';.vdisignr,'foi .development;than in supersonic .:.iiimjette.aiistbe::,#UX1111ed,SO :thatinMitee, and, higher thrust

Pr Chapter 4MISSILE PROPULSION SYSTEMS

DIFFUSER SECTION SPARK PLUG FLAME HOLDER EXHAUST NOZZLE

SONIC VELOCITY GASES

TO FUEL PRESSURE INJECTION NOZZLES BARRIER COMBUSTION CHAMBER HIGH PRESSURE GASES- A. AIR FUEL

SPARK PLUG PRESSURE ENERGY CONVERTED TO VELOCITY

Imis aaa

ADDITIONAL AIR PRESSURE PRODUCED HIGH PRESSURE BY DIFFUSER COMBUSTION GASES EXHAUST NOZZLE FUEL

CENTER BODY DIFFUSER EXHAUST NOZZLE

SUPERSONIC now . '4AIR POSITION 0PNORMAL".SHOCK' KAYE...... -FUEL 144.22 -4e. , igure 4-11.-7StrAleture,Pf A. Subsonic vramjet; B. ,11thliet° andleembuettqu processesIn them , Low supersonic, ramjet; C. High:supersonic rim et._ PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS jet engines.Because of the high pressuressystems.In the stored-pressure system, air developed in rocket motors, theconvergent-or some other gas is storedunder pressure in divergent nozzle is used so that moreof thethe missile before launching.It is injected, energy can be extracted fromthe gases afterin controlled amounts, into the propellantstor- they have passed the throat section.The basicage tanks, causing a pressurizedflow toward principles involved in the action ofother jet-thecombustion chamber. Ina generated- . propulsion units also apply to rockets. pressure system, substances arecarried within Depending on the physical state of thePro-the missile to generate the high-pressure gas pellant used; rockets are designated aseitheras it is needed. An exampleof such a. substance solid or liquid type. ishydrogenperoxide,which, when passed A solid rocket has a short burning time,through a catalyst, decomposes to form a high- simple design, heavy construction, andnon-pressure vapor. This vapor isthen injected into intermittent operation..It is therefore pri-the propellant storage tanks. marily used for booster units, and as a power- Many other devices such as valves, regulators, delivery tubes, and injectors, are nec- plant for relatively short-duration, high-speed operation of either missiles. Recent research seems to indi-essary for the successful cate that solid fuels will have increasingfuturesystem. applications in long-range missiles. TheNavy's Figure 4-12 shows the general relationship Polaris (ICBM) is propelled by a solid-fuelof the various major parts of astored-pressure feed 'system. In the system shown, airis stored rocket. under pressure.The hand-arming valve is The liquid rocket unit has a longer burning This timerelatively complicated design, and in-opened manually, just before hunching. termittent operation possibilities. This systemallows the system to be pressurized upto the has been widely used as a powerplant forhigh-motor-start valve. The air-pressureregulator altitude, long-range missiles, and spacecraft.decreases the pressure to the desiredvalue To summarize, the more important char-require l for operation of the system components. Most liquid-fuel rocket systems . usehigher acteristics of all rocket engines are: . constant,pressure than shown in theillustration. Also, 1. The thrust of a' rocket is nearly helium, and is independent, of speed. instead of air, alight, inert gas, watts 2. Rockets will operate in a vacuum. is used. This permits weight reductionand also 3. Rockets have relatively few moving parts.eliminates a fire and explosion hazard whichis present with pressurized air.Nitrogenalso may 4. Rockets have a very high rate of propel- be lant consumption. be used because it is fire-safe; tanks may 5. Burning time of the propellant Ina rocketpressurized to about 2000 psi.The pressure is short. on the fuel and oxidizer. tankshas to be greater 6. Rockets need no booster. They have fullthan the pressure in the combustionchamber, thrust at takeoff; therefore, when. rocketsdobut much less 'than in the nitrogenflask. Re- employ boOsters it is for the purpose ofreach-ducing valves are'used to reduce the pressure. ing a high velocity in minimum time. The motor-start 'valve is electrically operated.It is opened from a safe distance after all persomiel have cleared the immediatelaunch- LIQUID-FUEL ROCKETS ing area.. Pressurized air or inert gasenters and pressurizes the. fuel and. oxidizertanks. The major 'components of a liquid-rocket that is sytitem are,the propellant,propellant-feed sys-These tanks must be made of material tem, combustion.. chamber,. igniter, andexhaustnot affected by the respectivepropellants. In nozzle. The propellant -feed systemis theonly. addition, they must' be .strong enough to with- Part which.has not been explained; rin, principle,stand .the;:added. pressure.. At the ,sametime in .the preceding sections of this chapter.Feedthat the propellant tanks are pressurized,air systems..may be ;of the -.pressure-feed :type. 'oralso enters the 'hydraulic. accumulatorand pressurizes thkhydraulic fluid.(PresOurized the:pump-feed. type.. nitrogen may;. be used te.openIthe.fuel valve, or Pressure -Feed Systems other ..flowcontrol._ may be used instead of . ,'!; control.) :The -hyditulic 'fluid dis ,..Pressure =feed systems maype...:80bdi*idedplates the Pisten in the propellant valveactuating turn opens -the. propellant into ,.?Stored=preasUre:).1,and, cyitioei; 4hieh .. . Chapter 4MISSILE PROPULSIONSYSTEMS ..

I PUB. TANK

MIXTURE ORIFICES REG EN ERATIVELY COOLED LIQUID AIR STORAGE TANK ROCKET 200 PSI PROPELLANT VALVES HAND ARMING VALVE ll..ter 1r1.111.11.011,11"..11.11.4

35 krat..!iL-er CHAMBER

ACTUATING ''''' /- ''''''' CYLINDER AIR PRESSURE MOTOR REGULATOR START 100 PSI VALVE HYDRAULIC ACCUMULATOR Ino". OXIDIZER TANK

Figure 4-12.Stored-pressurefeed system of a liquid rocket. 144.23 valves. Fuel and oxidizer, under pressure, now Figure 4-13A sketches the flow through the respectivemixtures orifices, main parts of a which regulate the flow generated-pressure system. Thegas is pro- so that the correctduced by chemically reactinga liquid or solid mixture ratio is maintained.These orificespropellant at a steady,_ are simply restrictions in the line, uniform rate. Note and are flow-. that there to a return flowfrom the combustion checked prior to installation.In some caseschamber to the chemical the injectors perform thisoperation, and orifices pressure system. are not necessary. The propellanteare atomizedPump-Feed System by the injectors. Notethat the oxidizer (propellant: in some syitems)firet circulatesbetween the walls of the combustion chamber The Pumpfeed system (fig..4-1313)is nearly beforethe same as the pressure-feedsysteni, except passing through the cutoffvalVe. This action isthat the pressurized &Skis called: regenerative Cooling.It makes pOssible replaced by pumps the use of thin-walled- Combiistion which force the Propellant'and oxidiker into the Chamberscombustion. chamber. Topower the pumps, a (reducing:the. weight).. Thefeet that the enginesteamgenerating plant is cooled'Permits longerburning than if it were' may be providedto oper- a turbine which in 'turn-drives thepumps. not: coOleck r. -.A furtheradvantage' is that theThis system has the advantage propellant 'is,, preheated beforeinjection into of, having light- the combustion chamber, weight tanks-but;of course; more complicated which retinits'in morethan the pressurefeed system. coMplete:COMbustion and greater,.release ofate PnmP-feed sYsteMsare Used:with power heat energy. Other: methodsof cooling ire..alsOPlante 'detiigned to in tine,Three, general: methods ixon lerge':vOlUnies of.pro= of cooling roCket and:V4thplants requiring motors area film Method;regenerative (Men- a high weight tione& abeire );:ind sweat rate,:of:AOW.''''piiMp.4eed system consistsof Nit necessarya : fuel p iinpp and an oxidizer pump, both to :control, the temperaturetOPreivent deititietiOnby a :'tUrti driven ..rOf,"thfkiiietiilliCperti'Of the rocket wheel. Power for d theielii motor before.bins Wheel iney:,bkprailded'i*iilkilAeheieted by7 chemicals "Idithet

*i4 , 444113.4, 41' PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

CHEMICAL PRESSURE SYSTEM w_ OXIDIZER

1/ 41111=111); FPN;11/7/7,k7, -7P ////figanumq,) h, OXIDIZER is" MeR PUMP "Li ////ii ,

3 144.24 Figure 4-13.Liquid propellant. feedsystems: A. Generated pressure system;B. Pump-feed system. I of low- purpose (turbine-pumpsystem), or the turbine A film-cooling procedure consists from the exhaustvelocity injection of a portionof the fuel, wheel may receive its power oxidizer, or some nonreactive liquidinto the gases of a rocket motor(turbo-pump system). The fluid forms Figure 4-13B illustrates the majorcoMponentschamber at critical points. aturbine pump-a protective film onthe inner walls, and ab- of a liquid fuel rocket that.uses sorbs heat from the walls as itevaporates. It feed system. , Because pressure is felt only on the com-may be used in combinationwith regenerative bustion chamber side of the pumps,the fuel andcooling. oxidizer tanks can be of lighterweight than in Sweat (transpiration) cooling is achievedby pressure -feed systeMs. A'disadvantage is thatuse of a porous chamber'wall through which the auxiliary . devices andcontrols of a pump -the liquid slowly flows. Theevaporation of the feed 'system are far more complicatedthanthoseliquid from the surfaces causescooling of the of a stored-bregisuressystem.This complexitysurfaces.It is used on aerodynamically heated means that a 'complicated checkoutis necessarysurfaces and combustion chambers. and .the reliability ieles8Pned A look at the names of missilesthat use Because of -the intense heatdierCloPed inliquid-fuel rocket engines shows thatmost of liqeidideliet::Conthestion Chamber:3, it is iM-them are earlier day 'missiles orarebeingused pcirtintrthifllie inner walls r of the chamber,to boost space vehicles into orbit:Corporal, throat, Xnd', be coded: "UnCoOled opeiiitionWAC Corporal, Centaur, Titan,Thor, Jupiter, over a :.ptolongedPeriod ; reduces physicalRedstone Aerobee Explorer, Gargoyle,Gorgon striMgth and may the II A N;ehViking Nike, Rascal, and. Van The large Missiles use one or more The regenerative -cooling;.inetinid shown inguard. ligiire412:iii.oftgin used. Before rtojecticiiititoStages with solid propellant. ,Thedevelopment of dfsZer ,ittii ted i,a prepackaged liquid-fuel . engine: as used, in the :,,cliaMbeki-ithei'inelicir Bellpup, may be the start of a trendto the use -ft3.mi.,-0i.oh -4410ii;.ligtir011. 014#41.le of he :091227 One of the important -iiiiiii*,,, iii': 'iit.41?siiited by tie.of propellants.- amber 'and...:, ad daito:disadvantages of the liquid-ftiel engines was that' 014, i, cools the they couldina be fueled and storedfore any energy~ 4co0 therPrope t,:. Chapter 4MISSILE PROPULSIONSYSTEMS

length of time.The prepacking methodmay overcome this handicap. Liquid oxygen tends toreact violently with oil vapors, oftencausing them to burnspon- Description of Liquid Fuels taneously. Any bituminousmaterials or petro- leum products must bekept away fromareas where it is handled. Earlier in this chapter,liquid propellants in general were described, The extremely lowtemperature of liquid and advantages andoxygen causes water vapor from disadvantages were stated.Specific fuels will the surround- be. described here. ing atmosphere to collectand freeze on pipes and valves.This is a serious Aniline, hydrazine hydrate,and ethyl alcoholhas yet tc be fully solved. problem, which are among the more commonly usedliquid rocket Liquid oxygen is fuels. Aniline is an oily noncorrosive and nontoxic, butwill cause severe clear liquid with aspe-damage ifit comes into contact cific gravity of 1.022. (Specificgravity of water with skin. is 1.000.)It has a boiling point In spite of themany problems connected with of about 363°Fits manufacture and handling, and a freezing point ofabout 21° F. On contact liquid oxygen is an excellent propellant; it is thebest oxidizing agent with red fuming nitricacid, it ignitesspon- available. tanously. A fuel andoxidizer combination that reacts in thismanner is said to be HYPER, Nitric acid is usedin several different GOLIC. This combination forms as an oxidizer forliqUid rockets. The was successfully usedmost commonly used and in the WAC Corporal, Corporal,Aerobes (sound- the most powerful of these is RED FUMING NITRICACID (RFNA), ing rocket) and Gorgon II-Amissiles. which consists of nitric Hydrazine, hydrate isa colorless liquid, acid in which nitrogen slightly heavier than water. dioxide is dissolved.It varies in colorfrom Rio explosive whenorange to brick red, andgets its name from its concentration is above 25%.Hydrazine hy-the reddish color of the drate gives a hypergolicreaction with hydrogen nitric oxide fumes it peroxide. gives off. RFNA is highlycorrosive, and stainless steel must be usedfor storage tanks Ethyl alcoholis a clear. liquid, lighterthanand delivery pipes. Its water.It is stable to shockand temperature high vapor pressure changes.It is readily available presents storage and transferproblems. The because of itsfumes are extremelypoisonous, and severe wide icoMmercial marketin the chemical andburns result from bodily liquoir industries.Ethyl alcohol (ethanol)has contact with the a low heat value and liquid.This oxidizer has beeneuccessfully a lovi vapor pressure.used with aniline,giving up approximately For use in missiles itis commonly mixed with03.5% of its distilled or deionized water.Methyl and fur- oxygen content for combustion. It is alio used with,kerosene, hydrazine, and furyl alcohols are alsoused for propellants.compounds of hydrazine. Liquid oxygen, referredto as _Lox, and Hydrogen peroxide various forms' of nitric acid,are among the most is a colorless liquid commonly which, In concentrationsof from 7016 to 906, oxidizers'' in ;: liquidrockets.maq.:be' used oxygen is made byliquefying air and as a monopropellant in guided boiling .9ff. the nitrogek missiles. When in contact witha suitable and other gases. Thiscatalyst (calcium bluish 410'11d-2;12as ;a.bOilingPOintofAbOUt minus permanganate, manganese di- 297° 0;..-lind' a 'freezinepotht..Ctininus- oxide, platinum, silver,and other materials) it 363° F. decomposes, forming steam Because of - its low :boilingpoint, its rate of and gaseous oxygen. When 90% hydrogen peroxidedecomposes, about evaPOration:is very high. :?,9.t.:t440reason, stor-42% of the `'total weight age Aiii4!Aiiiiiiieiit,.to,:hi*Chieg sareas of the decomposition , presentsproducts is gaseousoxygen. Therefore, it is also serious Probleinei:-ent -ikapPreciableused' as an diddizer with logs.: WhekpOuredon metal at ordinary ,tem- such fuels as alcOhol and.hydreZthe hYdrati.., A third:use for hydrogen PeretUre;'11quid oxygen iacts:likemater droppedperoxide is as a pressurizing on 'toiS.! egent..The go:aeons- POratiOn;.*ss... in theproductS of decomposition:may be jetted against GerMen V =2 ,1:4:tiotindgi:per infinite betviien e.:tUrbine wheelwhich drives fuel and oxidizer. e time Of foelixig and leunChing...cPumtis connected -Under 'the, 'sbe:conditions, to the turbine shaft.. Owe* 'the ;19sS%- of liquids In theSeerch Or:storable liquid propellants by, 0.40#6304 097:010 iierp9. X; high specific ombined -malt .. StorageAequRes.:6014:4).',4*. insulation and/or,some form of alin4 and.Eithring,:availability,and r numerous -.;Corchinations"...Ve; been I PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS Operation of a solid rocketis simple. tried. Among the most promising isnitrogen form of Nitrogen tetroxideTo start the combustion process, some tetroxide plus hydrazine. electrically detonated squib isordinarily used (N204) can be stored without refrigeration and black powder charge. is not difficult to handle. It isalso noncorrosiveto ignite a smokeless or storable liquid fuel isUpon igniting, the powder chargeprovides suf- to steel. Another good ficient heat and the pressure toraise the ex- perchloryl fluoride, which is alsononcorrosive. grain to a point Fuels which have a higher heat energythanposed surface of the propellant where combustion will takeplace. the hydrocarbons aresometimes called exotic compounds are fre- fuels, or zip fuels. Boron Charges quently the basic ingredient. Types of Solid Propellant Solid propellant charges are oftwo basic SOLID -FUEL ROCKETS types: restricted burning orunrestricted burning. A restricted-burningcharge has some of A solid rocket unit consists ofthe propel- with an inhibitor lant, combustion chamber, igniter,and exhaustits exposed surfaces covered (fig. 4-14).This makes it possible tocontrol nozzle (fig. 4-14). the burning rate by confiningthe burning area The combustion chamber of asolid rocket surfaces. The use serves two purposes.First, it acts as a stor-to the desired surface or propellant. Second, it servesof inhibitors lengthens theburning time of the age place for the charge, and helps to controlthe combustion- as a chamber inwhich burning takes place. A burning cigarette can Depending on the grain configurationused,chamber pressure. device forbe considered as a model of aninhibited rocket this chamber may also contain a grain, with the paper representingthe inhibitor. holding the grain in thedesired position, a is usually a ofpropellant A restricted-burning charge trap to prevent flying particles solid cylinder which completelyfills the com- from clogging the throat section,and rescnance only on the end. rods to absorb vibrations set upinthe chamber.bustion chamber and burns charge of(fig. 4-15A). The thrust isproportional to the The igniter consists of a small of the charge, and burning black powder, or some othermaterial that cancross section area 'ignited by either a spark dischargetime is proportional tolength.The restricted be easily burning charge providesrelatively low thrust or a hot wire. Asit burns, the igniter produces Uses of this type of a temperature highenough to ignite the mainand long burning time. propellant charge. The exhaust nozzle serves the same purpose as in any otherjet-propulsion system. It must be of heavy constructionand/or heat-resistant materials, because of the hightemperatures of the exhaust jet.

B ELECTRIC IGNITER NUM ClIANSER PROPELLANT INHIBITOR `NOZZLE C

SUNNING SURFACI

PROTECTIVE DIAPHRAGM 12.26 144.25Figure 4-15.Solid propellantgrains: A. Re - stricted burning; B.Restrictedbored; C. Un- Figure 4-14.Components of asolid rocket patterns. motor, with end-burning grain. restricted burning; D. Grain

..9e Chapter 4MISSILEPROPULSION SYSTEMS charge include JATO (jet-assistedtakeoff )units, the outer portion of barrage rockets, and sustainingrockets for the grain providesa shield guided missiles. between the intenseheat and thecombustion chamber wall until thegrain is almost A modification of the restrictedburningd), consumed. complete- charge is the bored restrictedcharge (fig. 4- 15B ). The main differenceis that the longitudinal hole in the charge providessomewhat moreBurning Rate of Solid burning surface and thusa higher thrust andPropellant Grains shorter burning time. Unrestricted-burning chargesare permitted The burning rate of to burn on all surfaces atonce. The unrestricted a solid propellant is the rate at which thegrain is consumed; it grain delivers a relativelylarge thrust for ais a measure of linear short time.An unrestricted burning distance burned, in chargeinches per second, ina direction perpendicular is usually hollow, andburns on both the outsideto a burning surface. and inside surfaces (fig.4-15C).Thrust is As stated earlier, thrust again proportional to theburning area. Since depends on mass the inside area increases rate of flow and the changein velocity of the while the outsideworking fluid.For large thrust, a large area decreases during burning, itis possibleing area is necessary in burn- to maintain a nearlyconstant burning area. order to yield a The burning time of hollow large mass flow.A smaller burningarea the web thicknessthe grains depends onproduces less mass flowand less thrust. distance between theTherefore, by varying thegeometrical shape inside and outside surfaces.This type of chargeand arrangement of the is commonly used in boosterrockets. charge, the thrust developed by a given amountof propellant in a It should be clearlyunderstood that in both given combustion chambercan be greatly in- the restricted and unrestrictedburning charges,fluenced. the burning rateis controlledthere isno The burning characteristicsof a solid propel- explosion. Controlling the burningrate of a solidlant depend on its chemicalcomposition, initial propellant has always presenteda problem totemperature, combustion-chambertemperature rocket designers.You will recall thatone of and pressure, gas velocityadjacent to the the properties ofan ideal solid propellantburning surface, and size andshape of the grain. would be that it Ignite andburn evenly. TheOne propellant grainmay burn in such a way burning rate may becontrolled in severalways.that the burningarea remains constant,pro- One is by means ofinhibitors. An inhibitorducing constant thrust. Thistype of burning is is any substance whichinterferes with or re- known as UTRAL BURNING.End-burning tards combustion.The lining and the washerpropell sins are of this type. Anotherim- shown in figure 4-15 are examplesof inhibitors.portant utral-grain design is the uninhibited, Another way that burning iscontrolled is by useinternalxternal burning cylinder (fig.4-15C), of various grain shapes.Examples are thewhich is used wherea short-duration thrust is shapes shown in the lower partof figure 4-15D.needed, as in bazooka typerockets. The pro- Resonant burningor "chugging" may be offsetpellant burns so rapidlythat heating of the by the use ofresonance rods. These metalorchamber walls is not excessive. plastic rods are sometimesincluded in the Another type of grainincreases its burning combustion chamber to breakup regular fluctu- area as burning progresses.In this case, ations in the burning rateand their accompany- PROGRESSIVE BURNING istaking place. Thrust ing pressure variations.The purpose of theincreases as the burningarea increases. Still various designs is tomaintain a constantanother grain may showa constantly decreasing burning area while the surfaceof the grain isburning area as burningprogresses.This is being consumed. called DEGRESSIVE BURNING.It results in a Until recently decreasing thrust.Various star-shapedper- a serious - disadvantage of forations(fig. 4-15D) the solid propellant hadto do with the problem -" can be used to give of 'dissipating the extreme neutral or degressive burningcharacteristics, heat of combustion. but design changescan make them progressive One way this has beenovercome is by use of burning. the internal burninggrain. Since the burning process actually takes place within Propellant grains are oftenformed by ex- the grain, trusion; these, ofcourse, are installed in their PRINCIPLES OF GUIDEDMISSILES AND NUCLEARWEAPONS by the area of theex- But certain types of com-pressure is determined cases after forming. haust nozzle throat.If the throat area is too posite propellants,bonded by elastomeric fuels, chamber pressure directly in the rocketchamber,large, for example, proper can be cast cannot bemaintained. where the binder cures to arubber and supports tendencies to the chamber walls. Decomposition and hygroscopic the grain by adhesion are otherweaknesses of solid propellantsbut This is called case-bonding. both can be minimizedby the use of certain It' permits full use ofthe chamber space. content rockets are made byadditives. Change in the moisture Most high-performance changes the gaseous energyoutput of the pro- this technique. pellant with unpredictableresults. Some of the more commonpropellants are Description of Solid Propellants discussed below.The chemical formulasof some of them aregiven, to show the carbon and/or hydrogen content, andthe oxygen con- One limitation of solidpropellants is sen- The initial tempera-tent of the oxidizers. sitivity to temperature. One of the first solidpropellants used was ture of a grain noticeablyaffects its perform- approximate composi- ance. A givengrain will produce morethrustBLACK POWDER. Its day. Thetion is: on a hot daythan it will on a cold Potassium nitrate (KNO3) 61.6% percentage change in thrust perdegree Fahren- is referred to as the Charcoal (C) 23.0% heit temperature change Sulphur (S) 15.4% temperature sensitivity ofthe propellant. A react readily with grain designed to produce1000 pounds ofBoth charcoal and sulphur by its deliver only 600 poundsOxygen. Potassium nitrate, as shown thrust at 80° F may formula, contains largequantities of oxygen. of thrust at 30° F.The initial temperatureThe three ingredients arethoroughly mixed, alsoaffects the burning rate.Because of such as glue or oil as a solid propellants mustusing some substance these characteristics, BINDER. be stored in areas ofcontrolled temperature When heat is applied toblack powder, the until they are used. potasciam nitrate gives up oxygen.The oxygen Temperature also affects thephysical statereacts with the sulphurand carbon, producing of solid...propellantgrains. At extremely lowintense heat and largevolumes of carbon become brittle and These two gases temperatures, some grains dioxide and sulphur dioxide. jet. are subject tocracking.Cracks increase themake up the majorpart of the exhaust burning area and burningrate and thereforeThe heat produced bythe reaction giveshigh increase the combustion-chamberpressure.velocity to the exhaust gases.Black powder If this pressure exceedsthat for which thehas a specific impulseof about 65lb-sec/lb. chamber was designed,the chamber may ex-One of its drawbacks isthat it is quite sensi- plode. A propellant exposedto high tempera-tiveto storage temperatures,and tends to ture before firing maylose its shape, andcrack.Its exhaust velocity rangesfrom 1500 become soft and weak.This, too, results into 2,500 feet persecond.It is now used pri- unsatisfactory performance.The temperaturemarily for signal rockets,and as an igniter range for most solidpropellants is from aboutfor other solid-propellantgrains. 25° F to 120° F. Correctstorage temperature BALLISTITE is a double-basepropellant; retards the decompositionof propellants thatit contains two propellantbases, NITROCEL- contain nitrocellulose(almost all of them do),LULOSE and NITROGLYCERINE.It also con- which inevitably deterioratewith time, in spitetains small amounts ofadditives, each performing a specific function.A STABILIZER of the addition of stabilizers. products of slow decom- Pressure limits play animportant part inabsorbs the gaseous Below a certainposition, and rdducesthe tendency to absorb solid propellant performance. moisture during storage.A PLASTICIZER chamber pressure,combustion becomes highly agent. An OPACIFIER is Some propellants will notjustainserves as a binding unstable. Ordi-added to absorb the heatof reaction and pre- combustion at atmosphericpressure. vent rapid thermaldecomposition of the un- narily, chamber pressurefor solid propellantsburned part of the grain.A FLASH DEPRES- must be relativelyhigh. For a given propellant before they escape composition and burning area,the chamberSOR cools the exhaust gases Chapter 4MISSILEPROPULSION SYSTEMS to the atmosphere, thuspreventing a burning- tail effect. A typical ADVANCED PROPELLANTSAND ballistite composition is PROPULSION SYSTEMS Nitrocellulose The need for greater C2484002003)51.38% (propellant) specific impulse and Nitroglycerine higher energy propellants,particularly for use in space flights but E.lso for C3H5(NO3)3 43.38% (propellant) missile use, has stim- ulated research.The achievements Diethylphthalate 3.09% (Plasticizer) nations have spurred of other Potassium nitrate1.45% (flash de- our own efforts in this field.The future ofspace flight is closely pressor) dependent upon propellants Diphenylamine 0.07% (stabilizer) that yield far, higher Nigrosine dye 0.16 (opacifier) energy and impulse thanare available from combustion of chemicalpropellants. Thus far, we have Ballistite has aspecific impulse of about discussed only combustion 210 lb-sec/lb. Its exhaust of chemical propellants,liquid and solid, is relatively smoke-source of energy. as a less.Storage temperaturesbetween 40° F and It is possible to getenergy 120° F are from chemical propellantsby free radical (mo- necessary to prevent rapid decom-lecular fragment) position. The ingredients ofballistite are recombination, or byexo- subject to detonation,and are toxic when thermic decomposition(controlled explosion). theyFree radical propulsionis still in the research come in contact with theskin. The manufac-stage and it may turing process is difficultand dangerous. take a long time toyield Galcit consists ofabout 25% asphalt-oilpraCtical results. As forexothermic decom- mixture, which position, at the presenttime no material is serves as both fuel and binder,available that releases and 75% potassiumperchlorate (K C104), which sufficient energyupon serves as an oxidizer.In its. finished form, controlled decompositionto make it preferable Galcit resembles to combustion systems.Further research stiff paving tar. ReCom- change this. may mended temperaturelimits for firingare 40°F to 100° F. Experiments !laic: beenmade in the use of The specific impulseof galcit issolar energy and about 186 lb- sec /lb.It is quite stable totem- arc-heated or electricsys- perature; storage temperature tems, but thus far,their low efficiency limits are minusmade them impractical. has 9°F to 120° F.Galcit is relativelyeasy to Progress in the field manufacture.It is nonhygroscopicthat of direct powerconversion or large improve- does not absorb is, itments in conversion moisture.Its major disad-this. A solar-heatedefficiency could change vantage is thatits exhaust developsdense system uses the radiant clouds of white smoke. energy of the sun. An electricsystem uses the It is only aboutone- acceleration of charged fifth as sensitive totemperature changes atoms, moleculesor ballistite, but it becomes asparticles in electricfields.If the particles brittle at low tem-are atoms or molecules, peratures and soft at hightemperatures. the system isan ion NDRC propellants (or ionic) system;if they are solidparticles were developed throughor droplets, the systemis a charged particle research sponsored bythe National Defense system. Research Committee.A typical composition consists of about equalparts of ammonium pic- NUCLEAR-POWERED ROCKETS rate and sodium nitrate(46.5% each), and '7% resin binder (usuallyurea formaldehyde). This propellant has goodtli6rmal stability.It is Considerable researchand development work hygroscopic, and mast is being done to achievethe use of nuclear therefore be stored infor missile propulsion. power sealed containers. Heavysmoke develops inthe A nuclear powerplant exhaust gases. would greatlyincrease both thespeed and Solid propellant range of missiles.Present propulsion rockets are particularlytems would become sys- adaptable to ship harduse. They are easily obsolete as majorpower- stored and ready for plants for longrange missiles or forspace immediate use. qo greatflights.But they may still have been theimprovements in solid'propel- serve as boosters lants in the past fewyears that they arenowfor takeoff and initialaccelration, to prevent used in such long-range radioactive contaminationof the launching missiles as the Navy's One of the main area. Polaris and the AirForce's Minuteman. advantages in theupe of nuclear power is thatit providesan almost

t 4 9995%.0 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS inexhaustible source of heat.In a missile supply propelled by nuclear energy, the fuel CONTROL NOZZLE would remain practically constantthroughout VALVE the flight.Enough fuel to start the reaction would be enough for sustainedoperation. But other material, such as water,is required in the missile to absorb the heatdeveloped by the powerplant, and to beaccelerated to produce thrust. GAS The major problems confronting theengi- GENERATOR neers are protecting thelaunching personnel 144.26 from radiation damage, and developing anuclear powerplant small enough to be carriedin a Figure 4-16.Sketch of a hybrid guided missile. Many years of extensive propulsion engine. technical development may be neededbefore nuclear energy can be harnessed for use as But the outlook isof the elements of a simple forwardhybrid en- a missile powerplant. Combustion takes place on the inside promising. gine. Nuclear systems can be fission, fusion, or surface of the solid fuel, after the liquidfuel is photon systems.(A photon is a quantum ofinjected, and the combustion products are ex- electromagnetic energy.) A photon system uses hausted through the nozzle to produce thrust as a source of lightphotons to develop thrust. in other rockets.Nozzle systems and vector The only sufficiently powerful photon sourceiscontrol methods are the same as in other re- the fusion process.There is much develop- action engines.Variable thrust is achieved by ment work yet to be done on this type ofrocket varying the flow of the liquid oxidizer.Thrust termination and restart are accomplishedby engine. Much greater advancement has been flow achieved in the development of anuclear fission shutting down and re-opening the oxidizer rocket engine than in fusion-photonsystems.system. Most of the research on advanced propel- Missiles which use a solid-fuel boosterand lants is being done for use in spaceflights.a liquid engine, such asthe Taloa, are not Significant reduction in weight and size require- hybrids; the propellants do not interact. make new The biggestadvantage of hybrids is the ments may be achieved and may ability to use reactions denied to other pro- propulsion methods applicable to guidedmis- is that siles as well as space ships.. pulsion systems. A second advantage high density can be achieved, with concurrently good specific impulse (Isp).The third great HYBRID PROPULSION advantage is safety. The solid grain isinert. Noimal grain defects do not affect performance. A malfunction in combustion is unlikelyexcess A hybrid engine consists of a liquid oxidizer, could a solid fuel, and its associatedhardware. Theliquid and a badly cracked solid grain liquid oxidizer is valved into a chamber con-cause a pressure surge, but thechances of both usuallydefects occurring together is small. taining the solid propellant. Ignition is have hypergolic. Neither of the propellants will Although research and development hybridbeen carried on in several areas sincethe support combustion by itself in a true be rocket.Thestnbustion chamber is within the 1950's, there are still many problems to solid grain, as in a solid-fuel rocket; the liquidsolved before a hybrid engine can beused in missiles.European research apparently is portion is in a tank with pumping elements as launching in a liquid-fuel rocket. Thistype is sometimes'ahead of ours. A successful hybrid it fromwas made in France on25 April 1964. Re- called a .forward hybrid to distinguish continuing in a reverse hybrid, inwhich the oxidizer is solidsearch and development work is and the fuel is liquid. Figure 4-16 is asketchthe U.S., but much of it is classified. CHAPTER 5

MISSILE CONTROLCOMPONENTS ANDSYSTEMS

INTRODUCTION are continuously determined; (2)COMPUTING, GENERAL in which the trackinginformation is used to determine the directionsnecessary for control; This chapter will (3) DIRECTING, inwhich the directionsare introduce some of thesent to the control units;and (4) STEERING, numerous devices thatmay be used to controlwhich is the process of the flight of a guidedmissile. We will discuss using the directing basic types of control signals to move the missilecontrol surfaces systems: pneumatic,by power units. The first pneumatic-electric,hydraulic-electric, and three processes of electric.Throughout the chapter path control areperformed by the guidance we will-dealsystem, and steering is doneby the control with general principles,rather than the actualsystem. design of any specificmissile. In order for theseprocesses to be accom- Chapter 2 describedthe external controlplished the missile must surfaces of guided missiles,such as wings, be in stable flight. fins, elevators, tails, The control of missilestability is called ATTI- and tabs, and describedTUDE CONTROL, and the effects of naturalforces acting upon them. is usually accomplished The use of internal by an AUTOPILOT, whichis a part of the control mechanisms such as jetsystem. vanes and fixed jetswas described briefly and illustrated. Flight attitude stabilizationis absolutely This chapter tells howthe controlnecessary if the missile is to respond surfaces are controlled tokeep the missile in properly its proper attitudeon its ordered trajectory.to guidance signals.When the control system determines that a change inmissile attitude is DEFINITIONS necessary, it makes use of certaincontrollers and actuators to move themissile control surfaces. The guidance Guidance and controlare sometimes spoken system, when itdetermines of as if theywere one and the same. They that a change in missilecourse is necessary, two parts of the problem areuses these same devices tomove the control of getting the missilesurface. Thus the guidance to the selected targetafter it isfired. The main and control systems reason for controlling overlap. For convenience,we will assume that a missile in flight is tothe controllers and gain increasedaccuracy for long ranges. actuators are a part of the A missile guidance control system, ratherthan the guidancesys- system keeps the missiletem.We can thereforesay that the output on the proper flight pathfrom launcher tosignals from the guidance target,in accordance withsignals received system are put into from control points from effect by, a part of thecontrol system. The input the target, or fromsignal represents the other sources of information.The missile desired course to the target.The missile controlsystem operates control system keeps themissile in the properto bring the missile onto flightattitude. Together, the guidance and the desired course. If there is a difference betweenthe desired flight control components ofany guided missile deter-path and the one the missile mine the proper flightpath to hit the target, is actually on, then the control system operatesto change the posi- and control the missileso that it follows thistidn of the missile in determined path.They accomplish this "path space to reduce the error. control" by the To summarize: themissile control system, processes of (1) TRACKING, indiscussed in this chapter, which the positions ofthe target and the missile is responsible for missile attitude control. Theguidance system, PRINCIPLES OF GUIDEDMISSILES AND NUCLEARWEAPONS ments or visually observesangular and linear discussedin chapter 6,is responsible for Let us not forgetmovement.On the basis of his observations, missile flight path control. he repositions the controlsurfaces as necessary that missile guidance andmissile control are he wants it. part of the overall weaponscontrol systemto keep the plane where direction system and Since there is no pilot in aguided missile which includes the weapons to note these movements, weinstall devices the fire control system,linked by communica- important to mention tion systems, all workingtogether to get thethat will detert them. It is (and sonars) forhere that some guidedmissiles do not detect missile to the target. Radars linear movement while others do.All guided detecting and tracking targets,and computers This will control system. The speedmissiles detect angularmovement. are part of the fire be explained clearly in thechapters which dis- of modern aircraft andmissiles makes com- of guidance. The control puters a practical necessityto compute targetcuss the various types in time to align thesystem is made up of severalsections that are speed, target angle, etc., designed to perform, insofar aspossible, the launcher and missile and sendthe missile to To accomplish this intercept the target.The weapons directionfunctions of a human pilot. equipmentpurpose, the controlsurfaces must function at equipment is a roomful of electronic the proper time and inthe correct sequence. that includes a targetselection and tracking launched, it receives console, director assignmentconsole, weapon After a missile has beep missile statuscertain controlling Orderscalled guidance sig- assignment console, and guided nals. The guidance signals mayoriginate from indicator. This chapter will not discussthe from within the missile operation of any of the aboveequipments; itan external point or behavioritself. To respond to theguidance signals, the willtellonly how they affect the missile must "know" two things:it must con- of the missile in flight. tinuously "know" informationregarding its movement, and it mustcontinuously "know" the PURPOSE AND FUNCTION: positions of the control surfaces. BASIC REQUIREMENTS Figure 5-1 shows a simplifiedblockdiagram of a missile control system.As mentioned be- The first requirement of acontrol system will be +a the control operationsfore, not all of these components is a means of sensing when missile itself: The locationof some of'.,com- are needed.The system must thendetermine of guids13 used what controls must be operated,and in whatponents varies with the type way. In an airplane,the pilot checkable instru-by the missile.

DEVICES FOR DETECTING MISSILE MOVEMENT CONTROL SURFACE OR MOVEMENT INFORMATION JET CONTROLS

SUMMATION ERROR SERVO AND .COMPUTER SIGNALS MECHANISMS NETWORK GUIDANCE SIGNALS

DEVICES WHICH PRODUCE GUIDANCE CONTROL SURFACE OR SIGNALS JET CONTROL POSITION INFORMATION DEVICE FOR DETECTING CONTROL SURFACE OR JET CONTROL POSITION 33.59 Figure 5-1.Simplifiedmissile control system. 162 Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS FACTORS CONTROLLED in any direction, and each jetmust respond to signals from any of the three control Missile course stability is madepossible by channels devices which control the (pitch, roll, and yaw). angular movement A control system using fourmovable jets is (also called rotational movement)of the mis-shown in figure 5-2. Each jet sile about its threeaxes. turns in only one The three flight plane:Two of the jets, #1 and #3, controlyaw. control axes are shown in figure 2 -7.These areJets 2 and 4 control pitch, and allfour jets are the pitch, yaw, and rollaxes. Chapter 2 de- used together to control roll.. scribes how missile controlsurfaces are used to maintain the stability of The first stage of Polaris A3uses four the missile in flight.movable nozzles to control pitch,yaw, and roll The second type of movementcalled translation,of the missile. The actuators, includes any LINEAR movementof the mivaile. which are moved For example, a sudden gust by hydraulic power,are connected directly to the of wind or an airrotatable nozzles. Control signalsare received pocket could throwa. missile a consieerablefrom the electronics package distanceoff the desired trajectory without in the missile. causing any significant angular The second stage of Polaris A3uses a fluid movement.Ifinjection system in which pressurizedFreon is you have ever flown in an airplane, thisshould be fairly easy to understand. If injected' into one ormore of four fixed nozzles, the plane hits anupon signal from the electronics package ofthe air pocket, it may drop several hundredfeet but missile. Two injector valves still maintain a straight and level are mounted dia- attitude. Anymetrically opposite each otheron each motor linear movement, regardlessof direction, can be resolved into nozzle.Older mods of Polarisuse jetevators three components: lateral (see chapter 2) to controlmissile movement. movement, vertical movement, andmovement Positions of the jetsare controlled by hy- in the direction of thrust. Thus,in addition to the three angular degrees of draulic cylinders linked to theengine housing. movement, we have One cylinder and linkage isrequired for each three linear degrees ofmovement. A missile engine. The direction in which hydraulic in flight can therefore be saidto have six pres- degrees of movement. sure is applied is determined byan actuator. The signals produced byerrors about the METHODS OF CONTROL missile axes of translation and rotationare combined by the missile compt.ternetwork to form We have discussed missile controlfrom the standpoint of moving the missilecontrol surfaces.Since some operational guidedmissiles function at extremely high altitudeswhere control surfaces are not effective (dueto low air density), other means ofcorrecting the missile flight path have been devised.The basic con- cepts of missile controlwithoutthe use of control surfacesare outlinedin chapter 2. These are the exhaustor jet vanes placed in the jet stream of thepropulsion system (fig. 2 -18B); fixed jets placedaround the missile (fig. 2-18A); and' the movablejet (fig. 2-18C), which is a gimbaled enginemounting.(The gimbaled arrangement is not unlikethat used to permit universal movement ofa free gyro.) The engine is mountedso that its exhaust. end is free to move and thus directthe exhauSt JETS 1 AND 3 CONTROL YAW gases in a desired direction. JETS 2 AND 4 CONTROL PITCH ALL JETS CONTROL ROLL The gimbaled engine mountingdoes not...4give ARROWS INDICATEJET MOVEMENT full control about.all three axes.It cannot control roll. To get control on all axes, two 33.180 gimbal-mounted jets can be positionedas shown Figure 5-2.Control by four jets in figure 2-18C., Both jets mustbefree to move (aft view of missile). PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS correction signals. When these correctionsig- MIXERS. The mixer combines guidance and nals are applied to the controllermechanisms,control signals in the correct proportion, sense, action of these mechanisms results in keepingand amplitude.In other words, a correction the missile in its correct flight path andat thesignal must have the correct proportionto the error, must sense the directionof error, then proper attitude. apply corrections in the proper amplitude. PROPORTIONAL.The proportional control TYPES OF CONTROL ACTION operates the load by producing an error signal proportional to the amount of deviation from the control signal produced by a sensor. The basic control signals may come from RATE.Rate control operates the load by inside the Missile, from an outside source, the or both.To coordinate the signals, computersproducing an error signal proportional to are used to mix, integrate,and rate the sig-speed at which the deviation is changing.This nal impulses. In a missile control system,theyoutput is usually combined with a proportional remembering is done by integrating devicesand'signal to produce the desired changein mis- the anticipation (of what to do next) is done bysile attitude or direction. These are not names of single components, rate devices. . The computer network can be thought of asbut rather, they designate the type ofaction the brain (or the pilot) of the missile.Theperformed by one or more components inthe computer network takes into account guidancesystem. signals, missile movement; and controlsurface positions.By doing this continuously, it canTYPES OF CONTROL SYSTEMS generate error signals.These signals cause control surface movements, or a change in the Regardless of which method of trajectory jet stream direction as describedabove, thatcontrol is used, whether by movement of con- tend to keep the missile at its design attitudetrol surfaces; jet vanes, movable orfixed jets, and on its correct trajectory. Actually, amis-movable or fixed nozzles, or fluidinjection, sile is rarely at its design attitude orexactlyall must use some source of power tomake on its prescribed trajectory.Like a ship, thethe movements. This power is initiallyproduced missile continuously yaws, rolls, andpitches,by hot gases, compressed or high pressureair, and experiences movements of translation.Theor electrical means. The poweristransmitted computer network can be compared to the helms-from the supply sources to the movablecontrols man on a ship.Both are always making cor-by PNEUMATIC, ELECTRICAL orMECHANI- rections. Seldom is either absolutely right. CAL means, or by using a HYDRAULIC trans- The terms "error signal" and "correctionfer systemin conjunction with the sources men- signal"are used almost interchangeably.tioned above. Strictly speaking, the signal that orders movement of the control surfaces to correct errors Before getting into the detailsof specific is a correction signal. It originates in thecontroltypes of control, let us firsttake a general section of the missile. Signals that tell the com-look at several possible controllersand computer about deviations an flight path are errorpare some of theiradvantages and disadvan- signals and originate in the guidance system.tages. Since all of these signals concern errors they of may be called error signals. A pneumatic system which depends on tanks An automatic control system of this type iscompressed air is obviously limited in range. generally referred to as a SERVOMECHANISM,Since air or any other gas is compressible, discussed later in this chapter. the movement of a pneumatic actuator is slow The job of a computer in a fire control sys-due to the time it takes to compress the air tem is to convert available information such asin the actuator to a pressure sufficient to move speeds, locations, and ballistic data, into re- it.Hydraulic fluid is practically incompress- quired information such as fuze settings, andible and will produce a faster reaction on an missile orders. It does thisbyuse of a complexactuator, especially when the actuator must of components and devices that makeupthe com-move against large forces.Thus, large, high puter network. According to theirmanipulationspeed missiles arecontrolled by hydraulic of control signals, they may be classed as: actuators. 3C4.'"°' Chapter' 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

A hydraulic system normallyweighs more because it needs a pump, reservoir, the APS systems relyon the main combustion and accu-chamber as the initial source ofenergy. Others mulator. Also a hydraulicsystem isard tohave their own energy maintain, requiring filling andbleeding opera- sources completely sepa- tions. rate from the main propulsionunit.Whateirer the At the high altitudes at initial source of energy, APSsystems may be which most missilesplaced in two broad categoriesSTATICand are intended to fly, temperatureand pressureDYNAMIC. In the static systems are severely reduced.This has an effect on energy is any type of control system. At extreme used in the same form in whichit is stored. In altitudesthe dynamic systemsenergy is changed from one hydraulic fluid may be uselessdue to severeform to another by a conversion changes in its viscosity. Airbubbles in metal unit. parts may expand and createmalfunctions. HighSystem Requirements altitude lubrication ofmechanically moving parts must be - onsidered.Changes of temperature also affect the operation Before taking up specificsystems, there are of electronic parts.several general requirements foran APS system Very few missiles havebeen designed whichthat we will mention briefly. First, do not have some part thatoperates by elec- the system tricity.The use of an all electric must be able to deliver thenecessary power controlduring all conditions of missileflight. Second, system would place all theequipment, exceptthe system must be able to the propulsion unit, withinthe electrical field. respond quickly and This would simplify accurately to domands madeon it. Third, the manufacture, assembly,system must be of minimum:size and weight con- and maintenance.Also, it would be easier tosistent with the requirements transmit informationor power to all parts of it must meet. the missile by wires, rather Fourth, the system must bedurable enough to than by hydraulicwithstand long storage undersevere conditions. or pneumitic tubing.Disadvantages of all- STATIC SYSTEMS.As electric control systems will bediscussed later previously men- in this chapter. tioned, the static APS systemsuse energy inthe same form in which it is stored. For An all-mechanical controlsystem in a mis- example, sile is not very probable. In the electrical energy ina storage battery may an all-mechanicalbe used directly to operatesolenoids. Com- system, error information wouldbe transferredpressed air also may be used from a mechanicalsensor by some mechanical directly to op- means such as a gear train, cable, erate control system components.Static sys- rotating ortems require no rotating machineryfor energy sliding shaft, or chainlinkage.+hislinkageconversion. would then connect to thecorrecting devices such as control surfaces DYNAMIC SYSTEMS.Indynamic systems or movable jets.Inenergy is changed from one form to addition, any computing devicesin the system another. would also be mechanical. For example, the potentialenergy in compressed air may be changed to electricalenergy through The major disadvantagesof a mechanicalan air-driven turbine and electric control system are thattoo much power would generator. be required to move the The same is true of combustiongases taken from necessary (and heavy)either the main combustionchamber or a sep- gear trains and linkages, and thefact that in-arate auxiliary combustion stallation of an all-mechanicalsystem would chamber. Liquid be extremely difficult in the fuel may be tapped off the mainpropulsion fuel small space allotted.tank and used to drivean auxiliary engine. To gain advantages andoffset disadvantages of the different types ofcontrol, combinationsAuxiliary Power Supply Unit are used, such as pneumatic-electric,hydraulic- electric, hydraulic-mechanical, or others. The components of the auxiliarypower supply ENERGY SOURCES may be packaged as a unit. The unitincludes a separate and special generator,usually of the gas turbine variety, used for the Missiles contain aue.liPxypower supply production (APS) systems in of on-board power.It can be either a solid addition to the main enginepropellant or a liquid propellanthot gas gen- required for thrust.The APS systemspro-erator that is duct-conneded vide a source ofpower for the many devices to a turbine which required for successful missile in turn is connected bya shaft to an electric flight. Some ofgenerator. The turbine isan energy conversion .105_ 101 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS has an air-driven hydraulic pumpassembly unit,converting potential energy to kinetic diffuser energy.The Terrier BT-3 missile, for ex-which uses air taken in through the ample, has two hot-gas generators, eachwithin the missile nose.The power system con- its package of solid propellant.The hot-gassists of an accumulator, rsureft, and the air- exhaust from one generator is fed to themis-driven hydraulic pump. sile's turbohydraulic system and theother goes Descriptions of solid-propellant and liquid- to the turboelectric system. The Tartarmis-propellant hot-gad auxiliary systems follow. sile has similar hot-gas generatorsystems to power the hydraulic and the electric compo- A BASIC SOLID PROPELLANT SYSTEM is nents of the missile. These hot-gas generatorsdiagrammed in figure 5-3.It does not repre- provide a significant saving in space andweightsent any spacific auxiliary power supplysystem over the compressed air systemformerly usednow in use. in the Terrier missile. They are placedin the The propellant chamber or combustor con- aft section, near the tail, which iscontrolledtains the propellant chargeaballistite or re- by the hydraulic system. All-electricsystemslated type of powder grainand a black-powder are planned to replacehot-gas generators. igniter and squib, in a propellant train sequence. Other power supply units, usually with aAfter the squib is ignited(usually just before battery source, areassembledas "packagelaunch) the propellant burns and evolves hot gas units" that can be easily installed orremovedto build up pressure in the chamber. The pres- from the missile.The Tartar missile, forsure is regulated by aregulating valve, which example, has five "wheels" in its electronicadmits .11r to a gas turbine(either multiple- or section, each with its own power supply, soifsingle- stage). The turbine is geared to ahydrau- there is failure in one "wheel" itdoes notlic pump and pressure regulatorandtoan alter- affect the operation of the others andthe de-nator.In the system diagrammed, hydraulic fluid output goes direct to tne hydraulic servos fective one can be replaced withoutdisturbing is then the others. and other hydraulic system units, and These internal power supplies are notusedrecirculated back to the pumps.Alternator until after the missile is in flight.As long asoutput goes direct to those units that requires the missile is on the launcher, power is supplieda-c, and through a rectifierand voltage regu- from the ship's (or aircraft) power.(Talos useslator to furnish regulated d-c. Aflyball gov- some of its internal battery powermomentarilyernor On principle similar tothose on old- before warmup power is applied on thelauncher.)fashionedstationaryreciprocatingsteam engines) may be used to govern alternator speed Not all missiles use hot-gas generators to In one provide auxiliary power.The Taloa missile1.o regulate a-c frequency and voltage. 1

EXHAUST 10 10 HYDRAULIC ATMOSPHERE SYSTEM IN CONTROL SECTION

MECIHINICALLY COUPLED

TO ELECTRICAL. .1.ALTERNAToR AND ELECTRONIC MX TNT

RECTIFIER Dc TO ELECTRICAL AND L..PRFPEATniTstromieV(ec7seu. s' oaj) AND ECTRONIC VOLTAGE EQUIPMEELNT REGULATOR

144.27 Figure 5-3.Typical solid-propellantauxiliary power supply. Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS ... WM, design, a separate turbine-drivenrotor generates a current which is fed (Other chemical changers takeplace, too, but this back to an in-is the main power-producingreaction.) The heat duction brake to regulateturbine speed. energy produced in .this process is In other designs, there isno hydraulic as much as pump; instead, the turbine exhaust can be used efficiently in small turbines;hence charges anthere is no need to burn thefree oxygen produced accumulator to develop hydraulicpressure.by the decomposition of the If the system uses pneumaticactuators, com- peroxide. The turbine bustor exhaust may be leddirect to the actuator control valves. Both Terrier and Tartarhot-gas auxiliary systems use a single stage, axial flow impulse NOZZLE NO2 type turbine of the typeshown in figure 5-4A. NOZZLE NO.1 In this turbine, thegases expelled through the nozzles are not reversed indirection, but make only one pass through theturbine blades. In a Terry turbine(fig.5-4B), the products of combustion are led througha gas manifold ring and pass through thenozzles. The gases then impinge at high velocityon the semicircular recesses (buckets)milled into the periphery of the wheel.In passing through the buckets the directionof flow is reversed 180 degrees.The gases are then caughtby a semicircular reversing chamber inthe casing, where they are again reversed 180°andreturned to the wheel. Theprocess is repeated five times through a 90° are of the turbinehousing, after which the gases are exhausted.Reversing the hot gases several times givesa multiple-stage effect, thereby usingmore of the potential energy in the gases. The electrical, mechanical,and hydraulic components discussed heremay, of course, be used equally well withliquid-fueled gas turbines. A BASIC LIQUID PROPELLANTSYSTEM is shown in figure 5-5.High-pressure inert gas 4th flows from the gas flaskthrough the arming REVERSAL valve and the pressurereducer valve.The 3rd arming valve is tripped justbefore launch. REVERSAL The gas flows into and inflatesthe fuel tank 2nd bladder. The fuel tank (fig. 5-6)consists of a REVERSAL metal tank with a plastic bladderinside it. The 1st fuel (in this case concentrated11202hydrogen REVERSAL peroxide) is stored ina metal tank. As the pressurized gas fills the bag ata regulated rate the fuel is forced out ofthe tank at a corresponding rate. A check valveprevents a return I fuel flow and transmission ofpressure waves from the decomposition chamberto the fuel tank. The throttle valve regulatesfuel flow to the decomposition catalyst tank.When the fuel comesintocontact with the decomposition 33.45:.46 atalyet (NaMnO4 sodium Figure 5-4.Turbines usedin auxiliary power permanganate) it supply (APS): A. Impulse turbine;B. Terry breaks down into free oxygen. (02)and steam. turbine. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS less common types because of theirlower weight per unit energy storage,longer shelf life, better voltage characteristics; greatersturdiness, and UQUID The HIGH ARMING FUEL TANK resistance to extremes of temperature. PRESSURE GAS VALVE REDUCER types used are silver-zinc,nickel-cadmium (so-called "Edison" type), and mercury.The first two are technically secondary orstorage the last is ENEPRESSURIZED GAS cells that can be recharged, while a primary type thatcannot be easily recharged. raras LIQUID FUEL vocabulary 'MM. STEAM However, in the necessarily narrow of missile and space specialists, anychemical battery is considered a primary typeif it is intended to be used once only,regardless of TURBINE THROTTLE CHECK C*C43.41"11°4 VALVE VALVE its nominal rechargeability. CATALYST The silver-zinc battery, which requiredthe TANK addition of the electrolyte(potassium hydroxide 144.28solution) at the time the power was needed,has Figure 5-5.Basic liquid-propellant auxiliarybeen largely replaced by anickel-cadmium power supply. battery which can be recharged.The need for a viable battery inthe missile has motivated much research, and decidedimprovements have resulted.While the batteries in a missile will drives a hydraulic pump and electrical genera- missile is fired, tors much as in the solid propellantunit. be used only once, when the Because the shaft speed of the turbine is sothey may be in position in themissile a long very high it is necessary to use aset of reduc-time before this event.Long. storage life and tion gears between the turbine and thealterna-rechargeability are two importantqualities. The newer type nickel-cadmium batterieshave tor and the hydraulic pump. life is good for AUXILIARY SYSTEMSUSING OTHERboth of these. While their shelf POWER SOURCES.One Navy missile usedtheseveral years, to be absolutely sureof full main engine's propellant to drive anauxiliary power unit.This was Corvus, now obsolete, in which a small gas turbine wasused to drive GAS INLET the engine's fuel and oxidizer pumps. The auxiliary power supply of the Regulus was driven by the main engine (turbojet) of the missile. In Taloa, an air-driven turbinedrives the hydraulic pump which pressurizes thehydraulic fluid use.. to operate the externalcontrol surfaces. During the boost phase,accumulators of high-pressure nitrogen supply the pressureto the hydraulic fluid. ACCUMULATORS are used for storing high- pressure inert gas (such asnitrogen) in some missiles. This arrangement is one ofthe two types of static power units to be found inNavy missiles. The arrangement for fuel feedde- scribed above for liquid propellantauxiliary power supplies JO one typicalmethod of using such an energy storage unit.Another is to valve the gal directly WO pneumaticcylinders to operate aerodynamic control surfaces. CHEMICAL BATTERIES utilise diemicarre- 144.29 actions to develop cl-c voltages.Common dry cells and lead.acid storage batteries arefaniil- Figure 5-6.Fuel tank in liquid-propellant tar to every one. Means power suppliesrely on awillary 'power system. Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS battery power, the battery is removed from each Nuclear power cells similar to missile every 30 days and iscompletely re- those devel- charged. oped experimentally by theAtomic Energy Com- In this way, there isalways a freshmission's SNAP program might battery in the missile. Thesebatteries can be also be used in recharged 200 to 300 times. missiles, although at present thisseems unlikely In some missiles, because of the anticipated high costof such units mercury batteries areand because their principalcharacteristics do used instead of the oldtype dry cell batteriesnot seem to meet the requirements where a small voltage isdesired. of missile systems. Specifically, nuclearcells character- Another type of batterywhich is inert untilistically can produce activated is one in whichthe electrolyte is In a fairly constant current solid form until shortly over a period of years, but intheirpresent state before the missile is toof development requiresubstantial shielding. be launched. Thebatterywill not develop an out-Satellites require a reliable put voltage unless theelectrolyte is in liquid power supply over a prolonged period, but missiles donot, and the form. In this arrangement,a detonating voltagepenalty of either radioactive is transmitted toa squib in the battery just be- hazard or heavy shielding seems like anunnecessary one to pay fore launch. The squib ignitesa chemical heatingso far as missiles are concerned. mixture; this causes theelectrolyte to liquefy and the battery is energized. In use, batteries eitIr feedd-c directly to This type is called electronic and electrical unitsthat require it, or a thermal battery be-drive alternators to furnisha-c. D-c motor- cause it requires heat tocause it to activate.driven hydraulic Its storage life isindefinite, either in or out pumps furnish hydraulic fluid the missile. ofunder pressure.(A battery can alsodrive a Another advantage is thatit doesvibrator-type a-c supply.) not have caustic or acidelectrolyte that can spill out and be a hazard. REQUIREMENTS OF A MISSILE-CONTROL The fuel cell isa type of chemical battery unlike primary and storagebatteries of the kind SERVOSYSTEM discussed above. In fuelcells, electric current is produced directly fromoxidation of a fuel, or We mentioned before thatthe missile control from a similar chemicalreaction. The reactionsystem is a servomechanism.In performing its is speeded by a catalyst;platinum is used atfunction, a servomechanismtakes an order and present, but search is continuingfor a cheapercarries it out. In carryingout the order, it catalyst. So far no fuel cellhas been developeddetermines the type andamount of difference to a point where it hisbeen adopted for use inabetween what should be doneand what is being Navy missile, but itis likely that some suchdone. Having determinedthis difference, the development will come in therelatively near fu-servomechanism thengoes ahead to change ture. Successful experimentalfuel cells havewhat is being done to whatshould be done. In been produced whichuse hydrazine fuel withorder to perform thesefunctions, a servo- oxygen as the oxidizer. Ahydrogen-oxygen cellmechanism must be able to: is specified for thetwo-man Gemini flights. Fuel cells will also be used for the Apollomoon 1. Accept an order whichdefines the result flights. desired. OTHER TYPES OFBATTERIES.At least in 2. Evaluate the existing theory, batteries of typesother than chemical conditions. can be used in guided missiles 3. Compare the desiredresult with the for auxiliaryexisting conditions, obtaininga difference be- power supply. At the present writing,solar cellstween the two. have been used successfullyto power satellite 4. Issue an order basedon the difference so sensors and data transmitters, butso far theyes to change the existing have not been employed inguided missiles. ed result. conditions to the desir- A solar batteryconverts the energy of light into electric 5. Carry out the order. energy. The most common For a servomechanism to solar cell is a siliconphotovoltaic celif selen- meet the require- ium cells are also used. ments just stated, it mustbe made up of two Temperature' has asystemsanerror detecting system and a considerable effect on theoutput. Contrary to con- the usual effect, the output trolling system.The load, which is actually goes up as the temp-the output of theservo, can be considered part erature decreases. of the controller.

105 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS delivered By means of servosystems, some propertyof compared with the quantity of energy a load is made to conform to adesired condition.to the load. The property under control is usuallythe position, the rate of rotation, or theaccelerationOPEN- AND CLOSED-LOOP of the load.The system may be composed SERVOSYSTEMS of electrical, mechanical, hydraulic,pneumatic, or thermal units, or ofvarious combinations of In the examples given above, the power source these units. The load device maybe any one ofis controlled directly by manualadjustment of a an unlimited variety; amissile control surface,switch or of a rheostat.In more complicated the output shaft of an electricmotor, and aservosystems, control signals are appliedto typical ex-the power device by the action of anelectrical radar tracking antenna are a few rather than by manual amples. or a mechanical device means. DISCONTINUOUS AND CONTINUOUS Automatic servosystenls can be divided into CONTROL two basic types: open-loop andclosed-loop illus-systems. The essential features of each are The simplest formaof control can be 5-8. trated by the elementary circuit shownin figureindicated by the block diagrams in figure 5-7A. The circuit contains a source of power, In both systems, an input signal mustbe a switch, or controllingdevice; and an un-applied which represents in some way the de- specified load. The elements are connectedinsired condition of the load. series. When the switch is closed, energyflows In the open-loop system shown in figure 5-8 to the load and performs useful work;when the A, the input signal is applied to a controller. switch is opened, the energy source isdis-The controller positions the load in accordance connected from the load.Thus, the flow ofwith the input.The characteristic property of energy is either zero or afinite value de-open-loop operation is that the actionof the resistance of the circuit.controller is entirely independent of theoutput. termined by the The operation of the closed-loopsystem Operation of this general type is calledDISCON- The TINUOUS CONTROL. (fig. 5-8B) involves the use of followup. In figure 5-7B, the circuit ismodified byoutput as well as the input determinesthe and action of the controller.The system contains substitution of a rheostat for the switch; elements the circuit now provides CONTINUOUSCON- the open-loop components plus two By displacing the rheostat contact, which are added to provide the followupfunction. TROL. The output position is measured and afollowup the circuit resistance is varied continuously over fed back for a limited range of values.The energy expendedsignal proportional to the output is in the load is then varied over acorresponding range rather than byintermittent, or on-off these action as in discontinuous control. Both MOOT simple examples represent a fundamental prop- COMTISM!!! I LOAD I erty of Control systems in general:the en- A ergy required to control thesystem is small

COIMARDON MICK

COMMIOLLIM RISULTAMT

CI°7111411112 111 33.61 33.60 . Figure 5-7.--Elementary control circuit: Figure 5 -8. Basic types of automatic servo- A. Discontinuous control; B. Continuous control. systems: A. Open-loop; B. Closed-loop. Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS comparison with the input value. Theresultant is a signal which is proportional to position the movable controlsurfaces in ac- to the differ-cordance with this attitude information.It is ence between input and output. Thus, thesystemvery important that you understand that operation is dependent on inputand output rather the than on input alone. control surfaces are not positionedon the basis of attitude information alone. Itis again pointed Of the two basic types,closed-loop controlout that movement information, (also called followup control) guidance sig- is by far the morenals,and control surface positioninforma- widely used, particularly in applicationswhere speed and precision of control tion are continuously analyzed inthe computer are required.network. The correction signalsare contin- The superior accuracy of theclosed-loop sys-uously generated on the basis ofall this infor- tem results from the followupfunction which is mation. not present in open-loop systems.The closed- loop device goes into operationautomatically to correct any discrepancybetween the desiredOVERALL OPERATION output and the actual loadposition, responding to random disturbances of theload as well as to changes in the input signal. Before studying the individual components of the missile control 'system, letus take a brief look at the operation of thesystem as a CONTROLLABLE FACTORS whole.Figure 5-9 shows the basicmissile control system in block diagramform. You will notice that the system isshown in con- The missile control systemis actually asiderably more detail than that in closed-loop servomechanism initself.It is figure 5-1. able to detect roll, pitch, and Free gyroscopes provide physical (spatial)ref- yaw, and it is ableerences from which missile attitudecan be

SENSOR FREE GYRO MGNALS SUMMATION AND ERROR COMPUTER AMPLIFIER IM SUL E ROLL, PITCH. NETWORK SIGNALS CONTROLLER YAW

GYROSCOPES

FOLLOWUP SIGNALS CONTROL FOLLOWUP SURFACE MICHANISM OR JET EXTERNAL OCILLOWUP Ocomou L -4 MISSILE AnTulia imal

33.62 Figure 5-9.Basic missile controlsystem. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

For any particular missile at-direction system and the firecontrol systems determined. sent from theand their related componentscomprise the titude, free gyro signals are weapons control system. These shipboard gyroscopes to the computernetwork of the aboard, includ- missile. equipments control all weapons the amounting guns, missiles, andtorpedoes.The mis- These signals are proportional to sile control systems are inthe missile, and of roll, pitch, and yaw at anygiven instant. from shipboard equip- After these signals have beencompared withmay receive direction other information (for example,guidance sig-ment.. nals), correction signals result. Thecorrection signals are orders to the controllerto position REFERENCE DEVICES the control surfaces. The purpose of the accurately, amplifier is to build the weak correctionsig- In order to determine errors the complete control systemmust have refer- nals up to sufficient strength to causeactua- The system is then caption of the controller.As in any closed-ence values built in. information playsable of sensing a change, comparingthe change loop servosystem, followup to a reference, determining thedifference, then an important role. Afollowup mechanism con- reduce the differ- tinuously measures the positions ofthe controlstarting a process that will to the com-ence to zero. surfaces and relays signals back The reference units in a missilecontrol puter network. system are of three kindsvoltagereferences, references. External Followup time references, and physical In addition to the internal followupwhichPURPOSE AND FUNCTION is actually measured by amechanism, we can The reference device(comparison device, think of the missile's movementdetecting de- comparison with vices as providing an externalfollowup feature.fig. 5-8) provides a signal for continuously de-a sensor signal, sothat equipment in the missile The fact that the gyroscopes has deviated from tect changing missile attitudeintroduces the ideawill "know" when the missile This is represented bythe desired attitude. Thereference section is of external followup. connected to the computersection.If the the dotted line in figure 5-9. reference section were omittedfrom the control section, the computerwould be unable to COMPONENTS OF MISSILE CONTROL compute error signals. SYSTEMS Figures 5-1 and 5-9 have namedparts of aTYPES OF REFERENCE missile control system and someof the com- The components The three types of referencesignals will be ponents have been discussed. described separately to show howeach type func- may be grouped accordingto their functions. system. They cannot be strictlycompartmentalized astions in the complete control they must work together and there isoverlapping.Voltage Devices for detecting missile movement may In some control systems,the ERROR SIG- be called error-sensingdevices.The amount voltage which and direction of error must bemeasured by aNALS are in the form of an a-c provide thecontains the two characteristicsnecessary to fixed standard; reference devices make proper correctionsin the flight path. signal for comparison.Correction-computing deviation, and the devices compute the amount anddirection ofThese are the amount of devices carrydirection of sense of the deviation. correction needed and correction The amount of deviation maybe indicated by out the orders to correct anydeviation. Power signal so that, as output devices amplify the errorsignal, but thethe amplitude of the error the deviation increases, theamplitude increases; prime purpose is to build up asmall computer the amplitude output signal to a value great enoughto operateAand if the deviation decreases, feedback loops pro-decreases. Therefore, whenthe missile attitude the controls. The use of has been corrected and thereis no longer a vides for smooth operation of thecontrols. amplitude drops to Do not confuse the missile controlsystemdeviation, the error signal with the weapons control system.The weaponszero. Chapter 5MISSILE CONTROL COMPONENTSAND SYSTEMS

The direction of deviationmay be carriedThe use of timers in guidancesystems is de- by the a-c signal as a phase differencewithscribedin the chapters on the different types respect to the phase of a referencesignal.of guidance. Only two phases are requiredto show direc- MECHANICAL TIMERS.The mechanical tion of deviation aboutany one control axis.timers used in guided missiles are generally When a phase-sensitive circuit,such as a dis- of criminator, the clock type, and are very similar inoperation is used to compare the errorto a mechanical alarm clock. The ordinaryalarm signal with the a- c referente signal, thedirectionclock can be set for a time delayup to twelve of error is established and theoutput contain-hours. The timers used in guided missiles ing this information is fed toother control can sections. usually be set only for time durationsin seconds or minutes. As with the alarm clock, theme- In most cases, the a-c referencevoltage ischanical timer in a missile receives itspower the a-c power supply for the controlsystem. Itfrom a compressed spring.Since the timers also furnishes the excitation voltagefor theused in missiles are not normally starteduntil sensor unit that originates the error signal.the missile is in flight, it isnecessary to provide The controller unit(fig. 5-1) usually re-some type of triggering mechanism to initiate quires a d-c signal, which must includethethe timing operation.Usually the mechanism information contained in the originalerrorconsists of a linkage which is actuated byener- signal.The amplitude of the d-c signalshowsgizing a solenoid. the amount of deviation. The direction of de- It is also possible to triggertimers by the viation is indicated by the polarity ofthe d-cuse of other timers. For example, a 5-minute signal. To keep the d-c signal frombecomingtimer could trigger a 1- or 2-minute timer. so large that it would cause overcontrol,a ELECTRICAL TIMERS.Two types ofelec- limiter circuit is used.Limiters require atrical timers are commonly used in guidedmis- d-c reference voltage, andfunction as a partsiles. of the reference unit. These are motor timers and thermal timers. In either type, the triggering is doneby an electrical signal, and the time interval begins Time when the trigger voltage is applied. MOTOR TIMERS.Figure 5-10 illustrates the principle of the motor timer. Avoltage is The use of time asa reference is familiarapplied to the motor tocause it to rotate. The to everyone. One common applicationis in thespeed of the output shaft is reducedby a re- automatic home washer. A clock-typemotor drives a shaft, which turns discs duction gear calibrated in accordancewith the that operateamount of time delay required. The switchwill electric contacts. These contacts closecontrolbe opened or closed by the output shaft,depend- circuits that operate hot- and cold-watervalves,ing on the particular function under control.The start and stop the waterpump, change theoutput current could be applied toa gyro torquer washer speed, spin the clothes dry, andfinallyor a throttle valve. By the addition of several shut off the power. Each operationma for aitems, the timer may be made torecycle itself specified time interval. This kindof timer canas shown in figure 5-11. The automatic clutch be used for certain missile control operations.in the figure releases the actuatingarm when A timer may be used to starta variety of con-the arm makes contact with the trolfunctions. Sometimes a timer is used microswitch. strictly as a safety device. The spring returns thearm to its initial position and the cycle is repeated. Anothermethod Timer control units vary considerablyinof releasing the clutch uses mechanicalmeans. physical characteristics and operations.All ofIn this type, a linkage betweenthe actuating them require an initial, or triggering,pulse.arm and the clutch would perform thesame Since all timers in a completesysteni are notfunction as the electrical release signal. triggered at the same time, each musthave fts The length of time required for own trigger.This is usually an eledtrfcal the actuating signal. arm to travel from the starting position to the It may be fed to a sdf0nold whichpoint where contact is made is the delaytime of mechanically triggers the timing device. . the unit. Mechanical, electrical, and pneumatictinier. THERMAL TIMERS.Anothertriggering are used in missiles. The principles areap-method involves the application ofan electrical plicable to most variations you willrun across.signal to a heater coil which heatsa bimetal 00 PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

GEAR OUTPUT TRIGGERING VOLTAGE MOTOR REDUCTION SWITCH SOX

33.122 Figure 5-10.Principle of the motor timer.

GEAR MOTOR REDUCTION CLUTCH SOX

MICROSIRTCH TRNNNIRRIG VOLTAGE

CLUTCH RELEASE OUTPUT SIGNAL

33.123 Figure 5-11.Motor timer with automatic recyclingfeature. strip and causes it to bend, thus opening ortacts is determined by the contact spacing,the closing electrical contacts. This method maybetemperature characteristics of the metalsin more familiar when you contemplatethe opera-the strips, and the characteristics ofthe heater tion of a typical thermostat like the one found incoil.The delay time is preset by the manu- the home. facturer; the assembly is then placed in a tube- Thermal delay tubes and thermal relays havetype enclosure, and the air is pumpedout of been used extensively to perform time delaythe tale. This type of construction(electron functions. These timers have a great advantagetube) prevents any adjustment of the time delay. over the electrical timers in the ease with latch PNEUMATIC TIMERS. Pneumatic timers they recycle themselves; however, they are notoperate on the basis of the time requiredfor a as accurate as the electrical timers.Figurequantity of compressed air to escapethrough a 5-12 shows a thermal delay tube. Rs compo-needle valve.The opening in the needle valve nents are bimetallic strips, a heating coil, can be adjusted (time adjustment,Ng. 5-13). The and a set of contacbs. smaller the orifice, the longer it will takethe When a triggering voltage is applied, the close the heating coil heats ONE of the bithetallic strips.piston to come down far enough to contacts. As the temperature rises, the strip deforms and There are two general types of pneumatic its contact moves toward the °titer contact.timers-piston and diaphragm. When the bimetal strip has heated sofficientlyt the contacts touch and the output circuit is ..PISTON TYPE TIMERS. Figure 5-13A completed, causing the preset function tooceur.dims the operation of a piston type pneumatic 11** amount cot time between application attimer.This type of timer is often employed the triggering voltage and closing of the coo. iminediately on loatching a missile. The sudden Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

classifications we have discussed. Theremain- SI -METAL STRIPS ing types have been groupedunder theheading of physicalreferences.Theyinclude gyros, pendulums, magnetic devices, andthe missile HEATING COIL airframes. CONTACT They may be compared to bench POINTS marks, or fixed positions fromwhich measurements can be made. TRIGGERING VOLTAGE GYROS.Although gyrosare physical references, they are discussed under the heading of sensors.The gyro rotor in itselfcannot determine missile attitudeinformation. Pick- offs must be used in conjunctionwith gyros to determine missileattitude information. The gyro pickoff system can senseany change in missile attitude withrespect to the gyro.

OUTPUT Pendulum CIRCUIT The pendulum may be used toestablish a vertical reference line ina guided missile. 33.124Any object within the earth'sgravitational pull Figure 5-12.Thermal delaytube. is attracted directly toward thecenter of the earth. acceleration of the If a weight is suspendedon a string, missile at launch causes thethe weight will come to rest insuch a way as inertia block to move in the directionindicated.to cause the string to represent This releases the catch, andthe timer is then in the direction operation. of the true local vertical. Thisprinciple finds Compressed air under the felta common application in the carpenter'splumb- washer is permitted toescape throughthe presetbob. opening of the needle valve. Asthe plunger moves down, due to the decreasing air Some gyros are precessed toa vertical pressureposition by a pendulum device calleda "pendu- and the force of the spring,the contacts comelous pickoff and erection system." closer together.After the proper time delay, The com- the contacts will meet and the output plete gyro system is calleda vertical gyro; circuit willit may -be used to measure thepitch and roll of be energised, causing actuationof some mecha-a missile. nism in the missile. MAGNETIC DEVICES.Magneticcompasses DIAPHRAGM TIMERS.Anothertypeof pneumatic timer is the diaphragm have been used for centuriesto navigate the timer shownseas. The compass enables a navigatorto use in figure 5-19B. Thesame principle is involvedthe lines of flux of the earth's with this timer as with thepiston type. Prior magnetic field to being put into operation, as a reference. A similar device,known as a the solenoid is"flux valve" is used Aisome missile control energized, thus holding thecore and springsystems.Its primary purpose is to in the position shown. At thistime, the leather keep a diaphragm is stretched directional gyro aligned witha given magnetic so that air is per-heading. The directionalgyro can then be used mitted to enter the inlets.When the solenoidto control the yaw of a missile. is deenergized, the spring willforce the piston A bar magnet will attempt upward, closing the air inlets.The air will to align itself then be forced to in accordance with the directionof the earth's escape at a preset ratemagnetic field.When the bar is aligned ina through the needle valve. Aswith the pistonnorth-south direction, itmay be used as a type timer, a function in themissile will bereference to determine bearings actuated when sOfficient airescapes to allow around it. the contacts to meet, MISSILE AIRFRAME.Theairframe of the A missile must be used for certainreferences. Physical References For. example, the movement of flight control surfaces cannot be referencedto the vertical, There are a number of referencesfor missileor to a given heading, because such control systems other than the references voltage and timechange as the missile axeschange. Therefore, PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

WILL CAUSE SUDDEN 411. THE INERTIA CATCH FORWARD MOTION BLOCK TO OF THE PULL AWAY MISSILE OUTPUT CIRCUIT INERTIA BLOCK

SPRING CYLINDER (COMPRESSED) V

TIME ADJUSTMENT SCREW PELT WASHER

A NEEDLE VALVE

TIME ADJUSTMENT SCREW NEEDLE MT,

AIR MAU=

AIR INLET LEATNER aAPNRASM

TRIGGERING VOLTAGE SOLENOID

IRON ARE

WSW (COMPRISES" OUTPUT

'VW

33.1254127 Figure 6-130Pneumatic timers: A. Pisbin typepneumatic timer; B. Diaphragm timer.

112- Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

movement of flight surfacesare referenced to the The basic difference between missile airframe. and the rate gyro is the free gyro Synchro indicatorscan be used to indicate in the way theyare the angular position of control mounted. Figure 5-14B showsa simplified view surface withof a roll rate gyro.Notice that the rotor is respect to the missile airframe.A potentiometer can be used in the mounted in single gimbals ratherthan the two same way by mountingsets of gimbals which supported thefree gyro. it on the missile airframeso that its shaftThis arrangement restricts the will be driven by the flightcontrol surface freedom of the movements. gyro' rotor.When the missile rolls, thegyro mounting turns about the roll axis(arrow A), carrying the gyro rotor with it. SENSOR UNITS This causes a force of precession at a right angleto the roll axis, which causes the rotorto turn about GENERAL the pitch axis (arrow B). Restraining springs may be attachedto the The sensor unit ina guided missile controlgimbals as shown. The force system is a device usedto detect deviation on the springs 1 from the desired attitude.In this section, we will discuss the use ofgyroscopes, altimeters, and transducersas sensing units. Gyroscopes are generally considered to be thebasic sen- AXIS Z sor unit in any missile control system.Other types of sensors, suchas altimeters and trans- GYRO FRAME ducers, are classedas secondary units. SPIN AXIS As mentioned above, thegyro itself is a physical reference unit; thepickoff is the sensor. GYROS AXIS Y

One of the most importantcomponents of GIMBALS the missile control systemis the gyroscope, or gyro. A gyroscope containsan accurately ROTOR balanced rotor that spinson a central axis. Gyros used for missilecontrol applications are divided into classes: gyros usedfor stabi- alzing (control) purposes andgyros used for both guidance and stabilization.If turns or other maneuvers arenecessary, a third gyro A is required no that there willbe one gyro for Yaw AXIS NOSE each sensing axis. GMT A minimum of twogyros is necessary for missile right stabilization. Eachgyro sets up a fixed reference line from whichdeviations in missile pitch, roll, andyaw are detected and measured. These vertical and horizontalgyros are free gyros, that is, each is mounted in twoor more gimbal rings (fig. 5-14A)so that its spinsuds is free to maintain a fixedorientation in space. In addition to the controlsignals from the vertical and horizontal gyros,which are proportional to the deviation of themissile the desired attitude, a signal thatis to the rate of deviation is required for accurate 33.63:.71 control and Smooth operation. A RATEGYRO- Figtwe 5-14.Gyroscopes (fig. 5-141B) tarnishes the rate of used in missiles: deviation signal. A. Free gyroscope; B. Rollrate gyroscope. 113- PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS would then be proportional to angular acceleration about the roll axis. Three Tate gyros are normally installed in a missile to measure the accelerationsabout the three mutually perpendicular missile axes. When the input is torque and the output is precession, the gyro is called an integrating gyro. The restraining force is viscous damping instead of a spring restraint.It may be a her- metically sealed integrating gyro(RiG). Like a rate gyro, it has only a single degree of freedom. The restraining force is proportional to the gyro precession rate instead of displacement. Basic Properties of Gyros Gyroscopes have two properties which make them useful in serving as space references in guided missiles: 1. The gyro rotor tends to remain in a PRECESSION APPLIED fixed plane in space if no force is applied to it. PORCE 2. The gyro rotor has a tendency to turn at a right angle to the direction of an outside POINT X . force applied to it. 00, INERTIA.The idea of maintaining a fixed PRECESSION t TORQUE plane in space is easy to show. When any object CAUSED is spinning rapidly it tends to keep its axis SY WEIGHT pointed in the same direction. A toy top is a good SPIN example. As long as it is spinning fast, it stays balanced on its point. It resists the tendency of 'WEIGHT gravity to change the direction of its spin axis. The resistance of the gyro against any force 33.64:.65 which tends to displace the rotor from its planeFigure 5-15.Gyroscopic precession:A. Ap- of rotation is called rigidity in space. It mayplication of force; B. Direction of precession. also be called gyroscopic inertia. PRECESSION. The second property of the gyro is that its spin axis has a tendency to turn rotation.In the figure, a weight is attached to at a right angle to the direction of a force applied the spin axis.This is in effect the same as to it (fig. 5-15A). This characteristic of a gyro applying a force at pointX. The resulting torque is the cause of precession. There are two types tends to turn the rotor around axis CD.But due of gyro precession: REAL and APPARENT. to the property of precession, the applied force Real precession is sometimes called INDUCED will be transferred 90° in the direction of rotor PRECESSION. spin, causing the rotor to precess around axis DIRECTION OF GYROSCOPIC PRECES- AB. Thus, it may be seen that precession tends SION.. -When a downward force is applied at to rotate the spin axis toward the torqueaxis. point A, the force is transferred through pivot This type of precession is called REAL pre- B (fig. 5-15A).This force travels 90 and cession. causes downward movement at C. This move- A force applied to a gyro at its center of ment at a right angle to the direction of the gravity does not tend to tilt the spin axisfrom applied force is called PRECESSION. The force its established position, and therefore does not associated with this movement (also at right cause precession. A spinning gyrocanbe moved angles to the direction of the applied force) ill4n any direction without precession, ifits axis called the FORCE OF PRECESSION. can remain parallel to its originalposition in Figure 5-15B illustrates the direction of space.Therefore, the gyro can measure only precession caused by the application of a force those movements of the missile that tend totilt tending to turn the rotor out of its plane of or turn the gyro axis. Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS APPARENT PRECESSION.A spinning gyrorotor speeds. Rotor and gimbalbearing friction on the earth's surface will appear totilt (orpre-is actually the main cess). with thepassage of time. Actually, the cause of gyro drift. The spin axis does not tilt with problem of improvedgyro stability has been relation to space;approached with a view towardreducing this the apparent precession isdue to the earth'sfriction. rotation.Figure 5-16 shows the gyro at the The main cause of randomdrift in gyros is equator with its spin axishorizontal at timefriction in the gimbal bearings. 0000. The earth is rotating inthe direction of Energy is lost the arrow and is making whenever a gimbal rotates. Thelarger the mass one revolution in 24of the gimbal, the greater thedrift from this hours. An observer inspace would see that thesource. spin axis always points tothe same position in space while the earth rotates.But to an ob-Erection Systems server on earth, the spin axisappears to tilt 45° every 3 hours.This is called APPARENT Some missiles are providedwith compen- PRECESSION. sating mechanisms to keep the In some missiles, apparentgyro precession, gyros in their sometimes called apparent proper reference frames. Thesemechanisms gyro rotation, ad-are a vertical gyro erection system,and hori- versely affects flights of longduration, unlesszontal gyro slaving systems. some kind of compensation is used to keep the VERTICAL GYRO ERECTION.Avertical gyro in a fixed relation to the earth'ssurface.gyro erection system consists of The compensating mechanismsare gyro erection a precession and slaving circuits. sensor, the gyro, an amplifier, anda torque motor. This system representsone of the many UNWANTED GYRO PRECESSION (DRIFT). secondary servoloops within Once the gyros are spinningin their proper a guided missile. planes, they theoretically The precession sensor detectsthe deviation of should remain in theirthe gyro rotor from itsproper plane of rotation. same relationships with space.UnfortunatelyThe resultant electrical there are certain imperfectionsin the gyro- signal is amplified and scopes which result in a drift then used to drive a torquemotor which pre- away from theceases the gyro back to itsproper plane. original planes ofrotation. For example, The precession sensor even the slightest imperfection in thegyro rotor may consist of one will cause some unwanted of the pickoffs described inthis chapter. The precession at highvarying output of the pickoff willbe determined by the movement of a pendulousweight suspended in the gyro housing. Themovement of the weight in seeking the local verticalresults in corresponding signals which wouldcause the gyro rotor to retain its proper planeof rotation. HORIZONTAL GYRO SLAVINGSYSTEMS. In some missiles, horizontalgyro slaving systems are used to keep the horizontal 21 gyro rotor aligned with a specific magnetic headingfor a MAYOR portion, or for the duration ofa missile flight. This may be accomplished bythe use of a flux valvea unit that senses theearth's magnetic field. The flux valve consistsof an exciting coil and three pickoff coils woundon a metal core. The application of flux valvesin guidance systems is discussed in the nextchapter.

IVA 1260 Improvements in Gyros Figure 5-17 shows twotypes of improved gyros. FLOATED GYRO UNIT.Afloated gyro unit Figure 5-16.Apparent 27.132 .(fig. 5-17A) is an exampleof the progress that gyroscopic precession.bat been made in thedevelopment of more 115 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS axis bearings, thus riinimizirg frictionat these accurate gyros. In this gyro, thegyrohousing is also be used floated in a viscous dampingfluid. Because ofpoints. Gases other than air may the floating action, gimbalbearing friction isfor this purpose. greatly reduced.Thermostatically controlled heaters may be included in the unitto maintainUse of Gyros in Missiles the damping fluid at properviscosity. Another applications in type of gyro uses a nonviscousfluid. It is known While gyros have numerous gyro.It is used ex-many types of equipment,machinery, etc., we as a position-integrating will consider only their use inmissiles. tensively to control stable platforms. MISSILES.To AIR BEARING GYROS.An airbearing gyro FREE GYROS IN GUIDED reducing device.illustrate how free gyros are usedin detecting is another example of a friction missile attitude, let us first refertofigure 5-18. The gimbal bearing shown Infigure5-17B is missile is mounted in such a way that acushion of com-Suppose that the design attitude of the horizontal, as shown in figure5-18A.The gyro pressed air continuously flows aroundthe bear- in the ver- ing surfaces. Bearings usingcompressed air aswithin the missile has its spin axis precision-machined so that thetical plane, and is mounted ingimbals in such a a lubricant are manner that a deviationinthe horizontal attitude clearance at the bearing surfaceis only about physically affect the .002 inch.When the air is flowing aroundtheof the missile would not negli-gyro. In other words,the missile body can roll bearing surface, friction is practically around the gyro and the gyro willstill maintain gible.Although not shown In figure5-17B, (fig. 5-18B). Note compressed air may also be portedto the spinits same position in space that the missile has rolledapproximately 30°, but the gyro has remainedstable in space. If we could measure theangle between the rotor and a point on the missile body wewould know GYRO OUTPUT omen WHEEL AXIS exactly how far the missiledeviated from the GINS/ ,L 141. horizontal attitude.Having determined this, the control surfaces couldthen be positioned to return the missile to thehorizontal. Actually, a minimum of two free gyrosis required to keep track of pitch,roll, and yaw. The vertical gyro just described canalso be used 5- SPIN to detect missile pitch asshown in figure AXIS 18C. To detect yaw, a second gyrois used with its spin axis in the horizontalplane and its DAMPING will then be FLUID GYRO DAMPING rotor in the vertical plane. Yaw HOUSING FLUID detected as shown in figure5-18D. HOUSING RATE GYROS.The free gyros justdescribed provide a means of measuringthe A AMOUNT of roll, pitch, and yaw.The free gyros therefore can beused to develop signals, which are proportional to the amountof roll, pitch, and yaw. Due to the momentumof a missile in responding to free gyrosignals, large AIR IN overcorrections would result unless there were some means of determininghow fast the angular movement is occurring. For example, suppose that a correction signal is generatedwhich is proportional to an error of 10° to the leftof the proper heading. Thecontrol surfaces are auto- missile to the 8 matically positioned to bring the right.The missile responds by comingright. 33.80:.81 But because of its momentum it will passthe units: correct heading and introduce an errorto the Figure 5-17.Friction-reducing gyro signals that take A. Flnated gyro unit;B. Air breathing gyro.right. To provide correction

'*.i§fa Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

momentum of the missile intoaccount, r ate gyros are used. These gyros continuouslydetermine _At angular accelerationsabout the missile axes. By combining free gyro signalswith rate signals from the rate gyros, thetendencytoovercorrect is minimized anda better degree of stabilityis obtained.The rate gyro actuallyprovides a refinement or damping effectto the correcting process. Without rate gyros,a missile would overcorrect constantly. A rate gyro (fig. 5-14B)supplies the rate-of- deviation signal. Therate gyro is free to rotate about only one axis. Ayaw rate gyro is mounted with its spin axis parallelto the missile line of flight. A roll rategyro is mounted so that its spin axis is parallel tothe pitch axis, at right angles to the line of flight.A pitch rategyro is mounted with its spin axisparallel to the yaw )111' axis of the missile and atright angles to the line of flight. 4481;ingsweas# Pickoff Systems A "pickoff" isa device that receivesenergy from the sensors andtransmits this energy, either in the same formor in anotherform, to a 1 point where it is put topractical use. Most of the pickoffs used in guidedmissiles are electrical devices.In addition to transmittingenergy from the sensors, theyare alsousedto measure outputs of physical references,such as gyros. In this second respect, the pickoffsthemselves act as sensors. The gyro rotorin itself carrot determine missile attitudeinformation. Pickoffs must be used in conjunctionwith free and rate gyros to determine missile attitudeinformation. 4 The gyros indicatethe linear and angular displacement; the pickoff mustbe able to measure the amplitude and directionof the displacement and produce a signalthat represents both quantities. ALTIMETERS

To ensure that missilesstay within prescribed height limitsor perform functions at specified altitudes, devicescalled altimeters may be used. Two basictypes of altimeters - are pressure altimeters and absolute altimeters 33.67-.70(radar altimeters). Figure 5-18.Freegyro behavior in missiles:. A. Missile horisontalgyro stable in space;Pressure Altimeters B. Missile rollsgyroremains stable; C. Idle- Bile pitchesgyroremains stable; D. Missile yawsgyro remains stable. Pressure altimetersare simply mechanical aneroid barometers.The aneroid barometer PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

since both cells change withtemperature while consistsofa small, bellows-likeairtight chamber from which most ofthe air has beenonly one changes with pressure. (which varies An altimeter cell measuresaltitudes ashigh removed. Atmospheric pressure as 500,000 feet.This wide range gives the cell with altitude) works tocollapse the chamber mechanical aneroid. against spring pressure.As altitude increases,an advantage over a the compression effectdecreases. The slight motion of the spring ismagnified through link-Absolute (Radar) Altimeters ages or detectedby pickoffs. Theresulting signals may be used to precessthe pitch gyro, ab- converted directly into control Radar altimeters are used to measure or they may be solute altitudethe distancebetween the missile surface movement via themissile computer net- rather than above sea variations in pressure withand the terrain beneath it work. Unfortunately, level. It measures the timerequired for a radar altitude are not alwaysexactly constant, thereby be reflected, and requiring the use of a standardrate of change ofpulse to reach the ground, This rate is referred toreturn.Since the operation does notdepend on pressure with altitude. atmospheric data, the radaraltimeter is free as the "standard pressurelapse rate." For any altimeter is calibratedfrom some of thedisadvantages of the baro- change of pressure, the metric types.One type of radar altimeter is so that its output isproportional to the change (c-w) frequency -mi dulated of altitude in accordancewith the standardthe continuous-wave (i-n1) altimeter. pressure lapse rate. In the c-w system, thetransmitted microwave signal is variedregularly in frequency in Altimeter Cell accordance with a sawtoothmodulating voltage. The signal is directed towardthe ground wher e a An altimeter cell also detectschanges in to the receiving altitude and converts thisinformation into anportion of it is reflected back antenna.The echo wave is comparedin the electrical signal.The unit consists of a fila- output frequency ment of fine platinum wire,heated by an elec-receiver with the instantaneous vented envelope.of the transmitter. Aninterval of time passes tric current and enclosed in a between the moment thesignal is transmitted The vent is always connected to astatic pres- at the receiver. sure line. When thealtitude or static pressureand its arrival by reflection the filament canThis time interval is directlyproportional to changes, the rate at which the altitude of the missile.During this same release its heat changes, andthe temperature frequency has and resistance of the filamentalso change. Thistime interval, the transmitted characteristic is utilized byconnecting thebeen intentionally varied.By comparing the new transmittedfrequency with the echo fre- filament as an arm in a'Wheatstone bridge. time lag is ob- Usually two cells are placed inthe bridge asquency, adifference frequency or cellisvented and onetained which is proportional to theelapsed time shown in figure 5-19. One interval and to the altitude of the missile. sealed in order to compensatefor.surrounding temperature changes. The signaloutput of the bridge is proportional only to pressurechangesAIRSPEED TRANSDUCERS Speed measuring devices areused in some Missiles to cause specifiedfunctions to occur during flight.One of these devices shown in figure 5-20 is called an airspeedtransducer. Its principle of operation issimilar to that of the aneroid barometer justdiscussed. A transducer. is. a device which isoperated by power power to another .ifrom one source and supplies 'deice, in the same or a differentform. In most missile applications, a transduceris used to change mechanical motion toan electrical voltage.The ram air pressure'experiezieed by the missile in the atmosphere istransmitted to the 33.128 electrical signal Figure 5-19.Altimeter cell. bellows and converted- to an Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

A-C INPUT

BELLOWS

7; fralSIGNAL OUT

33.129 Figtre 5-20.Airspeedtransducer. through a bridge type electricalcircuit (fig. 5- 20) the output signal which make them useful inguided missiles. will vary with the ram airThe most common types pressure which is proportional to missilespeed. of electrical pickoffs Other types of electrical are: pickoffs also may be 1. Reluctance pickoffs used to convertbellowsmovement into electrical information. 2. Potentiometer pickoffs Another type of speed measuring 3. Synchro pickoffs device de- 4. Capacitance pickoffs pends on the transmission andreception of r-f energy, and is similar in principle to theradar VARIABLE RELUCTANCE altimeter:"A slight shift in frequencyof the PICKOFFS transmitted energy provides a bastii (Doppler Figure 5-21 shows effect) for electronicallydetermining missile an internally operated speed. The use of Dopplerradar will be dis-variable reluctance pickoff whichmay be used cussed in some detail ina later chapter of thiswith. a- rate gyro. The pickoffconsists of an course. E-shaped metal block withcoils wound around its ends and a permanentmagnet located in the PICKOFFS Pickoffs, briefly describedin connection with gyros, are important in themissile control system because they producesignals from the intelligence developedby a sensor unit. The GYRO ROTOR signal mnst be one that is suitablefor use in the BRASS-PILLED SPIN AXIS control astern. The pickoffmust be able to SLOTS determine the direCtion ofdisplacement and then produce a Opal that indicatesthe direction. In COILS electrical systems the indicationmay be a phase, AIR GAP polarity, or Voltage difference. LNICO CRYSTAL The ideal pickoff 'shouldhave a consider- MAGNET able change in output fora small movement. of DIODE thepickoff.. It .EhoUld also haveminimum torque or friction: leas since these losSes would be reflected to thesensor element and OUTPUT affect its operation.Small physical dimen- FILTER sions and .light weightare additional require CONDENSERS ments.The hull point (no output)should b sharply defirked. OUTPUT ElectriCal pickOffs' are extremelysensitive and reflect little torque backto the sensor or 33.72 referenCe unit, Figure 5- 21. Internallyoperated It ii:prinuirfly,these qualities reluctance pickoff. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS in center.The gyro rotor is made of ferrous When the rotor is in the position shown around itsfigure 5-22A, the flux lines from theexcitation metal and has brass strips spaced equal and periphery.The permanent magnet causes awindings cutting the secondary are magnetic flux to be established.The spinning180° out of phase.In this condition, no volt- rotor causes regular variations influx density.age is induced in thesecondary windings. When the gyro precesses because ofangular As a result, an a-c voltage componentis induced it is in the two coils. When there is noprecession theacceleration, the rotor turns because air gaps are equal and the a-c components can-directly coupled to the gyro gimbal.In figure be-5-22B, one end of the rotor is showndisplaced cel one another. When the gyro precesses the rotor de- cause of an angularacceleration, the air gap isto the left. This displacement of increased at one end and decreased atthe other.creases the reluctance tothe magnetic flux in the volt-left leg and increases the reluctancein the right This change in the air gaps causes different from the ages to be induced in thetwo coils. The dif-leg. This results in more flux lines ference between the two voltages isproportionalleft primary cutting the secondarywinding. Thus being rectifiedan a-c output is inducedin the secondary winding. to the angular acceleration. After This voltage is 180° out of phase withthe a-c and filtered, the resultant d-c Voltageisthe rate is pro- signal. The output sense (directionof deviation)excitation voltage. The output voltage is indicated by positive or negativepolarity.portional to the displacement of therotor. Dis- placement of the rotor to the rightwill have an opposite effect and an in-phase outputvoltage will EXTERNALLY OPERATED result. guided RELUCTANCE PICKOFF . This pickoff has many applications in missiles in addition to serving as arate gyro The externally operated reluctancepickoffpickoff. most commonly used in guidedmissiles is usually referred to as a differentialtransformer.POTENTIOMETER PICKOFFS This pickoff, shown in figure 5-22 consistsof a laminated steel rotor attached by a shaftto the A potentiometer is a device fortranslating rate gyro gimbal. Two E-shapedlaminateda quantitative motion(angular or linear) into steel cores are attached to the gyromounting.a proportional electricalresistance. It meas- isures by comparing thedifference between the Around the outer legs of each of the cores potentials. a primary windingconnected in series op-'mown and the unknown electrical position. There is a secondarywinding (pick-Figure 5-23 shows the principle of thepotentiom- off coil) around the center legof each core.eter pickoff. The circuit shown in thefigure is

A-C VOLTAGE OUTPUT A-C EXCITATION VOLTAGE

SHAFT ATTACHED TO GYRO GIMBAL

A-C EXCITATION VOLTAGE A-C OUTPUT A 33.73 Figure 5-22.Externally operatedreluctance pickoff: A. Balanced conditionno output; B.Rotor displaced to left, causing output. Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

33.74 Figure 5-23.Principle ofa potentiometer pickoff.

referred to as a bridge circuit.When the.wiper A arm is at C, there will be no output(eOUT) since the input (EAppuED)is placed .across RESISTANCE equal resistors. Now, if thewiper arm is moved ELEMENT to C' the output will beproportional to the displacement of the arm due toan imbalance in resistance in the line AB. Potentiometer pickoffs consistof wire-wound resistors and movable slidingcontacts (fig. 5-24A). The resistance wireis wound on a strip Which is bent in the shapeof a cylinder. 1000vvuu CS 0\ The wire and strip togetherare referred to as the resistance card. Thewiper arm can be positionedat any point around the circum- ference of the card. B The position of the movingarm determines the amount of voltage, but itis also possible to use the variation in resistanceas the control medium. If the shaft of thepotentiometer is mechanically connected to thesensor, the output voltage will vary according tothe moving arm displacement. .With the wire-woundmethod. of construction however the outputof the potentiometer does not change smoothlyas the wiper arm ismoved. Instead, .the output voltage changes in jumps, each jumpbeing proportional 11781hlifiliTsUrNf,P,V1RFilatttaraM to the distance between adjacentturns of wire and the voltage drop across eachturn. A potentiometer having 1,000 turns ofwire is said to C have a resolution of .1 partin 1,000 or a resolution, of .1 percent.: To. iMproyeresolution, the resistance wire is sometimeswound in a helix 33.75-.77 as shown inligure,.5-2413., Figure 5-24.Potentiometers:A. Wire wound . potentiometer; B. Helipot; C.Potentiometer .A.potenticimeter wound pickoff used with a free this manner .is . gyro. known as a helipOt. The wiperarm shoWn the figure wOUld.. make .tinturns around thewith the resistance wire, thus cirminference'of 'the' card cover the entire eliminating the voltage range: The advantageis in the fa&jumpy output inherent in theconventional po- that the wiper arm maintains continuous- tentiometer. Figure. 5-24C showsa potentiom- contacteter pickoff used with a freegyro. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS there is no out- SYNCHRO PICKOFF AND two outside plates is equal when put from the sensor. If, however, asignal from CONTROL TRANSFORMERS the sensor causes the center plateto move The term synchro is applied to a groupoftoward the bottom plate, the capacitancebetween devices used for transmitting eitherangularthese two plates will increase and thecapacitance data or torques of fairly small magnitudewith-between the top plate and the centerplate out the use of a mechanical linkage.The sim-will decrease. transmitter This change in capacitance can be used to vary plest synchro system contains a in oscil- which is electrically connected to areceiver.the tuning of an oscillator. The change The transmitter is a transformer with arotata-lator frequency is then used for sensecontrol. ble prinuiry that converts a mechanicalinput This type of pickoff is the mostsensitive of into an electrical signal, and transmitsthe sig-all, since a very slight change in platespacing nal to the receiver. The synchroreceiverwill cause a large change in frequency. receives the signal and converts it into a me- The electrical pickoffs just described are chanical output. If the rotor of thesynchrocommon to many guidedmissiles. Other types transmitter is coupled to a sensor orreference, and variations of those describedwill be cov- the -movement of the reference will cause aered in later chapters with the equipmentswith corresponding movement of the transmitter ro- which they are associated. tor. Due to the electrical connection ofthe receiver, its rotor will move in exactcorrespond- PICKOFFS AND FREE AND RATE ence to the motions of thetransmitter rotor. GYRO SIGNALS the Unlike the combination described above, of synchro control transformer is used toproduce Not that you have a basic understanding a voltage proportional tothe movement of thesome of the pickoffs usedin guided missiles, synchro transmitter rotor, rather than an an-let us see how signals from the free gyrosand gular movement. Such a voltage maybe am-signals from the rate gyros arecombined to within form resultant signals. plified and then used to power other units unwanted a control system. When a missile experiences an sel-angular acceleration, the rate signal iscombined Synchro pickoffs are sometimes called such a way as syns, autosyns, or microsyns. with. the free gyro signal in The fundamental types of synchro unitsand to return the missile smoothlyto its desired discussed inattitude. For example, assume thatthe pre- their principles of operation are horizontal, and Basic Electricity, NavPers 10086-A. scribed attitude of a missile is that an outside force causes the missileto roll in a clockwise direction. Figure5-26A shows CAPACITANC2 PICKOFF free gyro the roll rate gyro signal and the roll 4 signal during a period of 40° clockwiseroll and there is no As shown in figure 5-25 capacitancepickoff return to proper attitude. At time To is composed. of two outer plates that arefixed inoutput from either the rate gyro or thefree position. A .movable plate is centeredbetweengyro, because the missile is not rollingand is the sensor.in the proper attitude. As the missilebegins the two fixed plates -and connected to until the The capacitance betWeen the center plateand the to roll, the roll rate signal increases missile roll rate becomes steady, at.whichtime (T1) the rate signal reaches a constant level. Note that the roll rate signal alWays opposes roll movement of the missile.The free. gyro signal continues to increase as long asthe missile is rolling from its properattitude. SENSOR .At time T2, the control surfaces beginto slow OR the missile's roll and the. ratesignal begins RRPORENCE. -to drop off.The missile is still roiling, ' bittat, a slower ratebetween . T2 and T3. signal continues to in- , . The roll free gyro 33.78 crease until a maximum roll of 40° is reached igura,545....:Capaeitance pickoff. at T3, at which time the. ratesignal is zero. =12426 Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

The missile now begins to rollback to the de-return to correct attitude. sired attitude. Between timesT3 and T4, It is this opposing the roll or damping feature which preventsthe over- free gyro signal decreases,whilecorrecting effects which wouldoccur if only a the rate signal increasesin the opposite di-free gyro were used. rection. At time T4, the signalscancel each other and have caused the control surfaces to The free and rate signalsare continuously return to neutral. After T4, therate signalled by their pickoffs toa summing circuit in is greater than the roll free signaland causesthe missile computer network. the control surfaces to be actuated Here they are inoppositioncombined to form the resultantshown in figure to the direction of missilemovement. This5-26B. action continues until the missileis stabilized at the prescribed attitude. The dotted line in figure 5-268represents By opposing the freegyro signal duringcontrol surface movementduring the entire the roll back to the horizontalattitude, theperiod of roll. rate signal can be said to beanticipating the Although the actions describedabove apply to missile roll caused byan outside force, the same actions are applicable to pitchand yaw C W caused by outside forces. T T4 +40* The block diagram of themissile control 20 ROLL FREE SIGNAL system in figure 5-27 includesthe gyros and pickoffs covered in this chapter.

RuLL RATE SIGNAL COMPUTING DEVICES 20 GENERAL v<)4. 101 gOT <>4 CC W A Computers appear in missile systemsin a variety of forms. The computermay be a simple mixing circuit in a missile,or it may be a large console type unit suitable foruse at TO T T T3 T ground installations oron shipboard. 40* We have shown thatsensor units detect errors in pitch, roll, and yaw, and thata ref- ESULTANT SIGNAL erence unit furnishes a signal forcomparison with the sensor output. Although the sensor outputrepresents an 0 .0 ... error to be corrected, it is seldom usedto operate control % surfaces directly.It must % / be changed to include additional % information, e and then amplified in order to N. operate the con- e1/CCONTROL \ / SURFACE MOVEMENT trols.These operations are representedby .../ the block labeled "computer" (fig.5-1). The %,...... - computer section is normallycomposed of .... .4r mixers, integrators, and rate components. The large volume of informationto be processed, and the brief time availableto handle it, make the, use of high-speeddata processing 33.79 equipment essential in modern weaponsystems. Figure 5-26.Gyro signalscombined to correctData processing equipment missile attitude: A. Roll freegyro and roll is a group of de- rate gyro signals; vices, each capable of performinga mathe- B. Resultant signal andmatical operation on data furnishedto it, and control surface movement. of producing results in usableform. The term PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

RATE GYROS

AMP

CONTROLLER

FREE GYROS

CONTROL SURFACE

FOLLOW, SIGNAL FOLLOI/UP MECHANISM

EXTERNAL FOLLOWUP MISSILE ATTITUDE

33.86 Figure 5-27.Missile control systemshowing gyros and pickoffs.

"mathematical operation" includes notonly or missiles.Computers are also used against surface, underwater, and shore targets.Com- such obvious processes asmultiplication and the same addition, but includes analytic,arithmetic, andputers within the missiles operate on logic operations.It excludes such processesprinciples as those in the weapon system. as judgment, induction, conjecture,and generalizationa computer cannot think. FUNCTION AND REQUIREMENTS The term. "computer" refers tothe data of differ- processing device that is capable One important function of a computeris the entiating between data received.Other parts relating to of the data processing equipment maytranslatecoding and decoding of information datit from one form to another, storedata, orthe missile trajectory. It is necessaryto code produce data from stored information onde-and decode control informationin order to offset enemy countermeasures andto permit con- mand. time. Comp Uters produce answers innumericaltrol of more than one missile at the same form forstatisticians, or in physical form Another functionof the computer is the for use in fire control systemsand industrialmixing of signals from sensor andreference control equipment: By physical form we meanunits to produce error signals.Figures 5 -1 and Because5-9' show, in block form, how the computeris voltages or shaft and gear -revolutions. complete computers can quickly solve simultaneous equa- linked with other sections of the gunfire orsystem. The signals from the sensor and tions, they can be used to direct preset missiles against fast-moving enemyaircraftreference units may be mixed in a

. 41g8. 4 .40.,1 Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS ratio, or they may bemixed according topro. grammed instructions. variable as a wholequantity, such as displacement of a pointer, rotationof a shaft, and volt- The error signalsproduced by mixing,areage of a circuit. amplified and passed tothe control actuating The digital method is system and the followupsection. The output a counting method. The of the followup section digital device recognizesquantity as a number is then fed back to theof basic units:number of days, number computer for reprocessing.The purpose ofohms, etc. of feedback is to reduceovercontrol that would Analog computers cause the missile to oscillateabout the desired can be used in weapons attitude. systems wherever problemsof calculations from continuous data, The computer sectionmay also compare two simulation, or control or more voltages to produce are encountered. In targetdetection and track- error signals.ing, analog computersare used to direct search For this purpose, voltageor phase comparatorradars and tracking devices, circuits are added.The synchro units dis- store data on cussed in the previous target location and velocity,and predict future section are used intarget motion. The calculations computers to convert signalvoltages into forms necessary to di- that are better suited rect weapons launchers,and actually control for processing. launchers and missiles Airborne computersare generally classi- are performed by com- fied according to the puters. In addition to actualoperation of phase of missile flight inweapons, analog computers which they are used.The computers are used to sim- may beulate targets for trainingpurposes, and eval- separate units or theymay be combinations ofuate the performance of prelaunch, launch, azimuth,elevation, program, the weapons systems and dive-angle computers. in engaging the simulatedtargets. A digital computer alsocan solve problems, TYPES OF COMPUTERS but does it quite differently.The actual numbers are used; it performssimple arithmetic on them and produces theanswer in the form of Computers are classifiedaccording to pur-individual digits. pose as general or special,and according to whether they use analog Basically, the analog computerdeals with or digital principles.a continuous system, while the Computers used inweapons systems are de- digital computer works with discrete numbers.While the analog signed specifically tosolve problems arisingcomputer is faster than the in weapons systems,and therefore are usually digital, it is much special purpose computers. less accurate. They occur in a Also, the digital computercan only give wide variety, of formsand may have little inthe answer to common with each other.While general pur- one specific arithmetic problem at a time, but the analogcomputer can present pose computers are usedto solve problemsthe overall picture of directly related toweapons systems, most an entire system. The functions of the digitalcomputer in the computers that are part ofa weapons systemimproved Minuteman are special purpose, connectedto solve a missile include preflight particular problem, testing, countdown,staging, and control of or a small number ofpenetration aids suchas decoys or radar chaff, problems. A ballisticmissile guidance com-in addition to flight-path puter, for example, willsolve only the control. tion for a ballistic equa- Computers may solvethe problem by elec- trajectory, but can be madetrical means, using voltages to guide the missile toany target within range. and current; electromechanical, using voltagesand shaft po- Analog and Digital Computers sitions; and mechanical,using angular rotations of shafts and linearmovements of shafts and linkages. There are The two basic typesof computersanalog many electronic devices in digital computercircuits.Relays may be and digitalmay becombined to form a hybirdopen or closed; diodes computer with both analogand digital charac- pass current in one di- teristics. rection but not the other;vacuum tubes and transistors may be conducting The technique used todetermine the mag- or nonconducting; nitude of the Variable. magnetic cores may bemagnetized clockwise is different in the, twoor counterclockwise. types. The analog device willcontinuously In addition, a variety measure a changing variable; it of exotic devices withunique characteristics recognizes ahave been applied to digitalcircuits: cryotron,

tinn"*"- 5 PRINCIPLES OF GUIDEDMISSILES AND NUCLEARWEAPONS

twistor, and aper-can be controlledby changing the gearratios magnetic film, tunnel diode, in the differential. tured plate.To describe the functioningof transferred require a volume in itself. Sometimesinformation is each of these would through air or hydraulictubes. The signals Refer to Principles ofNaval Ordnance and the pressure inside the 16783-ATTOi more iiiiiiima-are created by varying Gunnery, I4avPers tube. Two signals canbe combined by joining tion on digital and analogcomputers. We will describe thecomputer elementstwo tubes into one. according to the general typeof function they perform. These types werebriefly describedIntegrators at the beginning of thischapter as MIXERS, mathematical op- COMPONENTS. An integrator performs a INTEGRATORS, and RATE eration on an input signal.The integral of a constant signal is proportionalto the amplitude Mixers multiplied by the time thesignal is present. Assume that the integratoroutput is four volts circuit or device thatwhen the duration at theconstant input signal is A mixer is basically a one minute. Thenif the same input signalhad combines information fromtwo or more sources. the output would have In order to functioncorrectly, the mixer mustlasted for one-half minute, combine the signals that arefed to it in thebeen two volts. signal is not SENSE, and AMPLI- But, an actual missile error proper PROPORTION, constant, as we assumed inthe above example. TUDE. The amplitude and senseof the error change The type of mixer used willdepend mostly is pro- Most systemscontinuously.The integrator output on the type ofcontrol system. portional to the product ofthe operating time use electronicmixers. However, mixers may pneumatic, or hydraulicand the average errorduring that time. Should also use mechanical, the sense of the errorchange during the inte- principles. sense would Electronic mixers may use avacuum tubegration period, a signal of opposite device. It is also possible .to use acause the final outputof the integrator to de- as a mixing crease.The integrator can beconsidered as network composed ofinductors, capacitors, computer, since it is always pro- and resistors for mixing.Regai'dless of thea continuous proportional to the to be combined areducing a voltage that is type of mixer, the signals product of the averageinput voltage and time. represented by the amplitudeand phase of the with re- Voltages from such sourcesTherefore, the integration of an error input voltages. spect to time represents anaccumulation of as pickoffs, ratecomponents, integrators, fol- intervals of time and errors overa specified lowup generators, andguidance sources may mixer section to formperiod. be combined by the Any integrator has a timelag effect. control signals. Although the input signal goes.from zero Mechanical mixers. consistingof shafts, be used to com- to maximum with zerotime lag, there is no levers, and gears can. output at that instant. Timeis required before bine information.Another mechanical mixer combine position or angularthe output reaches anappreciable amplitude. uses gears to Approximately the same lergthof time is re- velocity information. The geararrangement is amplitude to drop to zero automobile rear axle dif-quired for the output similar to that of an after the input pulse ends.The additive effect ferential.If the input shafts containposition negative pulses is made information, they will move slowlyand maintain. of two successive position.. Thepossible by the time lag,and is used to give approximately the same average. more precise controlaction. position of the -output shaftconstantly indicates the integrator is , The output signal from the differencebetween the two shaft positions. :represented by the speedused .to support theproportional error signal, If the information is o make sure thatenough correction willalways of the .shaftrotatfon, theangular velocity of the difference between-13Smade by the control system. output shaft represents the 'Keep' in mind that the degreeof control ex- the two input shaft speeds.. , (unamplified) sig- the input shafts soerted by a pure proportional It is. possible. to arrange nal is. limited.Overcontrol, or undercontrol that the .output represents the sumof the inputs movement of the missile about rather than the difference.Weighting factors causes excessive 1-26. 139 - G.4 6.: Chapter 5MISSILE CONTROL COMPONENTS ANDSYSTEMS the desired trajectory. There are times whenance (RC) circuits, proportionalcontrol alone is notenough to resistance-inductance (RI) overcome a strong, steady force circuits, and thermal devices.The ball-and-disk ing the missile to that is caus- type (fig. 5-28A) is theoldest type of integrator deviate from the correctstill in use in missiles. path.In a case of thiskind, the proportional A more sophisticated error signal will havea steady componentintegrating circuit is shownin figure 5-28B. It that affects the adds an amplifier toa simple resistor-capacitor integrator. The error signalcircuit. The resistor (R) sense remains constant,so that the integrator produces the propor- output increases with tional current from theinput signal voltage. time.This output in-The capacitor (C) crease reinforces theproportional signal until voltage is the integratorout- correction of the flight path put.The use of a highgain feedback ampli- takes place. fier producesmore accurate results. Integration may beperformed by a motor, the speed of whichis proportional to theamplitude of the inputsignal. The motor drivesRate Systems a pickoff, and the distance thepickoff moves isproportional to the integral of the input The rate sectionin a missile control signal. tem should produce sys- The direction ofmotor rotation will de- an output signal proportional pend on the polarity to the. RATE OF CHANGEof the input signal or phase of the input sig- amplitude. nal.The amplitude of theerror signal varies irregularly; the sense ofthe signal may re- The time lag present'in integrator circuits verse, causing reversal of themotor rotation.makes rate circuitnecessary. Missile devia- Other types of integraters tion cannot be correctedinstantly, because the use ball-and-diskcontrol system must firstdetect an error be- mechanical arrangement,resistance-capacit-fore it can begin to operate.

AMPLITUDE OF INPUT P FRICTION BALL

DISK

A EXCITATION

HIM GAIN DC AMPUFIER GAINalL

Figure 5-28.Someintegrators used in missile 144.30 A. Ball-and-disc integrator; control: Bo Integratingamplifier circuit and symbol. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

The ideal control system would have zero PURPOSE time lag, thus permitting zero deviationdur- amplifiers are ing the missile flight.Control surfaces are Both POWER and VOLTAGE used in missile controlsystems to build up a designed to correct missile flightdeviations that it can be rapidly. The control surfaces are movedweak signal from a sensor so byused to operate othersections of the control rapidly by actuators, which are operated These sections normallyrequire amplified errorsignals.But it is possiblesystem. voltage than is to have a signal so large that the missile isconsiderably more power or available from the sensor.Most amplifiers driven beyond the desired attitude, and an error method occurs in the opposite direction.This erroruse electronictubes. Regardless of the drives the missile back in the firstdirection.used, the prime purposeof an amplifier is to The end result is a series of swings back andbuild up a small sensorsignal to a value great forth across the desired trajectory. enough to operate the controls. These unwanted swings are known as oscillation (or hunting) and the addition of a rate OPERATING PRINCIPLES signal has the effect of damping(retarding) control systems the oscillation.The amount of damping may Some functions in missile UNDERDAMPING, require a series of flat-toppedpulses; called be classed as CRITICAL, definite frequency.It is or OVERDAMPING. Thefunction of damping square waves, at a of thesepossible to convert other waveshapes to square. is to reduce the amplitude and duration tube amplifiers and clippers. oscillations. waves with vacuum Itis also possible toaccomplish the same The simplest form of damping is viscous device known damping. Viscous damping is the applicationof result with an electromechanical friction, to .the output shaft or load, that isas a chopper, orby a vibrator. proportional to.the output velocity.Thia type of damper absorbs power from thesystem Choppers and slows up its response. You willfind viscous damping slows up its response..You will .A chopper is usually anelectromechanical older switch designed to operate afixed number of find viscous damping used on servos in the and closing the con- computers. times per second, opening tacts periodically.Fundamentally, a chopper Damping of servos in the newer computers carrier square-wave is provided by the rate generators.This method serves as a suppressed modulator.A cutaway view of amechanical of damping, sometimes called error-ratedamp- chopper is shown in figure5-29A.This unit ing, overcomes the disadvantages ofviscous for single-pole double- damping. By combining the rate signal and the has the contacts arranged throw switching, centerOFF position. error signal, the system canbe made to re- shown near spond to a constant error.It is also possible The contact arrangement is signal with athe bottom of the drawing. Leads arebrought to combine an attitude rate out separately from each of the twofixed con- guidance signal. tacts and the vibrating reed to pins onthe base. Perhaps the most common method of pro- chopper ducing a rate signal is byusing a separateThese pins are arranged .so that the sensor unit, such as a rate gyro.The gyrocan be plugged into aconventional radio tube and thesocket.In order to reduce operatingnoise, displacement is detected by a pickoff, the entire mechanism is enclosed in asponge output of the pickoff is the rate signal. rubber cushion before it is placed inthe metal AMPLIFIERS can. By using the chopperin connection with a An amplifier is a device for increasingthe conventional transformer, amplification canbe magnitude of a quantity. There are manytypes obtained at the pulse frequency. of amplifiers and many usesfor them. In three An electromagnet, driven by a sourceof electronics and electrical applications, vibration. types widely used are vacuum tube,transistor,-alte'rnating current, sets a reed in first two are dis-The reed carries a moving contactthat alter- and magnetic amplifiers. The two fixed cussed in Basic Electricity,NavPers 10087-A, nately' contacts one or the other of in. Basic contacts in a signal circuit. Thus thesignal is and the last named is described magnet Electricity, NavPers 10088-A. periodically interrupted. The permanent Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

The chief advantage ofelectromechanical choppers in their extremelylow noise and drift. They have been usedsuccessfully to amplify minute voltages such as thosegenerated by SOFT IRON thermocouples.

VIBRATING CRASS PLATE Vibrators REED

COIL A current can also be choppedelectronically by passing it througha multivibrator or other FIBRE SPACERS switchingcircuit.A vibrator, an electromechanical device used primarilyto convert direct current to alternatingcurrent but also ELECTRICAL LOADS used as a synchronous rectifier, POINTS is closely related to the chopper. Thereare two major classes METAL ELECTRICAL SPACER of vibrators: interrupters, inwhich the vibrator LEADS serves to interrupt, periodically,the direct current input, and synchronousvibrators, in CUSNION INSULATION which the vibrator periodically SPACER interrupts the input, then synchronouslyrectifies the resulting alternating current. 111 1111 IT IT Vacuum Tube Choppers

,..jNIGH GAIN AC AMPLIFIER Vacuum tubes can be usedas electronic choppers. Other amplifiers,known as saturable t=1-1 reactors, are used fora-c motor control. This RESISTOR type of amplifiermay sometimes be used in ..,r vvv--L-41 1 combination with vacuum tubes.Neither the CHOPPER vacuum tube nor the transistoralone can function as an amplifier; eachmust be associated with appropriate input,output, or biasing Figure 5-29.A. Cutaway 144.31 circuits. view of mechanical Control systems in guided chopper. B. Chopperstabilizedd-c amplifier. missiles make extensive use of chopping,generally to change a direct current signal into is incorporated in thepole structure of the coil an alternating current so as to polarize the coil. The signal, which can be morereadily amplified. the coil alternately a-c excitation of An autopilot amplifierreceives signals from reinforces and reduces thethe outputs ofthe gyroscopic magnetism supplied by thepermanent magnet, so reference system that the vibrating reed and the rate gyroscopes, andconverts the signals executes one oscillationto a form usable forguidance of the actuator for each oscillation of theapplied voltage. Theassemblies. resonant frequency of the reedis not made equal .to the excitation freqUehwbecause The use of amplifiers inthe guidance system then smallis discussed in the next chapter. changes in the excitingfrequency would result in large phase shifts'betWeen the reed Aosail- lations and the coil -drive. typical :circuit is CONTROLLER UNITS shown in figure 5498. Thed-c inputvoltage is modulated by one contact ofthe choppar.into an The first part of this a- c Nonage. Thiii.voltage is amplifiedina stand- chapter discussed the ard amplifier' end' it then demOdulated purpose and function of control, thefactors con- by the trolled, methods of control,types of control -other 'contact " of the .chopner;The' signal: is smoothed `in a low-pass filter to. action, and types of controlsystems. In this reconstruct assection we will discusscontroller units other an amplified version of the originalinput.' than amplifiers. 7- X M...4" 129 A

PRINCIPLES OF GUIDEDMISSILES AND NUCLEARWEAPONS

A controller unit in a missilecontrol system responds to an error signalfrom a sensor. In certain systems an amplifierwhich is furnish- 11+ ing power to a motor serves as acontroller. VARMMWM101 TYPES ACTUATOR3 POWER AM PL. There are several types ofcontroller units, POWER AMPL. and each type has somefeature that makes it A better suited for use in aparticular missile sys- PRESSURE tem. RETURN IN RETURN Solenoids A solenoid consists of acoil of wire wound around a nonmagnetic hollowtubepa moveable soft-iron core is placed inthe tube. When a magnetic field is createdaround the coil by current flow through thewinding, the core will center itself in the coil.This makes the solenoid useful in remote controlapplications, since the core can bemechanically connected to valve mechanisms, switch arms, andother regulating devices. Two solenoids can bearranged to give applications. double action in certain 1 Transfer Valves 33.184 application in whichFigure 5- 30. Transfer valve:A. Closed position Figure 5-30 shows an B. Hydraulic transfer valveand two solenoids areused to, operate alydraulic (schematic); transfer valve. The object isto move the -actu- actuator. ator which is mechanicallylinked to a control surface or comparable device. . of the windings en- The pressurized hydraulicfluid, after itthis control. With neither applied to the trans- ergized (or a balanced currentflowing through leaves the accumulator, is both), the magnetic reed iscentered as shown fer .valve shown in figure5-30B. The valve is high pressure automatically operated by the responseof the (fig.5-31). In this condition, generated by thehydraulic fluid from the inputline cannot pass solenoids to electrical signals to the actuator since thecenter land of the spool missile computer network.. port. The pressurized If solenoid #1 in the figureis energized, itvalve blocks the inlet to the left.fluid flows through the alternateroutes, through will cause the valve spool to move. the two .restrictors(fixed orifice), passes This wi l permit pressurizedfluid to be ported returns to the sump actuator and causethrough the two nozzles, and to the right-hand side of the without causing . any movementof the actuator. its movement to the left.If solenoid #2 is energized, the mag- energized,' the valve spool will moveto the right,If the. right-hand solenoid is netic reed will move tothe right, blocking off the causing actuator movementto the right in the. through the right- neither coil, is energized,flow .-of .high pressure fluid same manner. When hand nozzle; Pressure willbuild up in the right the valve is closed(fig.1-30A):. This will move the valve to The transfer valve justdescribed has onepressure chamber. in an on-off.the. left. In-moving left, thecenter land will open disadvantage. in. that it operates thehigh pressure inlet andpermit fluid flow manner. This:meansthat it provides positive either fulldirectly to the right -hand side of theactuator. movement of the control surfaces, , At the same time, the left -handland of the spool up or full down, full.right or full left. A finer Missilewill open the low pressurereturn line and permit control:is.usually more desirable in left-hand side .of the systems. The servovalve(fig. 5-31),providesflow to. the sump from the uo11241' Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

TO HIGH POWER CIRCUIT

LOW PRESSURE HIGH PRESSURE RETURN TO RESERVOIR INPUT MOVABLE CONTACTOR ORIFICE AXE° ORIR E tl 11 I l 1I 1I

771)PRESSURE II I PRESSURE II sCHAMBER PIVOT CNA/ABER tAmmon t Clingier\ \ INS It SCREW

X1-41111_141--Ir7.-- lo 1 so ID el SPRING SPOOL VALVE STATIONARY LANDS HYDRAULIC RETURN CONTACT TO RESERVOIR Lana

NOZZLES SOLENOID COIL

PERMANENT MABNET SOLENOID WINDINGS

33.185 A Figure 5-31.Servovalve. LOW CURRENT CONTROL actuator. This process willcause actuator movement to the left. By energizingthe left- hand solenoid, the reed willmove to the left, and the entire process will be reversed,the actuator then being moved to the right. Theactuator can be used to physically positiona control surface. Relays

Relays are used' for remote controlof heavy- current circuits. The relay coilmaybe designed to operate on very smallsignal values, such as the output Of a sensor. The relaycontacts can be designed to carry heavy currents. . Figure 5-32A shows a relay designedfor controlling heavy load currents.When the coil is energized, the' arMature is pulletdovmagainst the core. This action pulls themoving contact against-the stationary contact, and dolesthe high current circuit. The relay contactswill stay. closed as long as the magnetic pullof the coil is strong enough to overcome the pull of the spring.- 144.32 The relay just described hasa fixed core.Figure 5-32.Some types of HoWever, some relays resemble relays inmissiles: a solenoid in A. Low current relay; B.Air-actuated relay.

,131 PRINCIPLES OF GUIDEDMISSILES AND NUCLEARWEAPONS of the load driv- that part of the 'core is amoveable plunger. Theis then applied to the armature to the plunger, buting motor. (The fieldwinding of the motor is moving contacts are attached constantly excited by a d-cvoltage.) The am- are electricallyinsulated from it. of relay that canplidyne generator amplifies alow-power signal Figure 5-32B shows a form (error signal) into one strong enoughto move a be used in a pneumaticcontrol system. Two air pressure lines areconnected to the air inputheavy load. its arm is dis- The control field windingsof the generator ports. The relay operates when are arranged so thatthe polarity of the exci- placed by air pressure. Amodifieddesignof this will determine type relay might be used in ahydraulic-electrictation voltage from the sensor diaphragm would bethe polarity of the generatoroutput voltage. The system, in which case the generator output is connected tothe load driving moved by hydraulic fluid pressure. motor armature through thelatter's commutator. Since the field of themotor is constantly Ampildyne excited by a fixed polarity,the polarity of the voltage applied to the armaturewill determine combined the direction of armaturerotation. An amplidyne can be used as a Amplidynes have long been usedin power amplifier and controller, since asmall amount terminals controlsdrives for positioning gunsand launchers, al- of power applied to its input though none are used in currentmissiles. many times that amountof power at the output. Figure 5-33 shows an amplidynearrangement. 3 The generator is drivencontinously, at a constant speed, by the amplidynedrive motor. ACTUATOR UNITS The generator has two controlfield windings from an external The actuator unit is the devicethat converts that may be separately excited the error detected by the sensorinto mechanical source. When neitherfield winding is excited, motion to operate theappropriate control device 4 there is no output fromthe generator, even compensate for it. though it is running. If followsthat no voltagethat will correct the error or

AMPLIDYNE GENERATOR 4

GENERATOR AMPLIDYNE DRIVE MOTOR ARMATURE FIELD ARMATURE CONNECTION POLE TO LOAD 2

BRUSH

SHORT CIRCUITED BRUSHES

FIELD WINDING COMPENSATING DC SUPPLY FIELD WINDING

LOAD. DRIVING MOTOR. DC SIGNAL CONTROL INPUT FROM FIELD WINDINGS SENSOR 144.33 Figure 5-33:AmPliayng% controller.

'132: Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS The actuator must be able to respond rapidly,large forces available whenusing hydraulic with a minimum time lag between detection of tkeactuators. error and movement of the flight control sur- You have studied severalof the components faces or other control device. Atthe same time, it must produce shown in the simplified blockdiagram of a an output proportional to thehydraulic-electric controller (fig. 5-34).This error signal, and powerful enough tohandle the load. Figure 5-30B shows system is comprised of (1)a RESERVOIR which a double-acting piston-contains the supply of hydraulicfluid, (2) a type hydraulic actuator inwhich hydraulic fluidMOTOR and a PUMP to under pressure can be applied move the fluid through to either side ofthe system, (3) a RELIEF VALVEto prevent ex- the piston. The piston ismechanically connected to the load. cessive pressures in the system (4)an AC- CUMULATOR which actsas an auxiliary storage PRINCIPAL TYPES space for fluid under pressure andas a damping mechanism which smooths outpressure surges within the system, and (5) Actuating units useone or more of three a TRANSFER VALVE energy transfer methods: hydraulic, which controls the flow of fluidto the actuator. pneun4tic, Most of these components ofthe system have or electrical. Each of these has certainadvan- tages, as well as certain design been covered in the precedingpages. The theory problems, men-of hydraulic piston displacementis explained in tioned earlier in this chapter.Control' devices make use of more than Fluid Power, NavPers 16193-Aand hydraulic one method of energypumps are also illustrated and explained. Pumps transfer but are classifiedaccording to the majorused in missile systems generally one used. Combinations are hydraulic-electric, fall into two categoriesgear and piston. Theyare usually and pneumatic-electric. Mechanicallinkages aredriven by an electric motor withinthe missile. used to some extent by all ofthem. RESERVOIR.The reservoir isa storage HYDRAULIC ACTUATORS compartment for hydraulic fluid. Fluidis removed from the reservoir by thepump, and forced through the hydraulic systemunder pump Pascal's Law states that whenevera pres-pressure. After the fluid has done its work, it sure is applied to a confined liquid, thatpres-is returned to the reservoir to be sure is transferred undiminished inall direc- used again. tions throughout the liquid, The reservoir, calleda sump, is actually an regardless of theopen tank because of the atmosphericpressure shape of the confining system. inlets. This principle has beenused for years in VALVES.The valves in the piston such familiar applicationsas hydraulic door pump are stops, hydraulic his at of the flap type, which operatewith very small automobile servicechanges in pressure. Another typeof valve used stations, hydraulic brakes,, andautomatic trans- missions. Generally, hydraulic,transferunits are quite simple in design and construction.One advantage of a hydraulic systeni is that iteliminates complex gear, lever, andpulleyarrangements. Also, the reaction time ofa hydraulic system is rela- HYDRAUUC RELIEF ACCUMU- I tively short, because there, is little PUMP VALVE LATOR. slok or lost COUPLING motion.A hydraulic'' system,, does,however, h:..ve a slight efficiency loss dueto friction. Ik Hydraulic-Electric Control Devices IRESERVOIR ITRANSFER 111 VALVE The hydraulic-electric methodof 'actuating III movable control EurfaCes (ormovable, jets, = HYDRAULIC CONNECTION .1TO =ACTUATOR I nozzles or vanes) has been usedmore than any, igt MECHANICALCONNECTION other type of system. Aspreviously mentioned, the most important.. advantagesof this type of system are the high speed of 33.182 response and the Figure 5-34.Basic hydrauliccontroller. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

reliefaway from the opening, andfluid will flow into in hydraulic systems is the pressure return line. valve. As its name implies, it isusedtopreventthe port that leads to the reservoir damage to the system by high pressures.SomeThus the pressure can never exceed asafe limit; combination systems used hydraulic pressureand, since the fluid is returned tothe reservoir, regulating switches instead of pressurereliefno fluid is lost. valves. These valves, and others, are described and A typical hydraulic relief valve consistsof a illustrated in Fluid PoWer, NavPers 16193-A. metal housing with two ports. One portis con-Transfer valves were desctibed earlier inthis nected to the hydraulic pressure lineand thechapter. other to the reservoir return line.The valve ACCUMULATORS.Accumulatorsare of consists of a metal ball seated in arestrictedthree types as shown in figure 5-35.Part A of section of the pressure line. The ball isheld inthe figure shows the floating pistontype, con- place by a spring, the tension of whichis ad-sisting of a metal cylinder which isseparated justed to the desired lifting pressure.Thisinto two parts by a floating piston.The upper part of the cylinder contains hydraulicfluid. pressure is chosen so that itwill be within the is safe operating limits of the system. Below the piston is an air chamber which Should the system pressure becomegreatercharged with compressed air. Theaccumulator than the spring pressure, the ball will beforcedshown in figure 5-35B is thediaphragm type

NITROGEN FILTER

CONNECTION TO SYNTHETIC PRESSURE LINE RUBBER ti BLADDER HYDRAUUC FLUID METAL CYLINDER

SHELL FLOATING PISTON

COMPRESSED AIR CHARGE

FLUID

AIR FILL FITTING

CONNECTION TO PRESSURE LINE

HYDRAULIC FLUID METAL MANIFOLD SPHERE FLEXIBLE DIAPHRAGM

AIR CHARGE

AIR FILL FITTING B 33.183 Figure 5-35.Hydraulic accumulators:A. Floating piston type; B. Diaphragm type; C. Bag type,cutaway view. 2

Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS which consists of two hemisphericalsections separated by a flexible diaphragm. thus providing fine control.If missile attitude The upper(external followup)were the only guide to cor- chamber contains the hydraulicfluid and the lower chamber the compressed rect the control surfaces,reaction would occur air charge. too late to provide fine control.In other words, Although the construction of theaccumulatorsthe reaction would be too latebecause of aero- is somewhat different, they operateon the samedynamic lag. Suppose, forexample, that a mis- principle. The air chamber is chargedwith com- sile WITHOUT internalfollowup turns to the pressed air to a pressurecorresponding to theright due to a gust of wind. The desired pressure, which is less free gyros would than the linesense the amount of error andcause control pressure of the hydraulic system. Withthe hydr-surface deflection to bring themissile back to aulic line pressure higher thanthe airpressurethe left. The rate gyros would hydraulic fluidwill be forcedback into sense the rate of the upperattitude deviation and relaythis information to compartment. This fluid forces thediaphragmthe missile computer network. To (or floating piston)down make proper againattlie compresseduse of the free and rategyro information in aircharge, increasing thepressure until a working pressure is reached. providing control surfacecorrection signals, If the pressure outputthe missile computer networkmust also be kept of the pump should dropsuddenly, the compress- informed of the instantaneous ed air charge would force control surface the diaphragm or pist- positions. Devices suchas the pickoffs (also on upward, thereby maintaininga constant press-called followup orresponse generators) dis- ure in the system. By buildingup air pressurecussed in the chapter in the accumulator, are commonly used to any pressure surges in the measure deflection of the controlsurfaces with hydraulic system wlll be smoothedout, permitt-respect to the missile'airframe and to relay ing a smooth operation ofthe load. Air as the pressurizer this information to themissile computer net- is replaced withwori. As a result, the correctionsignals from nitrogen for reasons offire safety. The piston type of, accumulator is the computer network willprovide smooth and being phased out. fine control. Thereare various other types of The third type, illustratedin figure 5-35C,control surface pickoff devices. is the bag type. The outsideof the bag type isa metal shell; the bag, of An electrical followup (feedback)system is neoprene, is inside, andshown in figure 5-36. In thissystem, the error contains the nitrogen. The bladderwill fill ap- signal is supplied toan electronic mixer where proximately three-fourthsof the inside area ofit is combined with the the cylinder when the smaller signal from the hydraulic pump forces oilresponse generator. The difference,or result- into the flask. A spring-loadedpoppet valve at the bottom of the flask ant, of these signals is fed throughan ampli- prevents the bladderex- fier and controller to the actuatorsection that panding down into themanifold if there isno hydraulic fluid (or only operates the control surface. Aportion of this flask. a small amount) in thesignal is also fed to theresponse generator, so that the response signal isproportional to the CONTROL SYSTEM INTERNALflight surface deviation from FOLLOWUP.The followupunit (a servomech- the axis line. anism) in a missile IV is also possible touse a mechanical control system playsanfollowup. When this method isused, the followup important part in obtaininga smooth trajectorymechanisra may be a part of with minimum oscillation. Thereare two basic an air relay as types of followup associated with shown in figure 5-37. Thecontrol surface missile controlposition in relation to themissile axis is indi- (fig. 5-27). The firstis internal followup (alsocated by a force which is referred to as minor followup),and the second reflected to the con- is external followup (sometimes troller by a spring. called major To see how this systemoperates, assume followup).Internal followup involvesdevices installed to measure missile that the signal froma pneumatic pickoff moves control surfacethe air relay diaphragmup. The followup arm position, and to relay this positioninformation back to the missile computer will then move clockwise. Thismovement causes network. External,the valve spool of the air valveto move upward. or major, followup involves the sensingof mis-The valve action admits sile attitude by the gyros. high-pressure air to the 1 relay, and the pressure forcesthe piston of the The purpose of the internalfollowup loop (also called feedback loop)is to increase pneumatic actuator to the left. Whenthis happens, speed at which a missile responds the followup spring is compressedand tends to to an turn the followup arm ina counterclockwise PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS direction. Since the followup force is in op- A large signal will create a larger flight position to the original motion of thefollowup control surface deflection before the feedback arm, we have the desired inversefeedback. force becomes great enough toreturn the

AMPLIFIER ERROR SIGNAL RESULTANT SIGNAL CONTROLLER IXE ACTUATOR

RESPONSE GENERATOR

CONTROL SURFACE

144.8 Figure 5- 36. Followup loop of missile controlsystem.

AIR VALVE

IRON PRESSURE AIR -

TO CONTROL SURFACE

PO LOWUP SPRING

POLLOWUP ARM t I 4a, MR ---DIAPHRAGM PROM AIR PICEOFF .

33.195 Figure 5-3 tAir relay viktiftchanical followup. Chapter 5MISSILE CONTROL COMPONENTS ANDSYSTEMS followup arm tozero. The spring will then push the followup produce these requiredout-of-phase signals. arm and the air valve in theop-The yaw signal also posite direction,- tomove the flight control feeds into the other two surface back. Therefore, servoamplifiers in thesame manner. The roll the spring acts tosignal feeds into the input limit flight surfacedeflection to a value deter- of all four servo- mined by the error amplifiers, and affects theoperation of all four signal, and to return thejets. Rate control has flightcontrol surface toa position parallel also been included in the with the missile axis. system, the rate signals beingobtained fromthe rate gyros. Themany synchros are usedas Hydraulic-Electric Control System pickoffs and mixers tocombine information Figure 5-38 showsa simplified blockdiagramfrom the varioussources shown in the figure. of a hydraulic-electricchannel for roll control. Many followup pathsexist in this system. In Notice the similarity betweenthis figure and theeach case,actuator position informationis basic control systemdiagrams in figures 5-1fed to the input of therespective servoampli- and 5-9. Since the pitchandyaw control systemsfier. This feeding producesjet movement which are very nearly the sameas the roll controlis proportional to theservoamplifier input. Also, system, there is little necessityto describe themactuator-position informationis fed back to a in detail separately. certain two of the threechannels (yaw, roll, or pitch). This is CHANNEL INTERCONNECTION.Veryof- necessary because each actuator ten the roll, pitch, andyaw channels are inter-produces an effecton the missile in twoaxes. connected either electricallyor hydraulically.The roll channel hasfour followup signals, Figure 5-39 showsa possible method of elec-since each actuator affectsthe missile in roll. trically connecting thechannels. Four movableThus, the combinationof actuator followup jets are controlled bythe system (fig. 5-2). Insignalsto any channel producesa resultant figure 5-39 the interconnection signal which representsthe true followup for to the four servoamplifiers. occurs just priorthat channel. The electrical distributionoccurs by means HYDRAULIC INTERCONNECTION.The of the output of thethree channel amplifiers. control channels may also beinterconnected by The amplifiers producetwo outputs whicharehydraulic means. Thisinvolves a fairlycom- 180° out of phase.The pitch signal affectsjetsplex system of hydrauliclines which link the #4 and #2 by feedinginto the respectiveservo-actuators of the roll, pitch,and yaw channels. amplifiers. Assuming thata signal of certainSince such systemsrequire rather extensive phase produces clockwisemovement of all the hydraulic equipment, theyare seldom used in jets, then the signal toJets #4 and #2 mustmodern missiles becauseof their excessive receive signals ofopposite phase for pitchweight. All-electric systemswill replace hy- control. The double-endedchannel amplifiers draulic systems innew missiles. INTEGRATOR ACTION.Thepurpose of an integrator in a hydraulic-electricsystem is to detect an error ofa certain sense that has existed for a comparativelylong period of time. This is done by producingan output which is not only proportional to themagnitude of error, but also to the length of time theerror has existed. The integrator actuallyaccumulates the error over a period of time. The signalthus generated is then mixed with theother error signals to cause complete correction of theerror. Refer to explanation of integratoraction earlier inthis I chapter. PICIOPP I CONTROL SWAPI Pneumatic Control Systems Even though pneumaticcontrol systemsare not commonly used inmissiles today, it will be 33.188 helpful to look into thissystem before taking up Figure 5-38.Hydraulic-electricchannel the more widely used for roll control. tems. pneumatic-electric sys- PITCH MOTOR GYRORATE CHANNELAMPLIFIER UPFO L GLOWEN GYRO MEW .s.r .m.. .m. .m.. ..m. .m... s 1 kry mat OM .M .. motwom . 1 cep 1 1 RATE II11 1 GYRO UPFOLLOW GEN s GYROROLL 65 ZIa I 411111. TRANSFER VALVE ACTUATOR I 12 TO JET 2 TRANSFERUPFO GEMVALVE ACTUATOR II TO JET I- -0-- .. YAW frt------WM MM. MN 'I 4 ss 0 SYNCHIM3 SIGNALELECTRICAL PATH TRANSFER VALVE TO JET 3 onepow ..r DIFFERENTIAL SYNCHRO ,...... MECHANICAL HYDRAULLINKAGE =. IC AMPLIFIER Figure LINKAGE 5-39.Electrical interconnection of channels in hydraulic-electric control system. 33.187 Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS The principal differencebetween a hydraulic system and a pneumatic puter function is performedas spring-force in- system is the use of airformation is combined in rather than hydraulic fluid,as the working proper sense and ratio medium. with air pressure informationat the air relay. GENERAL OPERATION.The pneumatic YAW CONTROL.At theyaw rate gyro, the control system is almostentirely operated byrate signal appearsas an unbalanced air pres- compressed air. sure between two holes in an air-blockpickoff. The rotors of thegyros are powered by air.Now suppose thenose veers to the right. A dis- The gyro pickoffsare all air blocks; therefore,placement gyro signal developsat the pickoff the control information isin the form of vary- (yaw control air jet). Theyaw control air jet ing air pressures. Thecontrol surfaces arepivots to increase airpressure in the left hole moved by air pistons. Airfrom a pressure tankof the pickoff (when facing thedirection of flight). passes through delivery tubes,valves, and pres-This air pressure is transportedin the lower of sure regulators to operate mechanicalunits.the two air tubes to thediaphragm of the air After the air has done itswork, it is exhaustedrelay. The diaphragm is forcedto the left. This to the atmosphere. Itcannot be returned to thecontrols high pressure air whichforces the tank for reuse. Consequently,air must be storedactuator to the right. Mechanicallinkage moves at a much higherpressure than is necessarythe rudder to the left, correctinga nose-right for operating the loadsin order to have enoughdeviation. pressure to operate the controlsas the air Again consider the nose-rightattitude. As supply in the tank diminishes. the nose is moving right,an error signal is Figure 5-40 showsone possible pneumatiCproduced by the yaw rategyro. By the law of system. Note that thissystem contains threegyro precession, the yaw rategyro exerts more gyrosone displacement (free)gyro and twoforce on the right restrainingspring because rate gyros. force on the gimbalprecesses the gyro a small For simplicity ofillustration, the figureamount. As it precesses,more air is received shows conventional controlsurfaces. The basicby the left hole. This increasesthe pressure in principles outlined in thefollowing paragraphsthe same tube that containsthe high pressure hold regardless of whichcontrol method is used.signal from the displacementgyro. The rate Starting with the displacementgyro, thepitchgyro is SUPPORTING theerror signal of the and yaw errors are sensedby displacement gyro. Each signal is sent by air-blockpickoffs. means of varying air PITCH CONTROL.In the pressures to an air relay. Theair relay acts missile under dis- like a combination amplifier cussion, a pendulous device isused for pitch and controller. Thecontrol. Figure 5-40B shows therelationship of input to the relay is in theform of small chargesthe pendulous device, of air pressure from theairblock pickoffs. The yaw torquer coils, pitch output of the relay is pickoff, and barometricaltitude control. The a pressure which is highdiagram shows how the devices enough to actuate an air piston.The two rate operate together. gyros also produce a pneumatic When the missile deviates inpitch, more air signal whichis directed intoone hole of the pitch pickoff joins with the free gyro signalof the respectiveblock than the other. This channel. The addition ofthese signals in the pressure difference proper ratio can be considered to be represents a pitch error signalwhich connects computerto an air relay. The air relaycontrols air pres- functions of this system. sure used to move the elevator. The followup signal isactually a mechanical force exerted by a spring (fig. Since the rotor of thegyro tends to maintain 5-40A). Both the a constant plane of rotation inspace due to gyro diaphragm and spring exertforce on the servo- rigidity, the gimbal and valve spool. Movement of thespool to either side gyro disc also maintain of normal produces a constant angle since theymove with the gyro. a varying force on the airThe disc is rigidly connected relay valVe. This actiontends to return the to the gimbal. The servovalve spool to the normal gyro cradle normally moves withthe airframe. or midpositiontoThe pitch pickoff pivot andblock are connected produce streamlined controlsurfaces. to the cradle and also The corrective signal tothe move with the airframe. servovalve spoolWhen the missile deviates inpitch, the cradle must be somewhat dependenton the instantaneous and pitch pickoff also position of the control surface.This position is deviate in pitch, but the indicated by the followup gyro disc maintains the same positionin space. signal. Again, a com- The pitch arm pivotsas it rides in the slotted SECURED TO MISSILE DT TAM RATE GYRO YIN/ CONTROL Alit JET ICKOPF COLII0 DI ECTION 08LI . ELECTROMAGNGYM MUSING Azumn4.. op Fuca DIAPHRAGM SERVOVALVE FOLLOWUP SPRIM" co L.1441 EXTI RUDDER CO 7,:rvie vita: fi t's 0CD A Figure 5-40.A. Pneumatic control system; B. Detail of pitch control assembly. ELEVATOR 33.188:.189 Chapter 5MISSILE CONTROL COMPONENTSAND SYSTEMS

disc and produces thepressure difference be-enough torque to move the airfoils sufficiently. tween the two holes of the pickoff block. A large motor cannot be usedbecause of its BAROMETRIC ALTITUDE CONTROL. excessive weight. Pitch can also be controlled bya barometer A small motor running at high speedhas the servo. The servo (fig. 5-40B) is connectedsame power potential as a larger motor which mechanically to the gyro cradle. Thegyroruns at some lower speed. Therefore,a small cradle remains fixed with respect to theair-motor is connected to the control surface through frame unless the barometerservo should movea reduction gear train. The mechanical ad- it. When the barometer actuatormoves, thevantage yielded by the gear train resultsin a position of the gyro cradle with respectto thelarge torque exerted on the control-surface missile frame changes by pivoting. Also,whenpivot. The motor is eithera constant speed the gyro cradle moves, the nozzle and blockofmotor, operating through a clutch,or a vari- the pitch pickoff move With it. Since thegimbalable speed motor. and disc remain stationary, the pitchpickoff The high rotation speed ofan electric motor arm pivots and produces a pitch signal. This,introduces a major disadvantage toan electrical of course, also produces elevatormovementsystem. The inertia of an electric motorintro- and missile pitch reaction. duces a lag in the system which makesfine con- The stability of this missile in pitch ispro-trol difficult to achieve. If the lag isgreat duced by the relation of the missileand theenough, the system operates withinsufficient gyro. The initial climb angle and altitude of thesensitivity or with a tendency to oscillate. trajectory are controlled by the barometerservo VARIABLESPEED ACTUATOR0=Figure operating the gyro cradle. 5-41 illustrates a variable speedmotor used to move a control surface. A signal is sent toa Pneumatic-Electric Control Systems motor which rotates in a givendirection depending on the sense of the signal. The motorturns Some missile control systemshave beenat a speed which is roughly proportionalto the designed which use a combination of pneumatic strength of the signal. Since the motor is coupled and electrical apparatus. Such systemsusuallyto the elevator through a reductiongear train, use electrical pickoffs, which are the mostthe elevator movement is proportionalto the accurate and reliable. The pneumatic equipmentspeed of the motor. is used to move the actuators. CONSTANT SPEED ACTUATOR.The The change from electric to pneumaticop- effects of inertia when starting and stoppinga eration takes place at the air servovalve (fig.variable speed motor can be eliminatedbyusing 5-40A). The air servomotor rotatesthe torquea drive motor which runs continuously and tubes which are connected to the controlsur-maintains uniform speed. In thiscase the motor faces and extend into the center sectionof the is connected to the control surface througha missile. The deflection of the control surfacesclutch. The clutch varies the is proportional to the input signal. power transmission from the motor to the control surface.The use of two clutches and a gear differential would Electric Control Systems allow control in both directions. Figure 5-42 shows a systemoutput using An electric control system consistsentirelyclutches. The friction clutch discs makecon- of components powered by electricity.Thus, tact by means of a solenoid from the channel no pneumatic or hydraulic transfer systemispower amplifier. The amplifier needs to supply necessary. power only to operate the solenoids. Except for the controller and actuator,the components used are similar to those usedinMechanical Linkage the hydraulic-electric system. ACTUATORS OF ELECTRONIC CONTROL We have discussed the various controlsys- SYSTEMS.Electric motors are used foractu-tems, but have not discussed in detailthe ators in electric control systems.It is nptmechanical means of linking the flightcontrol practical to apply the torque of the motorsurfaces to the actuator. In addition to provid- directly to the control surface byusing theing a coupling means, the linkagemay also be motor shaft as the control-surface pivot. Suchused to amplify either the force appliedor the a motor would have to be 'very large to exert speed of movement. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

POWER GEA TRAIN

POLLOWUP SYNCHRO 33.190 Figure 5-41.Electric actuator (variable speed motor).

A mechanical linkage between an actuatormay consist of an arrangement of gears,levers, and a load is shown in figure 5-43A. The distanceor cables (fig. 5-43B). d, on the drawing represents the distance from A number of mechanical systems may be the control surface shaft to the point where thegrouped together to form a combination sys- force is applied. The control surface movestem. This system uses levers, cables, pulleys, because force exerted by the piston is appliedand a hydraulic actuator. However, a system at a distance from the axis of rotation, and thususing this kind of control is not suited for high produces a torque. Other mechanical linkagesspeed missiles.

.4 Chapter 5MISSILE CONTROLCOMPONENTS AND SYSTEMS

CONTROL SURFACE

OM fa= ,1111 1M11. GEAR REDUCTION

OPERATING SOLENOID CLUTCH CORK BRAKE CORK 0 PP BRAKE DISK IS TIGHTLY ENGAGED

GEAR THROUGH DIFFERENTIAL TO CABLE DRUM

OPERATING SHAFT MOTOR DRIVES CLUTCH GEAR CONTINUOUSLY c=4;;OZN. BRAKE ARM

BRAKE SO ENOID ON CLUTCH' AND BRAKE DISK BRAKE TENSION SPRING

33.191 Figure 5-42.Control system usingconstant speed actuator motor. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

SIGNAL OUTPUT CONTROL. SURFACE ACTUATING MOTOR

GEAR TRAIN

CONTROL SURFACE SHAFT AXIS OF ROTATION

CONTROL DEVICE

:=4.gmttis.:=

AIR OR A HYDRAULIC FLUID

33.194 Figure 5-43.Mechanical linkages: A.Actuator and load linked by lever arm; B. Gear train type of mechanical linkage. CHAPTER 6

PRINCIPLES OF MISSILEGUIDANCE

INTRODUCTION DEFINITIONS

Preceding chapters have discussedmissile A distinction was made in chapter 1between airframe and control surfaces, propulsionsys-missiles and guided missiles. Theymay also be tems, warheads, and control systems.Chaptercalled controlled missiles and uncontrolledmis- 5 defined guidance and control, andset up ansiles.Uncontrolled missiles forow a ballistic arbitrary division of factions andcomponentstrajectory which is determined by their initial of those two systems. This chaptershows thevelocity, initial attitude, and the forces of basic functional components of guidancesys-nature present (gravity, wind, and air resist- tems.Some of them are in the missileandance).Arrows, bullets, artillery projectiles, some are aboard the launching ship. and bombs are examples of missiles thatfollow a purely ballistic trajectory after release. Mis- There are several methods of providingsiles which are propelled by reaction propulsion guided missiles with the guidance signalsneces-systems and which are without control guidance sary to bring about a collision with a target,after flight, such as free (unguided) rockets, but two broad categories can includeallot them.follow ballistic paths after engine cutoff. The first category includes those guidedmissiles that maintain electromagnetic radiationcontact A missile whose flight path is controlled with manmade devices outside ofthe missileafter launching is considered to be guided. proper (devices on the ship or ground station).Internal equipment may sense deviation fromthe Examples of these devices include radartrans-prescribed path and operate to correctit, or mitters, radio transmitters, andthe targetthe missile may be commanded froman ex- veelf. The second category includes thoseternal source to make certain changesin its guided missiles which do not maintainelectro-flight path. Many missiles usea combination of magnetic radiation contact with manmadede-guided and unguided phases of flight. vices. In this category are missileswhich rely on either electromechanical guidance devicesPURPOSE AND FUNCTION or electromagnetic radiation contact with natural sources. The preset and inertially guided mis- The purpose of a guidance system is tocon- siles rely primarily on electromechanicalde-trol the path of the missile while it is inflight. vices within the missile.The celestial andThis makes it possible for personnel at ground terrestrial guided missiles rely primarilyonor mobile launching sites to hit a desired tar- electromagnetic radiation contact with naturalget, regardless of whether that targetis fixed sources. or moving, and regardless of whetheror not it takes deliberate evasive action. The guidance function may be based on information provided Modern guidance systems are far advanced.by sources inside the missile,or on informa- Progress in electronic and allied equipmentsistion sent from fixed or mobile controlpoints, rapid. The basic. principles stay the.same,or both. though the "hardwares' may change tremenyh Every missile guidance system consists of dowdy, such as the change from vacuum tubes. toam attitude control system and a path control transistors. This chapter and the followingonessystem. The attitude control system functions explain principles of different guidance systems. to maintain the missilein the desired attitude PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS on the ordered flight pathby controlling theThese names refer to different parts of the missile in pitch, roll, and yaw.The attitudeflight path. The boost phase may also becalled control system operates as an autopilot, dampingthe launching or initial phase. out fluctuations that tend to deflect the missile from its ordered flight path. The functionofINITIAL (BOOST) PHASE the path control system is to determine the flight path necessary for target interceptionand to generate the orders to the attitudecontrol Navy surface-to-air missiles are boostedto system to maintain that path. flight speed by means of theboostercomponent. Thus, the missile guidance system is es-This boosted period lasts from the time the sentially a weapon control system, inherentlymissile leaves the launcher until the booster associated with the weapon direction phase.burns up its fuel.In missiles with separate Although guidance and control systems haveboosters, the booster drops away fromthe distinct functions, they must operate together.missileVig. 6-1) at burnout.Discarding the The guidance system detects and tracks theburnt out booster shell reduces the weight car- target, determines the desired course .to theried by the missile and enables the missileto target, and. produces the electrical steeringtravel farther. signals that . indicate the position of the missile The problems of the initial phase and the with respect to the required path; thecontrolmethods of solving them vary for different mis- system responds to the signals to keep thesiles and their means of projection.However, the basic purposes are the same. Theboost missile on course. . phase must get the missile off to a goodstart BASIC PRINCIPLES or it will not hit the target.The launcher, The guidance system in a missile can beholding the missile, is aimed in a specific compared to the human pilot of an airplane. Asdirection on orders from the fire control com- a pilot guides his plane to the landingfield, theputer. This establishes the line . of sight guidance system guides the missile to the target.(trajectory or flight path) along which the mis- Using an optical device, the guidance systemsile must fly during the boosted portion ofits "sees" the target. If the target is far away orflight. At the end of the boost period the mis- otherwise obscured, radio or radar beams cansile must be at the calculated point. be used to locate it and dired the missile to it. There are several reasons why theboost Heat, light, television, the earth's magneticphase is important.If the missile is a homing field, and loran have all been found suitable formissile, it must "look" in the predetermined specific guidance purposes. When an electro-direction toward the target.The fire control magnetic source is used to guide themissile,computer (on the ship, or plane, or ground an antenna and a receiver are installedin thestation) calculates this predicted target position missile to form what is known as a sensor. The on the basis of where the missileshould be at sensor section picks up, or senses,the guidancethe end of the boost period. Before launch,this instructions. Missiles that are guided by otherinformation is fed into the missile. than electromagnetic means use other types of sensors. . When a beam-riding missile reaches the end The operation of the guidance and controlof its boosted period, it must be in a position system is based on the Closed-loop or servowhere it can be captured by the radar guidance principle.The control unity make correctivebeam.If the missile does not fly along the adjustments of the missile control surfacesprescribed launching trajectory as accurately when a guidance error is present. The controlas possible, it will not be inposition to be units will also adjust the control surfaces to captured by the radar guidance beam to continue its flight to the target. The boost phase guidance stabilize the Milibile,in roll, pitch, and yaw. GuidanCe and stabilization are two separateSystem keeps the missile heading exactly as it processes although they occur simultaneously.Was at launch. During the boost phase, in some missiles PHASES OF GUIDANCE 1A4 (fig. 6-1), the missile'sguidance systemandthe aerodynamic surfaces are locked in position. Missile guidance is generally divided intoSonte missiles (for example, Talos) are guided three phasea.bOost, midcourse, and terminal.during the boOst phase. Chapter6PRINCIPLES OF MISSILEGUIDANCE

01111111.11111....0 so. se.

TERMINAL BOOSTER BURNOUT )1111!11111.... I 10#'" BOOST MIDCOURSE (GUIDED) I

A- TARTAR ------BOOSTER BURNOUT - AND DROPOFF TERMINAL

MIDCOURSE

BOOST (UNGUIDED)

TIMOR

BOOSTER BURNOUT Ali .04111111P -0.1.1111W Am ,f.le I MIDCOURSE TERMINAL AOP

BOOST 11 t, (GUIDED)

Figure 6-1.Guidance.phasesof missile flight. MIDCOURSE PEASE time.During this part of the flight,changes. . may be required to bring the missile The., second, or midcourse-phase Of gut& onto the ance is often the, longest in both desired course, and to makecertain that it distance andstays on- that bourse.: this guidance 1

PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

to the mis-into usable form, and activate acontrol se- phase, information can be supplied the flight control sur- sile by any of several means.In most cases,quency that will move the midcourse guidance systemis used tofaces (or other controlforms) on the missile. place the missile near the target,where theItisdifficulttoseparate thecontrol and system to be used in the finalphase of guid-guidance operations.However, the flight control section is concerned with flightstability. ance can take over.But, in some cases, the of the midcourse guidance system isused for bothMissile" accuracy is primarily a function the second and third guidance phases. guidance section.Missile reliability depends on both sections.We will list the components and briefly describe the basicitmction of each TERMINAL PHASE before going into the individualtypes of guidance systems.The components of the control The terminal phase is of greatimportancesystem were described in chapter5. because it can mean a hit or a miss.The last phase of missile guidance must havehigh ac-SENSORS curacy as well as fast responseto guidance signals. unit is the Near the end of the flight, the missile may In some respects, the sensor lack the power necessary to makethe sharpmost important section of theguidance system and scorebecause it detects the form of energybeing turns that are required to overtake If the sensor unit a hit on a fast-movingtarget. In order to de-used to guide the missile. crease the possibility of misses,special sys-fails, there can be no guidance. These systems will be de- The kind of sensor that is used will bede- tems are used. termined by such factors as maximumoperat- scribed in the following chapters. the kind of In some missiles, especiallyshort-rangeing range, operating conditions, missiles, a single guidance system maybeinformation eeded, the accuracyrequired, used for all three phases of guidance.Otherviewing angle and weight andsize of the sen- systemsor, and the type of targetand its speed. missiles may have a different guidance Sensors used in the control system were for each phase. described in chapter 5, andincluded gyros, pickoffsystems, altimeters, and air-speed transducers. COMPONENTS OF GUIDANCE SYSTEMS Guidance sensors depend on some formof beelectromagnetic radiation, which Includesthe The units of the guidance system may electric and locatedin the missile(active and passiveentire range of propagationM by homing, inertial), or they may bedistributedmagnetic fields.The range includes gamma (beam-ridingrays, X-rays, ultraviolet rays,infrared rays, between the ship and the missile radar, and radio rays.Missiles use light, and semiactive homing). infrared, radar, and radio rays. Allradiations may be considered as a GENERAL REQUIREMENTS method of transmission of energy.All electromagnetic radiations propagate through space A missile guidance system involves a meansat thepeed of light, which is approximately missile in3 x 101u centimeters per second(cm/sec), or of determining the position of the materials, relation to known points.The system may186,300 miles per second. In other the mis-such as glass or water,the speed is less. obtain the required information from missile sile itself; it may use informationtransmitted By including devices within a guided from the launching station orother controlthat can detect the presence ofelectromagnetic from theradiations, several different types ofguidance point; or it may obtain information The devices in target itself.The guidance system must bemethods have been developed. stable, accurate, and reliable. the missile that detect the electromagnetic In order:, to achieve these :basic'requirev4radiations come under the general headingof ments,-the guidance system. must contain com-sensors.Following are brief descriptions of several types of such sensors. The advantages -- --ponnt*S-that will pick upguidance information covered in from some Source;'. convert. theinformationand disadvantages of each will be Chapter 6PRINCIPLES OFMISSILE GUIDANCE

the discussions of theguidance system in whichdevices. The first and most each is used, althoughsome will be mentioned important is that here. the target must beoptically visible.If the target is obscured by cloudsrain, snow, etc., Light-Sensitive Sensors the light-seekingsensors will be ineffective. The fact that lightsensors cannot discriminate between light sources with At about the end ofthe 19th century, Hertz any degree of cer- discovered that electrons tainty is also a handicap.A disadvantage of were ejected fromtelevision as a guidance deviceis the fact that certain metallic surfaceswhen these surfacestelevision is technically complicated. were exposed to light. Fromthis discovery Further- emerged the photoelectric more, television equipment placeslarge space cell.The photo-and weight requirementson a missile. Another electric cell shown in figure6-2 represents aserious disadvantage of the practical light sensor formissile guidance. light-seeking sen- The cell is composed of sors is that they can be jammedwith relative a light- sensitive cathode ease.For example, if the lights inthe target and an anode. These twoelements are covered(ship, plane) with a clear glass bulb.The unit is about the were turned off, the missile would size of the average radio be unable to reach thetarget. In view of these tube. As light wavesdisadvantages, light-seekingsensors are not impinge on the surface ofthe cathode, thepresently used in guided cathode emits electrons.These electrons are missiles which depend collected on the anode, resulting on the target for a source of light.They are in a currentused in the celestial guidancemethod, however, flow through the circuit. Byinstalling appro-which will be discussed later. priate pickoffs which detectthe direction of a light source, a missilemay be made to homeInfrared (Heat) Sensors (or guide) itself towarda light-emitting target, such as a factory, city, aircraft, or enemy The infrared portion of ship. Modern photoelectriccells are quite the electromagnetic sensitive to light variations, spectrum offers anothermeans ofmissile but, because light guidance. All objects on earth radiate is easily interrupted, thesystem is subject to some interference. heat energy in the formof electromagnetic waves. Devices whichcan sense this radiated Another device whichmay be thought of asheat energy are installed in a light sensor is a televisioncamera. Installa- some guided mis- tion of a television siles to enable them to homeon targets which camera and transmitter inradiate significant amounts a missile provides ameans of guidance based of heat. on a continuous picture of the Actually, the principle involvedis not unlike target which isthat of the photoelectriccell just described. relayed to a remote controlpoint. The invisible infrared There are severalvery serious disadvan- radiation causes certain tages associated with the substances to producean electron flow in the light-seeking sensorsame manner as does visible light.By carefully controlling thesensitivity of infrared seekers (sensors) theymay be used very successfully in missile guidance.Control of sen- sitivityisextremelyimportantsince the heat-seeking missile must beable to discriminate between the target andbackground sources of heat radiation. Heat, or infraredsensors use an active element called a THERMOCOUPLE,or an element known as a BOLOMETER.Either sensor may be used witha lens and reflector system. uGHT Missiles which :dependon detection of infrared radiationsare very suitable for against air targets. The use PIN propulsion systems of missiles and conventionalaircraft radiate tremendous amounts of heatin comparison with 33.89*background radiation. Figure 6-2.A photoelectriccell. The fact that these 'dunes; of heat radiation cannotbe turned off 149 PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS gives infrared guidance adistinct advantageRadar Sensors over the visible light sensors.In addition to adetection use against air targets(fig. 6-3), the infrared Shortly after World War II began, againstsystem known as RADAR(RAdio Detection And method is adaptable to effective use with great industrial areas and militaryinstallations. InRanging), was developed. It was used success in piloting andtarget detection during the latter application, however,it is possible to recently has decoy a heat-seeking missile bystarting firesand after World War II, and more at some distance from the target. come to provide oneof the most important means of missile guidance. As will be shown later, certainmissiles are Radio Sensors guided on the basis of radar energytransmitted from control points and detectedby receivers Although radio receivers are .notcommonly Other types of missiles thought of as sensors, they actually pc:form thewithin the missile. sensorthat is, theydetect reflected radar energy from atarget, same basic function as any for generating serve as energy detectors.Radio provided theand use this energy as a basis first method of controlling modelaircraft andguidance (steering) signals. target drones. A radio-controlledmodel airplane was first flown successfullyin 1995.Acoustic Sensors missile or air- The principle of controlling a Listening as a means of targetdetection is craft in flight by radio is very easyto under- Surface ships at stand.By installing a radio receiver intheused chiefly by submarines. at a remotehigh speed produce considerablenoise.This missile and a radio transmitter interferes with their detection ofthe sounds control point, we have establishedthe necessary the low fre- electromagnetic link between the controlpointmade by other ships, especially the missile'squency sounds ofsubmarines.On the other and the missile. By observing hand, this difference in noiseoutput enables a flight either optically or by radar,the control ship rather point determines what changes aredesired insubmarine to detect a surface transmitter is theneasily. the missile flight path. The Acoustics or sound detection systems were keyed in a manner representativeof the desired receiver inused in earlier days for thedetection and change. The signal travels to the These systems used the missile and is subsequentlyconverted intotracking of aircraft. large horn microphones, manuallyoperated, to control surface movement. Althoughcommonly Other devices, used in control of drone aircraft,radio controldetect approaching aircraft. missiles duecalled hydrophones, have beenused by the is little used in present day guided Navy to determine the presenceand position to the advantages of radar inhigh speed missile A hydrophone is a guidance. of submarines and ships.

INFRARED RADIATIONS 33.91 Figure 8-30.Missile using infraredhdming method against airtarget. 150 Chapter 6PRINCIPLES OFMISSILE GUIDANCE

microphone that works underwater,sensing vibrations given off by underwater Selsyns (synchro pickoffs)may be used to targets. indicate the angular position of theflight control surfaces with respect tothe missile axis. REFERENCE UNITS Itisalso possible to usepotentiometers (variable resistors) for thispurpose. this method is used, the When The preceding chapterdiscussed reference potentiometer is units used in the control fastened to the missile frameand the poten- system of the mis-tiometer wiper-arm shaftis moved by the sile. A quick review follows. control surface. The signals pickedup by the sensor must be compared with knownphysical references such as voltage, time,space,gravity, theAMPLIFIERS earth's magnetic field, barometricpressure, and the position of themissile frame. The The subject of amplifierswas introduced sensor signal and the referencesignal arein the preceding chapter.There are many compared by a computer, whichwill generatevariations in each of the three typesof ampli- an error signal if a course correctionis nec-fiers namedvacuum tube,transistor,and essary.The error signal then operatesthemagnetic. missile control system. Gyroscopes are used forspace reference.Vacuum-Tube Amplifiers A reference plan isestablished in space, and the gyro senses any change fromthatreference. Vacuum-tube amplifiersmay be classified The earth's gravitycan be used as a reference; a pendulum can sense the direction according to the method of couplingused of theresistance-coupled (RC), imp edanc e-, gravitationalforce. Some gyros are arrangedtransformer-, or direct-coupled. for vertical reference bya pendulous pickoff They may be and erection system. Gyros tuned, untitled, broad-band,or narrow-band used in this man-amplifiers. Tube type amplifiersmay use ner are called vertical gyros; theymay betriodes, tetrodes, pentodes, used to control the pitch androll of the missile. or beam power An instrument called tubes. According to their application,they may a FLUX VALVE hasbe audio-frequency (a-f),radio-frequency (r-f), the ability to sense the earth'smagnetic field, and can be used for guidance. or intermediate-frequency(i-f)amplifiers. The primaryRadar receivers commonlyuse 30 mc to 60 mc purpose of this device is to keepa directional gyro on a given magnetic heading. i-f amplifiers. A discussion ofelectron tube A gyrotheory may be found in BasicElectronics, operated in this mannermay be used to governNavPers 10087-A. the yaw controls of a missile. Vacuum tube amplifiersare often used as Barometric pressurecan be used to deter-voltage amplifiers. Many missile mine altitude. A guidedmissile that is set to applications travel at a require an amplifier whose outputis not only . predetermined altitude may use angreater than the input, butalso proportional altinteter to sense barometricpressure.to the input. Should the missile deviate Suppose the input is 1 volt and from the desiredthe output 15 volts.Then, if the input is 3 altitude, an error signal will begenerated and fed to the control section. volts the output must be 45volts. Most Another pressure type electronic amplifiers are basedon vacuum tubes. sensor is used to In any vacuum-tube amplifiercircuit, the determine airspeed.It compares static baro-fundamental operation is the metric air pressure withram .air pressure. use of grid voltage The difference between these to control the flow of platecurrent. The two pressuresplate-current change is utilised invarious provides an air speed indication. ways, giving rise to several standard classifica- The aids of the missile frameis used as ations of voltage amplifiers. reference to. measure the displacement'of the One type is a missile control surfaces. resistance-coupled circuit.With, the proper (The Movement ofchoice of circuit components, thevoltage on the control =Steel cannot be referencedto the vertical, or to a given the second grid can bemany times that im- heading, becausepressed 'on the first grid.Pentode tubes are the reference would. change when the missilenormally used for resistance-coupledamplifiers position changes.) because of their higher gain. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

Another type of amplifier is transformer-capabilities are not yet realized. At thepresent coupled, and uses the current changein thetime there are many types oftransistors in plate circuit.Because they give wider fre-use, and many more arebeing developed. quency range with transformersthan other Some of the transistors that are in use are used forthe point contact, junction, drift, tetrode,uni- types of tubes, triodes are normally Eachhas such circuits. junction dynistor, and surface barrier. A third type of amplifier, rarely used,isits own unique characteristics,advantages, and impedance coupled; its output voltage appearsareas of application. Thejunction transistor is across a choke or impedancecoil. the most commonly used. In many applications it is necessary toget , A serious problem with transistors What of power from an amplifier, soat least the finalunreliability at high temperatures. The use of stage is adjusted to give power ratherthan afeedback circuits tends to stabilize thecollector voltage output. The tubes used aresomewhatcurrent with respect to temperature.Also, they larger as a rule than those of voltagecircuits,are ineffective at the extremelyhigh frequencies and are specially designed for largecurrentpresent in many vacuum tube circuits.However, this problem has been largely overcomein outputs. transistor applications in missiles. Some Transistors modern missiles are completelytransistorized. The operation of transistor depends upon the The advent of the transistor in the field ofelectrical properties of a class of substances electronics has as much significanceand im-known as semiconductors. A semiconductortea portance as the development of the vacuum solidmaterial that has greater conductivity tube in the early days of radio. Thetransistorthan an insulator and less conductivitythan a proves that amplification,accomplished beforeconductor. Some semiconductors are com- mainly by vacuum tubes, can takeplace in apounds, such as copper oxide, zinc oxide,indium solid.This device has opened a new field ofantimonide, gallium arsenide, and silicon car- experiment and study in "solid-state"physics.bide, while other semiconductors areelements, Two scientists, John Bardeen and W. R.such as germanium and silicon.The most com- Braden, working under WilliamShockley ofmon semiconductors in useat present for tran- Bell Telephone Laboratories, developedthesistors are germanium and silicon towhich transistor (point-contact 'type) in 1948.Latercertain impurities have been added, inminute (1949), Bell Telephone Laboratories announcedquantities of specific materials. that William Shockley had developed a junction Transistors are generally connected in one of transistor.Since then, transistors have beenthree basic circuits. These configurations are: developed into practical and dependable elec-common-base amplifier, common-emitter am- tronic devices and the field of electronicshasplifier, and common-collector amplifier.The rapidly expanded the use of these "solid- state"term "grounded" is sometimes usedinstead of devices. the term "common" but the elementsaid to be The term transistor is coined from "TRANS- grounded is really Common to both the inputand fer" and "resISTOR." Transistors arelighter,output circuits and is not necessarilygounded. smaller, longer lived, more rugged, moreef-The common-collector circuit is rarely used. ficient; and potentially _less costly thanmost vacuum tubes. 'Furthermore,they require no Transistors may be combined with sources - filament power, 4hey draw comparativelysmallof power and passive elements(resistors, in- currents in operation, and they generate neg-ductors, and capacitors) to form transistor ligible amounts of heat. Another advantageis thatcircuits of many forms which are used for gen- the transistor is ready to operate instantlyateration, amplification, shaping, and controlof the application of operating voltagebecause theelectrical signals. Many transistor circuits are and con- similar to vacuum tube arrangements, butmuch transistor does not require preheating, replacing the elec- suites no standby polder. more is involved than merely BeCausethetransistor is a solid,At can with-tron tube with a transistor. stand the forde of acceleration anddecelera- For information on atomic structure and tion many times that of the force ofgravity.valence bonds in transistor materials,typesand Many new circuit ideas have been developedcombinations of Materials, operations of cir- from the use of the transistor, but itsfullcuits, uses of transistors as audio amplifiers, 156 152 Chapter 6PRINCIPLES OFMISSILE GUIDANCE cascade amplifiers, diodes,triodes, and oscillators, see Basic Electronics, COMPUTERS For a less comprehensiveNavPers 10087-A. coverage, see In- A computer isnecessary in missile guidance troduction to Electronics,NavPers 10084; itsystems in order to describes the principles ofoperation of tran- calculate course cor- sistors. rections rapidly. In one type ofmissile the computer is simply a mixingcircuit. On the other Magnetic Amplifiers hand, the computers used atlaunching sites may be large consoles performingmany calculations. Magnetic amplifiers Computers have beenmentioned in several are not new devices byplaces in the text, and chapter 5gave a brief any means, having been reportedin use overdescription of the two general fifty years ago. Amagnetic amplifier ises- types of com- sentially a device which puters, digital and analog.Either. or both may controls the a-c re-be used in missiles. In thePolaris missile, actance of a coil by utilizinga d-c signal tofor example, the modify the permeabilityof the magnetic material electronics package is in essence an analog computer. It respondsin a upon which the coil is wound. linear manner to input signals In the early stages ofdevelopment this basic from a variety idea was incorporated of sources, for example,the various gyros in into devices, usuallythe missile. The computergenerates commands designated as saturablereactors, and used to(based on the input information) control large electrical loadssuch as theatrical which are fed lighting and electric furnaces. to the flight control electronicspackage, where However, theusethe pulses are convertedinto signals that cause of the SATURABLE REACTOR,the heart of thethe flight controls to magnetic amplifier,was limited in its ability to maneuver the missile as control the load until the recent commanded. Pitch, roll, andyaw of the missile development ofare controlled by such commands.The com- improved magneticmaterials and efficientmands are a series of digital metallic rectifiers. Theutilization of these impulses which are proved materials resulted converted to analog informationin the autopilot in the use of theand cause the pitch, roll,or yaw maneuvers. saturable reactor inmore elaborate circuits In an electronic analog and led to the distinguishingterm MAGNETIC computer, the input amplifier. and output variablesare represented by voltages, and the computations are performedby Many different tradename devices, such aselectronic circuits. self-saturating magnetic amplifiers,Magamps, Transductors, and Amplistats,have been used to identify the moreelaborate saturable reactorSpecific Differences BetweenAnalog circuits. and Digital Computers The advantages of themagnetic amplifier are based principally on tiefact that it.is a com- INPUT.The input to the pletely static device. Withthe exception of the analog computer rectifiers used, its mechanical is never an absolute number, andan approximate construction 10position on a continuousscale. Thus, it is im- comparable to that of an iron-coretransformer.possible to set the potentiometer There are no contacts, movingparts, filainents, dial at exactly or other features which account 75 ohms; there is alwayssome error, no matter for Most of thehow small. On the other hand,the number fed failures associated with othertypes of amplifiersinto the digital computer (except for those usingtransistors). The need is precisely the one for frequent inspection and desired; no more, no less. maintenance is cut OUTPUT.The output ofan analog computer to a minimum. The lifeof the magneticam-15 never an absolute number, plifier is more or less indefinite,and it is but an approximate especiallysuited for shipboard position on a continuous scale.The digital com- installationputer, however, producesa specific series of where there are adverseoperating conditionsdigits for an output. such as vibration and shock. SPEED.Most analog In order to understand thetheory of agnetic computers will pro- amplffierS, it 15 necessary that duce an answer assoon as you have put in the youtpossess aproblem. This ability is vitalin military opera- knowledge of magnetism andmagnetic circuits.tions such as fire control, This information maybe found where there is not in the Nary Train-much time to compute theposition of a flying ing Course Basic Electricity,NavPers 10088-A.target.

153 f 7 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

A digital computer does not work instantane-new missile designswithout building actual ously. It produces an answer sometime afterprototype missiles, and this procedure results the problem is fed to it. Butdon't think thatin a considerable saving inboth time and money. this makes it a slow machine. The"some time after" may be a few millionths of asecond.CONTROLLERS AND ACTUATORS However, because the digital computer must do arithmetic, there is always a time lag between If a missile wanders off its proper course, problem and solution. this fact will be detected by the sensingmech- anism previously described.The computer Classification of Computers within the guidance system will evaluatethe information provided by the sensing mechanisms, determine the direction andmagnitude Computers may also be classified physically and and functionally.Physically, computers areof the error in missile course or position, classified as mechanical, electrical, and elec-produce a suitable error signal output. tromechanical computers. The classification of At this point, the functions of the guidance analog computers is determined by thetype ofand control systems overlap.The primary computing elements used.These computingpurpose of the control system isto correct elements may be mechanical, electromechani-errors in the attitude of themissile. The pri- cal, or electronic.Mechanical elements usedmary purpose of the guidancesystem is to in the mathematical processes include differ-correct errors in the missile flight path.Both entials,linkages, cams, slides, multipliers,types of error are corrected in the same way: and component solvers.Most explanations ofby moving the missile flight-controlsurfaces computer basics use the mechanical type becauseor the jetcontrols(jetevators, jet vanes). it is easier to illustrate graphically, and easierMovements are governedby the same controllers to understand. and actuators, regardless of whether the error In electromechanical computers, the mathe-signalis developed by the guidance or the matical processes are performed by using com-control system. binations of electrical signals and mechanical motions.Synchros, potentiometers, and re-. FEEDBACK SYSTEMS solvers are examples of partnused.Mechanical shifts and cams) are The final section of a guidance system is displacements(as of unit, converted into voltages. known as a "feedback" or "followup" Electronic computers use only electricalalso called a closed-loop system.This unit voltages to perform the computations. Ampli-measures the position of theflight control fiers, summing networks, and differentiating and surfaces or jet controls in relation tothe integrating circuits are components used inreference axis of the missile, and compares electronic computers. Lightness, compactness,this value with the error signal generatedby and speed of computation are achieved morethe computer. easily with electronic computers than with Without the followup signal, there would be mechanical ones. Therefore, the trend innothing but the varying air pressure to prevent development of computers has been toward thethe flight control surfaces from'swinging to electronic type. Vacuum tubes were a frequenttheir maximum limits any time the sensor source of failure, but this troublehas beencaused an error signal to be generated.By using feedback, the deflection of theflight con- largely eliminated by the use of transistors in to the place of the vacuum tubes. trol surface can be made proportional A type of electronic analogComputer thatsize of the error.The feedback loop thus has proved useful in missile design isthegradually returns the flight control surfaces DIFFERENTIAL ANALYZER. This device isto neutral as the error is corrected. sometimes called a SIMULATOR, becauseit To accomplish these results, the feedback can be given, electrical inputsthat simulatesignalis used to oppose the error signal. both the characteristiek of a propOled missileWhen the feedback signal becomes as large as and the conditions under' which it *ill operate.the error signal, no further deflection ofthe The action of the computer will thenahow howflight control surface takes place because the the proposed missile Will perform under thetwo signals are equal and opposite, andtheir specified conditions. It is thus possible to testsuit is zero. .:.158 '154 Chapter 6PRINCIPLES OF MISSILEGUIDANCE

If the error signal voltage islarge, a large deflection of the flight control types of guidance followed bya history of the surface candevelopment of guidance systems. Theguidance take place before the feedbacksignal voltagesystem is an important part in the becomes strong enough toexactly equal the descriptions error signal. of the individual missiles.At the beginning of this chapter, we classifiedmissile guidance As the missile approachesthe desiredsystems into two broad categories: course, the error signal becomes less than missiles thecontrolled by manmade electromagneticdevices, feedback signal, and the resultantvoltage dif- and those controlled by othermeans. ference reverses polarity. The reversalin po- All of the missiles which larity moves the flight control maintain electro- surfaces in themagnetic radiationc o n t a c twith manmade opposite directn until they are in neutral. Thissources may be subdivided into two further action is smooth and rapid, andcannot be dupli- categories. cated by systems thatuse ON-OFF switching. 1. Command guidance missiles Fo llowup loops were describedand illus- 2. Homing guidance missiles trated with block diagrams andschematics in Command guidance missiles chapter 5.Figure 6-4 shows a block diagram are those which of a servomechanism loop are guided on the basis of direct electromag- from a computernetic radiation contact with friendlycontrol (followup unit isa colloquialism for servo-points. mechanisms). The Homing guidance missilesare those error detector computes awhich are guided on the basis ofdirect electro- voltage proportional to theerror. This errormagnetic radiation contact withthe target. voltage is damped in the controller,amplified by the amplifier, and finally Command guidance generallydepends on the supplied to theuse of radio or radar links betweena control servomotor for its control,The mechanicalpoint and the missile. By output is furnished by the motor use of guidance in- and drives theformation transmitted from the controlpoint rate generator. From this generatora voltagevia a radio or radar link, themissile's flight proportional to the output velocityis supplied topath can be controlled. the controller.After being modified by the computing elements in the controller,the modified 'Voltage is combined with theerror voltage RADAR COMMAND GUIDANCE to stabilize operation andincrease the accuracy of the servomechanism. Radar command guidancemay be subdivided into two separate categories. Thefirst category TYPES OF GUIDANCE SYSTEMS is simply referred toas the command guidance method. The second is the beam-ridermethod, The subject of missile guidancewas introduced early in chapter which is actually a modificationof the first, but with a listing of thewith the radar being used ina different manner.

roilRATE I ERROR GENERATOR SIGNAL CONTROL I VOL

INPUT

DAMPED CONTROL SIGNAL

. FEED. I BACK FEEDBACKqtlECHANICAL OR ELECTRICAL DEVICE

144.50 Figure 6-4.Complete servomechanismloop block diagram for a computer. 159 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

RADIO COMMAND SYSTEMS. Radio has been used as a guidance link for such purposes as model airplane flying,steering model boats and cars, controlling target drones, and even for maneuvering oldbattleships during bombing tests.Therefore, when the question of command guidance for missiles came up, radio was among the first methods used.But once a radio command system wasdeveloped, a new problem arosethat ofkeeping track of MISSILE0 the missile when it was beyond the range of normal vision.Radar can locate objects not visible by ordinary means.

COMMAND GUIDANCE The term COMMAND is used to describe a guidance method in which all guidance instructions, or CoMmands, come from sources out- COMMAND side the missile. To receive the commands, TRANSMITTER the missile contains a receiver that is capable of receiving instructions from ship or ground stations or from aircraft.The missile re- TARGET MISSILE COMPUTER ceiver then converts these commands to guid- TRACKER TRACKER ance information, which is fedto the sections rI following the sensor unit. In the command guidance method, radar is 33.92 used to track the missile and the. target. Guid- Figure 6-5.Command guidance system. ance signals are sent to the missileby varying the characteristics of the missile tracking radar beam, or by the use of a separate radio trans-is that the characteristics of the missiletrack- mitter. Figure 6-5 will give you an idea of howing radar beam are not changed in thebeam- this method works in actual practice. As soonrider system. Rather than sending individual as radar #1 in the figure islocked onthe target,orders to the missile via the trackingbeam, tracking information is fed to the computer.the missile has been designed so thatit is able The missile is then launched and is trackedbyto formulate correction signals on the basisof radar #2. Target and missile ranges, eleva-its position with respect to the radar scan tions, and bearings are continuouslyfed to theaxis. Usually, only one radar is used inbeam- computer. This information is continuouslyrider systems.Therefore, this method lends analyzed by the computer, which determinesitself extremely well to shipboard use. the correct flight path of the missile.The guidance signals generated by the computer k computer in the missile keeps it centered are sent to the missile via eitherthe missilein the radar beam. It locates the centerof the tracking radar or a radio command trans-beam and sends the necessary signalsto the mitter. They are subsequently converted intocontrol system to remain in it.The radar correctionsignals by the missile computersysteM keeps the beam pointed at thetarget network.The resulting control surface move-and, if desired, several missiles may"ride" ment citifies collision with the target. the beam. simultaneously.. Figure 6-6illus- The radar command guidance method cantrates a simple beam-rider guidance system,. be used in ship, air, or ground missiledeliveiya tyPical line of sight(LOS) course. The ac- systems. curacy bf this system decreaseswith range because the radar beam spreads out andit is BEAM-RIDER METHOD more difficult for the missileto remain in its The main difference between thebeam-ridercenter.If the target is moving, the missile method and the radar command guidance methodmust follow a continuously changing path, which

.16 Chapter 6PRINCIPLESOF MISSILE GUIDANCE

TRACKING AND GUIDANCE BEAM

BOOSTER SEPARATION TARGET POINT MISSILE TRACKING a GUIDANCE RADAR BOOSTER

BEAM -RIDER MISSILE-BOOSTER COMBINATION

Figure 6-6.Simplebeam-rider guidance system. 12.32 causes itto undergo excessivetransverse accelerations. system within the missilemust interpret the A modified beam-rider information and thenformulate its owncor- radars, a target-trackingsystem uses tworection signals. Themissile is said to "ride" radar and a missilethe beam to the target. guidance radar (fig. 6-7).The target-tracking radar feeds target datainto a computer, which calculates a collision point atwhich the missileHyperbolic Guidance will 'intercept the target.The second radar is pointed toward the calculated collision.point Another command and . themissile follows thisbeam. The guidance method is the so-called hyperbolicguidance.This method modified-beam-rider systemrequires equip-was designed primarily for ment that is too large andcomplex for aircraft long-range surface- use, but is used on shipboard. to-surface missiles.It depends on theloran principle. A loran systemis a modern elec- Modified beani-ridersystems are similartronic aid to navigationwhich was developed to command guidancesystems.In both sys-primarily for long-rangenavigation over water. tems, target informationis collected andana-The system requiresat least two transmitting lyzed by suitable devicesat the laUnching point stations.These two stationsare separated by or other control point, ratherthan by devicesa distance of severalhundred miles, and the within the missile. In bothsystems, the missilegeographic location ofeachstation is accurately makes use of the guidanceSignals transmittedpinpointed.The principle of loran isbased on from the control point. the difference in timefor pulsed radio signals to arrive at a givenpoint from these stations. The principal differencebetween radarcom-The, missile makes mand gUidance and.beam-riderguidance is that flight path correctionson in the command Stem the basis of the timedifference of reception the,giiidanCe .sigaalsthese "Master" of are specific coinmands. and "Slave" signals to the missile, to, "turnfrom the two fixed emanating left," ::"turn ;right," etc.,. transmitting stations. Cor- the,Cont041,. trade-rections, are made sitter of a beaM4ider,guidance gyitem trans.. only in azimuth bythis Mita MAY information, rnethOds not Cominande:. . The hyperbolic indicates the :'diiection Ofthe target or,. the guidance system hasnot calculated point of been ;used inany missile and will therefore interception. The jUidinienot be explained in detail.

151. PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

TARGET COURSE TARGET \ - - -

TARGET TRACKING KAM

MISSILE GUIDANCE BEAM CONTAINING CONTROL SIGNALS

TARGET TRACKING RADAR

COMPUTER LOCATED MISSILE INSIDE SUPERSTRUCTURE GUIDANCE RADAR N N 12.33 Figure 6-7.Modifted beamriderguidance, infrared is commonly used inpassive homing HOMING GUIDANCE against air targets. ' Homing guidance systems contvOithe path of the missUe by a device inthe missile that ACTIVE HOMING.In active homing, the 'diatingnighing feature of therdso4.2:: contains both a radartransmitter and reacts to it sends signals target, The homing device; usualtyUnited inreceivtk. With the transmitter Of Atc4nt1on given to. 'strike' the target. A noseantenna receives the 'nose; 'Maeda .tionte.tYpe the return signal reflectedfrom the target. off by-the target.: 'Homingguidattee depends transmitted upon. the .hiiiirtenitneeof electroniagnetic radia-From the tithe Uttered between the Itdi6eile and 'theand received "Pitlies, the computercalculates tioncolitict" between the the dig:tined to the target. Themissile is able .gaidande Inethods.MaY be its own cor- divided : into three types:ACME hereitie,to track' the target and generate 8EMIACTWB !joining.; ;PAStr.Vic ncmingriction signals 'oh the basis of the tracking (fig. '24)4All.three Worn:lath:O. Chapter 6PRINCIPLES OFMISSILE GUIDANCE

described earlier providemeans of passive homing.Missiles may also be made on radar or radio radiations to home REFLECTED TARGET emanating from RADAR ships,aircraft,etc.Television is another SIGNALS homing guidance mediumwhich, while otherwise suitable for thispurpose, has limited value because itcan be used only in daylight, and only when visibilityis good. One of the most common uses ofpassive homing is in air-to-air missiles whichdepend on heat sen- RADAR WAVES sors.As in the other homing FROM MISSILE methods, the missile generates itsown correction signals MISSILE A on the basis of energy receivedfrom the target rather than froma control point. TARGET Horning is the most accurateof all guidance systems becauseit uses the targetas its RADAR WAVES source for guidance error signals.Its superior FROM LAUNCHING ,/ accuracy is shown when used againstmoving PLANE ;\ targets.There are severalways in which the homing device may control MISSILE the path of a missile against a moving target.Of these, themore generally used are PURSUIThoming and LEAD REFLECTED homing. These will bediscussed in the chapter -RADAR on homing guidance. SIGNALS COMPOSITE SYSTEMS B No one system is bestsuited for all phases of guidance.It is logical then tocombine a TARGET system that has excellent INFRARED WAVES midcourse guidance FROM TARGET characteristics with a system thathas excellent terminal guidancecharacteristics in order to increase the number ofhits. Combined systems are known as compositeguidance systems, or combination systems. Many missiles relyon combinations of the various types of guidance.For example, one MISSILE type of missilemay ride a radar beam until it is within ri certainrange of a target. At this time the beam-rider guidancemay be terminated 144.34 and a type of homing Figure 6-8.Homingguidance: A. Active horn- guidance commenced. ing; B. Semiactive homing; The homing guidancewould then be used until C. Passive homing.impact with the targetor detonation of a proximity-fuzed warhead. SEM1ACTIVE HOMING.Insemiactive hom- CONTROL MATRIX.Whencomposite sys- Inc the target is illuminatedby a trackingtems are used, components radar at the launchingsite or other control of each system point. must be carried in themissile. Obviously, The missile is equippedwith a radarthe sections must be receiver (no transmitter)and, by means of the separated so there is no reflected radar energy from interaction between them andyet be located the target, formu-close to the circuits theyare to control. In lates its own correctionsignals as in the activeaddition, some provision homing method. _ must be made to -44' PASSIVE ROMING.i-Passive switch from one guidancesystem to the other. homing depends Control of the missileguidance system Only on the target asa source of electromag-may come from more than netic radiations.The heat and light one source. A sensorssignal is set up to designatewhen one phase PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS is used, all of the controlequipment is inside of guidance is over andthe nekt phase begins. This means that before the mis- This signal may come from atape, an elec-the missile. radio command.sile is launched, allinformation relative to tronic timing device, or from a target location and thetrajectory the missile The device that switchescontrol systems target must be calcu- is called a control matrix.It automaticallymust follow to strike the lated.After this is done, the missileguidance transfers the correct signalto the control follow the course to the system regardless ofconditions.If the mid-system must be set to system should fail, the matrixtarget, to hold the missile atthe desired alti- course guidance tude, to measure its air speed,and, at the cor- switches in an auxiliaryguidance system to to start the termi- hold the missile on course.Should the originalrect time, cause the missile become activenal phase of its flight anddive on the target. midcourse guidance system A major advantage of presetguidance is again, the matrix will switchcontrol from the be used auxiliary back to the primarysystem. that only limited countermeasures can devices the-against it.One disadvantage is that after the If the target uses jamming missile is launched, its trajectorycannot be matrix can switch to anotherguidance method, been preset at even in the terminalphase of flight.Severalchanged from that which has sophisticated guidancethe launch point.It is relatively simple com- of our missiles have such pared to other types ofguidance; it does not systems. require tracking or visibility. HYBRID GUIDANCE.A combinationof coin guidance sys- mend guidance and semiactivehoming guidance An early example of a preset It achieves manytem was the German V-2,where range and is termed hybrid guidance. bearing of the target werepredetermined and advantages of both systems.It attains long-. The earliest range capabilities bymaintaining the trackingset into the control mechanism. vehicle (ship, aircraft,mod of the Polaris missile wasdesigned to sensors on the delivery use preset guidanceduring the first part of its or land base) andtransmitting the data to the modified to permit By having the missilecompute itsflight, but this was soon missile. changing the course duringflight. own weapon linedrive orders, the entire guidance is used mechanization of the fire controlproblem can The preset method of targets of large size fi be 'simplified. only against stationary guidance such as land masses orcities.Since the 1 Some texts call the beam-riding guidance information is determinedcompletely sYstem a hybrid system. Themodified beam- would, of course, rider system is similar tocommand systemsprior to launch, this method position thenot be suitable for use againstships, aircraft, with the conunands , being used to moving land targets. antenna of the guidance beamrider and thusenemy missiles, or predicted point of directing the missile to the Navigational Guidance Systems collision. The missile must determineits location with respect to thebeam and must distances move to keep itself inthe center of the beam. When targets are located at great from the launching site, someform of naviga- 4 used. Accuracy at SELF-CONTAINED GUIDANCE SYSTEMS tional guidance must be long distances is achievedonly after exacting of the flight The self-contained group consistsof theand comprehensive calculations which all the guidance andpath have been made. Themathematical equa- guidance systems in tion for. a navigation problemof this type may control equipment is entirelyWithinthe missile. control the move- Some of the systems of this type are:PRESET, contain factors designed to three axes TERRESTRIAL, INERTIAL, andCELESTIAL- ment of the missile about the NAVIGATION. These systems are most com-pitch, roll, and yaw.In addition, the equation mis-may contain factorsthat take into account monly. applicable to surface-to-surface acceleration due to outside forces(tail winds, siles,and ; countermeasures areineffective of the missile against theni.The system neither transmitsfor example) and the inertia that can be jammed. itself.Three navigational systems that may or receivesiignals be used for long-rangemissile guidance 'are Preset Guidance inertial, celestial, and terrestrial. INERTIAL GUIDANCE.The simplestprin- The term PRESET completely,describes of inertia.In one guidance nlethoci:When preset guidanceciple 'for" guidance is the law 160 Chapter 6PRINCIPLES OFMISSILE GUIDANCE

aiming a basketball ata goal, you attempt to An accelerometer, give the ball a trajectorythat will terminate as its name implies, is in the basket. a device for measuring the forceof an accel- In other words,you give aneration.In their basic principles, impetus to the ball thatcauses it to travel the such de- proper path to the basket. However, vices are simple. For example,a pendulum, once youfree to swing ona transverse ;xis, could be have let the ball go,you have no fu;ther con-used to measure acceleration trol over it.If you have not aimedcorrectly, along the fore- or if the ball is touched by another and-aft axis of the missile.When the missile person, itis given a forward accelerationthe pendulum will miss the basket.Howeverit is possiblewill tend to lag aft; the actual displacement for the ball to be incorrectly aimedand then of have anotherperson touch it to change itsthe pendulum from its originalposition will be a function of the magnitude Ofthe accelerating course so it will hit the basket.In this case,force. the second player has Another simple device mightconsist provided a form of guid-of a weight supportedbetween two springs. ance. The inertial guidance systemsuppliesWhen an accelerating force the intermediate push to getthe missile back is applied, the on the proper trajectory. weight will move from itsoriginal position in a direction opposite to that ofthe applied force.The movement of themass (weight) is The inertial guidance methodis used for thein accordance with Newton'ssecond law of same purpose-as the preset methodand ismotion, which states that theacceleration of a actually a refinement of thepreset method. Thebody is directly proportionalto the force ap- inertially guided missile alsoreceives pro-plied, and inversely proportionalto the mass grammed information prior tolaunch. Althoughof the body. there is no electromagnetic contact between the A simple illustration ofthe principle in- launching site and the missileafter launch, thevolved in accelerometer operation missile is able to makecorrections to its flight is the action of the human body inan automobile. If an path with amazing precisioncontrolling theautomobile is subjected to flight path with ACCELEROMETERSwhich are acceleration in a mounted on a gyro-stabilized forward direction, youare forced backward in platform. AUthe seat.If the auto comes toa sudden stop, in-flight accelerationsare continuously meas-you are thrown forward. When the ured by this arrangemlittrand the missileinto a turn, auto goes generates corresponding correction you tend to be forced away from signals tothe direction of the turn. Theamount of move- maintain the proper trajectory.The use ofment is proportional to the inertial guidance takes muchof the guesswork force causing the out of long-range missile, acceleration.'The direction of movementin delivery.The un-relation to the auto-is oppositeto the direction predictable outside forces workingon the mis-of acceleration. ) sile are continuously sensedby the accelerometers. If the acceleration alongthe fore-and-aft The generated solutionenables theaxiswere constant, we could determine missile to continuously correct-its flight path. the The inertial method has speed of the missile at. any instant simply by proved far moremultiplying the accelerationby the' elapsed reliable than any otherlong-range guidancetime. method developed to date. However, the accelerationmay change considerably over a .period oftime.. Under these conditions, integrationis necessary to Inertial guidance is soaccurate that thedetermine .the speed. submarine Nautilus, on its first cruise under If the missile speedwere constant, we the polar ice cap,was able to use an inertial.could caleulate the distance navigation system that wasoriginally devel-. covered simply by oped. for use in long4range multiplying speed by time;But because the guided missiles.acceleration. varies, the speedalso varies. ACCELEROMETERS...4%e' imartof theFor that reason,a second integration is nec-. inertial navigation Systeni forships and missilesessary. is an arrangenient of aCCeleirOineterswhich will detect any change in Vehicular.. The moving element 'ofthe accelerometer motion. Tocan be connected to a potentiometer,or to a understand the use of accelerometers*inertialvariable inductor guidance,. let us first examinethe principle core, or to some Other de- of, accelerometers iti general vice capable of producinga voltage propor- Winne. tional'. to the displacementof 'the element. PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

VERTICAL ACCELEROMETERIP

LATERAL ..tor ACCELEROMETER b. _..4140;%4, A LONGITUDINAL ACCELEROMETER 33.134 Figure 6-9.Accelerometersin guided missiles.

suspended by Usually there are threedouble-integrating Figure 6-10 shows a mass measuring theone spring in aliquid-damped system.If the accelerometerscontinuously case experiences anacceleration in the direc- distance traveled by themissile in three the spring will andazimuth.tion indicated by the arrow, altitude, offer a restraining forceproportional to the (fig. 6-9).Double- integrating accelerometers The sensitive to accelera-downward displacement ofthe mass. are devices which are viscous fluid tends to opposethe movement of tion, and by a double-stepproCess measure damps its action and distance.These measured distanceSare-thenthe mass, and therefore distances, whichprevents its oscillation.By including an elec- compared with the desired trical pickoff in the system, we canmeasure are preset intothe: missile;- if the missileis off course, correction signals aresent to the control system. ACcelerometers are sensitiveto the acceleration of gravity as wellas missile accelerations.For this reason, theaccelero- meters which measure rangeand azimuth distances must be mounted in afixed position with respect. to the pullof gravity. This can be done in a movingmissile by mounting. them on a platform whichis stabilized by gyroscopes or by star-trackingtelescopes. This platforni, however,must be moved as the missile passes over theearth to keep the sensitive axis of :each'accelerometer in a fixed position with respect tothe Pull of gravity. These requirement's cause theaccuracy of the inertial system to.;decrease as the time of . flight of the missilekincreases. . To Unwanted:: oticillatiOns,', a DAMPER, is included in theaCcelerometer unit. The din** effortishoUld be just great enough to. prevent anyoscillations from4 Oc- curring but still permitazigniffaant.displace- Me*, of .the ,When thiS. nonditiOn exists., 33.131 the movement: ofIthe .mass",4iill, be exactly system. proportional to the acceleratione of thevehicle. Figure 6-10.Liquid-damped

F Chapter 6PRINCIPLES OFMISSILE GUIDANCE the displacement of themass, Which is pro-The strain gauges form the portional to 'force and acceleration. arms of a bridge. A change of accelerationcauses a change of the Figure 6-11 showsa system which is electrically damped. electrical resistance of the circuit,giving an The mass (m) is free toa-c output that is an indication of theac- slide back and forth in relation tothe iron coreceleration. (c). When the vehicle experiences an accelera- Still another type ofaccelerometer is the tion, the voltage (e), which isproportional to themanometer.In this type (fig. 6-12), accelera- displacement of themass, is picked off andtions are measured by the amplified. The current (1) (still proportional electrolyte flow totoward one or the other end of themanometer. mass displacement) is sent back tothe coilThis action provides currentcontrol between around the core.The resulting magnetic fieldpairs of electrodes. The venturi around the coil createsa force on the mass, shown in the which damps the oscillation. figure damps the oscillations ofthe manometer In this systemby controlling the electrolytemovement. the acceleration could be measuredby the dis- You will undoubtedly runacross other types placement of the mass, by the voltage (e),orof accelerometers; however, thebasic princi- by the current (0. ples will always hold. VARIATIONS IN ACCELEROMETERDE- SIGN.There are actuallymany variations in CELESTIAL REFERENCESA celestial accelerometer design.For example, one typenavigation guidance system isa syst em designed of accelerometer dependson a change of induct-for a predetermined path in whichthe missile ance between two electrically excitedcoils.course is adjusted continuously by referenceto If one coil is attached to themass and anotherfixed stars. The system is basedon the known to the vehicle, the inductancebetween themapparent positions of stars or othercelestial will vary due to their relativemovement broughtbodies with respect to a pointon the surface of about by vehicular accelerations. the earth at a given time. Navigationby fixed Another accelerometeruses wire strainstars and the sun has been practicedfor cen- gauges as the suspension elements for themass.turies and is very dependable.It is highly desirable for long-range missilessince its accuracy is not dependent 'on range. Figure 6-13 sketches the application ofthe system as it might be used for a guided missile. The missile must be providedwith a horizontal or a vertical reference to'the earth, automatic star tracking telescopestodetermine star-elevation angles with respect to thereference, a time base, and navigational startables

33.132 33.133 Figure 6-11.Electricallydamped Figure 6-12.Manometeraccelerometer accelerometer.. with venturi damper. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

------* ------.:+

LAUNCH

-4 33.94 Figure 6- 13. Celestial guidance.

electrically recorded. A com- PROPORTIONAL NAVIGATION. This is a mechanically or homing guidance technique in which themissile puter in the missile continuously comparesstar the turn observations with the time base and the naviga-turn rate is directly proportional to rate in space of the line of sight.The seeker tional tables to determine the missile'spresent the target semi- position.From this, the proper signals are (inthemissile) tracks towardindependently from themissile maneuvers. computed to steer the missile correctly determines the flight the target.The missile must carry all thisThe control system used complicated equipment and must fly abovethepath followed by the missile. Visibility. clouds to. assure star APPLICATION OF NATURAL PHENOMENA Celestial guidance (also-called stellar guid- mice) was used Air the ..hfariner(unmanned Two types will be discussedbriefly as spacecraft) interplanetary mission to the vicinityapplied in missile systems: magneticfield of of Mars and Venus. No guidedmissile systemthe earth, and Doppler effects. at present uses celestialguidance. TERRESTRIAL GUIDANCE METHOD. Var - EARTH'S MAGNETIC FIELD ious picture and mapmatchingguidance methods Three characteristics of the earth's mag- have been suggested -anddevised.: The principle is basically the sail* for all. ;It involves thenetic field that are useful inmissile guidance terrainare:(1) lines of equal magnetiCdeviation, comparison ..of a photo or map or the inclination, and over which' the*eine is flying-With observa-(2) lines of equal magnetic equip-(3) lines of equal magneticintensity.The tions of the terrain.by optical or. radar the angle ment in the missile. On thebaste of the'coni-magnetic deviation or declination is parison (fig. 644); the missile is able tocausebetween the magnetic and the truemeridians. the actual track to*nettle:NM the deSredThe magnetic inclination or dip isthe angle I track. The system is, of course, quite com-from the horizOntal. The dip variesfrom the plicated and is usable only againststationaryhorizontal at the magnetic equator to90degrees indusrat the magnetic polei3: targets' such as large land masses and available trial areas. Magnetic charts. of the world are described. in a'which show the dip, the intensity ofthe hori- Rada'. .mapmitching will be tal component and of the verticalcomponent, later chapter. zon 1 _Chapter 6PRINCIPLES OF MISSILEGUIDANCE

MAP.MATCHING EQUIPMENT IN THE MISSILE :4'it!i5'43%*

33.93 Figure 6-14.Terrestrial guidance. the total magnetic force, the north-south com-flux valve is properly aligned with theexternal ponent, the east-west component, andthe variation. magneticfield, the amplitude of the second The earth's magnetic field issubject toharmonic voltage will be proportionalto the changes in intensity and direction,and duringstrength of that field. magnetic storms the changesare unpredictable. In figure 6-15A and B,you will see that Despite all the possible andunpredictablethe number of flux lines setup by the earth's variations, Magnetic devices havebeen usedmagnetic field will vary in three spiderlegs, for missile guidance.The German V-1 used a magnetic compass as part of its gUidancedepending on the heading of the missile.By system. The magnetic exciting the core with ana-c current, these compass controlled theflux lines may be caused to alternateback and missile in azimuth only; its altitudewas con-lorth across the pickoff coils.The hxhiced trolled by a barometric .altimeter,and its range by an air log. current in each pickoff coil will thenbe pro- This ,was a relatively simpleportional to' the number of flux linescutting but rugged guidance system that.could guidethat coil. The resultant of the inducedcurrents the missiles to a selectedgeographical areawill be proportional tothe amount of preces- but could-not pinpoint targets,and could notsion of the gyro away from the original be used against moving, targets. magnetic heading. Again, an amplifierand torque A refinement of the magnetic'compass ismotor are used to exerta force on the gyro, the flux valVe. The .Auxvalve consists ofthe force being equal and oppositeto the force primary and secondary windingson an ironof preceseion. core.The primary is supplied with a-C ofa The flux valve is ,sometimes called fixed voltage and frequency. When a flux no externalgate compass. Beeause of the physicalarrange- magnetic field, isliresed, the'device acts as ament of the nly one possible combina- simple .tranSformer; the freqUencyof the sec-tion ofvoltages`willexist for any given compass ondary 'voltage is the same as that of theMOM heading.It' is a type of gyrostabilizedmagnetic voltage. But when an external field hi'present;compass. A gyrostabilized magnetic Compass it Will, alternately ,add to and subtract %rota' theis' one in which the magneticcompass element field. 'generated. by the PiiniarY-Miireid,dUising is stabilized by a verticalgyro so that it meas- successive 'hialiCycles. 'As'a result a secondures only the horizontal Component of the earth's harniOnid,. at twice the input frequency, ismagnetic field. A gyromagneticcompass 'con- supeiiraposed on the -output voltage If thesists of A gyroscope which is positionedby a PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

33.85 Figure 6-15.Flux valve: A. Missile headingnorth; B. Missile heiding east. magnetic compass. Its function is to maintain 2. An optical frequency change isobserv- a steady directional indication. able when the source or the observer moves at right angles to the line connecting the source and the observer. (No acoustical change in DOPPLER PRINCIPLE this case.) 3. The motion of the medium throughwhich The Doppler effectis a change in thethe waves are propagated does not affectopti- observed frequency of sound, light, or othercal frequency. waves, caused by the motionof the source or The laws affecting light and other electro- of the Observer.A familiar example is themagnetic waves, applied to radar, gave us increase or decrease in sound waves, as of athe Doppler radar system to measurethe train whistle.As, the train approaches, therelative velocity of the system and the target. pitch (frequency) of the whistle increases,The operation of those systems is based on and appears to decrease as thetrain' passesthe fact that the Doppler frequencyshift in and moves into the distance.The effect isthe target echo is proportional to theradial based on the fact that the listener perceivescomponent of the. target velocity. Onehoming as frequency the number ofsound waves ar-guidance system makes use of doppler princi- riving per second.The, acoustical Dopplerples. effect varies With the relative motion ofthe Doppler homing equipment can be divided listener and the source, and themedium throughinto: two groupsFM-CW dopplerSystems, which the sound passes.., The opticalDopplerand pulse doppler systems. There are major effect is similar to the acoustical Dopplerdifferences in the circuitry of the two systems. In the FM4W system, the frequencyof an effect in some wigs but is definitely different of in three fundamental ways: echiksignal has a relationship to the speed 1. The optical frequency change doesnotthe target with respect to the receiving. an- depend, upon whether it is the source orthetenna.This echo signal can be converted into obsirirer that Is moving with respect to thean indication of target. velocitywith respect to other. the missile. Chapter 6PRINCIPLES OFMISSILE GUIDANCE

The difference between thefrequency of thethe selected target. transmittedsignal and the frequency of the At the closest approach echo is due to the doppler effect. point to the target, the dopplershift becomes This principle is illustrated zero because there 'is then no relativemotion in figure 6-16.between the missile and the target.The Note that the receivedwave from a distantzero shift can be used to detonate moving object is shifted both to a missile the right andand destroy a target thatwould otherwise upward with respect to the originaltransmis- sion. be missed.This system does not provide Consequently, the beat frequencywilla means of range measurement.If this fea- be alternately very smalland very large ontureis desired, additional circuitsare re- succeeding half cycles.The sum of the twoquired. different values of beat frequency thusproduced is a measure of the distance A pulsed doppler system performsthe same of the missilefunctions as an FM-CW system and,in addi- from the target and the differencebetween thetion, can select a target by two values of beat frequencyis a measure of its range. Like velocity of the missile with other pulsed radar systems, ithas greater respect to theoperating range for a givenaverage power target. output than a CW system. Thus frequency-modulatedradar determines the distance to a reflectingsurfaceby measuring The guidance control signalsare sent as a the frequency shift betweentransmitted andseries of timed pulses. Thereceiving system reflected waves. in the missile must contain circuitsthat will When the two signalsare mixed in anmatch the transmitted pulses inboth pulse electronic circuit, the circuit willdevelop atiming and r-f cycles. The matchingis ac- "beat" frequency equal to thedifference betweencomplished in electronic circuitryknown as the two signal frequencies.The beat notethe coherent pulse doppler system.In this developed in this manner willhave a pitchsystem the transmissionsare short pulses at thatis proportional to the relativevelocitya repetition frequency that can be continuously between the target and the radarantenna. Tovaried.Low-intensity power, which is used to eliminate the possibility of homingon objectsobtain phase coherence betweensuccessive other than the target, a band-passfilter (whichpulses, is generated by the stabilizedlocal will pass only a narrow bandof frequencies)oscillator. A duplexer provideslow-impedance is inserted in the control circuitto eliminatepaths to keep the oscillatorenergy ikthe de- interfering signals. sired circuits. A receiver which isautomatically tuned over the frequency range passed by the The stabilized oscillator alsoprovides a filtersuitable local oscillator signal whichis mixed is used to choose and lockon a target. An automatic frequency control with the receiver signals togenerate a re- (AFC),in theceiver intermediate frequency.The doppler missile receiver, maintains thereceiver onreceiver contains a type of filter,called a

A /A \ A\

FREQUENCY

REFLECTED WAVE FROM DISTANT MOVINGOBJECT ORIGINAL TRANSMISSION. REFLECTED WAVE FROM DISTANT STATIONARYOBJECT

TIME

Figure 6-16.Doppler effecton frequency modulation (sawtooth wave). 411 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS velocity gate, which filters out all undesiredthe flight path can be measured to nullify errors that a drift angle creates. doppler frequencies. The antenna mounting has two antennas Velocity-Damping Doppler Radar looking down and forward at a slight angle away from the roll axis of themissile. A third A Doppler radar used for velocitydampingantenna looks to the rear.A comparison of an inertial system is somewhatdifferentbetween the signals from the two front antennas from the hoining type of Doppler.Thevelocity-is' used to align the direction of the missile. damping Doppler requires antennas to measureA comparison between the forward and rear the forward and lateral components ofvelocity.antenna signals gives the forward velocity, These antennas have to be direction stabilizedDrift is computed from the angle between the so that the 'velocitiesalong, and normal to,antennas' fore and aft axis and aircraft heading.

it CHAPTER 7

COMMAND GUIDANCE

INTRODUCTION of command-guided missiles andglide bombs which they used with effectivenessin World GENERAL War H.

For maximum effectiveness, the FIRSTmis-DEFINITIONS sile fired at a target should strikethat target. Cost, size, and the necessity for surprise COMMAND GUIDANCEmeans that intelli- prohibit the firing of ranging shots (asis done with gunfire). gency (in the form of commands) is transmitted To strike the target from an outside source to the missilewhile the on the first shot, themissile is in flight to the target.Missiles trajectory of the missile must beaccuratelywhich use command guidanceare guided by controlled.This control is necessary becausedirectelectromagnetic radiation from forces, natural or otherwise,can cause the a missile to FRIENDLY control point. deviate from its Predetermined 3 A command guidance systemincorporates course. Even though' it fUnctions perfectly,atwo links between the missile andthe control missile 'without accurate guidancemay miss apoint. selected fixed target by several miles. Moving One, an INFORMATION LINK,enables the targets can take evasive action;without guid-control point to determine the position ance, the missile would be unable to compen- of the sate for this .action. missile relative to the target; theother, the Therefore, an accurate,COMMAND LINK, makes it possiblefor the fast-acting guidance system is ofprime im-control point to correct any deviationsfrom the portance. desired path. As with other guidancetechniques, applied command systems vary from simpleto complex. However, command systemscan be the simplestPURPOSE AND APPLICATIONS of all the techniques considered.Command guidance was therefore the first guidancesystem The purpose of any guidancesystem is to to be demonstrated, bothon the surface withsecure direct hits on a selected target. Per- remote control, of boats,....taan,and cars, andfect performance is difficult to obtain in the air with remote control of drone because aircraftof natural disturbances and, in wartime,enemy and glide bombs... Command .guidance is the most broadly applied of all the countermeasures. However, because command guidance tech-guidance makes. it possible to change theflight niques that we willdieCuss. It is usedfor con-path of the missile by signals fromthe control trol of many mechanisms otherthan guidedpoint, most of these difficultiescan be over- missiles.. come. Current missile0 controlledby command guidance include Bonierc, .Bullpup,and Nike.COMPONENTS A review of the history of guidedmissiles

(chapter 1) will recall the.names of. earlyMissile Components missiles, drone aircraft, and glide bOrnb0 :that used command guidance. or a combination of The command guidance equipmentcompo- command guidance and -.Scime- other 'type,such as preset. nents that are built into themissile will be The germans had several Versionsdetermined by the guidance systembeing used. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

The most complex guidance system has a tele-may be plotted on a visual display, or both. vision camera, television transmitter, radioWhen the tracking data indicates that the mis- command receiver, and the tone filter equip-sile has turned from its calculated course, ment built into the missile. commands can be transmitted to return it to A relatively simple guidance system, so farthe desired course.The commands to the as total equipment in the missile is concerned,missile are transmitted by a radio transmitter is based on a radar transmitter that sendsin a radio command system and by a radar guidance commands to the missile on thetransmitter in a radar command system. For tracking radar beam. With this system, onlylong-range command guidanCe missiles, control a receiver for the radar pulses isneededincan be shifted from the launching ship to ships the missile. The output of the receiver con-or aircraft down range. trols activatingcircuits that function when pulses of the correct amplitude and sequence INFORMATION LINKS are received. The most widely used command guidance The use of command guidance requires an system uses a radar tracking unit and a radioaccurate knowledge of the missile position, command link. The missile contains a ire-- since all guidance comes from outside the mis- quency modulated (fm) receiver and audiofre-sile. This knowledge is obtained through infor- quency (a) channel selectors. mation links.The accuracy and dependability of the infOrmation link determines to a great Launching Station Components extent the overall accuracy of the complete system. Themissilecoursecomputer,missile The information link enables the control tracking radar, missile plotting system com-point to determine the amount of error existing ponents, and the command transmitter arebetween the actual position of the missile and located at or, near the launcher.These, andthe desired position. Once this is known cor- the guidance components in the missile, arerection signals can be sent to themissile. discussed later in this chapter. Information links may use optical or electronic observation methods. OPERATION OF A TYPICAL SYSTEM OPTICAL OBSERVATION. The optical, or

visual, command guidance system has limited r. When command guidance is used, a ground,value, since the missile must-always be visible shipboard, or airborne station determines thefrom the command station. Such,a system position of the missile by radar tracking equip-might use the unaided eye, telescopes, or op- 1 ment or other means. It determines the error,tical rangefinders. Butthese devicesare not if any, between the actual position of the mis-effective at long range; and smoke, fog, clouds, sile and the desired position. It then sends outor darkness make them useless.Some target control impulses (commands) to bring the.mis-drones and air-launched missiles still employ Ole to the desired course. an optical observation link. If the flight path is long, and a large part of ELECTRONIC OBSERVATION. Much effort the path is over friendly, territory or waters,has been expended to develop an accurate and dependable electronic information link. A num- several 'stations might track the 'missile as it F comes into their range.These stations wouldber of electronic systems have been designed The limitations of each system then. send 'commands to the missile to correctand tested. any deviations from the desired course. have been determined, and continuing efforts A typical command: guidance syiteni might beare being made to improve the most promising used to control a. surface-to-surface missilesystems.Electronic observation is accom- fired by a ship against .a fixed installationplished by radar both in the radio command ashore.. The missile, during the early part of itsand radar command guidance systems. flight; would be tracked by. radar hoard .the firing ship. Because the. geographical locationCOMMAND LINKS of the target and the firing ship are both-known, the required missile course can be accurately The' equipment used to send commands to a calculated. InformatiOn front the missile-missile' may be compared to a radiotelephone traCking radar may be fed to a computer, or itcircuit between a piloted plane and a ground Chapter 7COMMAND GUIDANCE

station.Instead of voice communications,the instructions are sentas a single pulse or a series of spaced pulses. The pulses may be TARGET modulated or unmodulated,depending on the complexity of the system inuse. In other words, missilefunctions (dives, turns, etc.) are controlled byeither radio or radar commands. Wire links were usedin some early missiles as command links,and are presently COMMAND used in an antitank TARGET weapon. The German X-4 LINK TRACK missiles(air-to-air) used in WorldWar II RADAR had wire links.Limitations on the use of ..--17UIDANCECOMMAND wire guidance for supersonicmissiles are A obvious. The signals cannot be jammed,but r AUTOPILOT AND a very limited length of wirecan be unrolled STABILIZATION and trailed behind a missile.

COMPONENTS AND FUNCTIONS 4 I AIRFRAME COMMAND LINK Insofar as guidance isconcerned, the prin- INTEGRATION cipal functions prescribedfor command sys- RADIO LINK tems, are thesighting and tracking means, MISSILE computation of flight path TARGET error, communication BIT1 SENSING of this intelligence to themissile, and sensing MEANS and respOnding mechanismsin the missile to effect flight path correction.In the command 83.22 guidancesystem,measurement of relativeFigure 7-I.Generalizedcommand guidance position and motion of missileand target are system:A. Ground (shipboard)station com- accomplished at a location outsidethe missile. ponents;B. Missile componentswith con- Computers perform thecalculations. The necting link. information gained must be sentto the missile in the form of commandsto correct missile position with relation to thetarget. cipally the receiver-demodulator Except at shortranges where visual detec- (detection), tion and tracking of targets servodrive for airframe controlmembers, the is possible, radarairframeitself,and autopilot feedback for detection and tracking isthe method used.stabilization and reference. Detection, lock-on, and tracking Missile sensing are the normaland tracking equipment (trackingradar, fig. sequence.Continuous monitoring ofa moving7-1) .locate the 'missile targetis,necessary. by measuring its posi- Detection may involvetion and motion, obtaininginformation on mis- search, identification, designation,and acquisition. sile range and time derivatives.. Guidance The function of the commands are computed from thisinformation. computer is to generateThe integratedrange and 'angle information command signals that willresult *in. collisionusually, requires coordinate of the missile, with thetarget. conversion before Frani thedelivery to the computer.Requirements for pOsition and,rate informationreceived from thetarget sensing and tracking radar tracking system, the Compiter. :are similar. ,prediCts The, command signals generatedby the com- the optimuni point of impact,and sends theputer are ;sent to the, receiver steering. signals to the missile, tocause it to in the missile fly the indicated course. via the. command link,which usually is a . radio link..Guidance intelligence is:derived Figure 7 -1 is a bloOlt diagramof the com-in the missile by demodulation ponents of. ageneralized command of the modulated guidance radio frequency carrier. Theelectrical inior- system.Many variations arepOsaible.The local missile guidance 'nation ,10 converted to mechanicaldisplacement System contains Prin-Of-the airfranie control members,the airframe 0% ix' PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS receiv- itself, and the autopilot feedback forstabiliza-sets were replaced by superheterodyne themissileers.These sets are identical to standard tion and reference, correcting frequencymodulation (FM) receivers(PM can flight path. The type of trajectory requiredfor thebe picked up by an FMset) up through the tactical situation influences the ref ponceof thediscriminator stage. elements of the guidance system.Besides The receiver is in the missile andtherefore steering instructions, the commandlink r.c:..yita size and weight are importantconsidera- be required to transfer otherinformation totions.Designers aim toward the reduction in the missile, such as arming, receivergainsize and weight of the componentsthat are setting, detonation of warhead nearthe target,placed in the missile. or self-destruction.Carrier frequency 7,. ad power requirements mustbe :Tutted to the effective range in which the missilesystem TYPES OF COMMAND GUIDANCE is to be applied. The N block in figure 7-1 is the comm'41 reference direction, such as "up," whichmust Command guidance may be exercisedby be established for the control loopand main-one or more ground stations,shipboard sta- tained throughout the control period.It takestions, or aircraft.The guidance point influences the typeof command guidance used. the place of the .pilot in keeping themissile to correctly oriented.The prealignment of theSince all command systems are subject missile gyros establishes this reference. enemy jamming ci thecontrol circuit, the closer the missile can be launched tothe target TRANSMITTERS. Early target drone com-the better.A shorter time required for the mand transmitters were simple one-tubeunitsmissile to travel from the launcherto the that sent out a pulse when keyed bythe opera-target means less time for the enemyto jam tor. This system made it possibleto controlthe controls. the rudder.But to control engine speed and altitude, additional transmitters turnedto other Electronic command guidance systems are frequencieti were required. As a result,thedivided into four principal groups:television. system became so large and complexthat itradio radar, and hyperbolic. Withineach group was unsuitable. Consequently,work was startedare one or moresubgroups. The paragraphs on a simpler, morereliable transmitter thatgives a brief introduction to each group. would reduce the number. ofradio-frequency (RF) channels needed for command guidance. The result of this work is the moderncommandTELEVISION GUIDANCE SYSTEM guidance transmitter which issimilar to. any medium power. PM (phasemodulated) trans-- Television command guidance is wellsuited mitter. for some missions where thecontrol point is RECEIVERS.In early missile systems, re-in a mother aircraft.The control aircraft ceivers used for remote control weresimplecan stay out of rangeof hostile antiaircraft one-tube superregenerative sets. A relay wasdefenses and yet launch the missilereasonably connected in the platecircuit of the tube;close to the target.Because the target is when a signal was applied to theinput of thepicked up by the missile's TV camerabefore 1 tube, its plate current changed andoperatedthe missile is launched fromthe aircraft, the relay. The closing of. the relaycontactsthe personnel in the plane can seethe target activated another circuit kehich moved the con-through the missile camera from thetime the trol surfaces: targetis first picked up until themissile The ;disadvantage of this system .is thatstrikes.Because of the close range at the separate receivers, are required for. each con-time of firing, the system is quite accurate; trol function.. In addition, thesuperregenera-and because of the short time betweenlaunch- tive receiver, in:its most sensitive.condition,'ing and strildng, there is less chance of enemy is a low-powered ;transmitter that couldinter-lamming.But this is essentially an optical fere with other. receivers in the missile. system, and is not suitable for use whenthe Butreceiver develOpMent, kept withtarget is obscured by overcast, smoke, fog, transmitter development,and simple one -tubeor darkness. Chapter 7COMMAND GUIDANCE

RADIO AND RADAR COMMAND in the missile.The receiver activates the GUIDANCE missile control circuits when it receivescom- mand signals from the transmitter. This These two systems are much alike.Eachequipment makes it possible to follow the mis- is based on a transmitter at the control point,sile's flight and correct for errors which would and a receiver in the missile. The transmittercause a miss. sends out a carrier wave, which is modulated Many of the earlymissiles were radio in accordance with the command signals. Thecontrolled.The use of radio for command receiver interprets the modulation so that theguidance of high-speed missiles makes itnec- missile can execute the transmitted commands.essary to use a transmitter that can do more The two systems differ in twoways.First,than send simple ON-OFF pulses(Bang-bang con- radar operates at a higher frequency. Secondtrol). Further experimentation with missiles led the 'radio transmitter usually sends out acon-. to the successful use of tone channels. By modu- tinuous carrier wave, whereas the radar trans-lating the transmitter with various audiofrequen- mitter sends out its signals in the form ofcies it became possible to control many missile short pulses, with resting intervals between.functions by using only one carrier frequency and therefore only one r-f transmitter and HYPERBOLIC GUIDANCE SYSTEM receiver.Each of the audiofrequencies was made to represent one particular function such A hyperbolic guidance system can be usedas fly right, fly left, etc. Whereas the number for both long and short range missile guidance.of operations capable of being handled by the It consists of master and slave stations that .system of multiple receivers was only about send out low- frequency pulses at constant in-four,the modulated system was capable of tervals.The slave station is triggered byhandling twenty possible functions. the master station, and sends. out its pulses a Tone systems, however, were troubled by few microseconds after the master pulse isinterference from outside sources. Radiofre- transmitted.These pulses are picked up byquency waves modulated by the same frequen- receivers in the missile and fed to an auto-cies as those used by the missile (but not matic computer in the missile. The computerassociated with the missile guidance system) then establishes the missile position byanwould sometimes cause unwanted actuation of imaginary line of position set up by the masterthe missile controls.An attempt to prevent and slave stations.Hyperbolic guidance isthis interference was made in using an f-m not used by any missiles and will not besystem.However, outside f-m interference discussed further in this course. also caused difficulties. Finally, a systemwas Long range hyperbolic navigation was de-developed which used coded tone pulses.In veloped primarily for long range 'navigationthis system a particular missile function would over water and for aircraft. LORAN (LOngoccur only on the missile's reception and RAnge Navigation) makes use ofa . masterrecognition of a specific series of pulses at radar station and one or more slave stationsthe correct tone.The chance that random or separated by several hundred miles. A formintentional interference would exactly duplicate of loran is Used by the Matador. missile. the coded pulses in this type. of system is minimized. RADIO COMMAND SYSTEM APPLICATIONS BASIC PRINCIPLES Radio command' guidance may be used to Aradio,command system contains a" meanscontrol missiles aimed at ground or air targets of accurately determining the missile positionfrom surface sites or from aircraft.The in relation to the control station, the target,controlled missile may be of any of the follow- and the desired trajectory.A compute# ising types: surface-to-surface, surface-to-air, usually used to determine the error betweenair -to- surface, or air-to-air.A recent use the actual missile position and the desired po-is in spacecraft boosters to replace inertial sition.A command transmitter is located atguidance systems.It permits a considerable the control point, and a receiver is containedreduction in weight. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS Missiles that are used against moving targets usually have another form of guidance for part of the trajectory.The Nike is an MASTER RF RF example of such a missile.Many of the PHASE (CRYSTAL) .40oMULTIPLIER POWER ODULATOR glide bombs in the World War II era were OSCILLATOR AMPLIFIERS AMPLIFIER radio controlled, as were target drones. IVENTENNA LIMITATIONS OUTP

AF The limitations of a radio command system AUDIO ' AUDIO TONE KEYER4.INPUT are imposed by transmission conditionsdis- PRE-EMPHASIS MIXER ENERATOR tance,and enemy countermeasures.Early 1 systems, which used AM tone modulation, had additional limitations. As an example, an in- 33.139 terfering signalcontaining the control-tone Figure 7-2.Phase modulated radio frequency would-cause the missile control sur- command transmitter. faces to ad... Often harmonics or sideband frequencies of voice-modulated carriers would upset the whole control system. power, and cost, since modulation takesplace The use of PM (phase modulation) elimi-at a low level and requires less audio. power nated a large part of the voice interference, that does high level AM. but manmade interference with PM character- Modulation is in the form of tones that are isticscould still affect the control system.generated by tone generators.Starting at the Thisdisadvantage was overcome by usinginput of the transmitter, each a-f tone genera- coded combinations' of tone channels. With thistor may be keyed separately or in combination system, no control operation can take placewith others. The 'tone generator outputs are unless the proper tones appear at the missilefed .to an audio' mixer circuit and, as a result receiver in the correct order and spacing. Theof the mixing, a 'composite tone appears at the adoption of thiscontrol method practicallyoutput of the mixer stage. eliminates the chance that an interfering signal The composite tone. is fed to an audio will duplicate the control combination. preemphasis network.The network builds up (emphasizes) the higher audio frequency com- COMPONENT OPERATION ponents of the composite signal; which are later deemphasized in a network of opposite Radio Command Transmitter characteristics in the receiver..: This action is :desirable becanse atmospheric noise usually Figure 7-2 shows a block diagram of theConsists of high frequency components. Because type of radio command transmitter used inthe noise. appearing with the,signal consists of modern systems.The master oscillator ishigh frequency component's, preemphasis is crystal-controlled and provides,yeti 'gableused only -: on : the high frequency tones, and carrier frequencY. Accurate frequenCf.COntrOlthus causes the signal-to-noise ratio to remain is of priMe importance sincythe commandmore constant throughout the audio range. receiver in the missile is tuned to the .comcom- As shoOniAn.figtire.:72,,thi-composite tone mand frequency before'themissile is fired,..from the preemphasis network is-fed to the and the receiver tuningcannot be changedphase 'Modulator stage which is'- connected be= while the .1s; in ilight..Therefore,tween. the crystal.OsCillator, and the. first fre- the transmitter .f requency: must remain stablequency ..maltiplierj Stage. After modulation, the or the command linlewill,be inst. fundamental' frequency:. is mUltiplied and .ampli- The Output of the :,9ryatakOaciilatornie ,built any other .transmitter..It then passes up by Siithe':Ortlieseto tite`,. antenna '. and is radiated into space. stages operite as frequency multipliers, but , 7.1 ' the output stage operates as a.straight- i "order UnderStand' hOW,phaSentOdulatiOn r7t M) ;takes,. neceeeary o re .4311th 'TRANsitiTto. the frequency yof an alternat , PM results' in:,-COnsiCiera le ace; e ermin rate it 'which phase, I ^ . . Chapter 7COMMAND GUIDANCE

changes.If the phase of the current ina cir-selector channel, a breakdown of which ispre- cuit is changed, there is an instantaneousfre-sented in figure 7-4, is usuallyan amplifier quency change during the time that the phase iswith a band-pass filter at the input anda re- being shifted. The amount of frequencychange,'lay in the plate circuit. or deviation, depends on how rapidly the phase USE OF TONE CHANNELS.The discrimin- shift is accomplished. It also dependson theator output is fed to a-f channel selectorsand amount of phase shift. In a properly operatingthere is one receiver channel selector for each PM system, the amount of phase shift ispro-tone the transmitter may send. portional to the instantaneous amplitude of the The sections of an a-f channel selectorare modulating signals The rapidity of the phaseshown in figure 7-4. A sharply tuned band- shift is directly proportional to the frequencypass filter (one that passes certain frequencies of the modulating signal. Consequently,thebetter than others) is at the input ofan ampli- frequency deviation to pm is proportional tobothfier stage. the amplitude and frequency of themodulating. The grid bias of this stage is adjustedso signal. Thus the crystal oscillator output signalthat plate current is cut off whenno signal is is varied in both amplitude and phase bythebeing fed to the stage. When a signal is applied modulating signal. to the input of the stage, the effective gridbias The rf section of the transmitter operatesis reduced to the point where plate current continuously, but is modulated only whenone orflows.The change in plate current- operates more of the tone generators .are operated bythe relay; its. contacts close, and activate the the keyer section. missile control surfaces in accordance with the commands. Missile Receiver

The receiver in the mission. is theconven- Proportional Control tional fm receiver shown in the block diagrani in figure 7-3. An addition to the -conventional Thus far, we have discussed radiocommand receiver is the carrier fail relay. When theguidance from the standpoint of on-off (bang- incoming carrier signal falls belowa specifiedbang) control. In some missiles,radio com- value (thus becoming unreliable); the fail relaymands are used in proportional control of missile is actuated. The operation of this relaymayfunctions. For example, throttle control, turn cause-self-deistruction of the missile or.keep itcontrol, and pitch control may be gradually on present course (depending 'on the deSiredvaried in proportion to the varying character- objective-O.:. . istics of the radio command signals. Usually, 'After 'amplification, the discriminator (de-pulse width is varied with pulse repetition rate tector) output is applied to the a-fselector(PRR) remaining constant.By manipulating con- channels:,There' is one selector`., channel fortrols at the command station, varying voltages every .torie that the transmitter may'send..Theare produced. These voltages are converted to varying width gated signals from subcarrier oscillators. The gate widths are directlyproportional to the desired changes in missile

BAND-PASS CONTROliS FILTER

k"4:4P,)-- Y,4A..laW PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS function. The missile will interpret the grad-modulator section, which in turn produces the ually varying characteristics of the subcarriershigh-voltage output pulse. and respond by correcting pitch, heading, and The same trigger pulse is also sent to the throttle Control in proportion to those variations.range unit, and starts itstime-measuring device. After a short, fixed delay, the range unit LAUNCHING STATION COMPONENTS forms a range gate. The gate is developed by a voltage which is present during arelatively MISSILE COURSE COMPUTER. Ordinaryshort part of the main time cycle. This voltage forms of missile course determination requireis applied to the gain control circuit of the re- a large number of calculations, andconsider-ceiver. When the range-gate voltage is present, able time. Since calculations are time con-the receiver gain is high; during the rest of suming, and since speed is an absolute neces-the time cycle, the gain is very low. Thus, when sity, electronic course computers have beenthe range gate is "open," signalspickedup by developed for this use. the antenna will pass through the receiver; The computer, located at or near the launch-when the gate is "closed," they will not ing site,performs two`functions.First, it A definite time is required -for the-trans- determinesthe course that should be followedmitted signal to reach the missile, and for the by the missile during its night to the target. Itreflected signal to return. The total time de= then compares this desired course with thepends, of course, on the range of the missile. actual course of the missile as determined byThe timing circuits can be adjusted to open the thetracking.radar. Anydeviation between therange gate shortly before the reflected signal two is instantly detected, and an error signal isis due to reach the radar antenna,-and to close sent to the command transmitter keying unit.it shortly afterward. Thus the range gate per- The keying unit modulates the transmitter withmits only the echo signals reflected from the the desired tone and spacing sequence. Whenmissile to pass through the receiver' echoes these signals are picked up by missile receiver,from other objects will be rejected. The re- the proper control surfaces are activated tobringflected signals, through servo systems, con- the missile back on course. trol the position Of the radar antenna, so that MISSILE TRACKING RADAR.. When com- it will track the missile automatically. mand guidance is used, the position of the mis- A single antenna is used for both transmit- sile in relation to the control point, desiredting and receiving. This requires some means course, and the target area must be 'mownatfor switching the antenna from the transmitter all times. to the receiver, and then back to the transmit- ..Since radar can provide information as toter again. The device usually used for this range, elevation, and direction,it is Well suitedpurpose is called a duplexer.The duplexer forsliort- and medium-range missile tracking.makes it possible to operate the transmitter In general, missiletracking radars use"theand receiversimultaneously, but keeps the same principles as search,fighter-direbtor,powerful transmitter signals from entering the and fire. control radars. receiver directly. Radar, ranging ..is accomplished by time For missile tracking, a lobing or conical measurement. The range. is found by measur-scanning system is used, because accurate ing time elapsedtime,between the transmissionangle data cannot be obtained from a single of a pulse and the arrival of the echo reflectedbeam on the antenna axis. This type of scan- from the missile. Radar Waves travel at thening is described chapter 8. speed of .light (188,000 miles per second). The Video signals produced by the reflected sig- distance, to the, target ; ie ...fOund ,by, multiplying nal, from the. missile. may be used to modulate the eliPsed tiinebY, the epeegrof,the.radar wavethe display on a cathode-ray tube. The method and then dividing the ,by tvie. The divi of MOdulating the display will depend on the obis by two is necessar'tibecause the elapsedtype` Of indicator used in the radar set. Either time inCludes tithe :out and tithe, back, so thatthe or theintensity,of the beam trace the,:actual, time to the ..tergetis.lone-half themay be;fitodelated. Comfaand systems using radar tracking have e41138e4 time. . ' The time sequence; for the .radar ; set a relsitiveli?' high degree ofaccuracy, and the the ,timing geSerater.,.:The-: triggerweight of the equipment required in the missile ac iming; ,generator controls :t4e comparatively Hoivever, tracking

as.-ttdit-t6 );54. 0410:4: Chapter 7COMMAND GUIDANCE

errors will be introduced by limitations of theelevation angle (or of the horizontal radar system. In general, radar range and range informa-the tangent of the elevation angle).Successive tion is accurate, and elevation and azimuthin-positions of the missile can be markedon the formation is accurate to withina few mils. Theplotting chart at regular intervals, toprovide range and accuracy of the guidance systemcanan indication of the missile's course. In modern be improved by using a different formof ter-systems, plotting of the target and the missile's minal guidance, such as homingguidance. position is usually done in the Combat Informa- tion Center (CIC) of the ship. Missile Plotting System TELEVISION COMMAND GUIDANCE The use of radar for missiletracking makes it possible to obtain information °lithe missile's Television has been used in variousweapon elevation; bearing, and horizontalrange. Thissystems to obtain target information. Assault information may be plotted .so thatpersonnelDrone, a pilotless aircraft, used by theU. S. controlling the missile will havea completeNavy against Japanese and German targets picture of the operation. in 1944, employed television and radio controlin An example of a basic plottingsystem' isa "mother" airplane to effect guidance. Several shown in figure 7-5. The tracking radarisguided bombs using television command guid- shown at the left of the drawing, and theplot-ance were -developed by the United States ting board at the right. The boomon the plottingWorld World War II..The GB-4 was success- board revolves around a center pivot,and isfully used by the U. S.Air Forceagainst U-boat positioned by- the missile bearing data. Thepens, V-1 and V-2 launching sites, and German tracing pen. trolley (mountedon the revolvingindustrial centers. The televisioncamera was boom). is ;positioned by thehorizontal, rangein the bomb; the operator in the "mother"or data. The pivot Of the boomrepresents thelaunch aircraft. monitored the TV pictureand tracichir radar: nd the pen positionguided the bomb to the target, usinga radio represents the instantaneouslocation of thecommand link. The Robin and the Rocwere missile:: similar types developed in the United States. The 'radar can -provide only slantrange Television guidance generally has madeuse bearing, and: elevation angle. The horizontalof the electromagnetic frequencies in the range range data used .'-to position the tracingpenbetween radio and radar applications for trans- trolleY can 'be obtained from theproduct of themission. The sensor units operateon the visual slant; range and the cosine of the elevationband of the spectrum. angle.: The elevation of. themissile is the Television is the information link of thesys- product of the slant range. and the sineof thetem; radio is normally used for the commandlink.

MISSILE

PEN

BOOM

ELEVATION

424%.1. itailtiaW1 WterPtiadr&itZlY 42sbi 42Vt. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

At present, the Navy has under development in the desired direction. If the PRRis unmod- an air-to-surface missile usingthe televisionulated, no control signal is sent to themissile. If the PRR is modulated so thatit increases, system. the missile will turn in a certaindirection; if I the PRR decreases, the missilewill turn in RADAR COMMAND SYSTEM the opposite direction. Since thePRR can be varied by the modulation frequency,it is possible to make the amount of turnproportional GENERAL to the deviation from the normalPRR, and If a command. system is to be usedwiththus obtain accurate control. supersonic missiles, some form ofradar track- This system requires some form of multi-. ing employing an automatic computermust beplexing or switching control, so thatoperations used to obtain a reasonable degree of accuracy.take place in a definite sequence.As an ex- In this system, both the' guided missileand theample, there may be five possibleoperations 7-1), and the and each may be controlled by a1/100-second target are tracked by radar (fig. A complete informationconcerning range, range-rate,signal of the proper pulse rate. azimuth, and elevation is fed to anautomatic set of control signals could then besent every computer. Telemetered information fromthe1/20 second. guided missile may also be sent to the com- The control pulses may be coded in se- puter. The computer determines thecontrolquence so that each pulsecontrols a particular signal which must be sent to the guided missileoperation. As soon as a full set of operations to steer it to a collision with the target. is covered, the sequence starts overagain. There is great similarity between radio andThe pulses may be modulated eitherin ampli- radar command guidance systems. Each isbasedtude or by their position on a time scale. on a transmitter at the controlpoint, and a Several means of controlling missile func- receiver in the missile. In both systemsthetions by the radartracking,beam are illustrated transmitter sends out a carrier wave, which isin figure 7-6. Multiple pulses maybe grouped modulated in accordance with the desired com-as shown in block A, thenumber of pulses in mands. The receiver interprets the modulationeach group determiningthe speCific command. so that the missile can executethe transmittedBlock B shows dual pulses with the spacing between the pulse determining thecommand. commands. In block C, every other pulse isdisplaced in time . time, the direction of displacement in OPERATION OF RADAR pulse COMMAND GUIDANCE determining the command. Block D shows width variation representative Of commands. Most radar command guidance systems de- The use of the missile tracking radar beam pend on "sampling" control; since it isnotas a control medium results in economyof equip- possible to control all Of the missile functionsment because the radio control transmitteris at once. Each must take itslurn in thecontrolno longer needed. sequence. Consequently, after a given function As in any other communications equipment, has received- a command, there will be atimethe bandwidth of the modulatedSignal determines delay before the next command is received.the amount of information that can betransmitted The length of this delay will -depend onthein a given time. A radar signalwith a pulse number of functions to be controlled. repetition rateOf.2000 cycles per second would When radar is used for control; the fidelitylimit the number of functions that couldbe con- control or accuracy of control' is Jimitedby the allow- . trolled as well as the rate at which the able -imitationsin pulse rate . or amplitude.signals' could be changed. But for some missile (Excessive variations will affeet the trackingsyStems this bandWidth is adeqUatebecauseonly accuracy.) The accuracy of control is alsoa few missile functions areunder control by limited by the-. ability, of the '-misaile equip-command guidance. And, if the rate ofsignal ment to ; measure: these *ariations. accurgely:ChaiigeAZ not too great, there will be enough There are"'several whiCh`,Coinmande alio*, modulation of the radar beam can be sent by ,radar.-For example,. 'the, pulBewith several signals simultaneously. repetition ,rate (PRIt)t of the radar 'MaY.tie ire- there are 'iniisiles in thevicinity of the quency modulated-4n :o to: -the. Missilebeam` other than the one being tracked, some

3;-.7P.ItA .4Mir Chapter 7COMMAND GUIDANCE

TURN LIFT TURN RIGHT TURN LEFT TURN RIGHT TrogIeR TURN LEFT PULSES

VARYING TURN LEFT TURN RIGHT TURN LEFT TIME TURN RIGHT TURN LEFT g INTERVAL*LW, BETWEEN DUAL PULSES

TURN RIGHT DISPLACING TURN LEFT C tgrtiIJV f \ TIME

VARYING TURN LEFT TURN RIGHT TURN LEFT TURN RIGHT TURN LEFT 1WIDTHOP AM TRANSMITTED 'WAN PULSE

TIN!

33.143 Figure 7- 6. Methods of transmittingcommands by radar pulses.

coding or frequency discriminationmethod must be used so that each missile will to accept command signals. Whenused for this respond onlypurpose, an additional set of coded pulsesis to its own command signals.This is true inadded to the transmitted signal for either the continuouswave or pulse system. the missile Therefore, if there is tracking radar. The beacon accepts thesesignals any likelihood that theand, channels them into a computerwhich decodes spacing between radar beams is notsufficient,them for the intelligence they contain. each missile launched froma particular control station must have either special coding equip- . There is no generalized radar beaconsystem; ment or at least a special receiveradjustmenteach system is designed fora particular ap- to ensure response to the correctsignal. plication.

RADAR BEACON FUTURE OF COMMAND GUIDANCE SYSTEMS To extend the trackingranges, some missiles have radar beacons installed. This beacon is It should be kept in mind-that command actually a small radar set which'is actuated by the remote missile tracking radar. guidance systems are ina state of constant When trig-development, and that future systemsmay differ gered by a coded pulse from thetracking radar, thS beacon returns a considerably from those describedhere. Sys- stronger signal to thetems that were tried in early missiledevelop- tracking receiver than would'. bereceived onlyments and were discarded by reflection. < Figure 7-7 shows a block may be improved and diagramplaced in new missiles. An examplelathe. Wall- of Stich -a-System., The coinbined action,:of the beacon receiver and transmitter raises; a guided air-to-surface bomb_ being de- theveloped. Television contrast homingguidance signal 1S+al. RadirrbeaCon ranges aregenerallyis beiSg used for it. Another example limited 001k; by. the is wire radar; guidance, which was considered inadequateand transmitter eie0t,.. freoiei' was ;,discontinued in the air-torair 'missilesa rece nuniher.;:Oi yearsago. It is being usedin some Oeeent. day sUrfacs;:toaurface..short-range er:frequency missiles, Ud }bout contusing it theFrench S&10:and1313-11 . hankrmissiles,and our on Army antitank e e:4)eiceii*edeityiko** Ennkes. and

41.0 OPhili. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

1r r Ii 1 1 RANGE MODULATOR TRANSMITTER TRANSMITTER HMODULATOR I UNIT 4 I

1 1 J II

II V II 1 1 I 1 RECEIVER INDICATORH RECEIVER}V".DUPLEXER I 1

I 1 RADAR J L BEACON -I

Figure 7-7.Radar beacon system in missile guidance. CHAPTER 8

BEAM-RIDER GUIDANCE

INTRODUCTION however, makes each missilelarge and expensive. The radar problem issimple since GENERAL .A only one radar set is required (tworadars may be used), but the controlling beammust be reasonably narrow to be directive,and this in- The beam-rider guidancemethod may be considered to be a form of command creases the chance of loss of the missile guidance,through target maneuvering andevasion. since the beam-rider missilemaintains direct electromagnetic radiation contact wItha friendly control point. APPLICATION TO U. S. NAVY MISSILES Beam-rider guidance is similarto radar The U. S.. Navy missileprogram is tone of command guidance. In both systems,target in-continuous research and improvementin all formation is collected and analyzedby devicesphases. Two missiles, .Terrierand Talos at the launching site or othercontrol point rather than by devices within developed under the Bumblebee (1944)program, the missile. Inhas been operational forsome time.Both of both systems, the missilemakes use of guid-these are surface-to-air missiles using beam- ance signals transmitted from the controlpoint.rider guidance. The BW-1 Terrier isa beam - The principal difference betweenradar com-riding, wing-controlled missile; the BTTerriers mand guidance and beam-riderguidance wasare beam-riding, .tail-controlled missiles; and stated in chapter 6. The guidanceequipment inthe. Terrier HT type uses homing guidance. the missile formulates itsown steering signalsThe Taloa is a beam rider in the from the information containedin the radar midcourse stage of its flight,'.switching to homing for beam. These correction signalsproduce controlthe terminal.phase of its flight. surface movement on the missileto keep it as This chapter will give information nearly as possible in the center ofthe radar of a gen- beam which pinpoints the target. eral nature on beim rider guidancesystems that The missilemight* used with tMs type missiles.R should be can .thus be said to "ride" the beainto the targiit., (See figs. 6-8 and 6-94 kept in mind that security 'requirementsprevent a detailed description of theguidance system of 'The beam-rider system ishighly effectiveany sPecific missile. for use with `short7ringe and.'mediunt-range sUrface-to-air and air -to -air missiles.For missiles of longer ranges' 'a 'beani-riding .sys.; SYSTEM COMPONENTS to* may be used during, the Mideouise',phase of flight, while the missileAs :still ef- GENERAL fectiv.e.rinie iieam7triSiniltting radar. Ae it aPPrOaChee tbe. beam4riding There are. several range;- the **Ole may switch overto some' iniportant components, otherlornf of gUtdifiCe:' other than the missile and radar,in a complete The beam -rider missile guided missile System. 'system ling 'both `' A major ;partof the 0011011e4 is at the ad*thteges and :dielicii*ntigeei..:1: Tlaunching launching of a large: number site.The number and type Ot.Z..0- #84N1,..013nents,',will ya171/-*th systeMs, a *e:iiiiiiie;eciiitii)f,beanf",iiiiieff;all cemobiej setup wall differ from'a fixed, per- tsprnt- is;.,inninent undli 'Bite.-.2 PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

Figure 6-6. is a simple diagram of a beam- speed of the target. The computer is also given riding missile guidance system which includesthe average speed of the missile. With thisin- the basic elements when a radar beam isused formation, it is able to determine thedirection as the guiding beam. The exampleshown is ain which the missile must be launchedto inter- surface-to-air application. The radar is used tocept the target. It is unlikely that a missilewill develop the beam along which the missile is tobe fired as soon as the tracking radaracquires travel. Its antenna is directed so that the centerthe target. The targetrange is constantly of the beam is on the target. Themissilechanging, and the target may change course or launcher, if trainable, in used to point the mis-speed as well.The computer must therefore sile so it is able to enter thebeam afterlaunch- produce a continuous solution to a continuously ing. The beam-riding missile contair-4 the mech- changing problem. At any given instant, the com- anisms that permit it to measu-its positionputer output provides the correct solution tothe with respect to the center of th, radar beamand problem as it exists at that instant. to move to correct its position. In a two-radar system, the computer con- Two types of beam-rider systems are inuse.tinues to calculate the missile course afterthe In the simplest type, a single radar is usedfor missile has been launched, and until thetarget both target tracking and missile guidance. In the has been destroyed. Through servo mechanisms, second type one radar is used for target track- it turns the control radar in the properdirec- ing, while another radar generates theguidance tion. The computer output is used totrain and beam. The monopulse system, which is not atype elevate the missile launchers in such adirection of guidance system, but a radar techniqueusedthat the missile will enter the capturebeam in tracking, is described later in this chapter.(described later) at the optimum angle. 1 :ilia angle is too large, the missile mustmake a LAUNCHING STATION COMPONENTS sharp turn to get into the control beam.If it is too small, there is aome dangerthattheptissile The launching station may be on or in thewill evade the capture beam and selfdestruct. ground, *card a ship, or in an aircraft.The components used in aircraft are necessarily MISSILE COMPONENTS limited in size, weight, and amount of power required to operate them. These components The receiving antenna in the missile is a are the radar (orradars), computer, informa- very important part of its electronicinstalla- tion display scopes (oicilloscopes) and,oftion. Through it must come all guidancesig- course, the missiles whichare tobe used. Figurenals from the control radar. There areseveral 8-1 pictures the components thatmay be found diffiCulties in determining the optimum location aboard a ship. The radars and launchers are,of an antenna on a missile. First, theantenna above deck, but the CoMputers, display consoles, Mlle not interfere with the aerodynamic stability and direction equipment are below decks., Of the misSile. Second, it must be locatedat a All changes detected by theradars :or Madepoint Where it will not be' damaged by the rapid by the missile, or the target areinstantly acceleration as the missile is launched, and flashed on the consoles below decks's° thecourse where wind will not tear it loose. Finally, the can be f011OwedindcoMbat decisions made onthe antenna must be located Where itcan effectively basis of the information iniPplied. pick up the signals of the guidance beam. The The.target is usually picked up at long rangeantenna iodation that has been found most sat, by a search radar. Whenthe ;target is identified, iafactory is at'or'near the Miaitile after surfaces. the tracking radii Witte over thejob of following The mitisile antenna is highly ,directional, it, and determineS direCtion (elevation andand Most isensitiie to Signals 'received; from bearing) range rate (radial velocity),and tinge.behind .the;:titisiiile. The roll.control Systent This inforristiOn .is converted rapidly intouaable of the keeps ; it stribilizeil. that the PPP, e co ante:1*i', PolarilatiOn'reMitinst CbtiStiritt.1 Another Because the Computer:Jo', e- course, iseof `the roll- control system 'is to speed, ,bearing,R eleVatiOn, ' establish ;an.,up-down ,:right,;left guidance : cit range of thezfarget,rit Can ' ' : 411MtilS PiCieed up by the .Inter 'ttie et µ at any future time The guidance 10010fikft0°60 change.course orsspeed.iiilic.inteitiii"ere fed to a. receiver. After the Iti SOnie corn are ampli fed and demodulated Ar,,,the 1-

..t .. we. . ar..r. . -

Chapter 8BEAM-RIDER GUIDANCE

I. DETECTION, LOCATION, AND IDENTIFICATIONUNITS .

,1 ...CM'

SEARCH OPTICAL TARGET IDENTIFICATION RADARS DESIGNATION FRIEND OR FOE TRANSMITTER

2.CONTROL UNITS (WEAPON CONTROL SYSTEM) FIRE CONTROL SYSTEM rWEAPON DIRECTION SYSTEM WAPON CONTROL I STATEON AND COMBAT .I GUIDED INFORMATION CENTER I MISSILE FC RADAR

RADAR CONSOLE WEAPON DIRECTION EQUIPMENT COMPUTER

4.1.= emlm .11 moms,

4.DESTRUCTION UNITS

12.41 tnponenti at the lannching station(shipboard representation). PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS receiver they are fed to a computingnetworkcompared to its surroundings andtherefore is a good radar target. An importantpoint is in themissile. Demodulation is the process of greater than extracting information (direction,etc.)about thethat the missile velocity must be target from the beam's carriersignal. If thethe target velocity. missile is off the scan axis ofthe guidance beam, the computer will, determineboth the PRINCIPLES OF BEAM-RIDER GUIDANCE direction and the magnitude of the error.It will then give the correction signalsrequired Since the beam used in beam-rider guidance to bring the missile back onto the scanaxis. is a radar beam, a knowledge ofthe basic Figure 8-2 is a block diagram of the es-principles of radar is necessary tounderstand sential' components of a beam-riderguidedhow the system operates. The firstvolume in missile. The computer includes allthe neces-this series, Principles of NavalOrdnance and sary circuitry to separatethe up/down andGunne NavPers 10783-A, contains a chapter left/right correction signals contained in the one detecting and assigningof air targets for output of the receiver. The separatesignalsguns. The radar principlesapply equally to are then amplified and drivethe servomotorsguidance systems for missiles. which actuate aerodynamic surfaces orother means of control to changethe position of the GUIDANCE ANTENNAS missile and cause it to move towardthe center of the beam. The antenna system consists of waveguides, The missile also needs to be roll-stabilized.switching tubes, a reflector forbeaming the This is done by placing a gyroscope insidetheradiated energy, a mechanism fornotating the missile with its axis oriented so that anoutputfeed ,during operation, and servounits which position the antenna reflector. Its purposeis to is produced 'if the missile tendsto- roll. The by the output is amplified to operate controlsurfacesradiate microwave energy developed of the missile totransmitter and to receive echo signalsfrom that neutralize the tendency receiver. roll. the target and apply them to the TARGET General must have The radar energy that forms theguidance The target for any guided missile at the con- some, unique characteristic aseeenby the track-beam is transmitted by an antenna often is the re-trol point. Radiated energy tendsto spread out ing radar. This characteristic mounting a flective property of the target comparedto itsequally in all directions, but by surroundings. For es:Ample, an airplane-flyingsuitable reflector behind the antennas,ale ge in free space has high radarreflectivity' aspart of the radiated energy can beformed into

CONTROL-....< SURFACE YAW

SERVO MOTOR Chapter 8BEAM-RIDER GUIDANCE

a relatively narrow beam. A narrow beamcanthe wavelength of light ranges from aboutthree point out the target direction withsufficientto seven ten-thousandths of a millimeter. accuracy for the missile to score a hit, and You are, of course, familiar with theuse of concentration of the radiatedenergy into apolished reflectors to form beamsof light. beam extends the effectiverange of the system.An automobile headlight isan example of this, Figure 8-3 compares the radiation fromaalthough it produces a fairly widebeam. A radio antenna with that froma lamp. Both light waves and radio spotlight produces a morenarrow beam. waves areelectro- Figure 8-4A represents the reflectionof magnetic radiation; the two are believedto belight by an "ideal" reflector. Theemerging identical,except in frequency of vibration.rays are parallel; the beam is no wider than From both sources, energy spreadsout in thethe reflector itself, and it does notdiverge. form of spherical waves.Unless they meetBut an Ideal reflector is hard toachieve in some obstruction, these waves will travel out-practice. It must be a paraboloid of revolution ward indefinitely at the speed of light.Becausethat is, the surface generated bya parabola of its much higher frequency, light hasa muchrotated on its axis. It must be highlypolished; shorter wavelength than radiowaves. This is suggested In figure 8-3, but it cannot beshoNim accurately to scale. The wavelengthof radar transmission may be measured in centimeters; LIGHT RAYS REFLECTOR

LAMP maw

LIGHT

. LIGHT WAVES

LIGHT RADAR RAYS REFLECTOR

ANTENNA

VA I

ioini ,14 it,41k 4 yet at 4, r,,:slArAlt1461;iirwav-nrcP.. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS its surface irregularities, must be small compared with the wavelengthjof light. And thelight source must be a single point,located at the focus of the paraboloid. AXIS SOURCE OF Figure 8-4B represents the reflection of LOSE .radar waves. Again, the surface of thereflector isparaboloid, but it need notbe highly polished, be%;.use of the longet wavelength of radar.The source of radiation is the endof a waveguide. Unfortunately, this is not a point source; it must 33.146 have a finite area. Figure 8-5.Lobe formation of radar beam. It should be noted that a light RAY is simply a convention used in diagrams.Such rays do not exist in nature. They are imaginarylinesfor our purpose (missile guidance ortarget that indicate the direction in which the wave-tracking). The lobe in figure 6-5 is not drawn fronts are moving. Although RADARRAYS areto scale. The diameter of the reflectoris in not a familiar convention, they areused inthe order of two feet; the length of thelobe may be from 20 to 50 miles. Its usefulwidth may be figure 8-4B to show the direction in which the .3 radar waves are moving. four or five degrees. At any givendistance Of course the lamp shown in figure 8-4A isfrom the transmitter, the signal isstrongest 4 directions. The lightalong the axis of the lobe. radiating lightin all radar from thefront,surface, which does not strike In a beam-rider guidance system, the reflector, will be scattered widely. In somemust accomplish two things; it must trackthe spotlights, the front .surface of the lamp istarget, and it must guide the missile. Itwould shielded, so that the only rays that leavethebe difficult to do either of thesethings with a spotlight, are Those that have beenreflected.simple lobe like the one in figure 8-5. Such a spotlight prodUces a sharply defined beam, with little or no scattered light.TheNutation same effect is achieved inradar by directing toward the opening of the waveguide backward, Nutation is difficult to describe in words, the reflector. but easy to demonstrate. Hold a pencilin two . But no radar can produce an ideal beam of parallel "rays." For one thing, the end ofthehands; while holding the eraser end asstill as viaveguide is larg te compared to the ideal pointpossible, swing the point through a circle. This source. For another, a reflector of practicalmotion of the pencil is nutation.(The pencil size is .not sUfficiently large compared withthepoint corresponds to the open, ortransmitting, wavelength of the radiated. energy. A radar beamend. of the waveguide. antenna.) Theimportant therefore diverges and forint a lobelike the onething is that polarization of the beam isnot in figure 8-5. This is :the main 'lobe-orbeam.changed during the scanning cycle. This means understand that suchthat the axis of the moving feed must notchange The student should clearly feed a lobe. is merely a.convenient way of represent-horizontal or vertical orientation while the ing. ,the beain on paper;it: isin no senseis moving. You might compare themovement to a "picture "; of, the beim.Some Of,the radiatedthat Of a fertis wheel; the position of theseats energy will be. scattered outside the main lObe,must remain the same regardless of theposition and, will form,.. sidelobea of lesserof the wheel. intensity, and' .much shprter range. They are NUTATING WAVEGUIDE.A waveguide is a Undesirable lcibefi proximityMetal pipe usually rectangular: in cross section, to the trariethitter andniiiionfnee the fire which. is' used to conduct the r-f energy from Andy the'7'rediatiOri- dOeS not endthe transmitter' to the antenna. The open end of controlman.' the waveguide faces the concave side ofthe cP:;'frOm.the.trans emitsiebOunced '10tek, .Wthe; reflector, and the r-f energy it PiCinked-li:three;41neiSionsi Can:be: .fitaii:the reflector ..surfaCe.. nutation 'ifIlOjgbCof of *hi A conical ' scan can be generated by tielottErAnteq**mo*icig*erigir.:,:171149;cari be..of the,:*vegu, ide this Process the axis of the considered the rmini um energy e:Wtigie '7,regaidsits 'MOO.th;Ougha "innell Chapter 8BEAM-RIDER GUIDANCE

conical pattern. This three-dimensionalmove-determine the direction and amount of ment in an actual installation of the antenna vraveguide, movement required to continue tracking.The is fast and of small amplitude. Toan observer,computer output can be used to controlservo- the waveguide appears merely tobe vibratingmechanisms that move the antenna, slightly. so that the target will be tracked accurately andauto- NUTATING LOBE.By movementof eithermatically. the waveguide or the antenna it ispossible to When a conically scanned radarbeam isused generate a conical scan pattern,as shown infor missile guidance, the desired pathof the figure 8-6. The axis of the radar lobe ismademissile is not along the axis of the beam, but to sweep out a cone inspace; the apex of thisalong the axis of scan. It is possible toproduce cone is, of course, at the radar transmittera conical scan by any of several methods. antenna or reflector. At any given distancefrom the antenna, the path of the lobe axis isa circle. Within the useful range of the beam,the innerTypes of Antennas .. edge of the lobe at' all times overlapsthe axis of scan. DIPOLE.Although not used byany of the Now assume that we usea conically scannednewest modifications of our missiles,several beam for target tracking. If the target ison thetypes of missiles have used a rotating dipole scan axis, the strength of the reflected signalsantenna. The antenna was not rotated about its will remain constant (or change graduallyas thecenter, for this would have changed the polar- range changes). But if the target is slightly offization as the antenna turned. Sucha condition the axis, the amplitude of the reflectedsignalswould have caused erratic control of themis- will change rapidly and periodically.Forsile. The antenna is mounted ina plane that example if the target is ABOVE thescan axis,passes through the focal point at a right angle the reflected signals will be of maximumstrengthto the reflector axis. As the antenna rotatesit as the 7obe sweeps through the highest part ofstays in this plane. The same relative motion its cone; they will quickly decrease toa minimumcan be produced by having a stationary antenna as the lobe sweeps through the lowest part. In-and rotating the reflector abouta point off its formation on the instantaneous positionof theaxis. beam relative to the scan axis, and'on the LENS ANTENNAS.Lens antennas oftwo strength of the reflected signals,can be fed totypee have been developed toprovide easy a computer. This eomputer in the radarmay beEteerability in both azimuth and. elevation for called angle tracking or angle servocircuit,ortracking radars, while avoiding the problems angle error detector.If the target moves offassociated with feed horn shadow in reflector the scan axis, the computer willinstantlyantennas. (The shadow isa dead spot directly in front of the feedhorn.) Theseare conducting type and dielectric 'or delay type. Theyare also called microwave lenses. The lens is'substantially transparent to microwavesbut in- PATH OF LOSE AXIS serts a phase change over thecross section of "-NMI OF SCAM the eidt Side of the lens to make the microwaves converge' or diverge. The lens is plaCedin front of a point, source of r-f energy, suchas a feed= horn. While a feedhorn is not,a "point" source, for analysis of electomagneticwave propagation it is 'often considered as a pointsource of energy. The ;conducting type, which isa wave guide, is illristrated. in figure 8-7A. This tYpe;:acceleratee wave transmissionas it .passes thiOugh the lens. Itconsists of flat :421941 strips placed, parallel to the electticfield of the Wive, and. in excess of one- half. Of a wavelength. To the leave these stripe look likeVraVeguides. with each hiPothetical waveguid6 7. ,a dimension 'in a direction . PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

wave passing through the lensis determined by the dielectric constant or refractiveindex of Ititt the material. In most cases, artificialdielec- trics consisting of conductincrqds orspheres that are small compared to the wavelength are used. Artificial dielectrics, or conductingin- -A sulators used in r-f transmission systems are coveredin Basic Electronics, NavPers 10087-A. A In this case the inner portion of the transmitted wave is decelerated for alonger interval of time than the outer portions. FEEDHORN In a lens antenna the exit side of thelens can be regarded as anaperture across which (1((((((((« there is a field distribution. This fieldacts as a source of radiation Just asfields across the It mouth of a reflector or horn. For a returning echo the reverse effects take place in thelens. B It can be seen that the reflector usesthe 55.62:.63law of reflection while the lens usesthe law Figure 8-7.Antenna lenses: A. Waveguideof refraction. The rear feed arrangementof the (acceleration) type microwave lens; B. Metallens antenna eliminates spilloverradiation in the backward direction. Also, thisarrangement strip (delay) type microwave lens. puts the radiator out of the path of thebeam, thus reducing shadows. perpendicular to the electric field correspond- MISSILE RECEIVER. -The purpose of the re- ing to the spacing between the parallelstrips.ceiving antenna, located in the missile, was de- The velocity of phase propagation of a waveisscribed briefly at the beginning of thischapter. greater in a waveguide than in air. This, sinceFigure 8-8 shows the location of receiver the lens is concave, the outer portions oftheantennas in a beam-rider missile, nearthe con- transmitted spherical wave are accelerated fortrol surfaces. In some missilesthe antennas are a longer interval of timethan the inner portion:part of the electronics section. Thefunction of sidethe missile receiver is to receive thesignals The spherical waves will emerge atthe exit and rectify of the lens (lens aperture)as flat-frontedparallelfrom the radar transmitter, amplify is frequencythe signals and feed them to the missile com- waves. The waveguide type lens tune sensitive. puter. In order to keep the receiver in The other type lens is the dielectric, orwith the guidance transmitter, a systemof auto- metallic delay lens, shown in figure 8-7B. Thematic frequency control isusedin the receiver. delay lens, as its name implies, slows downtheThis is to reduce acceptance of stray signals or phase propagation as the wave passes throughthecountermeasure signals. The automatic fre- lens. This lens is convex, and co sista ofdi-quency control keeps the receiverintermediate electric material. The delay in theth phase ofthe frequency from drifting.

BOOSTER FINS FIXED (4) NOSE SECTION CONTAINS ELECTRONIC SECTION RECEIVER ANTENNA BOOSTER

TAIL CONTROL SURFACES DORSAL FINS FIXED (4) SUSTAINEF4 MOVABLE (4) 83.29 Figure8-8.View of beam-rider missile, showing locationof control surfaces and receiver antennas. Chapter 8.-BEAM-RIDER GUIDANCE

SCANNING slow and inaccurate, and would belimited by In addition to radiating and conditions of visibility. An automatictracking focusing energysystem requires that the beamSCAN, or into a narrow circular beam,the antenna sys-search, the target area. tem must provide ameans for searching for a target and for determining its Again, assume that a missile isriding the position.Thisaxis of a simple beam. Thestrength of the process is called scanning or lobing.Lobing can be divided into two broad categoriessignals it receives (by means ofa radar receiver in the missile) will graduallydecrease (1) sequential lobing and (2)simultaneous lob-as its distance from the transmitter increases. ing.Examples of sequential lobing are conicalIf the signal strength decreasessuddenly, the scanning and lobe switching.. Simultaneouslob- ing is best illustrated by missile will know that it isno longer on the a fairly recent lobingaxis of the lobe.But it will NOT know which technique called monopulse.We shall discuss this method in considerable detail way to turn to get back on the axis. A simple later.Butbeam does not contain enough informationfor first a brief review ofmore familiar scanningmissile guidance. processes is in order so thatyou can see how and why monopulsingwas developed. Double-Lobe System Stationary Lobe and/or Single Lobe System The double-lobe system multipliesby several times the accuracy obtainablewith a single-lobe A single lobe system is thesimplest form of sequential lobing. A stationary system. The double-lobe system employstwo lobe cannotoverlapping beams. For ease ofillustration, satisfactorily track a moving airtarget, letassume that two antennas are used side by alone simultaneously provide guidance side. informa-Two signals are obtained when thebeams cross tion to the missile. a target, one from each beam. On the radar- Assume that a target is somewhereon the lobe axis, and that the scope they appear either side by sideor back to receiver is detectingback. The two signalsare the same amplitude signals reflected from the target.If theseonly when the target ison the line of intersec- reflected signals decrease instrength, it willtion of the two beams,as in figure 8-9. The be apparent that thetarget has flown off the axis, operator rotates the antennas untilthe signals and that the beam must be movedtoare matched in amplitude.At this point, he continue tracking.The beam might be movedknows that the target lies on the LINE OF by an operator who is trackingthe target with IN- an optical sight; but such tracking would TERSECTION of the two beams. Thetarget is belocated on the basis of returnsfrom the side of

LINE OF EARIN AXISOF LOSE 2

alt

33.114 Figure 8-9.Double-lobesystem, showing relation between axis of intersection and target bearing. PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

in position re- Figure 8-10 represents amissile below the each lobe, where a small change scan axis of theguidance beam. The path of suits in a large change insignal amplitude.the lobe axis is a circle.The amplitude of Therefore, if the antennas aremoved in either maximum along the direction away from this angle, oneof the sig-the radar signal is at a amplitude and the otheraxis of the lobe. As thelobe axis sweeps near nals increases greatly in the missile, the signal willbe strong; as it decreases. You can see that agreater degree the missile, the signal will of accuracy can be obtained inthis way. sweeps away from double-lobedecrease. To the missile, it;rill appear that Besides greater accuracy, the the signal strength isregularly changing in system has another advantage overthe, single- that of the lobe system. By watching to seewhich of theamplitude at the same frequency as two signals increases inamplitude as the an-scan cycle. provided with a tenna is rotated a few degrees,the operator can The missile receiver is must be moved todetector which eliminatesther-fcarrier tell the direction the antenna frequency and produces an a-msine wave sig- reach the on-target position. nal of the scan frequency.When this a-m Missile Response signal is present, the missileknows that it is When the a-m A beam-riding missile mustguide itself toOFF the scan axis of the beam. axis of itssignal is ibsent, the missileknows that it is the target by following the scan ON the axis.To see this clearly, look at guidance beam. How does themissile deter- missile on the mine whether or not it is onthe scan axis?figure 8-10 and imagine the available to thescan axis.It is now at the same distancefrom The only guidance information the lobe axis throughoutthe scan cycle, and missile is that contained inthe beam. From signal it receives this information, the missileguidance systemthe amplitude of the r-f remains constant. must determine throb' things:(1) whether or signal, not the missile is on the beamaxis; (2) if not, From the AMPLITUDE of the a-m and (3) which waythe missile can determinehow far it is from how far it is off the axis, the scan axis.When the missile is on the to go to get back on the axis.The first and signal is zero, third requirements are fairlyobvious.Theaxis, the amplitude of the a-m AMOUNT of errorindicating zero error.If it is only a short necessity for measuring the distance from the scan axis,its distaine from is less apparent. slightly during the During the early stages ofguided missilethe lobe axis changes only development, one of the moreserious problems was "overshooting."When a missile moved off course, and received asignal intended to correct the error, itwould turn back overshoot and go too PATH OF toward the course, but LOBE AXIS far in the opposite direction.This effect was SCAN caused by the lag in the. responseof the con- AXIS trol system to guidancesignals,and in the response of the missileitself to movement of its control surfaces.For practical purposes, by the use of this problem has been solved MISSILE error signals proportionalin magnitude to the errors they are intendedto correct. Thus, if a missile is farfrom the beam axis it will generate a large error signal,and its control through a relatively surfaces will be turned -t large angle.But, as the missile movesback toward the beam axis, its errorsignal steadily decreases, and the angle ofits control 'Bur-. faces is decreased accordingly.At the instant: the missile reaches the beamaxis, its control surfaces will (in theory atleast) have reached -4 overshooting Will 33.152 their neutral position, and Figure 8-10.Missile below the scanaxis. be prevented. 1911 OA FPI Chapter 8BEAM-RIDER GUIDANCE

scan cycle. The a-m signal willthus be small, indicating a small error. example, if the missile infigure 8-11 can de- Now, looking attermine that it is the LOWERlobe that has the figure 8-10, imagine themissile at some pointstronger signal, it will know on the circular path of thelobe axis. The that it must move variation in its distance up to get back on the scan axis. from the lobe axis There are two fairly simpleways in which dining the scan cycle isnow at a maximum.we can identify the two lobes The a-m signal willalso be at a maximum, so that the mis- producingthe maximum sile can distinguish betweenthem. (We cannot, error signal andof course, make themof different amplitude, maximum movement of thecontrol surfaces.since a missile (It is apparent thatif the missile moves to on the scan axis would then detect a false error signal.)Bcam-rider a point OUTSIDE the circularpath of the lobe radar transmission consists axis, the error signal willdecrease. But this of an extremely does not happen in practice, high-frequency carrierwave, which is trans- unless the missilemitted in short bursts,or pulses, separated is defective.The guidance and controlsys-by periods of no transmission. tems are too sensitive toallow so large an The pulse error to develop.) repetition rate is ordinarilyin the order of from one to a few thousandper second. We Using Two-Lobe Scanning can identify the two lobes shown infigure 8-11 System by making them differeither in carrier frequency or in pulse repetitionfrequency. How the missile determinesthe DIRECTION either case the missile could In of its error can best beexplained in two steps. easily be provided with a means fordistinguishing between Figure 8-11 showsan imaginary scanning sys-them, and could then determine tem in which the lobe of radarenergy, insteadof its error. the direction of sweeping out acone, has only two positions up or down. Thus the imaginary two-lobescanning sys- The two lobes are transmittedtem could be used for guiding alternately. The figure shows themissilea vertical plane. a beam rider in below the scan axis,near the axis of the lower If we add two additional lobe. lobes, each of which the missilecan distinguish The missile will receivesignals fromfrom the other two, it would both lobes, but those fromthe lower lobe will also be possible be of greater amplitude. If to guide the missile to rightor left. It should we can provide thenow be apparent that wecan guide the missile missile with somemeans for distinguishingin any direction by using between the two lobes,so that it can tell a conical scan. WHICH ONE has thestronger signal, it canConical Scanning determine the direction of itserror. For Look back at figure 8-10.Assume that we vary the signal frequency (eitherthe carrier. or the pulse rate) sinusoidallyat the Scan UPPER LOBE frequency.Assume .that when the lobeis r.c y AXIS its highest point, thesignal frequency is ata SCAN maximum.As it moves around to theright AXIS side of its circular path, LOWER LOBE the signal frequency ./". AXIS decreases to its average value.At the lowest >r position of the lobe, the signalfrequency is a minimum.It increases toaverage value as the lobe approaches theleft side of its path, and to a maximumas it returns to its highest position.Thus the signal of theguidance beam is frequency modulated atthe scan frequency. MISSILE Note that the f-m signalis always present at the missile, regardless ofwhethk-r it is on or off the scan axis. The missile receiver isprovided with an f-m section, the output ofwhich is a sine wave 33.10'3 Figure 8-11.Two-lobe that indicates the instantaneousposition of the scanning system. lobe in its scan cycle.The sine wave will PRINCIPLES OF GUIDED MISSILESAND NUCLEAR WEAPONS

when the sig-moved by the operator, and at the sametime he have a maximum positive value must compare the signals. Withfixed or slow- nal frequency is maximum; itwill pass through practice, perform passesthrough its averagemoving targets he can, with ,ero as the signal these functions efficiently;however, when a frequency; it will reach its maximumnegative almost im- signalfrequency is at atarget flies at a high speed, itis valuewhen the possible for a human being todo all the func- minimum: tions required for precisetarget tracking and The missile can determine thedirection of Some World War II fire ita error by comparing thephase of the f-mdirection finding. signal with that of the a-msignal.Refer tocontrol radars overcame thisproblem by using is directlyone antenna and amotor drive device to switch figure 8-10 again; here the missile lobes without moving the antenna.When this below the scan axis. The signalwill be strong- used, lob est, and the a-m signal will reachits maximumtechnique, called lobe switching, is through itstag takes place at a rapidrate; thus more positive value, as the lobe passes be made in a lowest point. At that time the signalfrequencysignal amplitude comparisons can given time. will be minimum, and thef-m signal will be works to at its maximum negative value.Thus the two Briefly, this is how the system If the missileprovide target direction in thehorizontal plane. signals are 180° out of phase. The antenna produces two beams, oneat a time, were above the scanaxis, the a-m signal would other. The be strongest at the instant whenthe f-m signalswitching rapidly from one to the feed is alternately changed inphase to create reached its highest frequency.Both signals This phase shifting is would be at their maximum positivevalue, andthe double-lobe effect. therefore exactly in phase. Thereis a definitedone mechanically or electricallyby switching off-axis positionfeed lines, which eliminates theneed for two phase relationship for every antennas and two receivers.The directions of of the missile. If the missileis directly to the angle equal to right of the axis, the f-m signalleads the a-mthe two lobes differ by a small about one beam width.Signals are returned signal by 90 °; if it is directly tothe left, the strikes the target. f-m signal lags 90° behind the a-m. to the radar as each beam job for When the two echoes arecompared, the strength Phase comparison is a fairly' easy other depends upon an electronic computer.The computer hasof one with respect to the the phase relation-the position of the targetin relation to the been designed to measure antenna direction, as shownin figure 8-12. ship to determine thedirection in which the to the scan axis The returning signals are equalin strength missile must move to return only when the reflecting objectlies on the line and to sendthenecessaryordersto the control system. The control system inturn, moves the control surfaces to change the missile course in the required direction. To summarize: The guidance beam is 40- TARGET 1 conically scanned, and frequency-modulatedat the scan rate.If the missile detects an a-m IR LI R signal, it will know that it is offthe scan axis; Is' if it detects no a-m signal, itwill know that it is on the axis. The amplitude ofthe a-m signal indicates the size of the error. Alarge error will produce a large movement ofthe missile control surfaces. As the missileapproaches the beam axis the error decreases,and the gradually re- position of the control surfaces ANTENNA DIRECTED ANTENNA DIRECTED ANTENNA DIRECTED TO RIGHT OF TARGET turns to neutral to prevent overshooting.The TO LEFT OF TARGET AT TARGET phase relation between the a-m andf-m signals indicates the direction of the error. RELATIVE SIGNALS FROM TWO SEAMS LI IR Lobe Switching or SequentialLobing LI IR LI I/1 55.84 In either single- or double-lobescanning, described above, the antenna or antennas are Figure 8-12.Lobe switching. Chapter 8BEAM-RIDER GUIDANCE

bisecting the angle of intersectionof the two lobes. If the target is situatedon either side of this line, the echoes differ inamplitude in such a way as to indicate whether it is to theleft or to the right of the antennadirection. The two signals are compared visually,and the radar operator moves his train handwheelsto adjust the antenna direction forequal amplitudes of the received signals. Totrack an air target, a second pair of beams is used todetermine target elevation.These beams are lobed ina vertical plane. When lobe switching is usedhowever, the process itself introduces mechanical andelectrical problems which reducethe reliability and tracking accuracy of theradar.The limitations just mentioned spurredthe development of newer techniques to 55.68 be used with Figure 8-13.Monopulee techniqueof automatic tracking circuits.Conical scanning radar scanning. was the result of this developmentprogram. It provides the three-dimenSionalsequential lobing necessary to determinea target's position and to track it with high The amplitude of returnedsignals received precision. by each horn is continuously comparedwith those received in the other horns, anderror signals MONOPULSE SCANNING are generated which indicate the relative position of the target with respect to theaxis of the beam. Angle servocircuits receivethese error The methods of, scanning thatyou have justsignals and correct the position of theradar studied are sometimes calledsequential lobing,beam to keep the beam axis on target. because target information must begathered The traverse (train) signal ismade up of from a series or sequence ofpulses. Anothersignals from horns A and C added scanning technique, called monopulse and from or simul-horns B and D added. By waveguidedesign the taneous lobing, can obtain informationon targetsum of B and D is made 180° out of phase with range, bearing, and elevation froma single pulse. the sum A and C. These twoare combined and the traverse signal is the differenceof (A +C) - For target tracking, the radardiscussed(B+D). Since the hornsare positioned as shown here produces a narrow circularbeam of pulsed r-f energy at in figure 8-14, the relative amplitudesof the a high pulse repetitionhorn signals give an indication of themagnitude rate.Each pulse is divided into foursignalsof the traverse error. which are equal in amplitude and The elevation signal phase. Theconsists of the signals from horns Cand D four signals are radiated at thesame time fromadded 180° out of phase with Aand B, i.e., each of four feed horns grouped ina cluster as (A +B)- (C +D). shown in figure 8-13. The radiated The sum or range signal is energy iscomposed of signals from all fourfeedhorns focused into a beam by a microwavelens of theadded together in phase.It provides a ref- type mentioned previously.Energy reflected from targets is refocused by erence from which target direction fromthe the lens intocenter of the beam axis ismeasured. The the feedhorns. The amount of thetotal energyrange signal is also used as a phase reference received by each horn willvary, dependingfor the traverse and elevationerror signals. on the position of the target relativeto the beam axis. The traverse and elevationerror signals This is illustrated in figure,8-14are compared in the radar receiver withthe for four targets at differentpositions withrange or reference signal.The output of the respect to the beam axis. Besure to notice,receiver may be positiveor negative pulses, and remember, that a phaseinversion takesthe amplitude of which isproportional to the place at the microwave lenssimilar to theangle between the beam axis and image inversion in a line drawn an optical system. to the target. The polarity of theoutput pulses PRINCIPLES OF GUIDED MISSILESANI? NUCLEAR WEAPONS

TARGET TARGET ABOVE TO RIGHT LINE OF OF LINE SIGHT OF SIGHT

LENS LENS

ASCO ASCE NORMS MORNS HORNS

'TARGET TARGET TO LEFT BE OW OF LINE LINE OHT F ,F SIGHT

LENS LOS

ASCE A S C O NORM NOUNS NOUNS NOM 55.69 with target position. Figure 8-14.Monopulsescanningamplitude changes of received energy indicates whether the target isabove or below,such as a whirling 'scannerto accommodate to the right or to the leftof the beam axis.while trying to do prenise tracking, Of course, if the target isdirectly on the line of sight, the output of thereceiver is zero, CONTROL AND TRACKING and no angle tracking error isproduced. RADAR TRANSMITTERS An important advantage of amonopulse conical scan is A missile fire control system may usetwo tracking radar over one using the tracking and that the instantaneous angularmeasurementsseparate radar sets to perform are not subject to errorscaused by targetguidance functions.When sets are grouped in (As the target maneuvers orthis manner, a separatesynchronizer unit scintillation. (called a master synchronizer)is used to moves, the radar beamsbounce off different radar set and areas of the target and causerandom reflectiv-generate timing pulses for each errors.) A to coordinate their operation. ity which may lead to tracking The transmitter's purpose isto generate monopulse tracking radar is notsubject to this waves of r-f error because each pulseprovides an angularand deliver pulses or continuous measurement without regard to therest of theenergy to the antennasystem where it is fluctuationedinradiated into space. Missile firecontrol radars pulse train; no cross-section usually operate in the. C-band,with a frequency affect the measurement. range, from approximately5400 to 6000 mc. An additional advantage of monopulsetrack- radar method, ing is that no mechanicalaction is required,Transmission may be by pulse Chapter 8BEAM-RIDER GUIDANCE continuous wave (c-w) method, or a combinationon a target illuminated by a radar otherthan pulse-Doppler radar method. Apulse radarthe missile's companion illuminator: transmitter generatesa very short pulse of The transmitter section of the control high energy radio frequency. Thepulse radar radar can measure range accurately and provides coded pulse groups of r-fenergy to can detectthe antenna (fig. 8-15A).The modulator re- both stationary and movingtargets. ceives the coded pulsegroups and provides In a c-w radar set, thetransmitter gen-triggers to the magnetron tocause it to oscil- erates a continuous wave of r-fenergy, whichlate for the duration of each individualpulse. is radiated from the antenna.When the radiated The r-f pulses then go to theantenna where energy strikes a target, a portion of theenergythey are radiated intospace. The transmitting isreflected back and is pickedup by theantenna or waveguide is nutated atthe same receiver antenna. If the target is movingrate as the tracking radar ante=by a nutation toward the transmitter, thefrequency of themotor.If desirable, a reference generatoris echo is higher than the transmittedfrequency;mechanically coupled to the nutationmotor to if the target. is movingaway, the echo frequencyprovide a reference signal to thesynchronizer is less than the transmittedfrequency.Ifto vary the PRR.Figure 8-15A is a block the target is not moving, thefrequency is notdiagram of a typical control radarincluding changed. The shift in the frequencyof thethe nutation motor and referencegenerator. reflected energy is due to thecharacteristicFigure 8-15B is a block diagramof a typical of wave motion called the Dopplereffect (dis-tracking radar. cussed previously), or Dopplershift. This The operation of fire control radarsdiffers difference is used for targetdetection.An from that of most search radarsin that a experienced operator can obtain muchinforma- single object is tracked. tion about the target. OVER-THE-HORIZON RADAR The pulse-Doppler radarcombines the best features of the c-w and pulse radar.The One of the factors limitingthe effective pulse-Doppler method uses highfrequency c-w,range of the radars described is the curvature in the form of short bursts,or pulses. Theof the earth.Increasing the height of either pulse repetition rate (PRR)is much higher than that of a conventional.pulse the transmitting or receiving antennawill inradar, and thecrease the effective range.Thus it appears pulse length is longer.The pulse-Doppler technique makes it possible to that a missile, because of the altitudeat which track targetsit travels, can be controlled atextremely low through unrelated noise and clutterthat wouldrange. Hui this is not true. The transmitter mask the targets for a conventionalpulseradar.power necessary to deliver a satisfactory The c-w radar- cannot beused to measure con- range of the target, but pulse-Doppler radartrol signal increases rapidly withdistance. can. Therefore, for longrange missiles, a single beam-rider guidance system would beunsatis- Basically, the transmitter isan r-f oscil-factory. These limitations lator that uses magnetrons, klystrons, can be overcome by or trav-using beam-rider guidance during thefirst part eling wave tubes to generate microwaveenergy. The operation of the transmitter of the missile flight, then switchingto a different is controlledguidance system before the missile fliesbeyond by a signal received from thesynchronizer.control of the radar beam. Strictly speaking, control ofthe transmitter, such as turning it on and off, is This method of extending therange has been provided by aused for some of our missiles.However, section within the transmitter calledthe modulator. missile-makers have not been content withthis In pulse and pulse-Dopplerradars, theexpedient.Work has been carriedon for a modulator is a special circuit designedto sup-*number of years to producea radar system ply power to the r-f oscillator whenit receivesthat could look over the horizon, the appropriate signal from the and a break- synchronizer.through has been announced. Thismay obsolete C-w radar transmittersare also controlledall the line-of-sight radarsnow in use. The by a modulator, whichmay have another name,Naval Research but its purpose is the sameto Laboratoryhas produced superimposesystem called Madre (magnetic drumreceiving intelligence on the carrier. Coding theillumi-equipment), and another nating signal prevents the missile one called Teepee from homing(so-called because the electromagneticwave

.1.41g11 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

PULSESPRF MUTATION REFERENCE CODING SYNCHRONIZED CIRCUIT GENERATOR REFERENCE SIG. REFLECTOR

CODED PULSE GROUPS

MODULATOR MUTATION TRANSMIT MOTOR ANTENNA

TRIGGERS TRANSMITTED CODED PULSE GROUPS

POSITION ANTENNA COMPUTER MAGNETRON ORDERS POSITIONING

TARGET POSITION .----T-. FROM TRACKING RADAR A

TRANSMITTING SYSTEM RF SYSTEM

r- MUTATION REFLECTOR Rgr. SIG. I REF. MODULATOR 111- SYNCHRONIZER GEM.

MUTATION RECEIVER MOTOR

MAGNETRON V memilimmr TRANSMIT j TR & RECEIVE L_ BOX ANTENNA .-TRANSMITTED PULSES alETL

ANGLE ERROR SIG. Sw ANTENNA FPI ...4mPOSITIONING SYSTEM

COMPUTER111".r:POSITION ORDERS TO LAUNCHER 33.150 Figure 8-15.Block diagrams of weaponsystem radars:A. Control radar; B. Tracking radar. follows a path that looks like a row ofIndianother type) is to achieve its purpose ofdestruc- tents). Industrial firms have alsobeendevelop- tion of the target.Radars used in the system ing similar systems.They all operate byhave been classified according to thetype of bouncing signals off the ionosphere.Technical modulation usad, the method of scanning, their made general or specific use, or themethod of details of the operation have not been transmission. There are other bases of classi- public. 3fication, but these are the ones most coins SYSTEM OPERATION =nig used.According to specific use, we have search radars, tracking radars,and con- Each component of a weapon systemmusttrol or guidance radars.Search radars scan function properly if the weapon(missile orthe surface and the air for possibleapproaching Chapter 8BEAM-RIDER GUIDANCE targets. When a possible target has be en detectedhighest and the lowest positions of itsscan a tracking radar is assigned to it. pattern.For each of these two positions, the CRT produces a pip, the height ofwhich is proportional to the strength of the reflected TRACKING RADAR signal.Since the two pips are of equal height, they indicate that the reflected signalsare of The tracking radar furnishes informationequal strength when the lobe is in itshighest as to the position of the target.All targetand lowest positions. This canoccur only when position references are made withrespect tothe target is vertically centered with the scan axis of the tracking lobe. respect to the lobesthat is, in a transverseplane The amount of energy in the beamfalls offthrough the axis of scan. rapidly at points away from the centerof the lobe.Figure 8-16 shows the relative amounts Figure 8-17B shows the effect ofa target of energy transmitted at variousangles to oneabove the scan axis of the beam. When thelobe side of the lobed.is. Because of the variationis in its highest position, the target isdirectly in transmitted energy, there willbe a corre-on the lobe axis, and the height of the CRT pip sponding variation in the strengthof signalsis a maximum. When the lobe is inits lowest reflected by targets at variousangular dis-position the target is far off the lobeaxis; its tances from the center of the lobe. reflected signal will be much weaker, andthe The tracking system is automatic.Afterpip on the CRT correspondinglysmall.This the tracking radar has acquiredthe target,indicates that the target is above thescan axis. tracking is maintained without thehelp of a A second CRT indicates the relativestrength human operator. But the action ofthe trackingof the reflected signals when thelobe is at its system is monitored by an observer, whomay extreme left and extreme right positions. Inan take over and track the target manuallyif theemergency, the operator can track the target automatic system fails. manually .by moving the radarso as to keep the pairs of pips of equal heighton both CRTs. Each console Display of Information (fig. 8-1, part 2,weapons direction system) has a visual indicatorwhich is an oscilloscope, a cathode-ray tubewith a At the monitor station (fig. 8-1,part 2)fluorescent screen.Figure 8-18A shows the indications of target position relativeto theprincipal indicator on a target selectionand scan axis of the tracking beam are presentedtracking console, called the Plan PositionIndi- on two cathode-ray tubes (CRTs) mountedincator (PPI).It displays the bearing and slant display consoles.Figure 8-17 shows how therange of all the targets picked up by a selected vertical position of the target, relativeto thesearch radar.Targets are displayed on the scan axis, is presented on a CRT.In figurescope as radar video (pips). To select a target 8-17A, the target ison the scan axis. Remem-and assign it to a tracking channel, theoperator ber that the tracking lobe is scanninga conicalpositions the pantograph sighting ringover the pattern in space.The lobe is shown in'thetarget pip and then pressesa channel button on theconsole.Pressing the button gains electrical access to that channel and simultaneously causes an identifying channelletter to appear next to the target pip.Successive corrections of pantograph position bythe op- OIRECITONOF 100x'"'-^11111% erator develop target course and speeddata 1111% INIXIMUM 50% DIRECTION OF that are inserted in the tracking channelsand 110% MAXIMUM the computer. sr% Figure 8-18B and C shows two plotspro- Sc vided on the director assignmentconsolethe OF IIMIMUNI Tlwounno MEW plan plot and the multipurpose plot.The plan plot shows three range rings with truebearing 144.39 nortl, at the top.Each target being tracked Figure 8-16.Variation in radiatedenergy appeaes on the display as a letter, and movesas with distance from lobe axis. the tat get moves.The sector between the

197 PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

CRT INDICATOR

A TARGET ON SCAN AXIS

CRT INDICATOR

BTARGET OFF SCAN AXIS 33.157 Figure 8-17.Pips on the cathode-ray tube indicatetarget position in relation to the scan axis. clearance lines (fig. 8-18B) indicates the area The speed of missiles makes computers in which a missile director would lose tracknecessary to perform the fire controlcalcula- because its radar beam would strike the ship'stions.The computer determines the proper superstructure.The clearance lines and thelead angle for the launcher and transmits the ship's heading mark move electronically as thesignals, electrically, that drive tb a 'tauncher to ship moves. the proper aiming position. The cc.mputer also The multipurpose plot is used primarily fortransmits tactical data such as present target making time comparisons, and is also used toposition, future target position, and missile indicate the speed and height of targets beingtime to target intercept (time of flight), to tracked. The three vertical lines A, B, ancjgdisplay units. in figure 8-18C represent the tracking channelsCONTROL RADAR being used to tracktargets A, B, and C. Changes are indicated vertically and you canread the The components of a control (guidance) radar values as you would read a thermometer*are shown in figure 8-15A; the componentsin the Chapter 8BEAM-RIDER GUIDANCE

PASITOOlUIPN

SYMBOLS IN "PARKE," POSITION

CNANNIL CIRCLE

SECONDS ON TARGET THOUS. SPUD FEET MOTS

GO al= 600 j.TiRGET 400 Ir.gr 20 200 PEW CIRCLE MIGRATE 'oREcTort FROM 0 mom 0 AND TPA:. LOAF I AI \ C

ogokosATE 0 TO FCS eC C

12.42:.43 Figure 8-18.Target informationdisplayed on weapon console display; B. Weapon direction equipment scopes: A. Target tracking console console plan plot display; C. Multipurposeplot. missile which make use of thesignals aremation transmitted by the controlradar. As shown in figure 8-2. with other types of missiles, As explained earlier,a conical scan is one gyroscopes are in which the lobe axis of the radar used to indicate deviations about themissile beam isaxis of rotation.Gyroscopes also providea moved s;; as to generate acone.The vertex of this cone is at the antenna. It is spatial reference for the missile whichis re- possible tolated to the vertical and horizontalaxes of the produce a conical scan byany of severalcontrol radar beam. In effect, themissile can methods. tell which way is up or down, right .:; or left, on STABILIZATION the basis of its attitude with relationshipto the gyros. For example, when it receivesan A '41tude stabilization of beam-ridermissilesindication from the control radarthat it is is netwssa.t7 in addition to theguidance infor-above the scan axis, thegyros provide the PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS internal references on which the missile deter- jam the guidance beam ,effectively, the jamming mines that it must turn downward to get backtransmitter must get behind the missile. Thus on the axis. a jamming transmitter would be oflittle value Accelerometers are also included in someas a defensive measure for a targetaircraft, beam-rider missiles. Instead of providingbecause once the target gets behind a given positional information as in the inertial naviga- missile, it has already successfully evaded that tion systems, they provide a refinement whichmissile. tends to prevent the missile from oscillating It is also possible to transmit the guidance along its axes of translation and prevent over-beam as a series of pulses having a definite, shoot as the missile slides into beam center. coded sequence and amplitude.The missile can be set to accept guidance signalsonly if they follow the proper coded sequence, and to ONE-RADAR SYSTEM reject all other signals. By using a variety of In a one-radar system, the. guidance beamcode sequences, and by changing them often, is always pointed directly at the target, sinceitis possible to make successful jamming the same beam is used for tracking.One orvery unlikely. more missiles can be in flight at the same time toward the same target.The trafficCapture Beam handling capacity of the system is limited only by mutual interference between missiles in Beam-rider guidance is used by both air- the beam.Once a missile has entered theto-air and surface-to-air missiles. In neither beam path, no further operations are necessaryapplication is the missile actually in the guid- at the launching site, except to maintain targetance beam at the instant of launching,and the tracking. problem of getting it there must be solved. For air-launched missiles, this is relatively Countermeasures easy; the missiles are carriedbeneath the wings of the aircraft, fairly close to the guid- One factor must always be considered whenance radar, and they are fired directlyfor- an offensive weapon is used.That is, theward.In most situations this is toward the enemy will always try to find countermeasurestarget, and thus parallel to the guidance beam. that will enable him to offset, or completely But when a surface-to-air missile is nullify, the effectiveness of the weapon. Somelaunched from the deck of a ship, the "capture" attempted countermeasures are fairly easy toproblem is more complex. The missile may overcome; others may be highly effective.be trained at almost any angle (except into the Since radar is used as a guidance control,ship's superstructure).Because the blast of the system is subject to any form of counter-hot gases from the missile booster is deflected measure that willinterfere with the radaralong the deck at the time of launching, a large beam. The interference may take the form ofarea around the launcher must be keptclear. small sheets of metal foil, called "window,"The guidance radar must therefore be located dropped by the target to give false informationat some distance from the launcher.The to the tracking radar. The radar might, undermissile cannot be launched directly toward some conditions, be led to track the foil sheetsthe target, on a course parallel with the guid- rather than the target. ance beam. Instead, it must be launched in Another form of countermeasure might be such a direction that it will CROSS the guidance an enemy radar set working on the same fre-beam a few seconds after launching.It will quency at the guidante radar. This type ofthen turn toward the target, after it has been interference is called "jamming." The naturecaptured by the beam. of the beam-rider guidance system gives good But because the guidance beam is narrow, antijamming characteristics because the beammerely aiming the missile to cross it isnot is narrow and directional. The missile -carriesenough to ensure capture. To make capture its receiving antennas on its alter end -oftfaimore certain, a broad CAPTURE BEAM(fig. on its rear airfoils.These antemas are alsO8-19) is superimposed on the narrow guidance directional; they are mast sensitive to signalsbeam. Because the energy in the capture beam originating behind the missile, and relativelyis spread out over a large area, its effective insensitive to signals originating in front. Torange is short. Chapter 8BEAM-RIDER GUIDANCE

TRACKING ri. REAM

.+ NARROW GUIDANCE BEAN

CAPTION! REAM MISSILE (WIDR, LOW POWER) CONTROL RADAR %.,16 ROOSTER SIIPARATION B

LAUNCH!,

33.154:12.38 Figure 8-19.Beam-rider guidance:A. Relationship of guidance lobeand capture lobe; B. The missile and capture,guidance, and tracking beams. During the launching phase ofmissile flight, the control surfaces has the advantage of simplicity.But the use on the missile usuallyareof a single radar results ina serious problem. locked and the guidancesystem is inoperative. The booster propels Remember that the guidance beamis also the the missile ina directiontracking beam, and must thereforebe pointed calculated to place itwithin the capture beam. at When the booster drops the target throughout the missileflight. away, the imetrolExcept in one special casewhenthe target is surfaces are unlocked and the guidancesystemflying directly toward thetransmitterthe takes over. The missile receiveris tuned toradar must be trained in order respond to the capture beam, and to follow the to seek itstarget.For a nearby, high-speed,crossing axis.In so doing, it turns itselftoward the target and' aligns Itself in the target, the angular rate of trainwill be high. guidance beam,The missile course, therefore,cannot be a which has the same scan axisas the capturestraight line.The missile must constantly beam. After a preset interval,a timing device within the missile changes the move sideways in order to stay in thebeam. receiver timing.While the missile is relativelyclose to the The missile will then rejectsignals from the capture beam, and respond only to transmitter, its lateral rate issmall.But, those in theas the missile approaches the target, thesame guidance beam, which hasa different coded signal angular. rate of train will requireincreasing -44 lateral acceleration of the missile. Close-In Targets Figure 8-20 illustrates thisproblem by The single-radar beam-rider showing three successive positionsof the tar- system, be-get and the missile. In this example,the beam cause it uses only one radar instead oftwo,is trained to the left atan almost uniform PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS collision point is computed from thesefacts. The guidance beam can then be directed(pro- TARGET grammed) to the calculated point, and the COURSE Pew ,' missile follows the guidance beam as soon as it orients itself after capture by thecapture beam.This is sometimes called an "up-and- MISSILE' TRAJECTORYlb over" type of flight path.It permits the missile to reach high altitudesrapidly, where the 2 propulsion system can operate more efficiently, thereby achieving greater speed and range..It also makes enemy countermeasures moredif- ANGULAR ficult. MOTION OF BEAM AXIS Equipment

. The two-radar beam-guidance systemis more complex insofar as groundequipment is concerned, because of the addition of a computer and a second radar(fig. 8-21A). The 33.155 either Figure 8 - 20 . Beam-rider missile followinglineequipment in the missile is the same for of sight (LOS) course, increases lateral ac-system. celeration as it nears target. From the information that has been given, it may be seen that the computer is animportant part of a two-radar guidancesystem. The computer takes informationspeed, range, rate.The missile, in order to stay in theand coursefrom the trackingradar. From beam, must accelerate to the left at a rapidlythis information, it computes the coursethat must befollowed by the missile.Since the increasing rate.In the extreme case shown it in the figure, the missile as it nears thetarget,computer receives information constantly, must follow a path almost at a right angletocan and does alter themissile course as nec- the beam.Even with its control surfaces inessary to offset evasiveaction or changes in their extreme positions, the missilewould course by the target. The outputof the computer controls the direction of the guidanceradar probably be unable to turn at the required instantly rate.Thus a one-radar beam rider might beantenna. Required course changes are useful against approaching targets, but ineffec-transmitted to the missile by pointingthe tive against high-speed crossing targets. guidance beam toward the newpoint ofintercept. TWO-RADAR SYSTEM Countermeasures The two-radar beam-riding system uses The same countermeasures whichwould one radar to track the targetand a secondaffect a one-radar system could be usedagainst radar to guide the missile (fig.8-21A). Athe two-radar system. But it would be more computer is used between the two radarsanddifficult to destroy control effectiveness,bee controls the guidance radar. The computingcause of the two radar beamsand the computer system uses information from the trackingaction.The computer stores guidance infor- radar to determine the trajectory necessarymation as it determines the trajectorythe to ensure a collision behveen the missileand missile is to follow.Therefore, even if the the target. Because the same radar beam istracking beam were interrupted bycounter- no longer used for both trackingand guidance,measures for a short time, thecomputer would the missile need not follow a line ofsightat be able to maintain theguidance beam, path, as was the case with a one-radar systetne4and hold the missile on a probablecollision The guidance beam may be directed into spacecourse with the target. along a programmed target intercept path(fig. As we mentioned earlier, lateral accelera- 8-21B).The speed of the missile is lmown,tion presents a serious problem when a one- the speed of the target is cadixdated,and theradar guidance system is used, becausethe Chapter 8 BEAM -RIDER GUIDANCE

TARGET

COLLISION POINT

GUIDANCE TRACKING BEAM BEAM

TARGET SEARING, /BEAM RANGE, RIDING `ELEVATION MISSILE A p://, UIDANCE RADAR A

144.40 Figure 8-21.Beam-rider guidance:A. Two-radar beath ridingguidance; B. The programmed beam-rider. missile course is changed by theangular It is imperative that false targetsbe recog- movement of the tracking beam. Thisproblem is not present in a two-radar nized in the initial stages, foronce the weapon guidance systemsystem starts tracking the falsetarget, the because the missile course is directedtowardpurpose of the false target is accomplished. a collision point (fig. 8 -21B), rather thantovardA large number of targets,real or false, can the constantly changing positionof the target.overload the tracking system andcause a Because course information iscontinuously fedbreakdown. to the missile guidance radar,the missile trajectory is straight or only slightlycurved from the launching point to thetarget. LIMITATIONS Countermeasures have becomea standard Every mechanical or electricalsystem has part of military operations.The counter-limitations that cannot be exceeded. Whenwork- countermeasure must eliminate theeffects ofing with complex mechanisms, suchas guided the countermeasure so thesystem can stillmissiles, it is as important to knowlimitations perform successfully. as it is to know the capabilities.Unless the limitations are known, a costly missilemight Any countermeasuresuch as chaff andbe wasted. decoys, which gives false target information One important limitation is themaximum tends to obscure the true targetposition andrange at which reliable control can be main- may overload the system with false targets.tained.We ha v e mentioned line ofsight A highly trained operator'or an accurate dis-limitation.Bear in mind that this statement cerning mechanism capable ofdistinguishingdoes not mean that the missilemust remain false targets from realones is the most ef-within range of vision.It does mean that con- fective counter-countermeasure.dammingtrol may be lost if the path between signals cause loss. of the target signal the missile and there-and the guidance radar extendsover the hori- fore loss of target position. Effectiveantijam- ming devices have been developed zon or is blocked by hills or mountains.The and areperfection of over-the-horison radarsystems installed on some ships and aircraft. _ will make this limitationa thing of the past. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS The susceptibility of a guidedmissile to Another limitation, previduslymentioned, its use. is transmitter power.In theory, at least, anycountermeasures is a limitation to RadarThe effectiveness of countermeasureaction can amount of power can be generated. coded-pulse modu- systems through pulse techniquesmake it pos-be greatly reduced by using sible to get large peak power outputwhile keep-lation of the radar guidance beam. ing the average power output withinreasonable Missile enthusiasts at first believed that have powermissiles would replace all other types oford- limits. Practical guidance systems nance, including small arms.Reflection and limitations due to cost, size, andweight. Obvi- guided missiles ously, bulky equipment cannot beeasily trans-experience have shown that ported or installed aboard ships oraircraft.are not the complete answerto the defense Therefore, a compromise must bereached toproblem. Most guided missile ships areequipped with equipment of rea-with 3-inch or 5-inch guns as well asmissiles ensure useful results and other forms of ordnance.Some of the sonable size. ships, in It should also be kept in mind thatthe radarearly conversions to guided missile beam increases in width anddecreases inwhich the guns were removed to make roomfor extended, resulting in aan all-missile installation, arenow being re- power as the range is equipped with guns to supplement themissiles. decrease in both tracking and guidance accu- Although there are many sizes and types ofmis- racy at long ranges.Great improvements in for every both range and accuracy havebeen made bysiles, they are not the best solution modern advances in radar technology. defensive or offensive tactic. CHAPTER 9

HOMING GUIDANCE

INTRODUCTION as a means of attracting the missile. In other words the target becomes a lure, in much the GENERAL same manner as a strong light attracts bugs at In previous chapters, we have discussed night.Just as certain lights attract more bugs guidance systems that are designed to placethan others, certain target characteristicspro- and hold a missile on a collision path with itsvide more effective homing information than target. As we have explained previously, mis-others.And some target characteristics are sile guidance can be divided into three phases: such that missiles depending onthem forhoming launching, intermediate or midcourse guid- guidance are very susceptible to countermeas- ance, and terminal guidance. The proper func-ures. tioning of the guidance system during the Other homing systems illuminate the target terminal phase, when the missile is rapidlyby radar or other electromagneticmeans, and approaching its target, is of extreme impor-use the signals reflected by the target for tance. A great deal of work has been done tohoming guidance. develop extremely accurate equipment foruse The various homing guidance systems have in terminal-phase guidance. been divided into PASSIVE, SEMIACTIVE, and This chapter will discuss some of the hom-ACTIVE classes. The name of the class indi- ing systems that have been found to be effectivecates the type of homing guidance in use. for terminal guidance, as well assome sys- The PASSIVE homing systemsare based on tems that, in their present state of develop-use of the characteristics of the target itself ment, have serious limitations. as a means of attracting the missile.The The expression HOMING GUIDANCE is usedtarget becomes a lure, as described above. to describe a missile system that can"see" theOne such system uses radio broadcastwaves target by some means, and thenby sending com-from the target area as signals to homeon. mands to its own control surfaces, guide itself If the target is illuminated by somesource to the target.(Use of the word "see" in thisother than itself or equipment in the minas, context does not necessarily mean that an optical the system is known as a SEMIACTIVE HOM- system is used. It simply means that the targetING system. For example, the target might be is detected by one or more of the sensingsys-illuminated by radar equipment at the missile tems that will be described later halide chapter).hunching station. Homing guidance is used not only for the If the target is illuminated by equipment in terminal guidance of some missiles, but alsothe missile, the system is called an ACTIVE for the entire flight, particularly ior short-HOMING guidance system. An example isa range missiles. The radar-homing Lark is thesystem that uses a radar set in the missile to first antiaircraft missile Mown to have inter-illuminate the target, and then uses the radar cepted and destroyed a target drone. The Bat,reflections from the target for missile guidance. used against Japanese shipping in World War U., A modified version of the semiactive guidance was the first successful radar homing missile.technique is berm as a quasi-active homing guidance system. BASIC PRINCIPLES The components of homing guidance systems are essentially the same in all types of homing, Some homing guidance systems are baledbut there are differences in location and in on use of the characteristics of the target itselfmethods of using the components.

psi PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

TYPES OF MISSILE RESPONSE operating under war conditions.In addition, radio jamming can do a most effective job of When the control surfaces of the missileconfusing a missile that uses radio for homing are activated by one of the guidance systems,guidance forit would receive signals from the missile is showing response to the guidanceseveral directions at the same time. signals. A number of systems have been While it is possible to do a thorough job of developed to respond to .a variety of signalconfusing a radio homing guidance system, sources.These sources are:sound, radio,there is one possibility that cannot be over- radar, heat, and light. looked. The enemy must use electromagnetic systems for communications and search, and these systems can be used as a source of Sound guidance signals. Also,it is possible for sub- versive agents to plant small, hidden radio If we go through the frequency spectrumtransmitters in target areas. from low to high, we can list systems in order Several radio navigation techniques have been of frequency and start in the audio (low) range.applied to missile guidance. During World War II Sound has been used for guidance of navalthe Germans devised a complex radial system torpedoes, which home on noise from the targetcalled Sonne.Circular methods of radio owl, ship's propellers. But a guidance systembasedgallon were used for blind bombing. Position on sound is limited in range. The missile orof the target was determined by finding the tbrpedo must use a carefully shielded soundlocation on a circle or circles about known pickup, so that it will not be affected by itslocations, measured by two ground station own propulsion noise. And while the speed of a torpedo is low compared to the speed ofsignals. sound, most guided missiles are supersonic. Because of these limitations, no current missileRadar uses a guidance system based on sound detection. A system based on sound detection is known Although radar can be used for all classes as an acoustic system.During World War IIof homing guidance, it is best suited for the the Germans were developing two typed of acous-semiactive and active classes.At present, tic guidance systems for use on the X-4 missile,radar is the most effective source of informa- but the war ended before they were tried intion for homing guidance systems.It is not combat situations. An acoustic homing systemrestricted by weather or visibility, but under is practically impossible to jam, and decoysome conditions it may be subject to jamming devices are equally impractical. But the dis-by enemy countermeasure equipment. advantages mentioned above have notbeen offset Radar guidance is the type most used for by discoveries or inventions that make adequatehoming. Terrier, Taloa, Tartar, and Sparrow III use of the advantages. However, sound wavesuse the semiactive homing. behave differently under water than in the air. Guided missiles whose terminal phase launder-Heat water make use of sound waves for guidance. One form of passive homing system uses heat Torpedoes and antisubmarine missiles are ofas a source of target information.Another this category. name appliql to this system is INFRARED homing guidance. Heat generated by aircraft Radio engines or rockets is difficult to shield. In addition, a heated path is left in the air for a Most homing guidance systems use electro-short time after the target has passed, and an magnetic radiations. Radio wave! are used inultra-sensitive heat sensor can follow the heated one passive homing system. Homing is accom-path to the object One present limitation is plished by an automatic radio direction finderthe sensitivity of sensor milts. As sensor units in the missile.The equipment is to aof higher sensitivity become available, infrared station in the target area, and the alonehoming guidance will become ftreasingly ef- homes on that station. This homing system isfective.Such systems will make it difficult to not restricted by weather or viability. But illjam the homing circuits, or to decoythe missile is tmlikely that a radio transmitter would beaway from the target. Chapter 9HOMING GUIDANCE

Light switchover is usually accomplished by radio 1 command. At long range, it is controlled bya A passive homing system could be designednavigational device, or by some form of built-in to home on light given off by the target. But,programing system. like any optical system, this one would be The U.S. Navy missile program makesuse limited by conditions of weather and visibility.of composite guidance systems in several of And it would be highly susceptible toenemyits operational missiles.Taloa is a beam countermeasures. rider during its midcourse phase, and switches A quasi-optical system whichuses a tele-to radar homing for terminal guidance. Other vision camera in the nose of the missile hasmissiles, such as Terrier, Sparrow, Shrike some interesting possibilities. The TV sensesand Tartar, use homing guidance systems inone the missile-aiming error, transmits the pictureform or another for terminal guidance. Although to the launching aircraft, ground station,orAsroc is called an unguided missile, ituses ship, where the corrective orders are computedactive acoustic homing guidance in its under- and sent to the missile. water phase. USE IN COMPOSITE SYSTEMS HOMING TRAJECTORIES In command and beam-rider guidance, the missile is controlled from the launching site, A homing missile uses one of two methods in or from some other point at a considerableapproaching a moving air target.When the distance from the target. But neither of thesemissile flies directly toward the target at all systems is very effective against moving tar-times, its flight path is described as PURSUIT gets, except at relatively shortranges.TheHOMING,or ZERO BEARING HOMING. When reason is obvious. The closer the missile getsthe missile anticipates the future position of to the target, the farther it is from its controltarget,it uses the LEAD HOMING method. point.At long range, a very small angular error in target tracking, missile tracking, orPURSUIT HOMING beam riding could cause the missile to miss its target by a wide margin. As shown in figure 9-1, the use of pursuit Sidewinder is a Navy missile thatuseshoming results in a rigorous chase. Note that homing as its only source of guidance. It hasthe line of sight (LOS) is always pointing been used very effectively at relatively shortdirectly ahead of the missile, thus the term range. But homing systems are based oninfor-zero bearing. mation radiated from, or reflected by, the All of the homing guidance systems we have targetitself. For targets at intermediatedescribed have had the sensor unit (thermopile, ranges, such signals are extremely weak, andlight cell, microphone, television camera,or could be used only by missiles with powerfulantenna) mounted in thenose of the missile. and heavy guidance equipment. At longrange,The sensor is OM to the missile frameso such signals are entirely unavailable. that it maintains a constant relationship to the An answer to this problem lies in theusemissile axis.The equipment in the missile is of a composite guidance system.In this sys-then able to process the information pickedup tem, the missile is guided during its interme-by the sensor, so that the missilecan be diate phase by information transmitted fromcontinually pointed toward the target. the latmching site, or other friendly control Notice in figure 9-1 how the flight path must point. During the terminal phase, it is guided bycurve as the missile approaches the target. information from the target. For intermediate-The sharp curvature In the path setsup strong range missiles, either command or beam-riderlateral accelerations during the terminal phase guidance is suitable duringthemideoursephase.of flight. These transverse accelerationspre- A long-range missile would depend eitheronsent a strong objection to the use ofa zero- preset or navigational guidance to bring it tobearing approach against high-speed air targets. the target vicinity.Missiles of both classes There are two basic objections tothe pursuit can Switch over to homing guidance, based onmethod. First, the maneuvers required of the infrared or radar radiations, as they enter themissile become Increasingly difficult during the terminal phase.At intermediate range, thelast (and critical) stages of flight.Second, PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

LINE OF SIGHT (LOS4)

SNAP, CURVATURII CAUSES HIGH ACCELERATIONS

MISSILE FLIGHT PATH

12.35 Figure 9-I.Pursuit homing, or zero bearing flight path. missile speed must be considerably greater than The most favorable application of pursuit target speed.As shown in the figure, thecourses is against slow moving targets, or sharpest curvature of the missile flight pathfor missiles launched from a point to the rear occurs near the end of the flight.At thisof the target or directly toward a head-on time, the missile must overtake the target.incoming target. If the target is attempting to evade, the last minute acceleration , requirements placed onLEAD ANGLE OR COLLISION COURSE the missile could exceed its aerodynamic capability, thereby causing a miss. Near the end The second method of approach to the of the flight, the missile is "coasting" becausetarget is called LEAD ANGLE course.It is the booster and rocket rooter thrusts hit foralso known as a CONSTANT BEARING or a abort part of the flight.More power is re-COLLISION course or PROPORTIONAL NAVI- quired to make sharp radius, high speed turns,GATION.The trajectory of a ground-to-air at a time when the missile is losing speed andmissile ueing this method of approach is shown has least turning capability. in figure 9-2. Chapter 9HOMING GUIDANCE

33.158 Figure 9-2.Lead angle method ofapproach to target.

Notice that the missile path fromthe launcheraction, the computer automatically determines to the collision point isa straight line. Thea new collision point.It then sends signals to missile has been made to lead thetarget inthe guidance package or control unit (autopilot) the same manner as a hunter leadsa bird inin the missile, to correct thecourse so that it flight.In order to lead the target and obtainbears on the new collision point. a hit, a computer must be used. The systems As shown in figure 9-2, the collisionpoint devised for computing lead angle forguns haveand the successive positions of missileand been adapted for missile firing. Leadangletarget form a series of similar triangles.If has always had to be computed in orderto obtain a hit on a moving target. the missile path is the longer leg of thetri- The hunter has toangle, as it is in the figure, the missilespeed estimate mentally how far ahead to aiminmust be greater than the target speedbutit order to hit the running gameor flying bird.need not be as great proportionallyas with a Early gunners devised various mechanicalaidszero-bearing approach. to help them locate the target,estimate its The transverse acceleration required ofa speed, determine its direction ofmovement,missile using the lead-angle approach iscom- and compute the amount of "lead"necessaryparatively small. so they could fire where the targetwas going In lead homing missiles, the missilecom- to be at the time the bulletor shell mould get there. Modern rapid puter network calculates the rate of changeof - firing guns and supersoniclead angle and generates a solution which,when missiles are much too swift for such calcula-applied to the controllers, will tions. cause flight Computers are necessary to makepath corrections to reduce the rate ofchange calculations as speedy as possible, and elec-to zero. When this has been done, themissile tronic control signals are needed tokeep thewill be on a collision course with thetarget. missile on the calculated course. Should the target change course, the leadangle The computer continually predicts thepointwill change. The missilesensors will detect of missile Impact with the target. If thetargetthis change, and the computing networkwill takes no evasive action, the point ofimpastdetermine a new solution to put themissile remains the same from launching time untiltheback on a collision course. The missileturns missile strikes. Mould the target take evasiveat a rate proportional to the rateof the line of PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS sight rotation and in the proper direction to re-get is obviously on that side. A second pair of duce the rotation of the line of sight to zerosensors could be mounted verticallyto sense (proportional navigation). The final (and mostradiation above and below the pitch axis. important) part of the flight path will be a Another infrared passive homing system straight line.Therefore, the accelerationsmakes use of a sensing device mounted in gim- required by the missile at this time are negli-bals, and driven by servomechanisms. The sys- gible. tem is so designed that the sensing device will constantly be trained on the target.Thus the PASSIVE HOMING SYSTEM train angle of the sensor with relation to the heading of the missile can be used to produce GENERAL correction signals. A passive homing device that uses radiofre- As mentioned earlier inthis chapter, passivequency intelligence is a radiodirection finder. homing systems can be used when the targetIntelligence may be derived by comparison of itself radiates information.Therefore, all ofphases, as with a pulse type radar. However, the response systems, with the possible excep-detectors of this type depend on radio or radar tion of radar, might be used.The exceptionradiation from the target.If the target main- to .radar would not apply if a signal from thetains radio and radar silence during an attack, target could be picked upby a radar receiver setthis means of detection is useless. For practi- in the missile. This system would be unreliable;cal reasons, therefore, a passive homing system the only source of target information would be should rely on only those sources of energy that under enemy control, and could be switched offcannot be controlled by the target. Heat and at will.But missiles using such a systemlight are two such sources, althoughlights can be would have one distinct advantage: they wrAtleblacked out to prevent detection. deny the enemy the use of his own radar.Properties of Heat Radiation Passive homing guidance can be used for air-to-air, air-to-surface, surface-to-surface, Before examining several types of infrared or surface-to-air missiles. One mainadvantage sensors, let us take a closer look at the subject of a passive system is missile equipment sim- of heat radiation. plicity. No transmitter is needed in the missile, Heat is produced by any material whose and the missile tracking equipment can be verytemperature is above absolute zero(-273.16°C. small and compact. A second advantage is thator -459.69° F.). Heat is a resultof the motion the passive system is an independent systemof molecules; it is a form of kinetic energy once the target is acquired. which can be transferred by only three processes. BASIC PRINCIPLES In the process of CONDUCTION, the heat energy is transferred frommolecule to mole- The passive homing systems most widelycule by actual contact. Metals, in general, are used at present are based on infrared radiationgood conductors of heat. Oases are much poorer from the target. The sensing mechanism is soconductors of heat than solids, due to the rela- designed that It candeterminethe direction fromtively large distances separatinggas molecules. which the infrared radiation is received; the CONVECTION is the process of transferring guidance system can then steer the missile inheat by movement of a heated substance. For that direction. There are several ways in whichexample, a home furnace warms the air around the sensing device can be made todeterminetheit. Due to its increase in temperature, the air direction of an infrared source. For example,will rise and therefore carry the heat to another two sensors could be mounted with a baffle be-location. tween them, so that the one on the right can re- Our main source of heatthe sunsupplies ceive radiation from straight aheid, or from anyus with heat energy throughthevacuumof space. point to the right of the missile yaw axis. TheThis heat energy is transferred by the process other sensor will receive radiation cominefromOf RADIATION, that is, the process of electro- straight ahead or from the other side of the yawmagnetic wave transmission. The electromag- axis.When both sensors receive the samenetic waves which produce heat in any object amoimt of radiation, the target isdirectlyahead.that absorbs them are called infrared waves. If the radiation is stronger on one side, the tar-Figure 9-3 shows the infrared portion of the UV Chapter 9HOMING GUIDANCE

cussed earlier in this text), the infraredsensors FREQUENCY IN MEGACYCLES have proved most satisfactory forthe passive 3x101 3z10e 3007 &MOO homing systems.Some of the heat sensors which might be used in passive homingmissiles are described below. THERMOCOUPLE.One of the basic heat detectors is the thermocouple. When twodis- similar metals such as iron andcopper are joined together and heat is applied tothe junc- 100 10 1 0.1 tion, a measurable voltage will be generated WAVELENGTH IN MICRONS between them. This is sometimes calledthe See- 33.159 beck (a German physicist) effect.Figure 9-5 Figure 9-3.Infrared portion of shows a basic thermocouple. electromagnetic spectrum. The voltage difference between the twometals is quite small, but the sensitivitycan be in- electromagnetic spectrum.It is between thecreased to a point where the thermocouplebe- visible light and the microwave (radarand radio)comes useful as a detector of heat.The in- regions. The frequencies in the infraredspec-crease in sensitivity is obtained by connecting, trum are in the millions of megacycles.In thisor stacking, a number of thermocouples inse- illustration, the wavelengthsare in microns. Aries, so that they form what is knownas a micron is equal to 1 x 10-6 meters inlength.THERMOPILE. The complete thermopileac- The infrared spectrum maybe subdividedin-tion is similar to that obtained whena number to the near-infrared (NIR ) (0.76 to 2.00microns),of flashlight cells are connected inseries. That the intermediate' infrared (IIR) (2.00to 6.00is, the output of each individualthermocouple microns), and the far infrared (FIR)(6.00 tois added to the output of the others.Thus, ten 1000 microns)., thermocouples with individual output voltages of It is interesting to note that thefrequency of.001 volt, would have a total outputof .010 volt infrared radiations emanating froma body iswhen connected in series. determined by the motion of thesurface mole- The sensitivity of a thermopilecan be further cules. Since this motion is random,the infra-increased by mounting it at the focal pointof a red radiations consist ofmany frequencies.parabolic reflector. When this methodis used, The frequency of maximumradiation, however,heat given off by the target is focusedon the depends on the temperature of thebody. Figurethermopile by the reflector. By making thede- 9-4 is a plot of the radiation fromfour objectsvice rotatable, the source of highest intentityof of different temperatures. Note thatvery highheat radiation may be located. temperatures produce both visible andinfrared BOLOMETERS. A bolometer isa device radiation, and that cooler objectsproduce onlymade of a very sensitive material infrared. whose resistance will vary, dependingon the amount of Heat-Detecting Sensors infrared radiation to which it is exposed. There are two main classes of bolometers In view of the rather simplemethods ofBARRETTERS and THERMISTORS. Abarret- countering light sensors and radiosensors (dis-ter consists of a abort length ofvery fine wire

t (STRENGTH MI 74 ik WAVELENGTH 1 20 10 I 0.76 .4 IN MICRONS INFRARED VISIBLE LIGHT

. Figure 9- 4. Infrared radiation at different temperatures. 33.180 215 m PRINCIPLES OF GUIDEDMISSILES AND NUCLEAR WEAdONS

VOLTAGE OUT

IRON

THERMOCOUPLE

33.181 Figure 9-5.A basic thermocouple.

(usually platinum) which has a positive temperature coefficient of resistance. (A resistance has a positive temperature coefficient if itsvalue increases with temperature, and a negative coefficient if its value decreases with an increase in its temperature.) The thermistor is a type A of variable resistor made of semiconducting material, such as oxides of manganese, nickel, cobalt, selenium, and copper. The thermistor has a a negative temperature coefficient of resistance. Thermistors are made in the form of beads, disks, rods, and flakes, some of which GLASS LEAD are shown in figure 9-6. The beadthermistor SUPPORT (fig. 9-6B) could be used as a sensing-element WIRE THERMISTOR BULB WIRE pickoff unit as well as in a control system. It has small mass and a short time constant. B The heat-sensitive materials of thermistors are mixed in various proportions toprovide the 33.162 specific characteristics of resistance versusFigure 9-6.Thermistors: A. Various thermis- temperature necessary for target detection.tor forms; B. Construction of bead thermistor. The thermistor has the larger temperature coefficient of resistance, and therefore is the more sensitive. ciple that a pressure-volume change occurs in a Figure 9-7 shows a simple modern bolome-gas when its temperature is changed.At the ter; it consists of four nickel strips supportedforward end of the cell is a metal chamber by phosphor bronze springs. These springs arewhich encloses the gas. The front of the cham- supported by mounting bars, which have elec-ber is covered by a membrane, which acts as a trical connection leads attached to them. A sil- receiving element. The back of the chamber is vered parabolic reflector (mirror) is used toclosed by a flexible mirror membrane. Infra- focus infrared rays on the nickel strips. Thered energy entering the window raises the tem- bridge Imbalance current, produced as a resultperature of the gas in the chamber and causes of resistance changes, is used to set In motionexpansion of the gas. The resulting increase in the other sections of the guidance system topressure distends the mirror membrane. produce correction signals. The lamp at the after end of the detector GOLAY DETECTOR. Still another form ofemits alight beam which is focused by the lens infrared 'detector is a GOLAY DETECTOR shownand that passes.through the grid and onto the In figure 9-8.It is also knows as a pneumaticreflecting diaphragm. The expansion and con- detector. This detector is a miniature heat en-traction of the gases between the window and gine. The Golay heat cell operates on the prIn- the diaphragm will cause the diaphragm to change

212 Chapter 9HOMING GUIDANCE

Rapid advances in the theory of photocon- WINDOW ductivity and in the technology ofconstructing practical radiation detectors basedon this phenomenon have greatly improved the facility NICKEL with which measurements can be madein the STRIPS region 1 to 5 microns. The materialsuse" are sensitive throughout the visible spectrir. '.1 SPRINGS as in the infrared. The cell that ie over the widest range of wavelengwe MOUNTING is not BAR necessarily the best choice for each application. Photoconductive cells do not depend fortheir MIRROR response on being warmed by the incoming radiation. LEAD WIRES Photodetectors are of three typesphoto- conductive, photovoltaic, and photoemissive. The photoconductive type is theone we have 33.164been describing.It uses material that varies Figure 9-7.A simple modernbolometer. in resistance according to the radiationex- posur e . The elements used are usually lead its shape in proportion to the amountof infraredsulfide, lead selenide, lead telluride, andger- entering the window. Changes inshape of themanium. diaphragm will cause its light-reflectiveproper- Photovoltaic cells are used chiefly inphoto- ties to vary accordingly.The light reflectedgraphic light meters.They are usually not from the diaphragm will thenpass back throughsensitive enough for communicationpurposes. the grid, which is designed to intensifythevari- Photoemissive cells producean electrical ations of the reflected light.After passing charge when exposed to light waves. Theyare through the grid, some of thelight strikes therelatively insensitive but provide highfidelity mirror and is reflected to a photocellof highand low signal-noise levels. One of thelimiting sensitivity (not shown in the figure). Theoutputfactor in photocells is thesignal-to-noise of the photocell is a voltage proportionalto theratio. intensity of the infrared radiationentering the window. Other Radiation Detectors The Golay detector has the most rapidre- LUMINESCENT DETECTORS.Lumines- sponse of any infrared detector, but itcancent effects are those that appearas a visible operate only when radiant heat isreceived inter-glow on films or screens that have beenex- mittently. For some guidance systems thisfac-posed to radiation.The term fluorescence tor makes the Golay detector useless;in othersmeans that the process of emission of electro- it causes no difficulty. magnetic radiation is the result of absorption PHOTOELECTRIC CELLS.In thelight-of energy by the fluorescent system. Fluores- homing guidance systems, the pickupdevice orcent materials glow only as longas the radia- sensor is a photoelectric cell. The operation oftion continues, while phosphorescentmaterials this device is based on the fact thatcertaincontinue to glow for some time afterward. metallic substances emit electronswh- they are exposed to light.Modern ectric cells are quite sensitive to light variations;but, wim0Ow GAS REFLECTING SRO because light is easily interrupted, thesystem remASER. is subject to interference.One type of photoelectric cell is shown in figure 6-2. The objection to photoelectric cells hasbeen dm. partially removed by the recent developmentof MORONS cells with a sensitivity in the region. FIN However, the extension of therange of opera- PNEumAne tion changes the sensor froma pure photoelec- OWASES ROR LAMP tric device to a thermoelectric device. It is 33.165 then similar in operation to a heatsensor. Figure 9-8.A Golay detector. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS of CHEMICAL DETECTORS.Photographicdirected toward remedying this shortcoming emulsion plates chemically coatedwith sub-the early mots of the missile. stances that are sensitive to the shorter wave- A sound-homing system might also beused against a jet aircraft target, even thoughboth lengths are being developed by the Navy. target and missile are traveling fasterthan sound. Such a system might be used in atail TARGET CHARACTERISTICS chase, provided the target does not maneuver In passive homing, the target itselfmust radically. But you have probably observedthat provide all the necessary information formis-when a jet passes over at moderatealtitutde, sile guidance. For this reason thecharacteris-the sound appears to come from a pointat some tics of an individual target will determinewhich distance behind the aircraft. A sound-homing types of homing system can be usedagainst it,missile would steer itself toward the sourceof and under what conditions they can beused. sound, rather than toward the target itself.For If the target is fixed in location, and has an approaching or crossingtarget, the required some characteristic by whichthe missile cantrajectory would be too sharply curved forthe readily distinguish it from the surroundingarea, missile to follow. the homing guidance problem is simplified.Fig- ure 9-9 represents an air-to-surface cr.'stazee- MISSILE COMPONENTS to-surface missile, using a light-sensingguW.,. ance system to home on anindustrial building. When passive homing guidance is used, the While such a missile might be useful in a sur- missile must contain ALL of theequipment prise attack, industrial plants wouldcertainly needed to pick up, process, and use theinfor- be blacked out during a war. Alight-homingmation given off by the target. The kind and missile would then have no way to distinguishamount of equipment required is determinedto the target from its background. Butinfrareda large extent by theguidance system used, and passive homing could be used inthis application.by the characteristics of the target.Consider- And it would probably be more effectivethan ation must also be given to:the maximum light-homing, since the heat generated by anrange, informition required, accuracy,operat- industrial plant can not be readily controlled._ing conditions, type of target, and speed ofthe Figure 6-3 represents a passive infraredtarget. The components of the 'guidancesystem homing missile attacking an aircraft.The in the missile can be sectionalized forseparate Navy's Sidewinder uses this type of guidance.discussion. We will explain the purpose of each The tailpipe of a jet aircraft is a strong sourcesection. Figure 9-10 shows a blockdiagram of of infrared radiation, which cannot beconcealed.a passive homing guidancesystem. In a tail-chase attack, the Sidewinder ishighly 4 effective.Against an approaching jet aircraft,Antenna or Other Sensor missiles dependent upon this type of guidance would be quite useless. Improvements inthe Since information given off by the target is Sidewinder missile guidance system have beento be used for guidance, some meansmust be

LIGHT SEEKING MISSILE

TARGET 33.90 figure 9-9.Missile using light-homingguidance. .218 214,:, Chapter 9HOMING GUIDANCE

(SENSOR) ANTENNA REFERENCE ANTENNA (SENSOR) UNIT ..4111P PITCH DRIVE TO MISSILE (UP-DOWN) COMPARATORAUTOPILOT

elYAW TO MISSILE SIGNAL (LEFT-RIGHT) CONVERTER AUTOPILOT COMPARATOR

144.41 Figure 9-10.Passive homing guidancesystem, block diagram. provided to pick up the information. Forelec- Should the sensor temporarily lose sightof tromagnetic systems, a conventional radioorthe target, a spiral or sawtooth/scan,as shown radar antenna (streamlined into the missile)in figure 9-11, could be used to find the target would be used. again.Notice that both types ofscan cover a A heat - sensing detector, rather thanan an-large area. tenna, is used with infraredhoming guidance systems. In spiral scanning the amount of tiltgiventhe dish is varied as the dish is nutated, resulting Antenna or Sensor Drive in a spiral pattern. Sawtooth or verticalscan- ning is used to determine position angle andal- Previous chapters have describedantennatitude of the target. (Position angle istheangle scanning methods.The reflectors mentionedbetween the horizontal and the line of sight to for heat or light homing sensors act in thesamethe target.) way as a radar reflector. Therefore, greater The scanning action is controlled by thean- control accuracy can be obtained by scanningatenna or sensor drive unit, which is shown in target with the reflector and sensor units. the block diagram of figure 9-12.

I /I /II ANTENNA I / A ENERGY (SENSOR) I 1 PATTERN I I //1

/ /

ENERGY PATTERN ANTENNA (SENSOR) 144.42 Figure 9-11.Spiral scanning and sawtoothor vertical scanning. 219 215 , 1 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

INFRARED TARGET RADIATION SCANNING 6* COMMUTATOR ROTATING A TARGET IMAGE DETECTOR FLAK ES

ROTATING OFFSET PARABOLIC MIRROR

DOWN UP STEERING DIRECTIONS AS MIRROR REVOLVES TARGET IMAGE AMPLIFIER DESCRIBES CIRCLE RIGHT GYRO MIRROR S eCANNER BOLOMETER

CORRECTION INFRARED RAYS SIGNAL

ERROR CORRECTION CENTERS TARGET IMAGE

33.166 Figure 9-12.Infrared target detection: A. Infrared detector which usesfour bolometer arms; B. Guidance system using a bolometer.

After the antenna or sensor has picked up .Signal Converter the information, other equipment in the missile must convert the information into error signals, The output of the sensor unit is an extremely if the missile is off course. Before this can besmall voltage.This voltage is fed to a signal done, however, there must be something toconverter, which builds up the strength of the compare with the sensor signal. signal and interprets the information contained in it.The output of the signal converter is fed Reference Unit. to the pitch and yaw comparators along with the signal from the reference unit. The comparison voltage is taken from the reference unit.This voltage may be obtained from an outside source, or it may be takenComparators from recorded information that was put into the missile before launching. Actual operation of The comparators are electronic calculators the missile guidance controls takes place onlythat rapidly compare reference and signal volt- when an error signal is present. Note that.theages and determine the difference(error), if reference unit isconnected,to both tliepitch andany, between the two signals. It is possible for yim comparators in the block diagram of figurean error signal to be developed in the pitch 9-10.Various types of reference units andcomparator while no error signal is developed reference devices were discussed in chaptersin the yaw comparator. Should this happen, the 5 and 6. missile would be higher or lower than the desired 220 216 Chapter 9HOMING GUIDANCE trajectory.The output voltage from the pitchthe insulating segments, andno error signal comparator is then fed to the missile automaticresults. pilot. With an off-center target, the circle of the rotating target image isnow offset from the center of the bolometer. In this condition, Autopilot the bolometer arms divide the circle intoun- equal sectors and, as a result, the image inter- The automatic pilot, or autopilot,operatessects the flakes when the commutatorarms are missile flight controls in much thesame wayon the conducting segments, and the proper er- as a human pilot operates airplane controls.ror signals are developed. The components makingup the autopilot assem- As the mirror scans the targetarea (fig. 9- bly have been described elsewhere inthis text.-12B), the thermal image of the targetis re- In order to shift the flight controls,the autopilotflected onto the flakes, causing their resistance must get "orders" fromsome circuit.The to change. When the resistance of each changes, orders are in the form oferror signal voltagesthe voltage at the junction of each pair will rise from the comparators. Theerror signal volt-or fall, depending on which flake is affected, ages operate motors or hydraulic valves which,thus transforming the infrared signals into in turn, operate the flight control surfaces. $ electrical voltage pulses.These pulses are transmitted to the amplifier sectionas either INFRARED TARGET DETECTION vertical or horizontal information.The commutator converts the two channel signalsinto Regardless of whatmaterials are used infour channels of intelligence corresponding to infrared detectors, the sensing elementsareUP, DOWN, LEFT, or RIGHT. in the ERROR- usually placed at le focal point ofa parabolicDETECTOR section. The terms horizontal and mirror, or are used in conjunction withlensesvertical as used here refer to the signals de- which provide maximum concentrationof theveloped by the vertically and horizontally posi- infrared signals at the sensitive surface.Thetioned bolometer flakes, and do not necessarily sensor unit is commonly referred to as a homing head. imply that such signals will cause corresponding turning of the homing head.The exact One method of obtaining directionalinforma-designation of the intelligence is not available tion is by the use of a rotating mirrorwhosiiuntil the signals reach the SENSING CIRCUITS optical axis is offset from its axis ofrotationin the error detector. so that the focal point describes a small circle. The function of the amplifier section is to In this arrangement, the detector oftenconsistsamplify and rectify the pulse signals delivered of four bolometer elements arrangedincruci-by the bolometer so that only positive pulses of form pattern.It is placed so that the focusedhigh amplitude are available at the outputs for radiation sweeps across each of the elementsinthe error detector. There are two complete succession, as shown in figure 9-12A. channels in the signal amplifier anderror- In addition to the mirror and detector,twodetector sections; one channel processes the commutators' are included in the homing head,signals from the horizontal bolometer flakes; each of which contains a pair of conductingseg-the other uses the signals from the vertical pair. ments separated by insulatingspaces. One (The two channels are identical.) commutator connects one pair of bolometer The gyroscope is used for stabilizing the flakes to the left-right control circuits, whilehoming head and for measuring the angular the other connects the remaining pair to theup- rates about the line of sight (LOS). down circuits (fig. 9-12)3). Each commutator has a rotating arm which isdrivenbythemirrorRADIO FREQUENCY PASSIVE shaft. When the target is dead ahead, thero- HOMING GUIDANCE tating target image formed by the mirror describes a circle centered with respectto the A passive. homing device using radiofre- bolometer arms. As a result, thepolometerquency intelligence is the direction finder. The arms divide the circle into four .900 sectors.intelligenCe may be derived fromphase com- In this condition, each time the image intersectsparison techniques (such as an interferometer) one of the bolometer arms, the signals developedif the energy transmitted by thetarget is of such cannot pass to the control circuits, because atform as to make this possible. For example, if this instant the commutator armsare on one ofthe target is operating a pulse type radar, phase .221 217 PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS comparisontechniques would be possible.LAUNCHING STATION COMPONENTS Another means of deriving intelligence from the energy transmitted by the target isby compari- In a semiactive homing guidance system, the son of the amplitude of the receivedsignal dur-launching station components are similar to ing the scan cycle. Such techniques canbe usedthose required for a beam-rider guidance sys- only if information is available concerning thetem (chapter 8). The target is trackedby radar. frequency band in which the target is transmit-The tracking radar itself may be used asthe ting.In addition, it is necessary that the mis-source of target illumination for missileguid- sile receiver be capable of being tuned over thisance, or a separate radar may beused for this frequency band.. purpose. The transmitter may be a surface installation on the ship or at a shore station, or it maybe in SEMIACTWE HOMING SYSTEM an aircraft. The transmitted energy maybe in the form of radio, light, or heat. The missile BASIC PRINCIPLES launcher may be in close proximity to the transmitter, but not necessarily so. In a semiactive homing system the target is illuminated by some meansoutside the tar-MISSILE COMPONENTS get or the missile.Normally, radar is used for this type of homing guidance, by sending a The missile, throughout its flight, is be- radar beam to the target.The beam is re-tween the target and the radar that illuminates flected from the target, and picked up bythe target.It will receive radiation from the equipment in the missile. The radar trans-launching station, as well as reflections from mitter might be located at a ground site, orthe target.The missile must therefore have it might be aboard a ship or aircraft.See some means for distinguishing betweenthe two figure 6-8. Because the energy transmittersignals, so that it can home on the target rather is not in the missile, but on the larger deliverythan on the launching station. This can be done vehicle (ship, aircraft), the size and weight ofin several ways. For example, a highly direc- the transmitter can be much larger than intional antenna may be mounted in the nose of the passive homing missiles, permitting the use ofmissile. Or the doppler principle maybe used to longer- range, high power transmitters.Thedistinguish between the transmitter signal and missile,withouta transmitter, has space forthe target echoes. Since the missile is receding additional explosive material to increase thefrom the transmitter, and approaching the tar- area of damage, more propellantto increaseget, the echo signals will be of a higher fre- its range, or more guidance equipment to in- quency. crease its accuracy. However, theseadvan- The radar receiving antenna in the head of the tages are gained at a price.Since the missilemissile is called the seeker or seeker head.It operates solely on energy from the transmitterreceives echoes from the target. The semiactive on the ship (or aircraft), the shipcannot breakhoming antenna system locates the target and off the attack, or attack another target, whileautomatically tracks it.The tracking process it has missiles in flight.While the time oflocates the line of sight between the target and flight is very short,it could be a decisivethe missile. A computer in the guidance system moment during which the transmitter is notuses this tracking informationtoproduce steer- free. ing signals. The missile, however, does not fly A modified version of the semiactive tech-along a line of sight, but follows a collision nique has the transmitter located in themis= course, or rather, a refined collision course. sile and the receiver of the reflected energyThe missile receives this refinement before it at some remote point.Computation of theis launched.It receives this navigational in- desired flight path takes place at the remoteformation through the warmup contactor of the point and suitable commands are sent to thelaunching system.Most of our missiles are missile.This system is known .as a quasi-given a warmup period just before loading on the active homing guidance system. launcher and a final warmup while on the Semiactive homing is used for all or partlauncher, just before firing. of the trajectory of several of our best-known To intercept high-speed targets like a super- missiles, including Terrier, Taloa, and Tartar.sonic aircraft or a missile, the semiactive

218 222 Chapter 9HOMINGGUIDANCE homing missile must followa lead (collision) To achieve the desired straight-linecourse course. If the target flies a straight-lineduring the final and critical portion of the atconstant-velocity course, the missilecan alsotack, the missile must turn ata rate greater follow a straight-line collisioncourse if itsthan the line of sight is turning.By over- velocity does not change. In actualsituations,correcting the missile path, anew collision there usually are variations in speed,change inheading is reached and the bearing angle will path, maneuvers of the target, etc. Themissileremain almost constant, especiallynear inter- has to adjust its direction to maintaina constantcept.This technique results in a proportional bearing with the target. The componentsin thenavigation course (fig. 9-13B). It is sometimes missile must be able tosense the changes andcalled the N factor, or navigation ratio, which make the necessary adjustments in itscourse to the target. is the ratio of the rate of turn of the missileto Missile velocity seldom iscon-the rate of turn of the line of sight (rateof stant.Irregular propellant burning changeschange of target bearing).The missile fire thrust and therefore affects speed.Wind gustscontrol computer on shipboard computesthe and/or air densitycan change the speed andratio and transmits it to the missile launching path of the missile. Thesame factors can in-system for transfer to the missile's guidance fluence the target. The missile mustuse propor-and control system. tional navigation, described in chapters2 and 6, and at the beginning of this chapter, toachieve For the purposes of this text,we can think target intercept. If the missile path is changedof the missile guidance componentsas divided at the same rate as the target bearing (fig.into several distinct sections. Theseare shown 9-13A), the missile will have to turn atan in-in block diagram form in figure 9-14. Note that creasing rate (positions 1 to 6), and willend upthese are the components inthe missile; launch- chasing the target (positions 6 and 7).Thising station guidance componentsare not shown. flight path follows a pursuit curve and the missileA comparison of figures 9-10,9-14, and 9-15will cannot maintain a constant bearing withtheshow much similarity of components. As pointed target.It is just keeping up with changes inout at the beginning of this chapter, all typesof ,target bearing- and may not be able to catchuphoming guidance use the same blocks ofcom- with the target. ponents. Their location and/or use will differ.

83.28 Figure 9-13.Proportional navigation: A.Pursuit curve; B. Overcorrection to produce proportionalnavigation. 223" PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

ANTENNA ANTENNA REFERENCE ANTENNA ANTENNA DRIVE UNIT DRIVE UNIT

PITCH PITCH RIP -DOWN) OtIPLEXER TRANSMITTER COMPARATOR COMPARATOR T-- YAW 1 YAW SIGNAL SIGNAL REFT-RIGHT) RECEIVER (LEFT-MORT) [RECEIVER CONVERTER CONVERTER S COMPARATOR H COMPARATOR 144.43 144.44 Figure 9-14.Semicative homing systems; Figure 9-15.Active homing system; block diagram. block diagram.

In both the active and semiactive homing sys- shift is proportional to the range rate. The range tems, the missile receiving antennas and asso-rate, plus antenna turning rates and position, ciated equipment must be designed in such a wayare supplied to the autopilot, whichsteers the as to produce directional information whichwillmissile on a proportional navigation course to enable the missile to be guided to the target.intercept. To carry out this function, the receiving antennas are mounted in a gyro-stabilized hom- Antenna Drive ing head. The gyros provide the up-down, right- In some systems, the homing guidance an- left references on which the missile will base itstenna may use a form of conical (or nutating) maneuvers to approach the targetby the propor- scan in order to take full advantage ofthe guid- tional navigation method. ance signal.Conical scanning (fig. 8-6) has the advantage that the antenna can receive sig- Antenna nals from points off the missile axis. This decreases the chance that the missile, whilehom- Radar is generally used for semiactive homing, may lose its target and go out of control. ing guidance.The antenna in the missile mustThe drive unit keeps the antenna continually therefore be capable of detecting radiation atpointed at the target. radar frequencies. It is mounted in the nose of the missile, since information is being obtained from the target area and the missile is ap- Receiver proaching the target nose first. When a beam- A radar-type receiver must be used in the riding system is used for the intermediate phase missile when radar is used for semiactive hom- of guidance, a separate beam-rider antenna ising. The signals picked up by the antenna as it mounted near the tail of the missile. Some mis- scans the target area are fed into the receiver. siles with a semiactive homing system also have The receiver operates in a conventional manner a small antenna at the after end of the missile,as described in chapter 7.The signals at the rearward-looking, to receive illuminator energyoutput of the receiver are not suitable for use directly from the illuminator.radar. This rearin activating the missile flight controls without signal is used as a reference to which" the frontfurther processing. signal Is compared to determine the missile- target closing rate.This closing rate (rangeSignal Converter rate) is detected by measuring the Doppler effect which causes a frequency differencebetweenthe The receiver output is fed to the signal con- incoming front and rear signals. The Dopplerverter, which changes the signal to a form that

22420 . , .; Chapter 9HOMING GUIDANCE can be used for comparison with signals fromassistance from any other outsidesource. The another section of the missileelectronic equipment. semiactive homing system needssome source outside the target or missile in order toobtain Reference Unit course information. The advantage of the passive systemis that it needs no source of informationother than the The reference unit furnishesthe comparison signal. This information might target. The equipment carried by themissile is be placed in theless than that required for most othersystems. missile just prior to launching. Itcould b e stored in a variety of forms, such The disadvantage of the passiveguidance system as magnetic wires,is its dependence on the target. It is highlyun- magnetic tapes, punchedpaper tapes or punched cards. Before a guidance likely that an enemy would leave targetareas system can function,lighted, or permit electromagneticbroadcasting an error signal must be produced.The error in flight path, if from the target areas. any, can be determined by In the semiactive system, controlinforma- comparing the reference signaland the signaltion comes from a source outside the from the converter section. Comparison missileor of the target area. A semiactive homingsystem de- two signals takes place inother sections of thepends for guidance on equipment outside missile electronic equipment. the target area or the missile. Thisrequires extra Comparators equipment, both in the missile andat thelaunching or control point.Semiactive homing systems, like most guidance systems, The missile flight controls are subject may be used toto jamming and other forms ofinterference. correct the lateral or verticaltrajectory of the missile. Since it is possible for the However, antijamming devices inmodern missile tomissiles, and switching capability thatpermit be on the right course verticallybut off courseswitching laterally, two comparators to another method when the signalis are used. The outputjammed by the target, have greatly reducedthe from the reference unit and theoutput from theeffectiveness of jamming tactics. signal converter are fed to both thepitch and yaw comparators. Should there be no difference inthe two sig- ACTIVE HOMING GUIDANCE nals at either comparator, thecontrols would remain in neutral position.However, should BASIC PRINCIPLES there be a difference in the two signals ateither comparator, error signals will begenerated. The error signals The active guidance systemuses equipment are not suitable for use inin the missile to illuminate thetarget, and to controlling the missile flightsurfaces and mustguide the missile to the target. be sent to other sections of the (See fig. 6-8). guidance systemUsually, a radar set is used for targetillumina- before they can be used. tion. The signals return to the missileas radar echoes, which are processed foruse as guidance Autopilot signals.

The missile flight controlsurface operation MISSILE COMPONENTS is controlled by autopilots. Thesedevices area combination of gyroscopes andelectrical units The missile components inan active homing which have been described elsewherein this.guidance system include all those usedin a semi- manual. Theautopilot,controls operation of theactive homing guidance system, plusa radar hydraulic or erictric system which, inturn op- transmitter and duplexer. The principalcom- erates the flight control surfaces. Thereare two ponents are shown in the blockdiagramof figure autopilotsone for the pitch control surfaces9-15. and one for the yaw control surfaces. Antenna COMPARISON WITH PASSIVE HOMING The passive guidance system The antenna is the same as describedfor the obtains allsemiactive system; and is mountedinthenoseof guidance information frOm thetarget, withoutthe missile. 225 221 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

Antenna Drive Autopilot operated by When the target area is conicallyscanned, The missile flight controls are the powerthe hydraulic system, which isactivated by the the antenna driving unit provides for the needed for this purpose. autopilot in the same way as described semiactive system. Transmitter COMPARISON WITH SEMIACTIVE The transmitter carried in themissile isHOMING SYSTEM transmitter. It similar to a conventional radar The active homing guidance system maybe may use either FM orpulsed modulation. Since target can be homing guidance does not requirelong rangeused in any application where the be con-distinguished from the surrounding areaby the equipment, the transmitter power can radiation it reflects. Of course, the more prom- siderably less than that used for commandguid- the accuracy of ance or tracking. Themethod of modulating theinent the target, the greater transmitter can be changed frequentlyto lessenhoming guidance. countermeasures. An advantage of the active homingguidance the effectiveness of enemy system is its independencefrom any outside source of target illumination.At the same time, Duplexer this is a disadvantage becauseof the added equipment needed in the missile.Also, the system is The duplexer is a form of electronicswitch.subject to countermeasures.But this problem is In operation, it serves to connectthe antenna toless serious than it might be,because thehoming the transmitter during thesending of a pulse.guidance equipment is active foronly a relatively At the same time, it presents a highimpedancebrief part of the missile's flighttime. (electrical opposition) at the receiver input. This keeps the powerful transmitterpulse from INTERFEROMETER HOMING damaging the receiver. As soon as the pulse is transmitted,the du- Interferometer homing is homingguidance in plexer then offers a low impedancepath fromwhich target direction isdetermined by com- the antenna to the receiver. Theaction of theparing the phase of the echo signal asreceived duplexer provides an automatic switqhing means at two antennas precisely spaced afew.wave- so that the same antenna canbe tiSed forbothlengths apart.The interferometer is a device transmitting and receiving. for measuring interference, usingthe interference as the measuring tool.Acoustic inter- Reference Unit ferometers measure velocity andattenuation of sound waves in a gas or liquid.The Michelson The reference unit in the activehomingguid-stellar interferometer solves theproblem of ance system serves the same purposeas those inmeasuring the diameter of starstoo small or the passive and semiactivehoming guidancedistant for telescopic measurement.Various systems. other interferometers are used forother exacting measurements. Signal Converter Missile pitch and yaw rates arecompared with the interferometer signal andthe difference The output of the receiver is fed tothe signalis used as the steering signal.Both active and converter, so that the reflectedsignal will besemiactive homing systems make useof the suitable for comparison with the outputof theinterferometer principle. reference unit. The purpose and operationof the signal converter is the same as forthe semi- INTERFEROMETER PRINCIPLE active homing guidance system. To determine the target'sposition with respect to the missile, the receivingantenna Comparators system in the missile relies on theinterferometer principle.. To understand howthis principle The comparators serve the same purpose as 9-18.In this those in the semiactive system. is applied, first refer to figure 222 Chapter 9HOMING GUIDANCE

combined signal would vary at 4 cyclesper second, etc.Thus, by using the interferometer, we can determine both the direction and the rate TRANSMITTER of movement of the transmitter. Unfortunately, if the transmitterwere moved to the left in the foregoingexample, the same variations of the combined signal wouldresult. To allow the interferometerto determine whether a target is moving to rightor left, it is necessary to add a phase shifter toone antenna (fig. 9-17). The phase shifterprovides the effect of scanning the antenna B sensitivitylobes at, for example, 200 cyclesper second. With the transmitter on the center line, thesignal from antenna A will vary at 200 cyclesper second with respect to the signal from antennaB. Now, if the transmitter moves, the 200-cyclecom- ponent associated with antenna B willincrease or decrease to indicate the direction of target LOAD motion.If the target moves to the right,for example, this component might increaseto 201 cycles per second.If the target moves to the left, the component might decreaseto 199 cycles 33.170per second. Figure 9- 16. Interferometerprinciple. With the phase shifter included intheantenna system, the missile cannow detect changes in target motion to the right or leftas well as the figure, a pair of stationaryreceiving antennas (A and B) are receivinginformation from a transmitter. located equidistant fromthem (at point 1). (The transmittercan be considered to be relaying reflected radar energyfrom a target.)Since the antennasare equidistant from the transmitter, the signals fromthe transmitter will arrive at the two antennasin phase. The signals will therefore addacross the load to produce a resultant signal of maximumampli- tude. If the transmitterwere now moved to point 2, the differences in distancefrom the transmitter to the antennas wouldcause the signals to arrive at the antennas ina different phase relationship, thereby resulting ina different amplitude of the combined signal.If we continue to move the transmitter to the right, the amplitude of the combined signals willvary sinusoidally. PHASE SHIFTER We can thereforesay that the direction of the transmitter from the antenna systemcan be determined by the amplitude variationof the combined signal. The RATE of transmittermovement will cause the combined signal to vary ata specific rate. For example, if the transmitterMoved to the right at 4° persecond,, the combined signal 33.171 might vary at 2 cycles per second. Asthe trans- Figure9-17.Interferometer with phase mitter moved to the right at 8°per second, Ma shifter on antenna B. PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS rate of target motion in either direction.To de-described are produced by LOS rotation, the missile accepts these signals and generatescontrol tect target motion in the vertical, the same : principles are involved in installing a separatesurface correction signals which tend to reduce antenna system and phase shifter in themissilethe LOS rotation rate to zero. When thishas nose, one antenna being locatedabove the other.been achieved, the missile will be on a collision You will remember from the early part ofcourse with the target.Any changes in target this chapter that proportional navigation wascourse and speed will beimmediately sensedby resultantthe antenna system in the missile, and further based on a nonrotating LOS. Since the 6 signals produced in the antenna systemJustcorrections will be made as necessary. ti

V 4 CHAPTER 10

_OTHER GUIDANCESYSTEMS

PRESET GUIDANCE It may also be used forone phase, usually INTRODUCTION the initial phase, of the trajectoryof a missile. In setting up a flight plan forpreset guidance, missile speed is used to determine In earlier chapters we describedguidance . the systems in which the missiletrajectory de-required time of flight. Assume, forexample, pends on information receivedfrom one orthat a missile is to be firedat a target 500 more control points, or from the target itself. miles north of the launching site.The direc- But, under certain conditions,these systemstion and distance of the targetfrom the launch are impractical.This is especially true for site have been accurately determined.Assume long-range missiles.In this chapter, we willthat the speed of the missilecan be controlled, discuss several guidancesystems in whichor at least can be predicted with enoughaccu- the missile is independentof control points racy to program the flight. and target signals. If we assume an average missile Perhaps the simplest of theseis the PRE- speed of 2000 miles per hour, the missile wouldrequire SET GUIDANCE system. Inthis system, all the 15 minutes to travel from the launch information needed to make themissile follow a site to the desired courseand terminate its flight at target. The built-in control system wouldtake a the missile to cruising altitude, keep itheaded desired point, is set into themissile before itnorth for 15 minutes, and then is launched. This informationincludes the de- move its flight surfaces to make it dive straight downon the sired heading, altitude, timeor length of thetarget. flight, and programmed turns (if any). The preset missile isPROGRAMMED to Preset guidance has severallimitations. carry out certain functions along its flightpath. Such things as headwinds and crosswindswill Examples of the functions whicha preset mis- obviously affect the speed andcourse of the sile may carry out are changes ofcourse and missile. To compensate for the effectsof speed, arming of the warhead, andcommencing wind, the missile needs somemeans for meas- a dive on a target (terminal phase). uring its ground speed, and for changingits air In the preset missile, informationrelating speed. as required. But,. when solid fuels are to the target's location mustbe set into theused, changing the air speed of the missileis missile prior to launch. The positionof the difficult. launching site must also be knoWn with accuracy. Crosswinds may exist atone altitude but With this information known, thepreset functionsnot at another. Thus, the altitude at enable the missile to attain theproper altitude which a and course, measure its missile operates may .have a pronouncedeffect own airspeed, and, at on its course. If the effect of windon missile the correct, time, initiate the terminalphase of flight. heading cannot be controlled by choiceof altitude, then, it must be controlled by Preset guidance may be usedwhen the tar. programmed get is beyond the range of steering of the missile. One of thegreatest .control points; orliznitations of .a preset guidance systemis that when it is necessary to avoidcountermeasuresthe flight* program cannot be such as limn-ling of radioor radar signals, that changed after the might be effective 'if the missile.were missile is 'launched. Therefore,precise infor- guided by mation on winds along the missileflight path outside signals. *needed for accurate programming. ...229 225 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

The moat publicized preset guidedmissile,only after a specific altitude has been reached, the German V-1, achieveddevastating successthis altitude being determined by an altimeter. in spite of its limitations(until the BritishAs another example, missile booster separation found a way to intercept it). may be scheduled to occur 6 secondsafter launchor it may be programmed to occur at INFORMATION SET IN THE MISSILE the point that a certain thrust accelerationhas been achieved. Coui ae and speedchanges as The initial course, or heading, of a missilewell as other functions can be carriedout with may be preset by training the launcher totherelation to the elapse of specified timeinter- proper bearing. This operation is of coursevals or on the occurrence of other preset con- similar to training a gun mount. Some missilesditions. may be fired vertically, and thentskethe proper Depending on the objectives of a missile course on the basis ofprogrammedinformation.using preset guidance, various timers,speed Once the missile is started on the correct head-measuring devices, etc., have been devisedto ing (initial phase), its own control equipmentenable the missile to carry out the preset func- takes over. tions. Many of these devices may also befound Physical references such as gyros andin missiles which are not of the purelypreset magnetic compasses may be used to determinetype. For example, a homing guidancemissile, deviations from the preset course and to keepalthough not classified as a preset missile, may the missile on the correct heading. be equipped with one or more of the devices. The missile altitude may be corrected by Various types of timers used in missiles changing the pitch of the missile. A barometer-were described. and illustratedin chapter 5. type sensing element is Connected to a servoThe timing system in a missile activates a mechanism that operates theflight controlseries of actions from prelaunch to targetin- surfaces. When the barometric pressure changes.terception. because of a change in 'altitude, the servo acts It is reemphasized that the preset missileis to bring the pressure back to the preset value bydistinguished from other types of missiles in correcting the missile's altitude. Although thisthat there is no electromagnetic radiation con- method of altitude control is not extremely ac-tact between the control point and the missile curate, the control pressure can be preset toand that ALL missile functions are programmed. fairly close tolerances before the missile isHEADING REFERENCE launched. One of the most precise components of a The use of the term "reference" with regard preset guidance system is its timing section.to missiles was explained in chapter5.The Accurate timing elements are available to fitmissile control systems must have areference almost any requirement. The distance coveredfrom which to measure the up-down orright- by a missile during its flight is determined byleft deviation of the missile. Since thedesired its ground speed and the length of time it is inheading is a compass direction, the sensing the air. Therefore if the speed of the missileunit may be a form of compass. is known, the controls may be preset to dive The flux valve and its uses in control the missile at the end of a definite time inter-systems were described in chapter 6. If mag- val after launching. The timing element can benetic headings are to be followed, theflux anything from a simple watch movement tovalve may be used as the sensingelement. an electronic circuit controlled by atuningBy using a time reference in combination witha fork or a crystal oscillator. The time intervalmagnetic reference, the missile controls may may be set at, any time before launching,butbe preset to follow a single heading for the re- of course it cannot be 'changed during.flight. quired time. Or changes in heading can be It is 'important that you realize at this pointprogrammed to occur at preset nines. that the actions carried out by -4 missile in The electrically driven gyro is another type flight may be preset to occur either. after aof heading control. The gyro's spin axisis certain amount of.TIME his elapsed; or when atangent to:the earth's surface. At the time of certain CONDITION has.been achieved. launching, with the gyro wheel spinning rap- For example, a niiseile may be programmedidly, the axis is pointed in thedesired direc- to assume level flight' 30 seconds afterlaunch-tion before the gyro is uncaged. During the or it may be progranimed to assumelevel flightMissile flight the gyro axis continues to point

226 .:230 Chapter 10OTHER GUIDANCE SYSTEMS in the original direction, and themissile can therefore use it as a steering reference. Generally, an air log is attachedto the outer surface of the nose of themissile, and The function of gyros inmissiles wasconsistsofa smallfour-bladed impeller described and illustrated in chapter 5. mounted on a shaft that drivesa reduction ALTIMETERS gear with a ratio of 30 to 1; that is, forevery 30 revolutions of the airscrew, the driven In previous chapterswe have shown that angear makes 1 revolution. altimeter can be used to control missilealti- The driven gear is made of insulatingma- tude within small limits. Altitude controlis anterial, and carries a pair of contactsmounted important part of preset guidance, sinceit isat diametrically opposite points. Thesecon- possible to get favorable wind directionor avoidtacts close a magnetic relay circuit twicein unfavorablewinds by choosing thepropereach revolution of the gear, oronce for each altitude. 15 revolutions of the airscrew. With supersonic missiles it is important The magnetic relay is connected toa device to get the missile above the earth'satmospherecalled a digital indicator (originally calleda into the higher regions where the air isthinnerVeeder counter). The counter mechanismis and the pressure is much less,so that the mis-similar to that of the total mileage indicator sile can fly faster and farther. Thetrajectory(odometer) of an automobile. The counteris of the missile is dependent toa great extent onshown in cross-section in figure 10-1. the altitude at which it flies, and thealtitude To use the air log for length-of-flightregu- set for it is determined in pilot by the distancelation, the calibrated drums are turned to to the target. a setting that represents the desired distanceof The reference for preset altitude controlistravel for the missile. Each time the contacts normally a potentiometer in onearm of aof the magnetic circuit close, theytrip the bridge circuit.A potentiometer in an adjacent arm of the bridge is operated by apressure- sensitive bellows system. The bridgecan be preset for balance at the desired altitude.When VEEDER 4 FROM AIR LOG the missile reaches the presetaltitude,its COUNTER flight control surfaces will bring it intolevel flight.Any subsequent change inpressure will unbalance the bridge, and the amountand direction of unbalance will determine thecorrection to be applied. This systemwill be described in more detail later in thischapter. The two basic types of altimeters,barometric pressure altimeters and absoluteor radar altimeters, were discussed in chapter5. An altitude transducer isan altimeter with an electric output. Because of its simplicityand accuracy, the altitude transducer is usedas the primary altitude controlor reference in even the latest guidance systems. LENGTH OF FLIGHT In 1mi-speed missiles an AIR LOG,as well as a timing device, can be used to measure the distance covered during missile flight.The air log operates on the principle ofan air screw, or impeller which makes a specific number of revolutions while moving through lie air fora given distance at a given speed. The number of revolutions per unit of distance depends on both 144.45 the pitch of the blades and the densityof the Figure 10-1.Mechanical digital indicator, air. cross section.

1631 227 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS counter mechanism, thus indicating that acertain During the launching period, highacceler7 specific distance has been traveled.Each timeation puts a great strain on normalguidance the mechanism is tripped, it moves thedrumscomponents and prevents their use. The ac- back one digit from the preset figure. Whentheceleration forces may close relays, precess count reaches zero, the predetermineddes-gyros, an.d saturateaccelerometersiar beyond tination has been reached. This maybe eitherthethesensitivity needed for normal guidance. point where the warhead is to be detonated, orFor this reason, most midcourse guidance the point at which the missile is to start itssystems must be modified extensivelyto with- terminal dive on the target. stand the launch acceleration. Themodification may involve the use ofcomparatively insensitive Note that this method of measuring speed is the used for LOW SPEED missiles. components, or a temporary alteration of Figure 5-20 is a diagram of an airspeedregular components. reference and transducer unit, which maybe The precautions against high acceleration used to measure airspeed and to controlit. Seedamage to components include careful balanc- chapter 5 for a discussion of itsoperation.ing and positioning of elements that arenot used Transducers were also touched upon in chapterduring the launch cycle. In addition,movable locked 3, in connection with telemetering equipment. parts of regular guidance systems are The use of doppler radar to determine thein position, or the circuits in whichthey operate missile-target closing rate (rangerate) wasareneutralized to withstand the launch accelera- described briefly in chapter 9 for the homingtion. system. Doppler principles were explained in Missiles are designed to have sufficient chapter 8. The doppler signal varies directlyflight stability during the initial periodof high theacceleration, before the regular guidance sys- with the range rate. The application of system mechanical,electrical, and electronic com-tem takes over. The regular guidance ponents to measure the doppler frequency,may be unlockedby an internal timer or it filter out noises, amplify the differencefre-may be activated when theboostersection, if quency, and supply the informationto the com-any, drops off. puter vary with the missile system. Anelectronic A preset guidance system might beused for the midcourse part of a flight.When used circuit called a speedgate locates the doppler system signal, acts as a bandpass filter, and closelyin a composite system, the preset 7 follows any frequency shift in the signal.Thewould turn the missile control over to a sepa- range rate information gainedfrom the dopplerrate terminal guidance system whenthe mis- signal is fed to the autopilot to keep the missilesile approaches the target. In anapplication on course. (A "gage" in electricaland electronicof this type, the preset guidance systemmight terms is a circuit that permits anothercircuitbe set up to take over control againin the event to receive input signals only at 'set intervals,the terminal guidance system did notoperate. or only when a certain setof input conditionsThen, when the missile reached the approxi- have been met. The appropriate combinationmatelocation of its target, the preset guid- of "gating pulses" opens the gate.) ance system would eitherdetonate it or cause it to dive, depending on the setting. We've mentioned World War II missiles that used preset guidance or a combinationof USE IN COMPOSITE SYSTEMS guidance methods. Of later vintage is the Corporal, an .Army surface-to-surface nuclear A composite guidance system is made upweapon deployed in Europe(being replaced by the of two or more individual guidance systems.Sergeant).It uses a combination of preset and These systems may work' together during allcommand guidance. (The Corporal missile will phases of the missile's flight, or they may bebe used for other purposes, with adifferint programmed to operate successively.It istype .of warhead.) sometimes necessary_to combine systems be- Most missiles have some values preset into cause of the wide differences inrequirementsthe guidance system, although the preset values that must be met to ensure that the missilemay not control the whole flight.The time of reaches the target.Let us review these re-booster cutoff, for example, is a preset time quirements, to see how preset guidance mayas determined for a givenmissile, although be used in a composite system. the missile may be a beam rider. Before the 228.2V = A p

Chapter 10OTHER GUIDANCE SYSTEMS

missile is launched, a timer in it is setfor the calculated period.

BALLISTIC MISSILES

ELEVATION 45. Our best known ballistic missile,the Polaris, MAX. R NGE makes use of a number of preset values inits course. It therefore seems appropriate to discuss ballistic missiles Immediately after preset guidance systems. A ballistic missile isa missile which, during a major part of its flight,is neither guided nor propelled. During thispart of the 12.3 flightitfollows a free ballistic trajectory, Figure 10-2. Theor etical trajectories at like a bullet or a thrown rock. Anumber ofvarious gun elevations (ignoring air resistance). factors operate to determine thetrajectory of a bullet, a rock, or a ballistic missile. These factors include the point of origin, theinitial direction and velocity, airpressure, wind, and .. other factors. discussed in chapter2 of this ,. . TRAJECTORY Y text.If all of these factors are accurately ...... %./ IN VACUUM known, it is possible to calculate thepoint at ee . which the ballistic .object will strikethe earth. TRAJECTORY And, if the desired point of impactis a target IN AIR % at a known location it is possible,for any given HORIZONTAL launching point, to calculatean initial course and velocity that will result ina hit. The matter of "leading"a moving target in TRAJECTORY order to hit it was explained ina previous IN AIR chapter.If you have had any target practice you know that there are several factors to calculate when aiming at a stationary target and additional problems when thetarget is moving. YoU know about "allowing for the wind." The effect of the .wind varies, ofcourse, with its strength and direction. The forceof gravity steadily pulls the, projectile downward,so you have to raise your gun and aimabove the target to offset the downward pull. Thegreater the angle of gun elevation,. thegreater the rangeup to a point. Temporarily ignoring 12.4:.5 air resistance, we find thatrange increasesFigure 10-3.Comparison ofvacuum and air with the angle of launcher. orgun elevation, up trajectories: A. In range; B. In elevation.

to 45 degree;-, After , that point, increasing the elevation increases the height reached bythethat the missile is launched vertically.Since projectile, but decreases ..therange. Figurethe Polaris passes through 10-2 more than one shows. some. theoretical trajectories.atomospheric region, the effect of thedifferent Figure 10-3 compares trajectories in air .andinconditions upon the trajectory must becal- vacuum. Since many of our missiles have partculated. The proportionate differences between of their Arajectory through higher akeas oftheair and vacuum trajectories, representedin atmosphere where. the. pressure is very lowfigure 10-3 are not accurate for allprojectiles (not a complete. vacuum);.theeffect on the tra-or missiles because the effect varies with jectory must be calculated. Refer. to.figurecharacteristics of the object.It does show 2-24 (trajectory of the Polaris missile)..Notehow drastically air resistance affectstrajectory.

229 gooJo. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

A fourth factor that affects trajectory is drift, The foregoing discussion of preset guidance which is a product of the interaction of threeapplies principally to aerodynamic missiles, other factorsthe spin of the projectile,thein which the control surfaces are capableof force of gravity, and air resistance. These causecorrecting the trajectory throughout theflight. the projectile to veer toward the right orleft,But preset guidance has features that makeit and is determined by the direction of spin. useful in the initial control of ballisticmissiles. One possible ballistic systemcombines The fifth factor that distorts the trajectoryfeatures of both preset and command guidance. is the earth's rotation and curvature(reallyAnother combination is preset with inertial two separate factors). For most gun projectilesguidance for the guided portions of the tra- it makes little difference; but for long-rangejectory.The problem has already been stated: missiles both effects must be entered into thefrom known factors, it is possible tocalculate computations for missile trajectory. The de-an initial velocity and directionthat will produce flection in the flight path is known as the Coriolisa ballistic trajectory endingat the target. The effect.It affects the time of flight, the lateraltarget location is known; because of the great deviation, and the range deviation.In therange,target location isdetermined from northern hemisphere the deflection is to themaps, rather than by observation.The loca- right; in the southern hemisphere it is to thetion of the launching point is also known.In left. the development of the Polaris missile system, The mass of calculations necessary for eacha majOr part of the total effort wasdevoted to shot is performed by computers. Many of thedevelopment of a Ship's InertialNavigation calculations are performed in advance andSystem (SINS), by which the Polaris launching tables set up to be applied as needed.In ship can determine its own position with the modern missile systems the application of therequired accuracy.Note (fig. 2-24) that only calculations is also doneby computers. Remem-the laststage of the Polaris trajectory is ber, however, that the computer does not think;ballistic. it can work only with what is put into it. But other factors, such as air pressure and The ballistic missile presents a more com-wind at various altitudes, cannot be determined plex problem than a gun projectile.Its rangewith comparable accuracy. And, because of may be measured in thousands ofmiles, ratherthe extreme range, a small error in the initial than thousands of yards, and its initial velocitydirection or velocity will result in a large is lower than that of a gun projectile. Thus theerror at the target. Theballistic missile sys- forces that would tend to influence its trajectorytem deals with this problem by controllingthe have a much longer time to act.But, at longmissile's direction and velocity not at the in- ranges, ballistic missiles haveseveral out-stand of launching, but at a later timeafterthe standing advantages. First, they may leave themissile has risen above most of the atmos- earth's atmosphere completely; a large partphere, but while it is still within range of radio. of their flight is in space, where they cannot Ballistic missiles are launched vertically, be affected by wind or air pressure.Second, and climb straight up in order to getout of the they dive on the target at a steep angle,atatmosphere as quickly as possible. At a preset many times the speed of sound;this makesaltitude, the guidance system turns the missile interception nearly impossible. Finally, a bal-onto the required heading, with therequired listic missileis invulnerable to electronicangle of climb. The missile is tracked, con- countermeasures during the major portion oftinuously from the launching point, so thatits its flight.Any guided missile is subject toposition is known as long as it is withinradar jamming or deception by electronic counter-range. Its instantaneous velocity canbe deter- measures, although coded guidance systemsmined either by establishing a range rate, or may make this difficult, to do.But a ballisticmore accurately, by doppler ranging.In the missile, becauseitis unguided during thedoppler ranging system, a radio or radar signal terminal phase of its flight, is no more sus-is transmitted from the launching point.This ceptible to electronic countermeasures thansignal is received and re-transmitted bythe is a gun projectile or a rock. missile.By comparing the frequency of the original signal with that of the signal returned The ICBMs are, as the name tells you, the ballistic missiles.Tliese include Atlas, Minute-by the missile, it is possible to determine man, Thor, and Polaris. missile speed with great accuracy. 230 Chapter 10OTHER GUIDANCE SYSTEMS

There are a number of combinationsof mis- of Newton's second law of motion.This law, sile course, position, and speedthat wouldwhich relates acceleration, force, andmass, result in a ballistic trajectoryending at thestates that the acceleration of target. a body is di- But because the missile is Constantlyrectly proportional to the force applied,and changing position at high velocity,no humaninversely proportional to themass of the body. computation can keep up with the problem.The These devices, accelerometers,were described known factors (position of the targetand launch- and illustrated in chapter 6. ing site, and preset heading ofthe missile) and The three accelerometers (fig. 6-9)are the measured factors (velocityof the missile,usually set up with the sensitive axis and its position relative to the launching site) of one of are fed into an electronic computer, which them vertical and the other two in thehori- pro-zontal plane, one along the flight path andthe duces a continuous solution forthe instantan-other at right angles to it.The output of the eous values of the problem.When the com-onealong the flightpath is the distance puter determines that the missile'scourse, traveled in range.If the output of the one at position, and velocity will resultin the properright angles to the flight path is maintainedat ballistictrajectory, the missile propulsionzero, then the missile is on the desired path system is instantly and automaticallyshutin azimuth. The vertical accelerometer down. keeps The last stage of the missile thenfol-the missile at the desired altitude (somemis- lows a ballistictrajectory,without furthersiles use a barometric altimeter). propulsion or guidance. With an inertial guidance systema mis- This system can be used effectivelywith sile is able to navigate, from launchingpoint missilespropelledby liquid fuelrockets,to target, by means of a highly-refined since the propulsion system form can be shut downof dead reckoning. Dead reckoning issimply simply by stopping the fuel supply.If, likea Priiciiis of estimating your position from in- Polaris, the missile is propelledby a solidformation on:(a) previously known position; fuel rocket, the system cannot beused with- (b) course; (c) speed; and (d) timetraveled. out modification.Successful tests of propel-For example, assume thata ship's navigator lant cutoff and restarting have beenreporteddetermines his ship's position by astronomical for solid .propellant rockets. Applicationof this observations with a sextant. The ship'sposi- Method can make major changesin presenttion, and the time, are markedon the chart. management of propellant systems duringmis-Assume that the ;hip then travels forthree sile flight. A description of the guidancehours on course 024, at a rate of 20 knots. methods used in the present modsof PolarisFrom the known positionon the chart, the nav- may be foundinNavyMissile Systems,igator can draw a line 24° east of north, NavPers 10785-A. representing the ship's course. By measuringoff on this line a distance representing 60 nautical miles (20 knots times 3 hours), the navigator NAVIGATIONAL GUIDANCE SYSTEMS can estimate the ship's new position by dead reckoning.If the ship changes course, the In addition to the preset guidancesystemsnavigator will mark on the chart the point at discussed above, other guidance systemswhich which the change occurred, and drawa line do not depend on electromagnetic contactwith from that point representing thenew course. manmade sources are terrestrial,celestial, A missile with inertial guidancenavigates and inertial guidance methods.They werein a similar way, but with certain differences. introduced in chapter 6 with brief descriptionsIt determines the distance it hastraveled by of their principles. multiplying speed by time.But it can not measure its speed directly if it is traveling at INERTIAL GUIDANCE supersonic velocity outside the earth's atmosphere.However, it can use an accelerometer Inertial guidance is definedas a gUidanceto measure its acceleration, and determineits sygitem designed to projecta missile over aspeed by multiplying acceleration by time. predetermined path, wherein the pathof the missile is adjusted after launching bydevicesTo summarize: 7,--- "*holly within the missile and independentof velocity = acceleration x time outside information.These devices make use distance = velocity x time A35231 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

The acceleration, of course, is not constant.potentiometer output is a positive voltage; if It may vary because of uneven burning of thethe weight moves forward from the neutral propellant.It will tend to increase as the mis-point, the potentiometer output is a negative sile rises into thinner air. Positive (forward)voltage. For an integrator, we can use a acceleration will become zero at burnout.Ifsimple capacitor.During positive accelera- the missile is still rising at that time, it willtion, the capacitor will gradually take on a have a negative acceleration because of giavity;positive charge from the potentiometer. If the if it is still in the atmosphere, it will have aacceleration then becomes zero, the charge negative acceleration because of air resistance.on the capacitor will stop increasing,and will Acceleration will cause a constantly changingremain constant (indicating a constantspeed). speed, and changing acceleration will changeIf the acceleration becomes negative, the charge the rate at which the speed changes.If theon the capacitor will begin to drain off(indica- missile is to determine accurately the distanceting a decreasing speed). Thus the charge it has traveled under these conditions, itson the capacitor is the output of thefirst computer circuits must perform a double inte-integrator. gration.Integration is, in effect, the process If the first integrator output voltage is ap- of adding up all the instantaneous values of aplied to the grid of a vacuum tube, it can be changing quantity. The integrators are computerused to determine the rate at which current elements. flows through the tube and into a second ca- Both the accelerometers and the integratingpacitor. The rate of current flow at any instant circuits are fairly complex. But we can de-is proportional to the first integrator output, scribe a simple, hypothetical system that willand therefore to missile velocity at that instant. be correct in basic principles. Assume that theThus the charge on the second capacitor is the accelerometer (fig. 10-4) is a weight that canoutput of the second integrator, and represents slide back and forth along the axis of the mis-the total distance traveled up to any given in- sile. The weight is mounted between twostant. springs, which hold it in a neutral position Figure 10-5 is a block diagram of a simple when there is no acceleration.If there is ainertial guidance system. This system has two positiveacceleration(tending to make thechannelawcuie for lateral and one for longitu- missile go faster), the weight will lag aftdinal acceleration.It uses both the direction against the spring tension.If the accelerationchannel and distance channelto determine stops, the weight will return to neutral posi-missile position.Each channel contains an tion. If there is a negative accelerationaccelerometer and a circuit for double integra- (tending to slow the missile down), the weighttion.The accelerometeirs detect missile ve- will move forward from its neutral position.locity changes without the use of any reference Now assume that the weight is connected tooutside the missile.The acceleration signals a potentiometer, in such a way that the poten-are fed to a computer whichcontinuously pro- tiometer output is zero when the weight is atduces an indication of both lateral and forward the neutral point.If the weight lags aft, thedistance traveled by the missile.This is accomplished, in each channel, by integrating the missile acceleration signal to obtain a missile velocity signal.When this velocity signal is integrated, the result indicates the total dis- SCALE tance that the missile has traveled.This SPRING NOICATOR method of double integration is built into each channel. WEIGHT The actual electronic circuits used for integration are rather complex, but here again the basic principle is simple.In one type of 1 ACCELERATION VEHICLE integrator the input consists of a series of ..evenly spaced electrical pulses representing of time.The amplitude of each 144.46pulse is controlled by the accelerometer, so Figure 10-4.Elementary accelerometer, as to represent the instantaneous value of ac- spring-mounted. celeration.Thus the quantity of electricity in

26.2 Chapter 10OTHER GUIDANCESYSTEMS r

1 POSITION LATERAL ACCELEROMETER 110veLoaTy110

DIRECTION CHANNEL L______.______1 .1 Moims 41J AUTO - PILOT AND CONTROLS

r DISTANCE CHANNEL 1

LONGITUDINAL 1 ACCELEROMETER

INITIAL VELOCITY 1 II J 33.135 Figure 10-5.Simple inertial guidancesystem. each pulse represents an incrementof speed. The pulses are passed through If the missile drifts offcourse, the output voltage a rectifier (soof the second integrator willshow, by its ampli- that no current can flow in theopposite direction) and stored in tude and polarity, the distance anddirection the a capacitor. The capacitormissile is off course. The outputof the first will, in effect, add up all of theinput pulses.integrator in the direction channel isthe direc- Thus the voltageacross the capacitor will, attion rate signal. Both of the integrator any giveninstant, voltages provide an indication ofare used by the autopilot to determine theamount missile speed at that instant. and direction of control requiredto bring the An accelerationmay, of course, be appliedmissile back on course. to the missile in any direction.Thus, if the The accelerometermeasures any force ap- missile is to determine itsown position at any given blatant, two accelerometer plied to the missile. The forceof gravity is channelsapplied to the missile throughout itsflight, and are necessary.For any given acceleration,some types of accelerometers will be affected one of these measures the component offorceby it. along the fore-and-aft missile axis; In order to prevent a falseoutput, the the othereffect of gravity must be neutralized,so that measures the component across that axis. only the true acceleration of The distance and direction the missile will channels arebe measured. This can be done in eitherof two identical in operation.The output voltage ofways. A part of the second integrator output the first integrator indicates themissile velocity. can be fed back to the input of the first integra- The output voltage of the secondin-tor, as in figure 10-5. Anothersystem com- tegrator is proportional to thedistance thepensates for the effect of gravity byapplying a missile has traveled. fixed voltage bias to the outputof the first integrator. Direction Channel Distance Channel. If the missile is on course, the output of The operation of the distancechannel is much the direction channel will bezero at all times.like that of the direction channel.The output

233 ..007 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS magnitude of the first integrator indicates mis-using a specified velocity signal.The speci- sile longitudinal velocity. The second integratorfied velocity signal is combined with the first output voltage is proportional to the distanceintegrator output so that any voltage above or the missile has traveled. If the system does notbelow the specified voltage is fed to the second start operating until after the launching phaseintegrator as an error signal. The output of is completed, the missile velocity at that timethe second integrator is then proportional to must be accounted for in the distance computa-the missile error from the desired position on tion. A separate signal, representing initialthe course. velocity, must be fed to the input of the second A third channel for measuring missile alti- integrator.It can then be combined with thetude is usually included in the system. The output of the first integrator to indicate missileprinciples of integrat ion of the vertical accelero- velocity at any given instant. meter output are essentially the same as for A comparison must be made between thedistance and direction. distance the missile has traveled and the known (In deriving missile velocity and distance, distance between the launch point and the target.the integrators are electronically solving two To do this, a voltage representing the distancebasic formulas which relate acceleration, ve- to be traveled is set up as an initial conditionlocity, distance, and time.) For example, if a just before missile launching.This presetmissile is traveling at a velocity of 50 yards voltage is combined, with opposite polarity,per second and experiences anacceleration of with the output of the second integrator. Thus8 yards per second per second for 5 seconds, the output of the distance channel decreasesits new velocity can be determined by the as the flight progresses. When the outputfallsformula v = v + at, where vo is the initial to zero, the target has been reached. velocity, v is the final velocity, a is accelera- There is one drawback to this systemthetion, and t is time. By substitution: fact that for flights of several thousand miles, 8yd very large integrator output voltageswould be v = 50sec-71 x 5 sec= 90yd/sec required to get an accurate indication of dis- sec tance traveled. The preset voltage that represents the target range would be equally largo. In order to keep these voltages within reasonable The average velocity of the missile during the limits, the voltage representing distance covered 5-second period of acceleration is equal to is continuously programmed during the flight by a suitable device such as a tape recorder. v vo The programmed distance is compared to the 2 measured distance, as represented by the computer output, in such a way thatboth are carriedor as reasonably small quantities. Figure 10-6 shows another method of keep- 90 yd/sec + 50 yd/sec-70 yd/sec ing signal voltages within reasonable limits by 2

DISTANCE AHEAD OR MOND DESIRED POSITION

144.48 Figure 10-6.Computer using specified velocity.

238234 , f, sq. s Chapter 10 OTHER GUIDANCE SYSTEMS

Tije distance traveled duringthis 5-second period is equal to earth, it was decided to relate twoof the accelerometer axes to these north-south andeast- west lines. The thirdaccelerometer islogically V+ vo oriented to the center of the earth. These rela- x t tionships are shown in figure 10-7. (Shipboard 2 systems need only two accelerometerssince altitude is of no consequence.) To stabilizethe or accelerometers so that they will maintainthese relationships throughout a long flightover a round and moving earth at first posed 90 yd/sec + 50 yd /sec a difficult x 5 sec =350 yds).problem. It was overcome by mountingthe ac- 2 celerometers on a GYRO-STABILIZED platform.Since gyros are inherentlyspace ref- An inertial guidance system,such as theerences (rigidity of plane), they mustbe adapted one just described, would be all thatwas neededto maintain the platform in the desiredearth if the missile flew straight and levelat allrelationships in this type of system. In other times.But outside factors, as wellas somewords, if three gyroscopes can be maintained errors introduced by the equipment itself,pre-in east-west, north-south, and the verticalat- vent straight level flights. Thereforea meanstitudes, the platform (and the accelerometers) for stabilization must be provided. can be kept in the same earth relationships For an inertially guided missile toconstantlythroughout the flight or cruise. With the platform determine its position while in flight,all linearstable, all movements of the accelerometers will accelerations of the missile must be measured. indicate ship (or missile) movement withrespect To do this, three accelerometersare mountedto the center of the earth. in the missile as shown in figure6-9. Any movement of the accelerometers with relationto Assuming that we have stabilized the plat- the missile will be proportionalto the outsideform, let us now see how a missilecan determine forces acting on the missile, andtherefore toits position and control its trajectory. the accelerometers of the missile.Since these For the missile to keep track of its posi- accelerometers are mountedon three mutuallytion,it must continuously determine itsac- perpendicular axes, any accelerationsof thecelerations and velocity along the threesta- missile along axis AB will be measuredbybilized accelerometer axes. Sinceaccelera- movement of the lateral accelerometer.Anytion is defined as the rate of change ofvelocity, accelerations along axis CD will bemeasuredthe process of INTEGRATION will yieldmis- by the longitudinally mountedaccelerometer.silevelocity.Integration is, in effect, the Any accelerations along axis XYwill be meas-process of adding up all of the INSTANTANEOUS ured by the vertically mountedaccelerometer.values of a changing quantity. If the missile is to determineits position at any point along its flight path, theacceler- ometers must be mounted in mutuallyperpen- N dicular axes which continuouslymaintain their same relationships with some fixed reference point. In some missiles and in shipboardinertial systems, the center of the earth istaken as the fixed reference point. Whenthe center of w the earth is used as the reference,alivehicular motion is determined on the basis ofaccelerometer outputs with reference tothat point. In this type of inertial systemitbecomesneces- sary to stabilize the accelerometer ikebso that they always maintain theirsame relationship with the earth's center. Since the linesof lati- 12.150 tude and longitude on the earth'ssurface bear Figure10-7.Orientation of accelerometers a- permanent relationship to the centerof the with reference to the earth. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS

Attitude Control controlled platform. The gyros are arranged to detect errors in the pitch, roll and yaw axes Thus far we have considered the inertialof the missile. Thus the output of the gyros system from the standpoint of determining andwill indicate any departure from stable flight. correcting missile positionin a coordinateThe error signal voltage is amplified and fed system which is stabilized in reference to theto a servomechanism that corrects the platform earth. As mentioned earlier, this coordinateposition. system is maintained by mounting the three The accelerometer platform canbe stabilized accelerometers on three mutually perpendicularby mounting the platform in a gimbal system axes on the gyro-stabilizedplatform. Anyprovided with gyroscopes (fig.10-88,insert). linear deviations along the missile AXESOF Chapter 5 in this text explained how the TRANSLATION will be detected by accelero-gyro may drift because of bearingfriction. meter movement and corrected on the basisAccuracy requires that compensation for gyro of the accelerometer outputs.In addition todrift be provided. The compensation is obtain- correcting for deviations in position, we musted by adding an integrating loop to the system also keep the missile at its proper attitude along as shown in figure 10-9. the trajectory. By mounting pickoffs on the Two loops are shown, one representing fast missile frame, any deviation in roll, pitch,control and the other representing slow inte- or yaw will be detected with referenceto thegration.Both loops use the gyro error voltage stable platform. The resulting attitude signalsas a control signal.The fast loop functions are related to the missilepositionalinformationrapidly to correct platform deviations from a generated by the accelerometers.We canlevel condition.The slow loop sums up the therefore say that the correction signals gen-gyro drift error signals duringthe complete erated by the computer network of the missileflight, because it cannot respond to rapid var- are composed of corrections alongthe axes ofiations.During a normal flight, the random translation as detected by the accelerometers,drift from a straight, level condition maybe and corrections about the axes of rotation asfirst to one side and then to the other. As a determined by .missile angular movement withresult, the sum of random drift over the entire relation to the stabilized platforin. These cor-flight will usually produce only a small total rection signals will then be applied to thecon= error. troller in such a way as to keep the missile Pitch Correction for Earth's Curvature. on its proper trajectory AND inthe proper attitude throughout the flight. The provision for keeping the platform level and preventing drift introduces a new problem. Stabilizing the Platform A normal missile trajectory is an elliptical path above the earth's surface.The gyro's Up to this point we have assumed that thecharacteristic of being fixed in space would platform has been stabilized with reference tomean that the gyro stabilizedplatform could the earth.For a shipboard inertial system,be tangent to the earth's surface at only one the exact position of the ship must be knownplace(fig. 10-10A), at the time of launch. at the time of missile launch.It is thereforeUnless it is corrected, the missile might con- necessary to keep the Shipboard InertialNavi- clude that the line DE (fig. 10-10A) is tangent gation System (SINS) stabilized with referenceto the earth's surface.In order to keep the to the -center of the earth at all times. Thisplatform tangent to the earth as the missile is done by torquing the platform in accordancetravels along its trajectory, the forward edge with theship's movements over the earth.of the platform must be depressed at a rate Chapter 5 presented the effects of apparent gyro-proportional to the velocity of the missile scopic precession attheEquator. The characteraround the earth.This keeps the platform of the apparent, precession exhibited by a gyro-level about the pitch axis with respect to the scope as the earth turns depends on the gyro-surface of the earth, as shown in figure10-10B. scope's location on the earth's surface AND the Normally, gravity is used as a reference for angle that its spin axis makes with the spinslaving the gyro. But this is not done in an in- axis of the earth. ertial guidance system. Instead, the platform is Figure 10-8A shows how accelerometers may maintained in a level position by dividing, be stabilized by mounting them on a gyro-.4.in the computer, the measured missile velocity Chapter 10OTHER GUIDANCE SYSTEMS

YAW GYRO

PITCH GYRO

ACCELEROMETERS FLIGHT

PLATFORM ROLL GYRO

144.49 Figure 10-8.A. Basic gyro-stabilized system; B. Stabilization of accelerometer platform.

4Thintettl'(' 2.10 SLOW INTEGRATING t4'40 J'/°"4"'lfr,7441 LOOP 1.4?

ERROR SIGNAL

144.51 Figure 10-9.Gyio-drift compensation. by the distance between the missile and theThis precession is brought about by equipment center of the earth. The result of this divisionin the computer section of the missile control is a function of the angular velocity of the mis-system. sile. The geometric relationship of the velocity factor is shown in figure 10-11. A study .of the In operation, the output of the first integra- diagram will show that if the pitch angle of thetor, which is proportional to the missile veloc- platform is changsd at the same angular velocity, ity, is divided by the distance (R in fig. 10-11) the platform .will remain tangent to the earthto the center of the earth in order to give the as the pitch axis changes. The platform angleMissile angular velocity ANY in fig. 10-11) in can be changed by precession of the pitch gyro.radians.The result is fed through the gyro

..241 7 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

NO PRECESSION GYRO PRECESSION PRECESSION

EARTH EARTH

ONE POINT OF TANGENCY TABLE TANGENT AT ALL POINTS

A . 1 144.52 Figure 10-10.Pitch gyro precession for tangency with the earth: A. Gyro not depressedno precession; B. Gyro depressed at rate proportional to missile speed around the earth.

R = DISTANCE TO EARTH'S CENTER

Re = RADIUS OF EARTH

h = ALTITUDE OF MISSILE (DISTANCE IN NAUTICAL MILES)

v = LINEAR (OR TANGENTIAL) VELOCITY IN KNOTS

w = ANGULAR VELOCITY IN RADIANS

vt=V/R 0= ANGLE CREATED IN TRAVELING FROM x to x' 144.53 Figure 10-11.Applying angular velocity to platform leveling. torquer to precess the gyro at an identicalother sections of a complete control system can angular rate. take many different forms. Individual devices It would be possible to make similar cor-may be mechanical, electromechanical, elle- rections for roll axis motion.The error. intronic, or a combination of these types. tangency would be small, however, because the missile moves such a small distance to either TERMINAL INERTIAL SYSTEMS side of the desired course in comparison to the total length of the flight. Therefore, a simpler Short-range missiles that are transported to process is used to correct for roll. Instead ofthe vicinity. of the target, such as air-to-air leveling a Platforin, a prOportionallialvoltageMissiles and antitank missiles, do not need more is applied to the accelerometer to correct itsthan one type of guidance system. Longer range output sigSal. missiles may combine the midcourse phase and Previout chapters of this text have shownthe terminal phase of guidanCe. Main missiles that accelerometers, gyros, computers, andintended for long-range use that the midcourse

238 ..242 Chapter 10 -OTHER GUIDANCE SYSTEMS

and. terminal phases of guidance are distinctinoperative, and the terminal guidance system and more than one method of guidancemay be takes .over.There are two specific terminal used. As the range of the missile systemin-inertial guidance systems.They are known creases, the missile-to-target miss distanceas the constant-dive-angle system and the zero- tends to increase for both beam-riderand com- lift system. mand techniques.If the miss distance becomes excessive, a more accurate ,terminal guidance phase may be necessary. Ina numberConstant-Dive Angle of air-to-air and surface-to-air missiles,homing guidance is used in the terminal phase. A block diagram for a constant-dive-angle Falcon and Sparrow are two examples.It issystem is shown in figure 10-12. This equip- in the long range surface-to-surface missilesment is able to compute the missile's position, that combined systems are most useful.The during the dive to the target, with respect to the function of any terminal guidance system is torelease point. place the missile directly on the target, rather than just in the general vicinity of the target. The output signals from the accelerometers Thus, an accurate terminal guidancesystemare changed to velocity signals by the integra- can compensate for minor inadequacies in thetor.In the direction channel, signals then midcourse guidance system. undergo a second integration to convert them into signals representing position. For a In this section, we will discussa terminalconstant-dive-angleapproach,thedistance inertial guidance system. This systemuses achannel does not need position-error informa- stabilized platform as a reference plane tocarrytion.It therefore has only one integrator. the accelerometer sensors fora constant-dive- The velocity signal is sent to the pitchservo angle system. system.If the velocity signal has the correct value, there will be no output from thecom- The terminal guidance phase starts ata point puter to the pitch servo.If there is an error in space known as the release point.This issignal, it is fed to the pitch servo, which then where the midcourse guidance system is madecorrects the dive angle.

STABILIZED YAW LATERAL DIRECTION TO YAW PLATFORM SERVO ACCELERATOR COMPUTER SYSTEM CONTROL SURFACE

LONGITUDINAL ACCELEROMETER. TERMINAL EQUIPMENT

PITCH DISTANCE TO PITCH SERVO COMPUTER SYSTEM CONTROL SURFACE

MNI

MISSILE MISSILE 'PITCH CHANNEL VERTICAL OF MISSILE AUTOPILOT EQUIPMENT GYRO AUTO PILOT

144.54 Figure 10-12.Constarit-diie-angle system formissiles.

243230. ''t

PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Vertical-Dive System The vertical-dive system is a variation of the constant-dive-angle system. The principal difference between the two is the location of the A release point with respect to the target po- , sition.The constant-dive-angle system has LONGITUDINAL AXIS the dive starting at a considerable lateral distance from the target. The system then sets up a constant-dive-angle which is maintained all (WHICH PULLS THE the way to the target.The vertical-dive sys- MISSILE OFF THE VERTI- tem release point is almost directly over the CAL FLIGHT PATH ) target, so that the missile can dive straight down. The nose-over maneuver is accomplished by processing the vertical gyro of the missile autopilot about its pitch axis. While there are a number of factors that determine the amount and rate of precession of the vertical gyro, the A dive angle path to be followed is the primary factor in determining the number of degrees of vertical precession. The angle of incidence ANGLE OF _jL. of the wings is another factor.This angle of INCIDENCE incidence introduces a dive trajectory problem as shown in figure 10 -13.L'aoldng at figure 10-13A, we see that if the missile longitudinal. axis were absolutely vertical, there would be some lift from the wings, which would pull the missile out of its vertical dive. In LONGITUDINAL AXIS order to compensate for the lift of the wings, OF THE MISSILE the controls are set for a slight over-control, so that the lift from the wings will keep the missile in a vertical dive (fig 10-13B). When the pushover arc is completed, the missile is at the dive point.The autopilot is then cut off from the yaw and pitch servos, and has no further effect on the missile flight con- B trol surfaces.

Zero-Lift Inertial System ANGLE OF INCIDENCE FLIGHT MTH The block diagram in figure 10-14 shows the zero-lift, inertial system and the relation ANGLE OF ZERO LIFT between it and the missile autopilot.This equipment has two functions.The first is to 144.55 establish the flight path, which is programmedFigure 10-13.Missile dive attitude: A. Missile on tape. The programmed pulses drive a diverted from vertical path by lift of aerody- constant-speed motor, whoie rotor drives the namic surfaces; B. Over-control of missile is moving arm of a potentiometer. The second offset by lift to keep missile on vertical flight

function is to keep the . missile sjhe pro- path. grammed path through the action of the accelerometer. to the other end at a constant rate of speed. To accomplish the first function, the mov-Then, if the voltage between the moving arm ing contact of the potentiometer must be movedand ground is plotted against time on a graph,

from the ground end of the 'resistance .stripthe result will be a straight line.When this 244 240 Chapter 10OTHER GUIDANCE SYSTEMS

MISSILE AUTOPILOT EQUIPMENT

VERTICAL PITCH CHANNEL PITCH TO PITCH OF MISSILE AUTOPILOT SERVO GYRO CONTROL SYSTEM SURFACES TORQUER MOTOR

TERMINAL EQUIPMENT

POWER MISSILE AMP ACCELEROMETER DYNAMICS

RELEASE CONSTANT SIGNAL REFERENCE SPEED MOTOR FROM MIDCOURSE GUIDANCE VOLTAGE EQUIPMENT

144.56 Figure 10 -14. Zero -lift inertial system. straight-linestraight -line voltage is fed into a motor, theerting some lift due to a programmed signal, rermitAnt displacement of the motor's rotor isanthe signal from the accelerometer adds to iesgrAiion of the input voltage.Because thethe programmed signalin the mixer stage intogral of a constant-slope line isa parabolicand causes the gyro to precess at a faster rate. curve, the missile path from the release pointIf the missile noses over too far, there will be to the target will be as shown in figure 10-15.negative lift and the accelerometer sends a This is a zero-lift trajectory, in which thecon- signalthat subtracts from the programmed trol system acts to maintain a condition ofnosignal in the mixer, and slows up thepreces- aerodynamic lift on the missile. sion rate of the gyro.Thus the missile flies With a parabolic path as a reference for thethe course shown in figure 10-15. pitch axis, the missile will try to follow that The actions just described provide the basis patch.However, because of the wing angle andfor the name of the system. The namezero- the ehgine thrust, the missile will actually flylift is used because the signal from the ac- a different path Idess some compensation forcelerometer compensates for any lift in the these factors is made. vertical axis of the missile. Compensation is provided by an accelerom eter that is mounted so as to be sensitive to accelerations along the vertical sixia/Aof theCELESTIAL-INERTIAL SYSTEM missile.Therefore, if the wings exerta lifting force, the accelerometer senses the lift Celestial navigation has been used for many and originates a signal that corrects the ver-years.The navigator uses a sextant to meas- tical gyro precession.. If the wings areex-ure the angular elevation of two or more lmown

24141 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

The sextant is moved on two axes by motors. RELEASE These motors are connected to the sextant- positioning system. Figure 10-17 shows a sextant positioning system in block form. Note.that the elevation servo generator and the azimuth servo generator both receive signals.from the tape reader. The generators are connected to servo motors. The shafts of these motors are mechanically connected to the sextant positioning gears, so that the sextant position is actually controlled by the information on the tape. The desired flight path of the missile is programmed on a tape (fig. 10-17). The tape is pulled through a tape reader at a constant speed 144.57 by the drive motor. The signals onthe tape con- Figure 10-15.Flight path of zero-lift tain elevation and azimuth commands which are inertial missile. automatically fed to the sextant drive motors via servos. The tape is prepared prior to launching the missile and contains all the necessary posi- stars or planets. From these measurements,tion and rate data for the entire flight. To get a ship's position can be plotted. accurate position checks, the sextant azimuth The celestial-inertial navigation system usesand elevation information must be read from the a simplified approach to the problem.it usestape at the proper time. This is of paramount an inertialsystem that is supervised' by aimportance .since a. given star is at a particular series of fixes. One of these systems is known asangle with respect to a certain spot on earth only Stellar Supervised Inertial Autonavigator (SSIA)at a particular instant. another is called: The position of the sextant is checked by Automatic Celestial Navigation (ACN). a section called the STELLAR ERROR DE- The Snark missile used the SSIA system. TheTECTION CIRCUIT, which determines whether gyro that controls the position of the accelerom-or not the star is centered in the telescope eters is subject to random drift, and the result is If the star is not centered in the field, an error that tends to increase with time. Thefield. error may be as much as half a mile for aan error signal is generated and processed to flight that lasts 45 minutes. For longer flights,show the amount of sextant error. The error the error would naturally increase. Randomdetection circuit is shown in block form in gyro drift varies inboth direction and magnitude.figure 10-18. One method that may be used to overcome the random drift error involves the use of star eights.The checking is done in much the same manlier as a human navigator would check his position by observing an object, such as a star, having a known position. The missile does not carry a human navigator; it must use a mechanical substitute. ELESCOPE Stellar Supervised Inertial Autonavigator

In thestellar supervised autonavigator, ELEVATION MOTOR periodic sights are taken on known planets or.; stars to check on gyro drift. TO make the check, an automatic sextant is AZIMUTH MOTOR mounted on a platform in the missile so that it can be turned on elevation and azimuth sites. 99.172 An automatic sextant is shown in figure 10-18. Figure 10-18.Automatic sextant. Ae46 Chapter 10OTHER GUIDANCE SYSTEMS

ITIMING CIRCUIT

(DRIVE(DRIVE 0

ELEVATION MOTOR

TO SEXTANT COMMANDS RECORDED TAPE

AZIMUTH MOTOR

AZIMUTH

COMMANDS

33.173 Figure 10-17.Sextant-positioning system. The sextant is trained ona given star bywere raised and pointed directly forward along information taken from the tape,and thenthe missile heading, any elevationerror signal continues to follow the star on the basisof thefrom the sextant would be assumed to bean programmed tape. The output of the automaticerror about the pitch axis. If the sextant were sextant is fed into an error-detecting systempointed out the side, in a lateral direction,any (fig. 10-18). elevation error would be a function of missile The scanner is used to detecterrors inroll.Therefore a resolver is necessary to de- centering the star in the optical field ofthetermine whether the error signal is caused by sextant. The scanning system includesa light-pitch,roll, or by a combination of the two.) chopper, or interrupter, and a phototube.The An ideal way to use a star-sighting system output voltages of the error-detectionsystemis first to check a star whose line of position are proportional to the missile deviations inis parallel to the missile course, and then to roll, pitch, and yaw. The light froma star,check another whose line of position is at right after passing through the scanner, which containsangles to the missile course. The, information a chopper which 'modulates the light beam atafrom the first star would then be applied to the given rate, falls on the light-sensitive cathodecomputer direction channel, and that from the of the photo The cell output voltage ispro-second would go to the distance channel. These portional' to the light intensity. The outputis thensignals would then correct the gyros toa new fed to a selective amplifier that seleCtis the signalposition, and compensate for any gyro drift that from.the noise: The amplifier output is thenfedmight have occurred. With the gyros corrected, through' a detector section to a reedver,whicherrors in roll, pitch, and yaw can thenbe meas- breaks down the signal into azimuth and elevationured and used to position the control surfaces. error signal& Remember that the missile equipped withthis The direction resolver has bit), outputs. Onesystem is also inertially guided. The outputs of goes directly to the yaw -conilitirator the otherthe celestial system correctany errors made goes tn't second. resolver sieCtiOn. The secondby the inertial equipment. It is not possible to resolVer is ootatr011ed 'frord the 'tape signals.Obtain proportional control with this systembe- The same 'signal that Seta :the sextant positioncause of the delay in signals getting through the sets the resolver for elevation, error output.circnitei and damping by the rate -function. MINS the eleireliOn'aignat resolved in thisHowever, the system does tend to returnthe Manner, there is no' way to deter:nine whethermissile to the correct courseas soon as pos- the error exists inpitttor roll. (If ,the .teictantsible without over-control Oscillations.

.?..47 20 1>" 4 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

REFERENCE

SCANNER STAR LIGHT

CHOPPED LIGHT

SELECTIVE DIRECTION AMPLIFIER DETECTOR RESOLVER HOTOTUSE

AZIMUTH ERROR ELEVATION ERROR

AZIMUTH COMMAND FROM TAPS

YAW PITCH AND ROLL COMPARATOR RESOLVER

1 YAW FITCH ROLL ERROR ERRORERROR 33.174 Figure 10-18.--Stellar error-detection circuit.

AUTOMATIC CELESTIAL NAVIGATION chance of error.It is possible that a standby sextant might be added to the equipment, so The most difficult problem to overcome inthatitcan zero in on the next star -in the the system just described is gyro bearingnavigation sequence without interfering with friction.The problem may be solved by usingthe fixes that are being made. a continuously supervised system. Theauto- One disadvantage of the multiple sextant matic celestial navigation (ACN) system issystem is the need for a window big enough to continuously referenced by 'stellar fixes. Thisview a large area of the celestial sphere. Such does not mean that there is no longer a neces-a 'window would need optical characteristics sity for inertial supervision; the inertial prin-that would add greatly to its cost. In addition, ciple is still used by the autopilot betweenthe larger window area is more subject to guidance commands. damage by natural forces at high speeds. The platform equipment for ACN requires LIGHT DISPERSION BY SHOCK WAVES. one or more automatic sextantslit addition toAs light passes through any light-conductive those already mentioned. TWo sextants oper-material, a certain amount of refraction or ate simultaneously to obtain .a series of fixes,bending, takes, place.The higher the density rather than aline,of position.With MOB onof the material, the greater is the degree of two stars at the same . time, there . is lessbending. Rays of light are refracted when Chapter 10OTHER GUIDANCE SYSTEMS

they pass obliquely through the shockwaves The integrator section is designed tore- that are generated by any missiletravelingspond slowly to an input signal. Itmay take as (in air) at or above the speedof sound. Thislong as 10 minutes for the integratorsignal to effect may be severe enough to limit theusebuild up enough to cancel a steady amplifier of celestial navigation to missilesoperatinginput signal.Therefore, all voltages that vary at less than sonic speeds, or those operatingat a faster rate will go through the circuitbe- out of the atmosphere.Figure 10-19 showsfore the feedback becomes effective. the effect of shock waveson optical systems. NOISE FILTERS.Ina practical applica- TERRESTRIAL REFERENCE NAVIGATION tion, noise exists in the output of thevelocity- measuring component.The noise is in the The search for accurate, foolproofmissile formof short bursts,or peaks, of energy. Itguidance systems has turnedup many possi- may be effectively removed by choosingcom-bilities.Some of those that seem the most ponent values to give theproper time constantfantastic are based on sound reasoning.The (delay) in the circuit. Buta filter of this typeexamples that follow fall into this category. is not suitable for use in removingnoise of a Several picture and mapmatchingguidance continuous nature.If some steady error, duesystems have been suggested and tried.As to noise, is present in the signalthat indicatesmentioned in chapter 6, terrestrial reference velocity, the entire computer output willbe innavigation relies on comparisons of photosor error.The elimination of errors caused bymaps carried in the missile with an image of noise requires a circuit that will blocknoisethe terrain over which the missile is flyingat error signals but pass other signals. A cir-that time. cuit with the desired characteristics isa high- The basic idea can be shown by usingthe pass filter that uniformly passes a-c of thecommon photograph as an example. If a photo- higher frequencies, but blocksany signal of agraphic negative is placed over its coinciding lower frequency. positive, the entire area will be black.If the High-pass filters using inductive andcapac-positive were in the form of a transparency, itive components are easy to construct;butthe entire area would be opaque andno light precision components arenecessary to getwould get through. If-either the negatifteor the sharp frequency characteristics, and thisfactpositive is moved slightly with respect to the increases thecost considerably.To avoidother, light would show through where the two costly components, a d-c amplifier withinte-prints were not matched. If one transparency, grator feedback is used asa high-pass filter.say the negative, were in the form of a strip

STAR SHOCK MY WAVE

WINK*

TELESCOPE HURTING

BELOW SONIC SPEEDS AT SONIC SPEEDS

144.58 Figure 10.190Effect of high speedson optical systems. PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS that was pulled through a frame or windowbyThe left-right information is fedto a servo- a motor, it would be possibletodevise a controlamplifierwhich drivesthefilm carriage system that would automatically match thelaterally to keep the images matched.The images.However, instead of a transparencyposition of the carriage is picked off as an er- for the positive image, the projected imageror signal voltage for the missilecontrol sys- wouldtem. As the missile turns on its yaw axisto of the terrain from a lens of radarscope moved be used (6-14). the correct heading, the film carriage is Daylight systems are ruled out becauseand the error cancels out. they would be seriously affected by clouds, fog, Fore-aft information is fed to the longitud- and smoke. The use of photographs of the ac-inal servoloop that pulls the film throughthe tual course or target area would not be suitableholder at the correct speed to maintain a match for the reasons outlined above, andbecausebetween the film image and the PPI tube image. This means that the film speed mustbepropor- such a system would be susceptible to counter- It measures.On the other hand, a radar map-tional to the ground speed of the missile. matching system has greater. effective range,is possible to key the film to cause course and is not limited by conditions of visibility. changes or to start the terminal phase. Errors can result from a difference inalti- Radar Mapmatching tude between reconnaissance(radar mappirig) and tracking (actual missile flight) runsbecause A guidance system that uses radar map-of slant range distortion andaltitude-return matching has, among other parts, a radar,delay. PPI, lens, scanning motor, map holder,and It is necessary to have angular matching to ,phototube. Figure 10-20A represents the com-within one degree before accurate left-rightand ponents of a mapmatching system. fore-aft information can be obtained. Angular A map of the terrain over which the missile ismatching can be obtained by means of a mag- passing must be previously prepared on a nega-netic auxiliary such as a compass. Matching is tive transparent film. This fact calls attentionmaintained by the azimuth loop of the system. to a weak point in the map matching method. Two types of film holders can be used. The landmarks can change or disappear, or newframe type is the larger, and more complica- landmarks can be added; and therefore the map ofted mechanically. It switches separateframes the area must be very recent. into the scanning area and is easier to lock on In operation, the comparison is made bywith the system.However, a better method projecting the;War image from the PPI tube,seems to be the one shownin figure 10-20, in through a negative radar map transparency ofwhich, the film is scanned through a maskwith the same region, onto a photomultipliertube.a semicircular opening. (A photomultiplier tube is an electron tube so If the film strip used in this system is pulled constructed that it produces current amplifica-through the viewer at a speed corresponding to tion. A very weak light source can be greatlythe missile ground speed, its length willbeabout amplified by a tube with multiple stages.) The1/20 of that required for a frame-type map. lens (fig. 10-20B) through which the PPI image Errors can result from a difference in alti- passes is rotated in much the same manner as atude between reconnaissance (radarmapping) radar antenna is scanned. The mirrorrotationand tracking (actual missileflight) runs be- causes the PPI image to be moved in asmallcause of slant range distortionand altitude- circular pattern over the film. When the imagereturn delay. from the. PPI tube exactly coincides with the It is necessary to have angular matching to map image, minimum light getsthrough to thewithin one degree before accurate left-right photo-multiplier tube. and fore-aft information can be obtained. When the output of the photomultiplier tube The reference maps may be obtained by amplifier is properly commutated by the com-actual radar mapmalcing flights over the ter- mutator section, left -right and fore-aft informa-rain that is to be traversed by themissile. 'These flights may be made at high altitudes in tion is obtained. . The pulses from the commutator are ap-almost any kind of weather.Another method plied to d-c discriminators and integrators.involves the use of synthetic maps. Then, as shown in figure 10-20A, the informa- The synthetic maps are prepared by using tion is fed to two loops, lateral and longitudinal.maps of the area, aerial photos,and other .250246 Chapter 10--OTHER GUIDANCESYSTEMS

ALTITUDE COMMUTING ALTITUDE CIRCUIT INTEGRATOR ERROR` DETECTOR

LATERAL INTEGRATOR

LATERAL LOOP

LATERAL DISCRUNNATOR

LONGITUDINAL INSCRIMINATOR

LONGITUDINAL LONGITUDINAL SERVO INTEGRATOR

AZIMUTH ERROR DETECTOR

MLR (OR MAP HOLDER) SCANNING LENS CONDENSING PHOTO LENS TUBE

(PPI) CRT INDICATOR

FILM of GATE MASK TO AMPLIFIER

33.1175:.176 Figure 10-20.Radar mapmatching:A. Block diagram of system; B. Film holder operation forstrip map. information. A relief map is builtup from this information and then photographed. Radar maprnatching is limitedby the capac- Maps pre-ity of the film magazine. Alsoit cannot be used pared in this manner are onlyslightly inferior to actual maps. over water, or over land that lacks distinguishing features.The system is also subject to R51 247 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS electronic countermeasures, but it has somemagnetic reference systems will become more immunity because of the highly directive an-practicable. tenna system. The present accuracy of magnetic systems Therefore, this system is best suited foris within about 7 miles, but is limited to the use as a part of a composite system that usescourse line only.This means that a missile nonradiating midcourse guidance.The map-using this system would need to be launched matching system would be used for a mini-near, or flown to, the vicinity of a line of mag- mum time prior to the arrival of the missilenetic intensity that crossed the target area. at the target. This method affords the greatestMagnetic storms would prevent the use of the element of surprise, and represents the bestsystem until the earth's magnetic field re- method of evading countermeasures. turned to normal. Keep in mind that, as more knowledge is obtained about the behavior of the magnetic Magnetic References field, it may become possible to predict magnetic conditions in much the same manner as The use of the earth's magnetic field as aweather is predicted today. There is, accord- reference for missile guidance systems has beening to present knowledge, one major difference discussed in another chapter. The sensor unitsin the two types of predictions. Weather pre- used in this system are refinements of thedictions may prove inaccurate for a given area simple magnetic compass, and are called thebecause of purely local conditions.On the flux gate compass and the gyrosyn compass. other hand, the earth's entire magnetic field Studies made during the International Geo-is disturbed under magnetic storm conditions, physical Year, and the information obtained byand there are no strictly local effects. Should submarines cruising under the ice at the Northextremely accurate magnetic condition forecasts Pole, have given new insight into the nature ofbecome feasible, it is possible that the disturbed the earth's magnetic field. These studies willconditions might be used to advantage in missile continue.And, as more information is gained,guidknce. CHAPTER 11

GUIDED MISSILE SHIPS ANDSYSTEMS

INTRODUCTION fire support to permit the advance of friendly troops would be tactical in nature. The destruc- GENERAL tion of ball bearing factories deep inenemy country, thereby affecting the enemy'swar- making potential, would be strategic. This chapter describes the current guided Tactical targets, as opposed to strategic missile ships and systems of the Navy. It willones, are fleeting in nature; they can be success- orient the student to the missions, functions,fully attacked only by weapons thatcan reach and general nature of the Navy's missilepro- them in minimum time and with a high degree of gram. accuracy. One should not consider, however, that these definitions are hard-set. For example, The confidential text in this series willconsider the destruction of an enemy airfield. describe in more detail those characteristicsIn one phase of a battle this may have strategic of missile ships and systems which have beensignificance.But-the destruction of the same omitted here because of security. airfield in support of a landing operation would have tactical significance.

MISSION OF MISSILE SHIPS TYPES OF MISSILE SHIPS GENERAL Before proceeding with descriptions ofthe missions of missile ships, it isnecessary that Because of the rapid changes brought about the reader be familiar with certaindefinitions.by many recent scientific breakthroughs,the The MISSION of a ship isa broad statementdesign of missile ships or missile systemsis of its designed purpose in the Navy. Ina morestill changing.But there are certain patterns restricted sense, the term missioncan be ap-that can be considered fundamental. Atthetime plied to the component parts ofa ship. Thus theof writing this text, all but one ofour missile term is alio used in reference to missilesys-cruisers are conversions from older ships. tems. Conversion rather that construction isan eco- Tasks of the mission specifically define whatnomical approach to a guided missile Navy. In the ship is expected to do at a given time.Theremany ways it ie a necessary approach, since are two broad Categories into which missionsmany problems ih ship construction for missile are sometimes divided--STPATEGIC and TAC-needs must be worked out.In addition to the TICAL. A full discUssiOn of the,meaning andconversions, however, there are now incom- Significance of these terms could extendthemission many new ships designed from the keel length of this.chapter.Quick insight can beup as guided missile ships, and many moreare grasped however by remembering that tacticsin the building or planning stage.No guided is the art of battle, and that strategy la theartmissile destroyers are conversions. of war. Therefore, a tactitsd MiatiOnis one 'Mkt has a direct biflueilde on the cOUrerof battlein,GUIDED MISSILE CRUISERS progress. A strategic missionis far- reachingit is one that may haveno direct or In general, the mission of missilecruisers immediate influence. The Job of providing close.1e to provide AA defense, to bombardenemy PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS shore installations, to carry a force commander,indicates a possible task force formation of the to control aircraft, and to conduct combat oper-future.Note that the force is spread out over ations against enemy surface craft. many miles of ocean. Cruisers are being designed to include an There are five classes of guided missile ASW capability.This will enable them to pro-cruisers.First,. there are the CAG (Terrier) vide defense against enemy subsurface attack,conversions.Figure 11-2 is a picture of the and thus permit a field of action much greaterUSS Canberra (CAG-2). This class of ships is than that of conventional cruisers. Figure 11-1the result of conversion of World War II heavy cruisers. From outward appearances, the conversion consists of removing the after 8"/55 triple turret, three after 5"/38 twin mounts, and the after conventional fire control directors, and substituting two twin Terrier launchers and two Terrier directors. Figure 11-3 shows a second class of missile cruisersthe CLG (Terrier) class. These ships are conversions of World War II light cruisers. The armam.nt of the CLG (Terrier) consists of the following: 1-twin Terrier launcher 2-missile guidance systems 1 or 2-6"/47 triple turrets 1 or 3-5"/38 twin mounts A CLG (Terrier), converted to include fleet flag facilities, will have further modification of its gun batteries. I CVA (TERRIER) 2 CO TALOA , I TERRIER) Of the CLG (Terrier) conversions, the USS 7 CAA (TERRIER) Providence, Sprinjfield, and Topeka have be- tZhe LOs 6,7, and 8, resFMly. 144.59 Figure 11-1.A possible disposition of a The third class of guided missile cruiser is missile-equipped task force. the CLG (Talos). For the.purpose of this book, Chapter 11GUIDED MISSILE SHIPS AND SYSTEMS

33.263 Figure 11-3.USS Springfield (CLG-'n. the only significant difference between the Ter-GUIDED MISSILE DESTROYERS rier- and Ta los-equipped CLGs is in the capabilities of the missiles themselves. The CLG Present planning provides for four classes of (Taloa) is converted from thesame class of lightdestroyer types having a missile capability. The cruiser, and the resulting armament is essen-mission of each of these types is to screen task tially the same as that described for the CLGforces and convoys against enemy air, surface, (Terrier).In the CLG (Talos) class, there areand submarine threats. They also provide air the USS Galveston, Little Rock, and Oklahomacontrol, give radar picket duty, make offensive CLGs 3,4, and 5, respectively. strikes, and carry DASH. The first of these is l'he fourth class missile ship conversionsthe guided missile destroyer (DDG). The DDG is are the all-missile cruisers USS Albany, Chi-similar to the conventional destroyer in dis- cago, and Columbus, CGs 10,11, and 12, re-placement and other general characteristics. spectively. These were formerly World War IIFigure 11-8 shows USS Barney (DDG -6). The heavy cruisers. The conversion to guidedfollowing are typical armament installationson missile cruisers has been more complete witha DDG: this class, however, as all gun turrets,gun 2-5"/54 gun mounts mounts, and conventional fire control directors 1-twin or single Tartar launchei have been removed.In their stead, Taloa .1-Asroc launcher launchers have been installed fore and aft;a 2-Mk 32 triple torpedo tubes Tartar launcher on each side, and Taloa di- The second DD family is the guided missile rectors and Tartar directors have been em-frigate (DIG). The DLG is the big sister of the placed. However, two single 5"/38 twin mountsDDG, with longer endurance and bettersea- have been re-installed amidships. Figure 11-4keeping abilities.DLGs are equipped with the is an illustration of the USS Albany (CO-10). Terrier missile system. Those of the Leahy To complete the picture, there is the nuclear- Class (fig. 11-7) carry a Terrier launcher both powered guided missile cruiser, which is the onlyforward aft, while those of the Farragut class cruiser designed' since World War II from thehave but one Terrier launcher mounted aft. keel up.Figure 11-5 shoWs the USS In place of the forward launcher, a 5"/54gun Beach (CGN-9); Like 'the USS Albany class mount is installed on these ships. In addition is armed with both long and mediumrangeto the above, all DLGS carry two twin 3"/50 RF surface-to-air missiles, but it alga has the(rapid firing) gun mounts, Asroc, and ASW latest ASW armament.Nuclear propulsiontorpedoes.An important new addition to the gives this class a far greater operatingrangeDLG ranks is the nuclear-powered guided mis- than ships with conventional propulsion. sile frigate, USS Bainbridge (DLGN-25). The

251 .255 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

at 4 ,rk;11: . -4,

144.60 Figure 11- 4.. -USS Albany (CG-10).

6-: ii44,140pki,44,0.14. ...Arty.. 4., 01.44/041 (;

A I

rItk:.4'.1 i''' ',"

t ,f. : 4K? ti):fr. 14' ''.; '.:: 7ft4cti.444i73 , -. 4 t ,i.,7-.&A^,44. 1-- "..q- 4 ''''. r,- ''4,-.',-,-,...,` _-'7. r,..1.2-7-,' ...... ' 1 .,,,,,' ,... ' !:4 ..-....i . ..j ..',", , i 4:4.::: t . i eo.

134.82 Figure 11-5.--USB Long Beach (CGN-9). 256 252 Chapter 11GUIDED MISSILE SHIPS ANDSYSTEMS

IMO

3.76 Figure 11-6.USS Barney (DDG-6).

134.84 Figure 11-7.USS Leahy (DLG-16). armament of the USS Bainbridge is thesame astriple to cpedo tubes; and two Mk 25 torpedo that of the DLG-16 class (see fig. 111 -7, USStubes. Leahy (DLG-16)), but her operatingrange is vastly greater. GUIDED MISSILE SUBMARINES The newest members 'of the guided missile destroyer" faniily arethe DEGs, guided missile The primary mission of the guided missile destroyer escOrts. The DEGs are deiiigned tosubmarine is to deliver guided missile attacks locate and destroy enemy sUbmarines. They will against enemy shore installations. Its tasksin- be fitted with a Tartar missile launcher, and will clude the launching and control of missiles, also Carry a 5"/38 gun mount, Asroe,two Mk 32 andself-defense by means of underwater

253. 257 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS launched weapons. The foremost of our guidedConstellation (CVA-64) (fig. 11-8), are each missile submarines are those designed to carryfitted with twin Terrier launchers. It is planned the Polaris ballistic type missile. These longthat other carriers to come, plus some already ranging nuclear-powered ships with their for-in commission, will be fitted with missile sys- midable weapons are a powerful deterrenttems. fa any consideration our enemies might have of .1.721dng the "cold war" a "hot" one. SURFACE SHIP MISSILE SYSTEMS A new type of Subroc, an under- 3mter to air-to-unaerwater missile, is beingGENERAL ci,Nelopeci and is expected to be operational soon.Subroc is designed to be launched from This section will outline the fundamentals standard torpedo tubes using conventional ejec-of a surface-to-air missile system as it might tion methods. Subroc, when fully operational,be found on a surface ship.Speeches lly, this will provide submarines with a radically im-.section will take up the Tert,pr (RIM) system proved kill capability. as found on DLGs. The missile systems on these ships may tte considered typical of a OTHER MISSILE SHIPS surface ship ra?lsi.la system. The Navy intends to eventually replace, many ORGANIZATION OF MISSILE SHIPS of its r,onveetimal ardaircraft gunrstay systems with Liicne systems.In the future, Tlie- organization of missile ships is com- amphibious craft, and service craft will takeparable to that of other ships with similar their piaci; in the missfla Navy. At the pres-missions. Most of the equipment and personnel ea time, three CVAs, the UM Kitty Hawkassociated with the missiles are ticdet the a (CVA-63), USS America (C7A-66), and the USgcognt.,44.xe of the weapons officer.

4f 4i d'rt ,ovd ,

N4.4 )11,^''/.*10 '4411/

'? ,

3.71 Figure 11-8..-IJ38 Constellation '(e1l.k41,4) launching Terrier

ty .1258 254 Chapter 11GUIDED MISSILE SHIPS AND SYSTEMS

Figure 11-9is the Weapons Departmentweapons control system, and (4) the missile organizationalchartforthe USS Farragutstowage, loading, and launching system. (DLG-6). There are variations to suit the needs of each ship, but figure 11-9 illustratesThe Missile the type of organization. The men who are responsible for theop- As you will recall from the first part of this eration and maintenance of the missile itselfvolume, the Terrier (RIM) is a medium-range are under the missile officer.Weapons con-beam rider, or a homing missile, depending trol equipment of the missile system is underon the mod, propelled by a solid-fuel sustainer. the cognizance of the fire control officer. rocket, and launched with a solid-fuel booster. The missile system also getsan assistIt is capable of carrying a fragmentation ora from Operations Department personnel,as Ra-nuclear warhead.It can be used against sur- darmen perform certain plotting and liaisonface, shore, or air targets. functions in the weapons control system. The Ship TERRIER (RIM) MISSILE SYSTEM The second major subsystem is the ship itself, which provides the launching platform, Thearrier missile system of a guidedand transports the missile part way to the tar- missile ship consists of four major subsys-get.It also provides the basic services neces- tems: (1) the missile, (2) the ship, (3) thesary for the maintenance and operation of the

WEAPONS OFFICER (LT/ LCDR) TRAINING OFFICER SECOND DIVISION (WEAPONS CONTROL) I FIRST LIEUTENANT (LTJG) A/S OFFICER FIRE CONTROL OFFICER SFCP (NG/LT) (---/LT) LANDING PARTY FIRST DIVISION F DIVISION F DIVISION GUNNERY ASSISTANT MISSILE OFFICER A/S CONTROL PLOTTING ROOM AA BATT. CONTROL IENS/LTJG/ (----/LTJO) DIVISION J.O. DIVISION. J.O. MAIN BATT. CONTROL MISSILE CONTROL SOC IFOVSLE GROUP'

,1 BOS'N STORES 5" BATTERY LAUNCHER GROUP'1 SONAR EQUIP. 1 GFCS

PAINT LOCKER 3" BATTERY - 'MISSILE HANDLERS'4UWT/FATHOMETERI.rnS AGROUND TACKLE' SMALL ARMS EQUIP.' MISSILE TEST EQUIP1 B/T FANFARE I GMFCS I

H DECK FORCE 1 ASROC BATTERY 1 UFCS

HBOAT. CREWS 1 NUCLEAR WEAPONS'

TORPEDO BATTERY

GUNNERY OFFICE 1

63.4 Figure 11-9.Organization chart, Weapons Department, USS Farragut class DLG. PRINCIPLES OFGUIDED MISSILES AND NUCLEAR WEAPONS missile system.These basic services includerelease point more than 10,000 yards from its electric power, communications, testing fa-target.Consider, also, that this aircraft is cilities, compressed air and nitrogen, logisticstraveling 20,000iardsa minute, and that the support, etc. The ship also provides early warn-total problem may consist of two, three, or ing and other CIC functions required for target more aircraft.Finally, recall that in order acquisitions, target tracking, and computerto destroy an aircraft with a missile or a solutions for fire control problems. projectile it will be necessary to do all of the The armament of aDIGvaries, of course,following BEFORE the target aircraft reaches on one-ended (Farragutclass) or the double-its bomb-release point: ended (Leahy class) ships. Figure 11-10 (1) Detect the target aircraft with radar illustrates the placemrt of components on a (2) Identify the target as "friend or foe" DIG class 9 ship. (3) Designate to a selected director to acquire the target Weapons Control System (4) Obtain a solution with director's associated computer This is the third major subsystem. It en- (5) Assign weapons to the tracking direc- compasses both the gun and missile firecontrol tor on a priority basis, and position equipment. The weapons control system willbe these weapons in train and elevation described in some detail in this and the suc- (6) Fire ceeding section. (7) Wait until the projectile or missile Consider that an aircraft at 20,000 feet, reaches the point of impact with the tar- traveling at 600 knots, will reach its bomb- get

COISAT INFOINIATION CENTER

MN OWN

V/34 CAL MOUNT

SOON NUM CONTROL STATION IPANICNUtwaimartROOM 141113111 W4AZINE 141.38 Figure 1110.DIGclass 9 weapons system. 260 256 Chapter 11GUIDED MISSILE SHIPS ANDSYSTEMS

The need for urgency, and the complexityofmissiles, there is a need to solve forlauncher the AA problem, were thereasons for develop-and in-flight guidance orders. ment of the complex weapons controlsystem found on the missile ships. The WEAPONS DIRECTION EQUIPMENT The missile shipprovides the displays and controlsrequired weapons control system was conceived to holdfor the proper utilization of the to a minimum the time required for ship's weap- acquisitionons.This utilization requires fullevaluation of targets, and to permit simultaneousengage-of targets, assignment of missile (or gun)di- ment of multiple targets. rectors to the proper targets,proper selec- The weapons control systemcan be dividedtion of missiles and loading of launchers,tac- into fire control equipment andweapons direc-tical evaluation prior to firing, and,finally, tion equipment. continued evaluation to ascertain thattargets are effectively encountered and that target The FIRE CONTROL equipmentsupplies thepriorities remain as first evaluated.Figure basic intelligence and control functions fore-11-11 is a sketch of a weapons controlstation, lective engagement of targets by the ship'swhich contains most of theweapons direction weapons. Thus, with conventional gdnnery,equipment.Other missile ships use similar there is a need to computegun orders. Withequipment, often the same mark and mod.

UNATTENDED EQUIPMENT AREA GUIDED MISSILE STATUS INDICATOR PULSE STIMIOL GENERATOR WPM CONTROL INDICATOR MASTER CONTROL PAIML TAME! TRACKER TARGET SIZE 000 INDICATOR PANEL SIGNAL 0011 CONVERTER FCS SETUP INDICATOR INOICATOR III REQUESTS OIRECTOR INDICATOR UAW TV mown'

WEAPONS STATION BOARD 1

CONTROL 110CATOR

TARGET SELECTION AND TRACKING CONSOLE

PCS 1,4, AND 5 US DESIGNATION SWITCHES

MISSILE WARNING SWITCH DETECTION AND TRACKING AREA ARECTOR ASSIGNMENT CONSOLE

ORDNANCE CONTROL AREA WEAPON ASSIGNMENT

36.81 Figure 11-11.Weapons control station. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Missile Stowage, Loading, and Launching Tracking, Evaluation, and Systems Director Assignment In general, it can be said that the missile is In addition to the conventional search and handled in the same way that conventional am-firecontrol radar normally found on Navy munition and weapons are handled.However, ships, a designation radar is installed as part certain missile characteristics modify the han-of the weapons control system.The designa- dling and stowage problem. The Terrier missiletion radar is a hemispherical scan radar, and is heavy and unwieldy, since its length withit provides a continuous 360° HORIZON TO A booster is over 26 feet, and its weight is in theGIVEN ELEVATION radar scan.Thus, the neighborhood of 2400 pounds. The electronicdesignation radar will supply range, bearing, equipment, and the powder grains that make upand elevation of all targets within its range. the booster, require a controlled environmentAll targets within the scope of the hemispheri- in order to maintain missile reliability. If sub-cal scan radar are made available as inputs jected to cold, the boosters and sustainers be-to the automatic tracking (TWS: track-while- come brittle and are more likely tofracturescan system) feature of the weaponscontrol upon normal handling.A missile propellantsystem. Automatic tracking is necessary be- that is cracked will burn faster than it normallycause of the requirement for speed, and be- should, becoming unreliable and perhaps ex-cause the number of targets may exceed the tremelydangerous.. Excessive heat and/ornumber of directors available, or the capability moisture will also have an adverse effect on theof human tracking. The Terrier weapons con- missile booster and sustainer propellants. trol system is able to retain all target informa- Each missile launcher has an associatedtion in a ready-to-use form, for transmission magazine, ready service magazine, and wing-to directors as rapidly as they are able to take assembly area.The missiles are stored in asuccessive targets. condition ready to be launched on short notice. Too, because of the limited time available, Also because of the rapidity with which the AAprovision is made within the weapons control problem develops, provision is made for rapidsystem for as much automatic evaluation(as loading of additional missiles and the jettison-opposed to human operation) and director as- ing of malfunctions. With the exception of wingsigning features asis possible.Thus an and fin assembly, the Terrier loading cycle isaircraft attacking so as to be the most serious fully automatic. threat will automatically be given priority in A more detailed study of missile loading anddirector assignment. launching systems will be included in the confidential volUme of this series. Weapons Control System Phases

THE AA PROBLEM Within the weapons control system are three successive phases of actions and equipments, Figure 11-12 is a block diagram that willalthough the interaction of modern equipment help the reader to understand the functioninghas tended to break down separation into phases. of the Terrier weapons system as it concerns PHASE I.This is a combined phase I for gun the AA problem. and missile use, whereby targets are selected by the phase I equipment operators for automa- Detection and Identification tic tracking.These phase I operators, aided by what is presented on their radar scopes and A target18 detected by the ship's airby the information received from CIC, then search radar, by an Airborne Early Warninginstitute the automatic features of the TWS sys- (AEW) system, or perhaps by another shiptem. To summarize, phase I equipment pro- acting as a picket. Another source of informa-vides for display, detection, initial selection, tion is the Navy Tactical Data System (NTDS),and tracking of targets. discussed later.This target information is PHASE 11.Xhis and succeeding phases will presented to CIC and the weapons control stationbe discussed only insofar as they concern the in a conventional manner. The target is inter-missile problem. Parallel capabilities for tar- rogated, plotted; and assigned a designation ac-get acquisition are provided for the gunnery cording to its status as friend or foe. problem. Phase IIequipment for missilery

258 .262 (3) DELIVERY UNITS (2) WEAPON CONTROL UNITS (I) DETECTION, LOCATION, IDENTIFICATION , 1 UNITS i i LAUNCHING SYSTEM 1 TRACKING & GUIDANCE RADARS \ SEARCH RADARS .-no I i LOADERAREA \ \ \ \ I 1 \ \\\ \ \ 'I 1 1 II 1 - I \ \ \ / LAUNCHER \ \ \ Ii , \\ \\ \ 40Cry. V / \ CONTRO ROOM - - -J SSSR 2.I. RAIDRAID DATADESIGNATION 3. LOAD ORDERS TRANSMITTERDESIGNATION OPTICAL 131. 5.i RAIDIINNI 8.. 4.,6. 7.POSITION FIRE LAUNCHERMISSILEDIRECTOR DATAolIDERS ASSIGNMENTASSIGNMENT PLOTTING ROOM (WEAPON DIRECTION CONTROLWEAPONSTATION Figure 11-12.Terrier weapons system, flow of information and directions. EQUIPMENT ANDDESIGNATIONEQUIPMENT) 94.8-J PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS provides for evaluation and assignment to adepot's responsibility to test, assemble, and particular missile director, or for rejection astransfer a complete missile in the form re- a missile target.If the target is rejected forquired by the recipient. A missile, being ex- missilery at this point (or at any other time),tremely complex and of large unit size and designation to a gunnery director must be con-valuerequires more care in transport and sidered.(The phase II equipment for gunneryhandling than doesa conventional round of am- will function automatically to assign to a gunmunition.For this reason, all handling equip- director for acquisition any target that meetsment and shipping containers are designed to the priority requirements.) Duplication of ef-realize maximum missile reliability. fort is prevented by the fact that targets are Once aboard theship the missiles are normally engaged with missiles long beforeagain tested to ensure reliability.Missiles their priority dictates serious consideration bymust either pass the rigid tests or be repaired. the gunnery assignment equipment. To sum upWhen any missile component fails in test, it is the phase II equipment operators select andreplaced with a spare and the rejected part is assign priorities to missile targets; they thenshipped back to a depot for complete overhaul. assign the targets, in order of "threat", to theThe ship is equipped to make minor repairs missile directors for acquisition. and component substitutions, but not to make PHASE III.The function of the phase IIIextensive overhauls.All the steps in missile equipment is to receive and display all the com-manufacture, storage, handling, and testing are prehensive information necessary toselectfor maximum missile reliability. launchers and successfully fire the appropriate Missile ships are equipped to receive re- missiles against the selected targets. In- placement missiles both while in port and while formation, such as unclear areas, launcherunder way.Transfer at sea is usually con- availability, maximum and minimum missileducted by use of the burtoning method. Some of capabilities, present and advance target po-the newest ships use the FAST (Fast Automatic sition,etc.,are available to the phase IIIShuttle Transfer) system. Both the supply ship equipment operators. and the receiving ship must have the equipment. The FAST system compensates for roll, pitch, Fire Control and station alignment. It increases the missile transfer speed, and is able to handle the largest A director, having acquired the target des- missiles expeditiously and safely. It is planned ignated by the weapons direction equipment,to equip all ammunition supply ships (AEs) with will, together with its computer, complete athe FAST system. solution. The solution is in the form of missile launcher orders. and missile guidance NAVY TACTICAL DATA SYSTEM (NTDS) orders. The AA problem is completed when the target is destroyed, or when a director is re- The Navy Tactical Data System (NTDS) was leased because of change in target priorities.planned to provide more accurate target information to a task group.Six ships are now equipped with NTDS; current plans call for all MISSILE LOGISTICS major U.S. warships to be fitted with it. Future plans may extend it to smaller ships.It is a Missile logistics is the problem of keepingsystem for automatically and rapidly dissemi- the operating forces supplied with a stockpilenating among all the NTDS-equipped ships in of missiles and spare parts. Initially; missilethe data-gathering area such information as air- components are shipped in sections from thecraft early warning; positions and identities of manufacturersto storagedepotslocatedall aircraft, surface ships, and submarines; and throughout the continental United States and atcommand decisions. its advanced bases.Each of the sections that Own ship target data gathered by search make up the missile is packaged in a reusableradars and the fire control system are stored metal container.The containers. are sealed,and processed at high speed by one or more and contain desiccant in order to 'provide andigital computers and displayed on a target environment least likely to cause unreliabilityevaluation and weapon assignment console. The in the component. When necessary to 'supplyprocessed data are transmitted to all the other the operating forces with a missile, it is theNTDS- equipped ships in the area.Targets 264 260 Chapter 11GUIDED MISSILE SHIPS ANDSYSTEMS

detected by a screening ship, for example,aremissile; missile guidance equipment; the sub- automatically transmitted and displayedon othermarine; and missile stowage and launching ships' consoles, with provision for targetsortingsystems. to avoid duplication. To ensure a successful flight ofour first The existing NTDS network isbasically asubsystem, the missile itself, a reliable guid- surface operation, with airborne datalink, butance system must be employed. The principles it does not now includea direct tie-in with submarines. of the various missile guidance systemwere explained earlier in this book.The type of NTDS equipment includesup to four Univac USQ- 20 stored-program guidance used depends on such things asdesired general-purpose digitalaccuracy, cost, simplicity, reliability, andprob- computers aboard each ship; CVA'scarry four;able countermeasures. Guidance selection,al- DLG's carry two. Each shipalso carries fromthough it has a direct bearingon the design four to 25 displays which are direct -viewcathodeand operation of the missile system, isbeyond ray tubes (CRT's) and are used for on-linethe scope of this chapter. This chapter will digital computer information fromthe computersdeal primarily with the fundamentalsof the and for radar-derived data. submarine missile system thatare common In excercises with NTDS aboard carriers,theto all guidance techniques. system was able to handleany number of targets, beyond the saturation point ofconventional The third subsystem, the submarineitself, CIC equipment.In simulated raids with largeprovides a launching platforni, basic services, numbers of aircraft, NTDS could trackall theMel, and other logistic support functions. Also targets. included on the submarine area navigational The airborne portion of NTDSis carriedsystem, and missile fire control equipment. aboard E2A aircraft. Somesuccess has been The launching of missiles towardtargets achieved with it in over-water flightsbut tech-miles away can be compared toa very long- nical problems remain in developinga radarrange gunfire problem. The submarine will that can pick out moving targetsover a landusually have no direct observation of thetar- mass background (clutter and other radar inter-get, or of a known geographical reference. ference). But the position of the guiding craftmust be fixed with extreme accuracy. Location,heading, ground speed, and. other reference data, SUBMARINEMISSILE SYSTEMS all have an effect on the CEP (Circular Prob- able Error) of the missile. GENERAL The SINS system (ships inertialnavigation system) is presently the mostsophisticated Undoubtedly, the most feared and respectedof the navigational systemsnow installed on retaliatory weapon in our presentarsenal ismissile submarines. The heart of SINS isan the powerful and deadly accurate Polarismis-inertial guidance package basedon the prin- sile as carried by our nuclear-poweredballis-ciples of inertial guidance explained inpre- tic submarines (SSBNs).Another submarine cedingchapters. Included within SINS are missile system being developed fordefensenumerous gyros and accelerometers whose against enemy submarines isnearing opera- functionitis to generate the submarine's tional status.This system, Subroc, willeven- position and speed, and to establish true north tually be installed in most ofour submarines, and a vertical reference. SINS, then,acts like both conventional and nuclear-poweredtypes.a dead reckoning computer/analyzer whose Polaris and Subrocwere briefly describedfunction it is to provide continuousand ex- in chapter 1.In this chapter we will, withintremely accurate navigational andreference the limitations imposed by classification,givedata.It also has the ability to weigh,analyze you a fuller look at each of them. and make corrections to its deadreckoning solution based on optic* and electronicnavi- MAKEUP OF .A SUBMARINE ;C:1 gational inputs.. MISSILE SYSTEM In addition to the navigational system,a fire control system is includedon the submarine. Four major subsystems makeup the guidedThe function of the fire controlsystem is to missile submarine system.These are:the transfer reference information to themissile, 265 261 4 : PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS and to control and monitor the missile duringnature, vulnerability, size, and location. With preflight checks. strategic targets, these factors. are evaluated The last subsystem to be considered is forwell in advance of the mission. Tacticaltargets MISSILE STOWAGE AND LAUNCHING. Figurerequire faster military decisions.Both plan- 11-13 sketches the interior of a Polaris sub-ning estimates, however, are usually accomp- marine and shows arrangement of the missiles.lished on a much higher planning level than the The handling equipments and launcher com-launching ship. ponents are in the same area. Flight Planning THE UNDERWATER PROBLEM In addition to the target considerations, additional planning must be given to the flight Target Considerations plan of the missile. Thus, whereas the missile would be most likely to remain undetected at Because of the high unit value of submarine-very low altitudes, the range to the target may launched UGM and UUM missiles, certain fac-prohibit such employment. Intelligence and the tors must be considered, such as the im-immediate tactical situation also play an importance of the target to the enemy, and targetportant part in missile flight planning.

NAVIGATIONCENTER CONTROLROOM ATTACKCENTER OFFICERS.WARDROOM CPO QUARTERS CREWS QUARTERS MISSILE COMPARTMENT OFFICERS MISSILE QUARTERS TORPEDO ROOM CONTROL it I I ENGINROOM EL CENTER

A .- rr o 1 ,1 10111111111111111120N ------

BAT RY RE TOR GYRO ROOM CREWS MESS COReARTMENT AUXILIARY CREWS . CREV/S MACHINERY WASHROOM QUARTERS SPACE 71.1 Figure 11-13.S.SB class submarine.

262 '266 I 4, wt Chapter 11 GUIDED MISSILE SHIPS ANDSYSTEMS

POLARIS MISSILE SYSTEM the second stage rocket motorcontinues to propel the missile to a point abovethe earth's The Polaris (UGM) isa 2-stage surface-atmosphere. When the missile has reachedthe to-surface or underwater-to-surfaceinertiallyproper velocity and point on the trajectory, the guided ballistic missile withan approximatereentry subsystem separates and thewarhead range of 2500 nautical miles (Polaris A3).Thefollows a ballistic trajectory to thetarget. earlier Al and A2 Polaris missileshad some-The time of reentry subsystemseparation de- what lesser ranges. The Polarisis designed totermines the range which the missilewarhead be launched from a submarinecruising on orwill span.Polaris range can be varied in this below the surface. The twopowerful, solid-way from about 575 to about 2500nautical miles. propellant rocket motorsare capable of lifting Since there are no externalcontrol surfaces the warhead high above therange of any knownon Polaris, changes in the trajectoryare ac- anti-missile missile at a speedexceeding tencomplishedby deflecting the jet stream from times that of sound, and placingit into a free-its motors. A pre-computed idealtrajectory fall trajectory which willcarry it to its targetis preset into the missile. with deadly accuracy. The preset in- The warhead of theformation takes into account the movementsof Polaris is a compact and powerfulnuclear device. the target, the launching point, andthe missile The explosive power is one shiploadwith respect to inertialspace during the time of sixteen missiles exceeds the totalamount ofof flight. The warhead release velocitywhich explosive power expended by all of thepar-the missile must attain along itstrajectory on ticipating countries in World War II, INCLUD-the basis of a fixed time of flightis also preset. ING the two atomic bombs droppedon Japan. The launching submarine accuratelydetermines In a submerged launch, ignition of thefirstitslaunching position by use ofan inertial stage rocket takes place shortly afterthe missilenavigation system, and the position of thetarget breaks the surface of thesea (fig. 11 -14).. Thison the earth's surface is determined by reliable is the beginning of powered flight andthe inertialcharts.While in the power stage of flight, the guidance portion of the trajectory. Thefirst stage missile continuously measures itslinear ac- propelsthe missile far into the at-celerations on the basis of its inertialsystem mosphere. The first stage then separatesandand alters its trajectory to offset theoutside

BALLISTIC FLIGHT / 1.---.. TERMINATION POWERED / FLIGHT 141---...... 2NDSTAGE IGNITION 1ST STAGE SEPARATION ( INERTIAL GUIDANCE ONLY) ,...... -1S-1)STAGE IGNITION

33.269 Figure 11-14.Polaris trajectory (notto scale.) 267263 .4 e. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS forces causing unwanted accelerations. WhenSUBROC MISSILE SYSTEM the missile is on a proper trajectory and a correct velocity has been attained, the warhead is released and proceeds on toward the target with Subroc (UUM) is an underwater-to-air-to- no further correction possible. underwater missile designed to destroy enemy submarines at long range. The missile consists The warhead dives on its target at a steepessentially of a depth bomb and a rocket motor angle and at several times the speed of sound.joined together. Either a nuclear or a conven- The materials for the outer surface of thetional depth bomb warhead can be employed. warhead have been specially developed to resistThe launching submarine carries the equip- the high temperatures generated by friction withment for detecting and tracking the enemy sub- the atmosphere at reentry speeds, and suitablemarine, the fire control equipment for comput- insulation is provided between the outer skin anding the target information and providing the the internal components to prevent damage tonecessary pre-launch missile information, and the warhead. the equipment for launching the missile. The The SSBNs from which the Polaris is firedmissile is designed to be launched (fig. 11-15) provide a mobile launching platform which is ex-from a standard submarine torpedo tube using tremely difficult to detect. It can remain sub-conventional ejection methods. Upon being merged for very long periods of time and cruiselaunched, the rocket motor is ignited at a safe to most any position within the oceans of thedistance from the firing ship.The missile's world. By use of its inertial navigation system,flight through the air is controlled by an inertial it can provide the precise fire control dataguidance system which functions in accordance required to place Polaris right on target. with the fire control information set in prior

Figure 11- 15. Subroc launching from a submarine.

264 Chapter 11GUIDED MISSILESHIPS AND SYSTEMS

to launch.In addition to providing thepropul- 3. the aircraft, and sive force for the missile, therocket motor fur- 4. the missile guidance nishes power for controllingthe thrust vector- equipment. ing mechanism during The Sparrow I missile isa beam rider. It the boost phase and theincludes a warhead, an influence fuze, thrust reversalnecessary to accomplish rocket a guidance motor separation. and control section, power supplies,and a rocket At the proper point in itsmotor. Sparrow I was the nation'sfirst air-to- trajectory, the rocket motorseparates and theair guided missile, and is much missile continues ina free-fall flight. At the less sophisti- time of separation, the cated in guidance principles thanits more recent control of the missile issister, the Sparrow III. SparrowIis an optically switched from the thrustvectoring mechanismsighted beam rider, while Sparrow III to aerofins.During the ballistic portion of is fully theradar operated. Both missiles fulfillthe design flight, the aerofins controlthe missile in rollrequisite of having a high single-shot and azimuth.Pitch guidance is initiatedat, probability or near, the zenith of the trajectory of kill and a range longer thancan be achieved to directwith conventional AA guns. Up tofour Sparrow the missile to the desiredpoint of impact on the water surface. missiles are carried on appropriatelycon- Guidance is terminated atafigured aircraft.Missile aircraft can also predetermined height above, thewater, and thecarry mixed loads of Sparrow and Sidewinder aerofins are locked in thezero position to provide for proper underwater missiles (fig. 11-16). travel. At Additional data concerning specificairborne water impact, a timermechanism starts andmissiles is contained in chapter causes the warhead to detonate atthe proper 1, and in the time. confidential course supplementingthis text. The AIRCRAFT CARRIER (orland base) More detailed informationon both Subrocis needed to provide operational and Polaris can be foundin the appropriate and logistic classified publications. support for the missile andmissile aircraft. Test equipment, trainingfacilities, and provisions for handling and stowage AIRCRAFT MISSILE SYSTEMS are included on the mobile base. Additionally,asintegral GENERAL parts of the system,are the fighter director facilities which must direct the missileaircraft to the vicinity of the target. There are two broad classificationsof air- Maintenance of the craft missile systems: missile is on a "Go-No-Go"basis, as is the air-to-air and air-to-practice with many otheroperational missiles. ground. The Sidewinderand Sparrow familiesThat is, missiles which. are examples of AIM systems. do not pass surveil- Bullpup is anlance or preflight testsare rejected, and de- example of a Navy AGM system.Figures 11-16fective sections are returned and 11-17 are picturesof the Sparrow, Side- to centralized winder, and Bullpup missiles maintenance .facilities for repairor overhaul. on appropriatelyThis system speedsup acceptance testing, and configtiredaircraft. eliminates the widespread need The Sparrow family isa typical aircraft for extensive missile system. The student maintenance facilities. will recall that The missile AIRCRAFT is ofcourse the de- there are three majormissiles in the Sparrowlivery vehicle. family. Sparrow U willnot become operational Aircraft configured tocarry in the U. S. Navy. Sparrow III, and launch radar-guidedmissiles must carry while in manyextensive electronic equipment formissile guid- respects greatly different fromSparrow I, hasance.Other equipment to aid in the same general characteristicssuch as length, target ac- weight, and configuratiOn. quisition, and to furnish "course-to-steer" and "in-range" information,may alio be in- THE AIRCRAFT (SPARROW) cluded on the aircraftas part of the missile MISSILE SYSTEM system. The last subsystem is thatof the MISSILE GUIDANCE EQUIPMENT. Theprincipal func- There are four majorsubsystems that cantion of this equipment is to be considered to makeup the sparrow missile determine the dis- system: These are: placement of the Missilefrom the tracking radar 1. the missile beam, and to send thenecessary control informa tion to the missileso that the missile will fly the 2. the aircraft carrier, (orland base), beam.

265 269 PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

3.112 Figure 11-16.A4D Skyhawk with Sparrowand Sidewinder missiles.

'ff

3.112 4 Figure 11-17.A4D Skyhawk carryingthree Bullpup B missiles.

270 266 4.` Chapter 11GUIDED MISSILE SHIPS AND SYSTEMS

THE AIR-TO-AIR MISSILE PROBLEM tem. The more sophisticated the missilesystem becomes, the more automatic the various To illustrate the AIM missile steps problem, letbecome. The earliest AIM missilesrequired us take the classic example of an aircraftcar- visual contact and mental computations,whereas rier providing air cover fora task force atthe latest systems perform mostof the steps sea.Our missile aircraft will be alertedtoautomatically. the presence of enemy aircraft by. theforce fighter director organization. The missile BIBLIOGRAPHY aircraft will be vectored to the generalvicinity of the enemy, where it will be ina position to The confidential volume which expandsthis acquire the target. For the mission tobe fullytext, Navy Missile Systems, NavPers10785-A, successful, the attackers must be interceptedgives more detailed informationon missiles and and destroyed before theyare in position tomissile weapon systems. The followingmate- delivery an attack with theirweapons. Uponrial also may be consulted for furtherinforma- acquiring the target, a proper pursuitcoursetion. is then followed until firingrange is reached. Guided Missile Systems of the Departmentof When within range, the missile is firedand isthe Navy, dated 3/12/58. Copies should bere- captured by the guidance radar beam. Themis-quested from the Chief, BuWeps(ReS),Navy sile then follows the guidance beam untilwithinDepartment, Washington, D.C.- 20390 destructive range of the target, wherean in- BuWeps Information Bulletins fluence fuze will detonate the warhead. Theabove Navy Department technical manualson description is of the basic AIMbeam-ridersys-specific missiles or systems. PART II. - NUCLEAR WEAPONS

CHAPTER 12

FUNDAMENTALS OF NUCLEARPHYSICS

INTRODUCTION protactiniumwee sometimes split into two aporoemately equal parts when bombarded by There are some entirely new tuchrologicalneutrons, but that only want:nu 235 couldbe principles involved in nuclear weapons, as com-split or Hastened by slow(thermal) neutrons. pared with conventional weapons. In the caseofIt was also discovered that dux ing this process conventional explosivesenemy is released 1 to 3 more neutrons were released, through chemical reactions; i.e., rearrange-making the multiplying chain reaction adistinct ment of the atoms of theaplosive substance. In the nuclear explosion energy is prodwed as In 1942 a special govemment project,called a result of theformation of different atomicthe Manhattan Engineer District, wasestablished nuclei, by the redistribution of the protonsandin the Army Corps of Engineers.Scientists neutrons inside the atom itself. What is com-from various universities 'narking onthis proj- monly referred to as atomic energy isreallyect gathered at the University ofChicago to nuclear energy, since it results fromnuclearbuild a self-sustaining chain-reactingpile to interactions.For this reason atomic weaponsdetermine for sure if an atomic bomb was nuclear weapons.feasible. are now preferably called The pile was constructed on a lattice principle, with graphite bricks as a moderatorto SCOPE slow the neutrons, and with uraniumplaced This chapter will cover thoseaspects ofat intervals as the reacting material.Re- physics that pertain to the structure of thecording instruments at various points inside atom, the nature of its component parts,andand outside the pile gave an indicationof neu- atomictron intensity.Movable rods of neutron ab- the predictable behavior of the several intervals in- components. It will also cover very brieflysorbing material were placed at the means man has developed, or is nowde-side the pile during construction forsafety and veloping, for the liberation of the energyavail-control. It was fortunate theie strips wereused able inside the nucleus of the atom. in this manner, as the pito reached acritical Within the limits allowed by security re-condition at a much earlier stage of construction than was anticipated.On December 2, strictions, subsequent chapters will trace the if the uses of nuclear energy in naval weapons. 1942, all was in readiness to find out previous predictions were true.All but one then the ATOMIC RESEARCH PRECEDING control rod was removed from the pile* last rod was slowly removed. The predictions THE BOMB proved to be correct; . the pile was maintaining By 1939, a number of scientists had theo-a nuclear chain reaction. rised that an atomic bomb for military uses Much work was done in the following three was a possibility. Nuclearreactions had beenyears' and in 1945, this workproduced, on the studied extensively during the previoustenfloor of the New Mexico desert, the first ex- years. These studies had beenOne on only aplosion of an atom bomb. A few weekslater small scale because of the scarcity ofradio-two bombs were dropped over Japan, endingthe active materials. war and beginning a new erain warf..1:.. radio- As every reader of this text is undoubtedly By 1940, it was discovered that three industrial uses of atomic activeelements uranium,thorium,andaware, the military and 212 268 Chapter 12FUNDAMENTALSOF NUCLEAR PHYSICS energy have become a majorconcern of the United States,its ELEMENTSEach element has itsown char- allies, and itspotentialacteristics and its owncharacteristic atoms. enemies. Much military thinking hasbeenAn element is revised, and much more is in a substance which cannot be the process ofseparated into simpler susbtancesby ordinary revision. Regardless of his specialty,no chemical means. There military man can afford toignore the atom. are 92 natural elements These chapters ranging from hydrogen, the lightest,touranium, are intended to prepare pros-the heaviest.Several others have been pective naval officers forfurther study of this pro- subject. duced artificially, one of thesebeing plutonium. ATOMSAn atom is thesmallest unit of an element that possesses thechemical character- OBJECTIVES istics of that element.Scientists have broken the atom down to threefundamental particles This chapter will take called electrons, protons, andneutrons. up, first, the nature NUCLEUSProtons and neutrons' of matter.It will begin with thedefinitions of make up the component parts of the the central part of the atom;electrons move in atoms that make uporbits around this centralcore.This central matter. The interpretation ofatomic structurecore of the. atom is called the nucleus. will be covered, although themajor emphasis Most will be on the atom and its of the weight of the atom isin the nucleus. component particles. ATOMIC WEIGHTSincethe atom is very The second major division ofthe chapter will deal with radioactivity. This small, it is difficult to statethe mass of an natural phenomenonatom because thecommon units of mass are gave the scientists some of their mostsignifi- cant clues in learning the too large.For this purposea new unit was nature of the atom.defined:the atomic mass unit (amu). Because of its bearingon health and safety, Chem- radioactivity has become ists found that theoxygen atom is approximately a primary concern16 times as heavyas the hydrogen atom. There- for industrialists, communityleaders, and thefore, oxygen was assigned officers and men of the Armed the arbitrary figure Forces. of 16.00000 atomicmass units. The masses of The last part of the chapterwill be con-other atoms were then cerned with nuclearreactions. determinedby comparing These re-them to oxygen 16. Forexample, uranium 235 actions are the real source ofthe power thatwas assignedthe figure 235.11750 atomic is commonly called nuclearenergy. units. mass Since one amu is definedas 1/16 the mass of the oxygen atom, themass in grams cor- THE NATURE OF MATTER responding to onc atomicmass unit is ap- DEFINITIONS proximately 1.66 x 10-24grams. The most convenient unitfor describing Man has long wondered the energy of atomicor nuclear systems is the about the nature ofelectron volt, abbreviatedev.One ev is the matter. With the adventof better scientificenergy which an electron will pick methods, man has discoveredthe natural ele- up in ac- ments that make up all matter celerating through an electric fieldof jie volt in nature. potential. One ev is equal to 1.6x 10-14 ergs. COMPOUNDSUnder certain conditions,twoThe unit Mev (million or more elements can be combined. electron volts) is also chemicallyused.Since one Mev = 1.6x 10-0 ergs, one to form what is calleda compound. The resultingamu (1.66 x 10-24 grams), converted to susbstance may differ widely from energy any of itsin accordance with the formulaE = mc2, would component elements.For example, water iscorrespond to 931 Mev. formed from two gases, hydrogenand oxygen, chemically combined. Atomic Table Whenever a compound is formed,two or more atoms of the combining elements join Figure 12-1 is a standardtable of the ele- chemically into what is calleda molecule. Aments called, the periodic table. molecule is the smallest unit that The atoms are shares thegrouped according to the numberof electrons in chemical characteristics ofa compound. Watertheir outer shells. When in this instance consists ofone atom of oxygen successive elements and two atoms are built up by the addition of outerelectrons, hydrogen. there are fairly sharpchanges in cheMical 273 .269 I , PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS

i MI I I Eli 1 I 0 1 I n I in I in I i i III a le IN HEWN SIMMOIN NI IntoneNM N semn1444. Ronan'knew we sonnet.La 3. 4 I I, 0, 1 A Inel Ns 'ARMIN meanMess weMoe

40 e F *NO SU III II IC 14 NOON UTIMIA SERTUNIM woo EAMON NITROGEN OXYGEN FLUORINE 20, 21,t2 )2, 434 1405 16, 12 i6 M 2 44 9 9 10,11 . a

a CI s At Ns ta n a M MI n P Ps 1 MM SAMUM MSCOS MUIE SORM MAMMIM SN 35,37 34, 34 RO 3 An 34, 95, 24 2? 23.2530 31 32,34 34,36

is C. is Ma n Fs PC. as NI ee we.' Ilk n 0 Ill WINONA 12111011141 MANOMMI IRON MAW MOM POTASSIUM MACIUM MVOS MAIMS 51 10,52,53,54 55 59.161 56,60.0,112 311, g, 41 40,42,43,44 45 45,4741,41 KNOW 64 46, 411 50 . 14 10 4 n 01 )O Zs ).Ss It 114 IS A. ea Se atm NIIMON MUM MMIANIUM ARSENIC MOAN MX 74,71,77,70 75, 55 70.10.13.01 63,16 54.115.5751 55,71 70,72,71,74,16 75 KOLE 10 40.51 nurItraum SIRS so Id er ft snaSsium N Y Ill alai 121, liainoltsmum recualvw MOM MIAMI RUSIMUM YTTRIUM ENCOMIA 03 OC MAX" 11 32 1/ 2, !14,15 UP , f2 1,1100,10/ OW 141,1711,11 OAS % md 104 106,110.111 se Xs 5 se MI es Is 5015 5.14 IN 11 se I MIMI ilitiz TELLURIUM 1001112 CADMIUM INDIUM 114 ANTIMONY 1242110210114 10; 105,S 113,115 111,103 130,1111,132,134, i'llrlIttral Ilitaass 12.42 1311,9/ 114 ps W vs Rs 74 0. 77 1, vs P1 NCO in Ile RARE ea 111 vs Ts WORM MAMMA SAMNA IMOLA 714465701 MMUS OMMUNI COM SAPIRM MOMS 1a5, SL? Ittlar,1116,1011 114.113 111,1114,1115,11111,11111 1334a 130,162,134,135,136 51-71 114.1711,177,M1711 wag tscpskoruKin mr, "stag Nee Men 1110 . .5 55 6 acult el w MIN 51 14 es Ps IN At LOCO IsAs LEAD MOUTH POLONIUM ASTAME 0011) MUNN 026169.1 IS? 1741111011,100,201 IMAM 104,1106,2022011 t09,0 16412 lib NI

.7Fr .8 We PARS FROMM 114011A1 34111115 Lat11.11P20._ 55005 7 ?A 510 51414 . . . - se To 7/M II 1.4 se Es es 04 41.16alamp ern eMs Cr ev Le nee so h se INI In aft MURN 10114 UW 1UA i__.MIN lIST3T1101 COMA PRAMOMM NODYMPMAMMONI swmiimam 1115 152,314,135, III 1114,170,171, nazi iros. UMMANM 144,147,145, 151,153 142,144111. IN 154.1511 MO, IMAMS 1311,1311,140, 141 103,143,144.Ut vn, ess,no IM171,174, M5,146,144 1411,eqs, nem% 64 iiala,Iss. 1M BLUE 154 ISO

we les In se Am HEN el Mt es CI se Is NM% iel PM enateresai uN, mpg MIDELEVIUMMOTAMONSOWIDOW Arritul Natal AMEMMUM MIMI IMPIMUUMEMPORIUM1151001 FMNIUM URANIUM MillINIMIXIMAERISPU/1'0161111 Nits ,tit La am 253 256 WM 254 AMATIII WallgitutWainask . s 1 5.36 Figure 12-1.Periodic table of the elements. properties from element to element.(But inreasonably suppose that the atoms- of which the rare ear*. series, at the.bottom ,of thematter is composed are electrically neutral; table, this is not true. These successive ele-'that is, they. contain no net charge.Atoms -ments are built, up by the addition of electronsnormally contain exactly as many electrons in the Inner shells.) moving,, in.:,shells around the .nucleus as.there are proton's" .in the, nucleus.Neutrons, having charge.. do. not affect the chemical nature of ATOMIC STRUCTURE e -number ;Of protons in the cleus that determines the element to :which The Nucleus and..EleCtrone, atom :belongs.. 7For an-example, hydrogen has one proton and one orbital, electron.Helium The atom is composed of apositively charg has two protanS., and two . electrons, increasing' 7 central 'mass calledthe NUCLEUS.. :,This;mass Or each heavier atom, until we -come tothe last is Made up of protoziS,s which have a, positive turalleleilielit, uranium, which has 92 protons 'chak'ge, and neutrons, 92 electrons.. AiciUnd(*e'auCiOukbiit**0018*Ic9147:9*. it,areelectrons WhichroveIn .rlits. O1-lectron

: : charge.. Since the p.nicha . igepositively.. The electronsre' not distributed at random nd the electron is cha ged negatively, we can .t.:`:tiiC-.nUcleus,. but:exist.. in arrangements

`.?

. Chapter 12-FUNDAMENTALS OFNUCLEAR PHYSICS which follow definite laws.Figure 12-2 shows 12-3.) Atoms with outer shells an atom of oxygen with 8 protons,8 neutrons, completely and 8 electrons. Two of these filled.will not unite to forma molecule; for this electrons are inreason some elements cannot be combinedchem- the shell next to the nucleus.No more than twoically. electrons may be present in thisshell, no matter We have stated that the what atom is underconsideration. If a nucleus chemical properties has more than two protons, of an atom are determinedby the electrons. electrons in excessThe chemical identity ofan atom is determined of two lie in shells outside Ihefirst oneThese shells are normally designated by the number of protons,or positive charges, by capital let-in its nucleus. Hydrogenis hydrogen because ters, the first one being. K,the second,: K, the third,hit, etc. its nucleus containsone proton; uranium is uranium because its nucleuscontains 92 protons. Chemical Implications Electrical Implication's The electron structure of an atom determines Because electrons arevery small, and move its chemical properties.So far we have dis-in orbits at relatively great cussed the K shell. To fill the distances from the L shell, 8 elec-nucleus, an atom is mostlyempty space (fig. trons are required. Lookagain at figure 12-2.12-4). An atom is The oxygen atom has 8protons, 8 neutrons, about 10-15 cm in diameter. and 8 electrons. Two of (This figure refers tothe diameter of the outerter these electrons areelectron orbits.) A nucleusis about icru cm in the K shell.This leaves 6. in the L shell,in diameter. which C.an'told In order' to fill the L shell Since the electron isso far from the nucleus, and make it coMpletei. "twomore!. eleCtront arean atom can lose an outer electron needed. . under cer- 'For this reason. th)): Oxygen'atomtain conditions. These freeor stray electrons, combines readily with two hydrogenatoms to form a chemical compound.'-water. having a negative charge,usually seek an atom (See. figurewith a vacant space in its outershell.

. 66666666,.e..gLicioNs INNER ORBIT + +'+ S.} 9-PROTONS IN NUCLEUS 0 0 0 0 0 0 90:.01:REURICIlIRarNUCLEUS 43-`%.

I .0 . ". . % ..1.,..; .. ,... .%.. % 1 :r e' 7 ,_`k,. 1// Il oI .. ,! I .41 X 1, !fa .% I 1 1 /: :'..,,L,.:'7,t .. 11'',i.:1',/: ?. I'2 ....ift'.'.19\.:' I),,:----: /- 1.1,-..;.:1:- ;:. "...,..".".tii'iri.

1 . : ....c.. % :-.. , '.'x''':: ..'/.. -,ii .

: 7.!'.777.,""'.. 7 OXYGENv. r !- ' " PRINCIPLES OF GUIDED MISSILES ANDNUCLEAR WEAPONS shells around the nucleus. Thisnumber is the ATOMIC NUMBER, or SYMBOL Z.The next characteristic is the number ofNUCLEONS THE TWO HYDROGEN ELECTRONS HYDROGEN nucleus; FILL THE TWO VACANCIES IN (sum of protons and neutrons) in the THE OXYGEN SHELL this is called the ATOMICMASS NUMBER, or / the 0.--.. I 0 SYMBOL A. The standard notation takes following form: zXA, with Xrepresenting the 1,0" 110 symbol of the element to which theatombelongs, Z. the atomic number, and "A theatomic mass

I number. Using this notation, anyatom can be easily described. For example,92235 is an atom with 92 protons (symbol Ufor uranium), .41) 92 electrons in shells around thenucleus, and a total of 235 nucleonsin the nucleus. Since OXYGEN °..4b 92 of the nucleons are protons, thisleaves 143 ss I# neutrons in this particular atom. 1 0 1 ISOTOPES HYDROGEN 5.37 Isotopes are defined as atoms of the sameele- Figure 12-3.A molecule is formed by a ment, but different atomic mass numbers.Hy--) union of outer shells. drogenhas three isotopes. The mostabundant isotope of hydrogen has one protonand no .

. - When an atom loses or. gains..an ,electron, the electrical balance of theatomlis changed. It is said to be IONIZED.. When anatom loses an electron it becomes a POSITIVEION. When it gains an electron it becomes aNEGATIVE ION. The product of an ionizing eventip.usually an ion p,air.of equal and' opPOeifteCharge.' Ionization does .ntit' alter the 'ilUcleus,'.;and therefore doeS not Change one element la an other. 'As. soon. as 'conditions permit, anionized particle-. reverts to its balanCed or'electrically neutral state. . Through excitation eleCtron :cam Jump froni..-one shell ' to. the neit:' Inthis process a small amount ofelectranagnetic, energy is given off; this energy is called 's:PROTON. .

NUCLEAR StYMBOLS

t, 4 Before the; discoveiy of tne!neutron,acien.! tists' identified; the atom one or .Awo letteik ssymbols rePiesenti4g; itor"chiniCal , name. For example, H ,i/as helium,' etc.,4114e:is..!inioWn:taes SYMBOL. X. An order S 'APPROX. 400FT IF AO ,. discuss the Jelemeti

1. tit et..4" Chapter 12FUNDAMENTALS OF NUCLEARPHYSICS neutron, as shown in figure 124. Another iso- These different types of radiationare emitted tope of hydrogen, called deuterium,has onebecause the unstable nucleiare trying to reach proton and one neutron.The third isotope,stability.These nuclei can attempt to reach tritium, has one proton and twoneutrons. (See figure 12-54 stability by emitting a beta particle,an alpha, particle, or a gamma ray.Different types Another term which is sometimesimportant,of nuclei will have theirown characteristic and which you should not confuse withthe iso-mode of radioactive decay. Somemay always tope, is the isobar.Isobars are defined asemit alpha particles; othersmay emit beta, different elements with thesame atomic massgamma, or other particles. number, for example, iritium andhelium 3, which are shown as: ;114 and 2He3. STABILITY Isotopes will be mentioned frequentlyin later parts of this chapter and book. It has long been l&uwn that themore protons OTHER NUCLEAR PARTICLES a nucleus contains, the more neutrons it must have, proportionately, for stability.If a nu- Scientists found in certain uraniumsalts acleus contains relatively too fewneutrons it curious phenomenon that causedexposure ofwill be radioactive, emittinga positron when photographic plates, although the plateshad it decays; If it contains toomany neutrons it will been shielded from light.This phenomenonagain be radioactive, emitting this timea beta was called RADIATION, and it emanated fromparticle when' it decays. Stable lightelements the nucleus.Laterwork was done usingare found to have equal numbers of protons electric and magnetic fields to deflectthis radiation. and neutrons, but the heavier elementscontain In this way three basic types ofincreasing proportions of neutrons toprotons. radiation were separated and identified(fig. Thus, stable helium 4 has two protonsand two 12-6).One type could not be deflected byaneutrons in the nucleus; halfway magnetic or electric- field. up the table of This was calledelements a typical nucleusa stable isotopeof gamma radiation.Another type was deflectedsilverhas 47 protons and 60neutrons, a slightly and appeared to be positivelycharged; this was called alpha radiation. And neutron-protron ratio of 1.28; and, at the topof still an-the table, uranium 235 has 92 protonsand 143 other type appeared negative in charge,with aneutrons, a neutronproton ratio of 1.55. further deflection.This type was called beta radiation. The neutron-proton ratio is importantto Under some conditions an excited stability because of the slight tendencyof pro- nucleus emits another particle of thesame masstons to repel each other even though boundinto as an electron, but with a positive charge; thisa nucleus by nuclear forces. Because of their is a positron. Remember that all ofthese radia-charge, the protons will tend to separatefrom tions originate in the nucleus of the atom. one another.However, because of saturation

ee a

H2 D2 OR . 1 0'13oh173

.HYDROGEN . DEUTERIUM TRITIUM 5.40 e 12-5.The three' hydrogen isotopes. '

PRINCIPLES OF GUIDED MISSILES AND NUCLEARWEAPONS ar

PHOTOGRAPHIC PLATE

(0)

MAGNET

RADIOACTIVE SOURCE LEAD BLOCK SHIELD WITH HOLE IN TOP (b)

144.81 Figure 12-8A.Radiation deflection experiment, 9.11X10 4' GRAM showing three types of radiation. (.00055 AMU)

GAMMA PHOTON cannot allbe,on the nuclear surface. Totake + a9.11X10"" GRAM a:up nuclear space, then; an excessof neutrons ( .00055 AMU) will be required, since these particleswill (c) experience no charge repulsion, but only nuclear 5.159:.160 forces., PrOtons on opposite sides of theFigure 12-8B.Absorption of gamma rays, geuspeinw4lillepinendfaellte e#e ner force( but only an electrostatic force. How- showing (a) photoelectric effect; (b)Compton ever, they are bound nuclearlyto common effect; (c) pair production. intermediate interne nueleone, 'and so the small electric repulsion is notsufficient to exPel thent.. In other words,:since the bindingdifferent atomle numbers).In each case, the fofce of a micleon is greater than the electricproton. finds it desirable to change identity, repulsive force; thenecleue staystogethet. becoming a neutron, and kicking off its charge in the form' bf a positive'beta 'particle(post- When there are tee Inlay protenS: in a nu7 results clews the .geneiaily. 1107 trim); Therefore,. /3 + 'radioactivity Mairi'lioUnk-but ;it Mei be that a lower energyfrom too low a neutron - proton ratio.In a state will exist are ele Similar. process, and a moreCommon tYpe of meets haVethe same.-MeeiknuMbeks. kidioactivity, a . neutron may change itself into

20.4A-At 1. Chapter 12FUNDAMENTALS OFNUCLEAR PHYSICS

a proton and a negative beta particle -(electron),nuclear reactions is tremendously ry which is ejected. greater than This type of change resultsenergy release of chemical reactions. We from the fact that thereare too many neutronshave covered nuclear reactions only brieflyat in the nucleus, and there isa lower energy statethis time; they will be coveredmore thoroughly for the isobar with a lower nip ratio.There-in a later section of this chapter. Theirprac- fore, $ - radioactivity results fromtoo high antical importance will become evidentin later nip ratio. chapters. When a radioactive isotope containstoo many neutrons, a neutron in the nucleus changesto a RADIOACTIVITY proton and an electron, which isejected as a beta particle. The new nucleus whichis formedPRELIMINARY has no change in atomicmass number, but the atomic number increases byone.For an example: Radioactivity can be definedas the process by which one or more types ofradiation are emitted from a nucleus because thenucleus is H3--0-21le3 unstable. Although we can predict from 1 +beta particle + energy. experience. and observation whether a nucleus isun- stable, it is impossible to predictaccurately When an alpha particle is emitted fromthewhen a particular nucleus will undergoradio- nucleus, this nucleus changes toa new nucleusactive decay. The rate of decay fora particular because it loses the two protons andtwo neu-radioactive isotope is described statisticallyfor trons which make up the alphaparticle. Ana large number of atoms in much thesame way example of this would be: that an insurance companycan predict the life- span of an "average" man living in the United U235 States, although it is impossible to 92 Th291--0,-+ alpha particle +E predict when 90 any particular individual will die. Thisuse of a large number of atoms is valid becauseeven a The emission of a gammaray does not changesmall amount of material containsa very large the structure of the atom sinceit still has all ofnumber of atoms. its protons and neutrons. Gammadecay may occur alone if the nucleus has mole energy thanNatural Radioactivity is necessary for stability. Moreoften gamma rays are emitted in conjunction with other prod- With very few exceptions,aturally radio- ucts, especially beta rays. active materials will be found towardthe end of the table of elements., (Seefigure 12-1.) CHEMICAL VERSUS NUCLEAR REACTIONS Each nucleus has its own particular rateof radioactive decay; it may decay withina fraction of a Nuclear reactions involve atomicnuclei.second or it may take billions ofyears. Some They are quite different fromchemical reactions. scientists believe that allelements probably go In chemical reactions, changesoccurthrough the process of decay;, but forsome the in electron configurations, but theatomic nucleiprocess is so slow that our instruments cannot remain the same. Anexplosion results fromdetect it, so we say that theseelements are the: very rapid release, of a large amount ofstable.One of the active isotopes (uranium) energy.When equal masses are .considered,finally becomes lead througha series of radio- nuclear energy. release' is of a muchgreateractive decay, but the process takes billionsof Magnitude than chemicalenergy. Two kinds ofyears.. nuclear liiitcticins that satisfy the conditionsfor the productionot.a large amountof energyInduced Radioactivity. ilia 'Wirt time are "fission" and fusion."The complete fission of .1one: pound .,offissionable It is possible to change a stableelement into material can produce much` energy as 8,000a.--radioactive. element by bombardmentof its pounds Of TNT; the fusion of.ode. :poUnd atoms' in a nuclear reactor. AU of the existing fusionable :material Would releaseroughly theelements' can now -.be made radioactiveby same 'amount energy as 28,000.: pounds of bombardment.in this: manner..' Hundreds.of dif- TNT. So yoti can see that the energy: release,:offerent radioactive..Isotopes.can be produced

2'15 f-A.. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

artificially. Their use is widespread in medicine and industry, as well as in research. For example, radioactive phosphorus is used to treat BLOUNT SYMBOLS RALF Wit RADIATION skin cancer; it emits beta particles, which do not Uranium 00238 4.5 x 109 years a penetrate very deeply. 'Radioactive iodine is gon234 24.1 days 15, 7 used for the treatment of diseases of the thyroid Thorium because these glands have an affinity for iodine ProtacUnium 91pa234 1.14 minutes 0, 7 2.35 x 105 years a and attract it. Uranium 82U234 Figure 12-7 is a diagrammatic representa- Thorium 90Tb230 8 x 104 years ct, 7 tion of manmade radioactivity, in this case a obi2211 short-lived activity called TRANSMUTATION, Radium 1812 years a, 7 or the changing of one element to another. A Radon 10022 3.025 &LP a p0218 nitrogen 14 atom is bombarded by an alpha Polumoni 3.05 minutes a particle.It absorbs the alpha particle and is 84 20.8 minutes . 0, 7 very briefly fluorine 18. The fluorine 18 quickly Lead 82P9214 Bismuth 81114 19.7 minutes 5, 7 0 emits a proton, leaving a nucleus of 8 protons 1.5 x 10-4see a and 9 neutrons, which is oxygen 17, a stable Polonium 84P°214 isotope. n210 1.33 flatmates S Thallium 81 pb210 22.2 years 0, 7 RADIOACTIVE SERIES DECAY Lead 82 Bismuth 4.97 days 0 There are three families of naturally radio- 83111210 Polonium 100210 138 days a active elementsuranium (fig. 12-8, the uranium :A series), thorium, and actinium. Each of these Lead (0Pb298 stable families has a separate isotope. of lead as a final product.These isotopes disintegrate or 144.62 decay in a definite series of steps, until a stable Figure 12-8.Table of the uranium series end product is finally formed. At each step in of decay. this process, either an alpha or a beta particle is emitted from each reacting nucleus; in some of these processes gamma rays are emitted.Alpha Radiation Figure 12-8 shows the steps in the decay of It has already been noted that alpha radia- uranium. tions are positively charged and have relatively little penetrating power.Due to the Wive positive charge of an alpha particle (+2), it has a strong attraction for electrons.Alpha particles passing through a material tend to strip NITROGEN -14 NEUTRON OXYGEN -17 electrons from the atoms in-this material. O PROTON At first the alpha particles are traveling too fast to capture electrons. But while slow- FUJORINE-113 ing down, or after stopping, the alpha particle gains two electrons and becomei a stable helium 4 atom.Although the fast' alpha particles do not capture electrons, they are able to strip them from atoms ofthe material they pass through, so that positive ions remain in HYDROGEN1 (PROTON) their path: Alpha particles are the mostheavily ionizing radiation found in natural radioactivity, c. and can produce as many as 70,000 ion pairs

. 5.41 itioneventimeter of travel. Figure 12- 7.Artificial or inducted radioactivity. A. Bombardment of ,a nitrogen 14-.atcim with anBeta Radiation 'alpha 'particle; B. The :alpha particle' is mo- : . mentarily !absorbed; forming fluorine 18; C: One . You .will:recit117,that.,beta radiation is char- rprOtint east off; leaving ioxYgen;17:. ; acterized by a negative charge. Further analysis

...; S id 4toro' Iki3Okstx 440 w..,r Chapter 12FUNDAMENTALS OF NUCLEARPHYSICS

shows that beta particles have thesame chargea positron (a particle with the same and mass as electrons; thus they mass as the were identifiedelectron but with a positive charge). (Seefigure as high speed electrons of very highenergy.12-6B(c).) Energy-mass transformation is Beta particles also have theability to ionize atoms in material through represented by the equation E = mc2. Themass which they pass; butof each particle is 0.00055amu. One amu is because of the difference in sizeand speed, their ionizing convertible to 931 Mev. Using E= m x931, the ability is approximatelyoneminimum energy required for pair productionis one-hundredth that of an alpha particle.The(2) (0.00055) (931) = 1.02 Mev. Ithasbeenfound beta particle travels faster thanthe alpha par-that energy cannot be converted to ticle, and therefore is mass unless more penetrating. the nucleus is present toconserve momentum. There is another phenomenon called inverse Gamma Radiation pair production or ANNIHILATION.This occurs when a positron and an electron react to formtwo The loss of an alpha or betaparticle some- photons of 0.5 Mev each. times leaves a radioactive nucleuswith an excess quantity of energy, which it emitsalmostNeutron Radiation immediately as a gammaray. This radiation is different from the other typesin that it is The dangers from alpha, beta, and electromagnetic in nature. gamma Since gamma raysradiation have become well known. Anothertype have no charge, they are unaffected bymagnetic. or electric .ffelds (fig. 12-6). of radiation hazard is presented byneutrons. Their ionizingThese are usually found in dangerousnumbers ability is much less than thatof either alphaaround nuclear reactors or in depositsof fis- or beta radiations, although they have muchsionable material.Neutrons are neutral par- greater penetrating power. ticles with a mass slightly greater thanthat of Because gamma rays haveno charge, andthe proton, about one amu. Since neutronsare are electromagnetic in nature, you mightex-uncharged, they cannot ionize atoms by attracting pect that gamma interaction withmatter wouldnegative or positive particles. However, be impossible.This is incorrect, however, neu- because trons do cause ionization by indirectmeans. . gamma rays are able to interact inThis secondary ionizationmay be produced by a three. separate waysby the photoelectricef-recoil mechanism wherein a neutroncollides fect, by the Compton effect, and bypair pro- with a proton (the nucleus of thehydrogenatom); duction. the proton will then produce ionizationas it PHOTOELECTRIC EFFECT.Under certainmoves through matter. This recoil mechanism conditions,. a gamma ray can physically collide with an orbital electron. is important because the huinan body islargely The electron is thenmade up of compounds containinghydrogen ejected from the atom after absorbing thegainina (water being the most abundant). ray Completely (fig. 12-6B(a)), causing ioniza- Neutrons are both a cause anda result of fis- tion. Photoelectric ionization bygamma rays ission and fusion reactions. They donottravelfar primarily .a low energy interaction, andfalls offbecause they are either quickly captured rapidly with an increase or un- gamma energy. Thedergo decay, which results in therelease of greatest probability of the photoelectriceffectradiation. Their range of travel depends occurring -is in the higher Z numbered on their atomsspeed; there are both fast and slowneutrons. and low energy gamma rays. Thegamma rays emitted from the outer shells ofatoms are ofHALF LIFE lower energy then those from the innershells. COMPTON EFFECT..In this interaction, The spontaneous emission of radiation only part "of...ther ganima from ray. lwabsor.b.edbY theradioactive material is a gradualprocess.It electron.The gamma raY...suffere.aloss'. oftakes place, over a period of time, ata rate de- energy: andis.scattered. as itionizeOhe atompending on the nature and amount of the material. (fig: 44E04.. Thia effect is maintainedat higherA useful term for expressing therate of radio- energies than the- phOtOelectric:effeet,but dropsactive decay is HALF LIFE. The half life off :raPidlY..-;in.- much the Same .Manner. is the ; time required for one-half ofa given amount of a PRODUCTION.When'thigh-energyradioactive isotope to decay: Again, thisis a &Mina -.ray painies'.neara nucleus ; ..itcan changestatistical term based upon, avery large number .: from:electromagnetic.energy.intd,aheleCtron-and:of atoms. As Gong as we havea large number of PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS atoms of a radioactive isotope, one-half of thesePractical Application atoms will decay in one half life, so that eventually only a small fraction of the original Rate of decay is very important when consid- isotope remains. If a given number of atoms of a ering safety.It is this measurable feature of particular radioactive isotope is allowed to decay decay that makes it possible to reoccupy areas for one half life, only 50% of the original isotopethat have been contaminated by radiation from an will remain. If allowed to decay for another halfaccident or the debris from a nuclear explosion, life, only 25% will remain. Likewise, during eachafter waiting for the radiation to be reduced by additional half life of decay, one-half of the re-decay. After a few days or weeks (depending on maining atoms will decay (fig. 12-9). the type of radioactive material), too few of the Half life can be expressed in any convenientradioactive atoms are left to do much harm. time units. The half lives canbe found in suitableSome of these atoms, of course, remain radio- tables or nuclide charts. Some typical examplesactive for years. of half lives are: HALF THICKNESS U238 alpha emitter: 4.51 x109years 92 As has already been mentioned, radioactive substances emit particles and rays that produce 210 ionizing reactions in previously normal atoms Po alpha emitter: 138.4 days or molecules.Under competent control and proper safeguards, radiation can be harmless, as when a hospital corpsman makes a chest 94Pu2 39 alpha emitter: 24,300 years X-ray. It can even be a power for good, as when a surgeon trained in radiology destroys cancer- ous cells without damaging much of thepatient's 38Sr90beta emitter: 28 years normal tissue.But out of control, or without proper safeguariet radiation can be one ofthe When a nucleus undergoes radioactive decay,great hazards of our time. it is attempting to reach a more stable state, but It wad previously explained that alpha par- the new nucleus that is formed may, also beticles have low penetrative power. Ordinary radioactive. In fact; a whole chain of radioactive clothing, or even unbroken skin, will prevent "daughter" nuclei may be formedbefore a stablethem from entering the body from the outside. nucleus is finally reached.There are manyThe only way one can suffer much ionization chains of radioactive isotopes of this type. Seedamage from alpha particles isby eating, breath- figure 12-8 for the uranium series. ing, or otherwise taking into the system, some

THE HALF LIFE OF A RADIOACTIVE SUBSTANCE IS THE TIME REQUIRED FOR HALF THE ATOMS IN A GIVEN MASS TO DECAY

50 % ORIGINAL 25% OF ORIGINAL PROTAC - PROT AC . TIN I UM TINIU M

AFTER 34,000 YEARSF.

,12-9.=The principle of half life. Chapter 12FUNDAMENTALS OF NUCLEARPHYSICS

radioactive isotopes that will become lodgedin RADIATION UNITS the body and remain there througha series of half lives. In order to discuss the effects of radiation Beta particles traveling in airare effectivedamage quantitatively we must havea unit of within about 10 feet of theirsource. Denserradiation.The basic unit for the activity ofa substances, like wood or water, limit theirradioactive substance is the CURIE. This unit effective range to about a thousandth of its valueestablishes the activity (that is, the decay rate) in air. Normal clothing gives substantial (thoughof radium as the standard with which the activity not complete) protection against beta radiation.of any other substance can be compared. It is, however, the gammarays produced by By tieing a formula that takes into account all radioactive decay, and the free neutrons thatthe number of atoms per gram and the valueof characterise Manmade nuclear reactions, thathalf life in seconds, scientists have determined are grave threats to health and life. Nuclearthat the activity of radium is equal to 3.7x 1010 power plat .4 must be shielded to protect the op-nuclear disintegrations per gram per second. erators Ann other personnel from these radiation Slue is then a unit of comparison. hazards. k ale of any radioactive substance, there- Although gamma radiation isnever com-fore, is the amoqt# of that substance Alia will pletely absorbed in passing through matter,produce 3.7 x 10" disintegrationsper second. absorption can be discussed in terms of halfFor example, it would take 6,615 pounds of thickness. This is the thickness ofa shieldingnatural uranium to produce one curie.In the substance necessary to cut the radiation intensitymanufacture of radioactive isotopes for medical in half.As figure 12-10 shows, the half-thick-and industrial purposes, the curie is too large ness varies from one shielding substance toa unit for convenient use.A commonly used another. -It also varies with the type ofradia-submulttple of the curie is the microcurie, tion (neutron or gamma)that is underconsidera-3.7 x 10' disintegrations per second. tion. At the opposite extreme, the curie is too small a unit for measuring the high-order activity produced by a nuclear explosion. For this purpose the megacurie (3.7 x 1016) is used. Since radiation is detected by the ionization THE HALF THICKNESS it produces, and since its effects on organisms QF A MATERIAL IS TM THICKNESS THAT are.due to ionization, one wayto measure radia- CUTS INTENSITY IN HALF tion is by the amount of charge it produces in a given volume or mass. For thispurpose a unit called, the roentgen is used.A roentgen is STEEL defined only for gamma or X-radiations. It is the amount of X-ray or gamma radiationre- quired to produce by ionizationone electrostatic unit (eau) of charge in one cubic centi- meterofair at.standard temperature and pressure. In the Radiation Health Protection Manual, CONCRETE NavMed P-5055,a roentgen is defined as "That amount of or .gamma radiation which will produce 2.083. X .106 ion pairs in 1cc of air under....stande;;d. ionditiOns.One roentgen of X-. or, ,gamma..radiation. is considered to deliver one.Rad".,(radiation absorbed dose.) A rad .is,the. absorption of 100 ergs/gram 1n:whatever material is under diecutision.Note . , w00° ;.1 WOOD GAMMA RADIATION NEUTRON RADIATION that for. thisUnit 'the., type ..of. material mustbe specified... ,allows, fara.clistinction be- 5.43 tween. such things as soft tissue andbone. igUre,127l0.TVpical eXamplecofrelative the ..roentieh: is the., measurementof . , 'kali thickness.. . orgaisma-tadiation :we need.a term. for PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS alpha and beta radiations, as these particlessensitive to radiation; therefore the cells which also cause ionization.Theproper term fordivide the most rapidly are the most sensitive. this is the REM (roentgen equivalent mammal).You can classify cells into least sensitive and A rem is the quantity of ionizing radiation ofmost sensitive types.The most sensitive are any type which, when absorbed by man or somethose of bone marrow, lymph glands, hair fol- other mammal, produces a physiological effectlicles, and skin. Theleast sensitiveare those equivalent to that produced by the absorptionof the bones, nerves, muscles, -and brain. of one roentgen of X- or gamma radiation. All this seems somewhat intricate, but it is There is another factor which is used by thenecessary fOr a discussion of the effects of Bureau of Medicine and Surgery to obtain a quan- radiation on living matter. The effected radia- tity which equates to a common scale thetion exposure also depend on how fatitthe radia- biological effectiveness of any type of ionizingtion is delivered.If it is delivered slowly, the radiation to which an individual is exposed. Thisbody has time to repair some of the damage. For is the Quality Factor. example 1,000 roentgens delivered in afew sec- For X-, gamma, or beta radiationthe qualityonds would almost inevitably prove fatal within factor is 1 a month, but the same amount delivered uni- For neutrons of unknown energy, and protons,formly over a lifetime would produce relatively the quality factor is 10, that is, a given quantitylittle effect. of neutrons would cause ten times as much bodily damage as the same amount' of gammaUTILIZING IONIZATION PHENOMENA radiation. For ionizing particles heavier than protons There are two terms commonly used in the quality factor is 20. discussing ionization phenomena.They are dose and dose rate.Dose is the total quantity The Human Body of radiation absorbed by an organism during a single radiation experience. Since the roentgen The, human body is made up of many differentand the rad are concerned with the charge per systems, such as the respiratory system and theunit of volume and the energy absorption per digestive system.These systems are furtherunit of mass, the part of the organism involved divided into organs, which in turn are made upin a dose must be specified. For example, if a of tissue. Although tissue may differ from organ1,000-rad dose were received in theforefinger, to organ, there are remarkable similaritiesthe effects would be quite different fromthose of between tissues of different organs. Alltissuesa 1,000-rad whole body dose. are composed of cells. Because of difference's By dose rate is meant a radiation dose per in the response of various kinds of cells tounitof time.This could be expressed in radiation, the biological effect of radiation onroentgens per hour (r/h), milliroentgens per different tissues will vary.Cells vary fromhour (mr/h), or rem/hour. 1 tissue to tissue, 'but they have many common features. Radiation Detectors Sinceradiationaffectsthecell, and individuals are composed of a large number Radiation cannot be detected by any of the I Of cells,' yOU shOuld know something. of thehuman senses.Instruments must be used to 1 effects'otradiation on cells: detect the presenee of radiation. These instru- All Cells with theexceptio# of the redments, called 'radiacs (Radioactivity Detection, blood cells hOe'Comnion.7.coniPonents inclUdingIndication, and Computation), are used to detect the niembiani,-cytOplatiik ..nUcleir:Meinbrancs,the interaction of radiation with some type of and nuclenik(NOte that"iniClens"fitt'abiologicalmatter. term here unrelated "atomic nuelexii.). The Of the many ways that a particle or photon nucleus is the ,cotitiOlii#g'Oenter .' the :cell,of radiation can transfer energy to matter, and is the` part most radiationthe one that is of concern here is IONIZATION.

daMnge.:.':It'181.' well " kiitOw*that.#10 000' 10. In aRemember, that each time an ionizing event takes continUOile;:itite' repair;= Someplace,: an ion pair is formed.This pair con- cells' arediliitliiiiile-,Otheri ;intosists of a positively Ionized atom and a free two to iietolsee4*0411;3:p*iiig>,.*kikii0j,eitits ofelectron. ' .detectori.these free ithrtii0O1 the, nucleus of the ce11`is particularlyele'ctrions are bolleOted on a :'positive electrode. Chapter 12FUNDAMENTALS OF NUCLEAR PHYSICS

To collect the free electrons there must beanpositively charged electric field due to the pro- electric field in the detector. tons already in the target nuclfras, the neutron Figure 12-11 shows a basic radiac circuit.effectively does not "see" this electric field Radiation interacts with the detector sensitivesince it has no charge of its own. W1n the volume (usually a gas) and givesa pulse ofneutron comes within approximately 10""cen- electrons.. A power supply is needed topro-timeters of the nucleus, it will be subject to the vide the necessary power for detectoropera-great cohesive (attractive) nuclear forces. tion.The electronic circuits shown are amp- For the proton,or any other positively lifiers,multivibrators,andother standardcharged particle, the above process does not circuits.The output of the detector can behold. The proton, for example, will encounter displayed on either a scaler, ora count ratea positively charged force field due to the pro- meter. tons in the nucleus.Since the proton is posi- Most of the radiacs in currentuse are de-tively charged, the force field is repulsive in signated as beta-gamma detectors, alpha de-nature.The repulsive field increases very tectors, or neutron detectors.Although mostrapidly until the proton gets to about 10-13 of these instruments are designed to countcentimeters from the nucleus. The cohesive pulses, their output indication depends on the type attractive forces start acting at this distance of radiation they are designed to detect.. Beta-and overcome the repulsive forces. Thepro- gamma instruments are calibrated in roentgenston may then enter the nucleus. The effect is per hour or milliroentgens per hour.Alpha as if there were a "wall" that the proton must detectors are usually based on the number ofpenetrate.This "wall" is 'called a BARRIER. radioactive disintegrations per minute that theThe barrier ends approximately 10'12 centi- material is undergoing, or counts of disintegra-meters from the center of the nucleus. lion per minute that are being detected. LAWS OF MASS-ENERGY RELATIONSHIP NUCLEAR REACTIONS You no doubt have heard the expression that nothing is wasted or lost in nature. For In a nuclear reaction there. is usuallyahundreds of years, physics classes were taught bombarding particle called the INCIDENT PAR-that matter can be changed, but not destroyed. TICLE. When the incident particle hits aBurning a piece of wood changes it to smoke, 'nucleus at rest, this nucleus is:called the TAR-heat, and ashes. This is called the law ofcon- GET. It a particle is emitted in the reaction,servation of matter. this is the:EJECTED particle. Another conventional law of physics is the , The proton, neutron, electron, positron,law of conservation of energy. This law states alpha particle, .and gamma ray all may causeathat one form of energy can be converted to nuclear. reaction.. another form, but the energy is not lost or . Neutrons,. when used as. bombarding'par-destroyed. ticles, have very little difficulty in penetrating These two laws were the basison which all into a target nucleus.Although there is achemistry was built. The energy coming out of radirActive substances such as uranium puzzled the %dentistsit seemed that energy was being' created.Albert Einstein worked out the answer ta,this puzzle by his theory of relativity. He: showed that matter and energy are different forms of the same thing. Matter can be de- OR stroyed, but energy. is:created.Einstein de- clared (and proved mathematically) that mass and energy.: are: -exactly- equivalentmasscan be,, converted to.. energy, and even; the reverse POWER is ,trueenergy can sometimes be convertedto SUPPLY mass.It is the total-mass-energy of: the uni- verse that remains. .constants Whewan atom is ::14463split,someOf ii:vhangidita energy, Figure 12 -11.- Basic radiac circuit that is, mass As destroyed to .produce energy:

t-xe: 1.-.VP. ..2414=R-;).1. `rr... PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Chemical changes, as we have learned, in- From this example you can readily see that volve only the movement of the outermost1.02 mev of energy was created from the con- electrons of atoms, and therefore relativelyversion bf18.22 x 10-28 grams of matter littleenergy is used to make a chemical(.00110 amu). change, freeing the electrons of one atom and recombining them with the electrons of an-BINDING ENERGY; MASS DEFECT other atom.h:o form a molecule.The loss of energy t., so small it cannot be measured The table of atomic masses ahowsthe proton, with any laboratory instrument. neutron, and electron to have masses of 1.00759, The forces binding together the parts of nu-1.00899, and 0.00055 atomic mass units, re- clei are vastly stronger than the forces bind-spectively. One might suppose that the mass of ing together the atoms of molecules. To breakan atom could be determined bycounting the these forceii requires a large amount of energy.number of neutrons, protons, and electrons, and It is not entirely understood what forces hold thesimply adding the masses of these basic par- neutrons and protons together in the nucleus,ticles. Let's take a common isotope of fluorine, but it is called BINDING ENERGY. Electrons9F18, and see if this is true. This isotope has are held in place by electrical force.The9 protons, 9 electrons, and 10 neutrons. 9 pro-, amount of energy that appears in a chemicaltons would have a total mass of 9.06831, 9 change, such as the uniting of a carbon atomelectrons would have a total mass of 0.00495, with two oxygen atoms, is only a few electronand 10 neutrons would have a total mass of volts. When an unstable nucleus emits radiation,10.08990.The sum of the atomic mass units the nucleus that remains weighs slightly lesswould be 19.16316. From the table of atomic (that is, has leas mass) than the original nucleus.masses we find that the known mass ofthis The small amount of mass that disappears isisotope is 19.00445 amu. The difference be- transformedinto the tremendous amount oftween the known mass and the sum of the energy represented by the blast, heat,and radia-masses is 0.15871 amu.It appears that the tion. This is the conversion of mass intofluorine atom is missing this amount of mass. energy, the fundamental fact behind theentireThis is not really an error, as it would seem. atomic energy field. When an atom is formed from the basic par- The amount of energy that would be re-ticles, a certain amount. of mass disappears leased by the disappearance of a given amountandChanges toenergy, which is released in of matter can be computed by applying Ein-accordance with Einstein's E =mc2. The stein's ecouktion: mass that is lost is called theMASS DEFECT. E = mc4 Every different atom has a different mass de- E is energy in ergs fect.The energy that is released when the m is mass in grams. atom is formed is called TOTAL BINDING c is Ihe velocity of light(3 x 10centi-ENERGY. Conversely, this total binding energy meters per second; when squared or multipliedis what is necessary to break an atom into its by itself, this becomesx 1020, or 9 followedfundamental parts: protons,neutrons, and by 20 zeros) electrons. We can use the positron-electron annihila- The binding energy of an atom can be de- tion process 'as an example of the conversiontermined from the formula E = M x 931, in of maim, to energy (the form Of energy iswhich E is the energy in millions of electron gamma' "rays).The Amiss of, the positron andvolts (Mev), M is the lost mass (mass defect) eleetren is '9.11.10'46 grams.' The square ofin atomic mass units_ (amu), and 931 is the the speed of light ,is 9,x-1040, so constant" Thisforniula.is t- derived from E in-ergs ='2 x:1048 z 9 z 1020 orE biog.It can be used to epatermine energy :E; =1'1:64 it 10'8 ;ergs release whenever mass disappears, as, for ' Since 'the, energy 'of gamma' rays= is given.inexantple, in the isotope of ..fluorine discussed electron volts; we)inust -convett ergs- to elec.;above. The total binding energy would. be trcin:iroltsi) One electron volt ib- equivalent to0:15871 x 931.= 147.75901 Mev, or Approxi- 1:60 x:1 Cr 12,2eiggi hence ti : mately 147.8 Mev. important .factor in considering the sta- L:;: r;'Ll30:4` 1A F A bilitiOf a nucleus is the average binding energy per:: nucleon. This is 'simply'. the total binding Chapter 12FUNDAMENTALS OF NUCLEARPHYSICS

energy divided by the number of nucleons in the The physicists could explain thisphenom- nucleus.The binding energy per nucleon inenon in only one way.The heavy uranium the above example would be:147.8/19 = 7.8nucleus taxes its binding Mev per nucleon. energy almost to the This means it would takebreaking point, much as an oversizedewdrop approximately 7.8 Mev to removea proton ortaxes its surface tension. If all conditionsare neutron from this atom. favorable, a slight, sudden stab againstthe Although total binding energy is larger fordewdrop, or the impact of a singleneutron larger nuclei, binding energyper nucleonvariesagainst the uranium nucleus, suffices tosplit as shown in figure 12-12. either into two nearly equal parts. Because of the strong nuclear bondsin the The startling experiment was repeateda nucleus, those with the highest bindingenergiesnumber of times, and the energy liberatedby per nucleon are the most stable and the leastthe reaction was carefully measured.The likely to undergo FISSION, theprocess of split- energy per atom proved to be about 5,000,000 ting a necleus into two lighter nuclei,or FUSION, times that of burning coal.Here, then, was a the process of combining two lightnuclei intodiscovery that might have tremendous practical a larger nucleus. importance, provided the fission reaction could be sustained and controlled. NUCLEAR FISSION FISSIONABLE MATERIALS. An intensive search for fissionable materials revealed three PIONEER. STAGES. During the late 1930'ssubstances with practical possibilitiesas nu- scientists were conducting several typesofclear "fuel." They are as follows: "atom-smashing" experiments. One ofthese U235' experiments involved the use of the neutrons a uranium isotope constituting 0.7% from the deuterium (heavy hydrogen)atom as of natural uranium, high-velocity bullets to bombard smallquan- Pu239,an artifical isotope of an element tities of uranium.This experiment produced plutonium that is itself (for allprac- a result that even the specialists were reluc- tical purposes) man-made,. tant to believe until all other possibleexpla- U233,an artificial isotope of uranium, de- nations. had been tried and discounted. Some rived in a reaction involving thor- of the uranium atoms had been splitinto almost ium. equal parts, to form new atoms of bariumand NEUTRON PRODUCTION. Free neutrons kyrpton. are the major tools of the nuclear physicist. They have the proper size and weight toinvade the atomic nucleus, and their electricallyneu- tral character keeps them from being repelled 9 by the protons.For large-scale nuclear fission operations, man needs an abundant supply

of neutrons.. .

7 For laboratory purposes, the physicistcan bombard the atoms of a light element (boronor beryllium, for example) with alpha particles or gamma rays from certain radioactive isotopes, or with charged,particles froma cyclo- tron or other accelerator.All these methods result in neutron einission. 3 In the practical production of radioactive 2 materials, he secures free neutrons by the nuclear reactions themselves. Studies ofradio- activeseries. decay have. shown that some : 80 ; 40 60. 10 fissions result in the freeing of at leastone 100 120140 .. 160: 190 200.120 240 neutron. '2Undei. proper control, the freeneu- trons cante put' to work. CONTROLLING THE NEUTRON.Inany nuclear reaction except a planned explosion, both the production: rate and the speed' rate offree PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS neutrons must be kept under control. This When a free neutron enters a moderator, is an essential safety precaution. it collides with (but does not penetrate) one When emitted from their atoms, some neu-nucleus after another, losing energy with each trons travel fastat about 1/20 the speed ofcollision.Eventually it leaves the moderator light.For some purposes, such as the split-at a greatly reduced velocity. ting of the heavy but firmly bound nuclide like Moderating materials can be designed to U238, the high kinetic energy of fast neutronsserve as reflectors.These are layers or is required. In other nuclear processesstructures that turn stray neutrons back toward including the fissioning,_ of unstable heavy nu-the parts of the reactor where they will serve clides such as U233t U435, and Pu239a mucha useful purpose. lower neutron speed is desirable; fast neutrons Substances that allow free neutrons to enter would simply pass through these nuclides, ex-but tend to hold them captive are called ab- citing them but failing to produce fission. sorbers.These substances are used in the By control methods that will be mentionedsafety shields and control rods that are re- shortly, it is possible to decrease the speed ofquired in all designs for nuclear reactors. If neutrons to about 1/10,000 of the maximumunavoidably present where they are not de- possible value. At this low speed, the kineticsired, absorbing substances reduce efficiency. energy of the neutrons is about equal to that of NEUTRON REACTIONS.Not all emitted a gas under standard conditions. For this rea-neutrons behave alike.Frequently they cause son they are called thermal neutrons. non-fissioning reactions, typical examples of The term slow neutrons includes thermalwhich are sketched infigure 12-13. The mod- neutrons, but is much less restricted in meaning.erators and absorbers recently described are To slow down fast neutrons, the designersdeliberately used to produce non-fissioning of nuclear reactors usesubstancesor devicesreactions.It is possible, however, for such called moderators. Good moderating materialsreactions to occur even within fissionable sub- are elements from the low end of the table of thestances. nuclides, and compounds formed from these In elastic scatter (also called elastic col- elements.Moderating substances include (butlision) a neutron or other particle touches or are not limited to) hydrogen, carbon,beryllium,nearly touches the target nucleus, then bounces ordinary water, heavy water (in whose mole-away. No nuclear energy is released, though the cule deuterium replaces common hydrogen),colliding particle may transfer some of its and paraffin. kinetic energy to the nucleus.

ELASTIC INELASTIC CAPTURE SCATTER SCATTER

33.275 Figure 1243.Some non-fissioning reactions. ..288 284 .. Chapter 12FUNDAMENTALSOF NUCLEAR PHYSICS In inelastic scatter, partof the energy of the collision excites CHAIN REACTIONS.The twoneutrons lib- the target nucleus anderated by fissioning in figure 12-14may behave causes itto give off gamma radiation.The in any of the various ways that bombarding particlemay merely touch the have just been target nucleus, or it summarized.If conditions are especially fav- may actually pass throughorable to fissioning, theymay both produce it as shown in the centralpart of figure 12-13. The reaction called particle fissions.Under slightly different conditions, ejection onone may cause fissioning and onemay be cap- bombardment resembles inelasticscatter, with the difference that tured. As long as any fissioningreaction can be one particle enters the nuc-traced back, step by step, to theoriginal fis- leus and a different particleleaves it. Gammasion, the process is a chain reaction. radiation accompanies thisreaction. The term chain reaction is not In CAPTUREa neutron (or, rarely, some the exclus- other particle) enters the ive property of the nuclear physicist.It may target nucleus andbe used to describe any chemicalor physical stays there.This reaction, once again,excites the target nucleus and process in which the products ofone stage produces gamma (sometimes called a generation)act to produce radiation. By the capture ofa neutron, thethe next stage. nucleus changes fromone isotope to another. Chain reactions fallinto three classes: When the bombarding particlesplits the target nucleus into two smaller nonsustaining, sustaining, and multiplying.' nuclei, as shown A nonsustaining (or convergent)chain re- in figure12-14 the reaction is, ofcourse, FISSION. action comes to a dead stopsooner or later. Though omitted from thisdrawingIn this reaction, too few productsof the various for the sake of simplicity, theplanetary electrons of the fissioning nucleus stages are effective in producingnew stages. are divided be-The process, therefore,cannot continue very tween the product nuclei whenthe new atomslong. are formed. The result, then, is the produc- The nonsustaining chain reactionshown in tion of two lighter and oftenmore stable atoms.figure 12-15 starts with Since fissionablesubstances have a high one neutron as the ratio of neutrons to protons, initial fission particle.This produces three their transmuta-neutrons; 2 escape and 1causes a second fis- tion to medium-weightsubstances is usuallysion.The accompanied by the liberation of second fission produces 3 neutrons; at least one2 are captured by impurities,1 escapes, and spare neutron. This neutron is welcomedby the physicist, for it becomes the chain reaction stops. a tool for pos- In a SUSTAINING (or stationary)reaction sible use in producing the NEXTfission. It isthe gains by new fissions exactly the emission of free neutronsthat makes pos- balance the sible a self-sustaining chain various types of losses. Consequently, as reaction. shown in figure 12-16 the reaction continuesat a constant strength..Figure 12-17 shows a multiplying (or divergent) chainreaction.In each generation, the reaction products (inthis instance, free neutrons) thatare gained exceed those that are lost.If conditions werees- pecially favorable, the ratio of gainsto losses would be still higher. The nature of any nuclearchain reaction depends, in part, on the purity ofthe fissionable material used. 14" Impurities cause more neutrons to be lost through scatteror capture. The nature of the reaction alsodepends, in part, on the mass and shape of thefissionable material. Even for highly refinedfissionable substances, there are limits belowwhich there are too few atoms to support a chain reaction. This bangs us to the problem ofcriticality. 5.44 A mass (in a given shape)that is just great Figure 12-14.A representative enough to support a sustaining fission reaction. chain reaction is called a CRITICAL meas.A SUBCRITICAL

285 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

0 ESCAPE %""\\' \"\"""""/"\\""\\""""""\"""""""""\\I4- SURFACE-4.

-61 ESCAPE

10ESCAPE / CAPTURE , es

SECOND FISSION

144.65 Figure 12 15,,TExample of nonsustaining chain reaction.

(smaller than critical) mass will support onlyliberate two neutrons, and so on. The fissions a nonsustaining chain reaction.A SUPER-would then increase by geometric progression CRITICAL mass will support a multiplying (1,2,4, 8,16, 32, 64, 128, 256, 512, 1024, chain reaction. 2048, 4096, and so on). FISSION BOMB POSSIBILITIES.As a very The eighty-first step of this process results necessary safety precaution, the masses ofin 2.5.x 1024 fissions enough to transmute a fissionable material present in a nuclear bombkilogram of refined uranium. The time required must be kept subcritical until time for thefor the 81 steps is 1/108 second.These are bomb to be detonated.Then a supercriticalthe types of numbers that had to be considered mass must be formed very rapidly.One wayin the design of, the Hiroshima bomb. of producing a supercritical mass is by forcing UTILIZING SUSTAINING REACTIONS. two or more subcritical masses together. An-When "atomic fuel" is used to produce power other way is to squeeze a subcritical massas in some ships now in commission, other tightly into a new shape and/or a greater den-ships under construction, and certain experi- sity that becomes supercritical without themental electric plants ashorea sustaining addition of any more substance. type of chain. reaction is required. Neutron In a weapon, an efficient, xapicily multiply-production must not be allowed to get out of ing chain reaction is essentikl.Ideally, nocontrol; neither, must it be allowed to die out. free neutron should be' lost to the process. If The designers of nuclear reactors must the first fission produced two free neutrons,face and solve many problems related to the each of theseneutrons should produce twoproduction of an efficient, controllable chain more fissions, each of which, fissions shouldreaction.These problems are beyond the 290 286 Chapter 12FUNDAMENTALS OFNUCLEAR PHYSICS

(tESCAPE ESCAPE 4-SURFACE \\\\"\\\\-\\\"\\/ \\\\\\\\ \\\-\C/R\\\\.\\"\\\\\\\\\\\\"\\\I / / INITIAL FISSION SECOND FIFTH FISSION FISSION

CAPTURE CAPTURE

Jr -0-

ESCAPE)r THIRD FOURTH FISSION FISSION

144.86 Figure 12- 16. Example ofa sustaining chain reaction.

scope of this chapter, but are discussed inof one of the nuclei. Becauseprotons repel one texts on nuclear power engineering. . Other problems center about another, thus tending to keep thenuclei con- the safetytainingthem apart, the single-protonhydrogen factorsboth for the equipmentitself and fornuclei would seem to be the most the people who operate itor live near it. Even promising the disposal of waste products materials for the fusion reaction. must be care- Because they have no neutrons,two atoms fully planned to avoid present andfuture dangers.of ordinary hydrogen cannot fuseto form a heavier element. Deuteriumor heavy hydrogeu,, NUCLEARFUSION with one proton andone neutron per atom, is more promising. Experiments have shown that two atoms of deuteriumcan fuse, producing an As briefly mentioned before,fusion is theatom of tritium (radioactive hydrogen) merging of two light nuclei to form plus an a heavieratom of ordinary hydrogen.Alternatively, two one, with an accompanying conversionof mass to energy. For reasons that atoms of deuteriuga can react toproduce the will be mentionedhelium isotope .9He° plusa free neutron. Either soon, fusion reactions are oftei calledTHER- reaction liberates nuclearenergy. MONUCLEAR reactions. ..A. Any tritium produced byfusion can react SUITABLE SUBSTANC ES.Inorder to fuse, two nuclei must come with, deuterium to produce thehelium isotope very close together with2Heaa plus a free neutron. Thisreaction again enoughkinetic energy to break thebinding forcereleases nuclear energy. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

0 11 _ESCAPE ESCAPEtF17 ESCAPE SURFACE*

INITIAL MX&FISSION

CAPTURE+ 11. (4)FISSIONFISSION FISSION

935

/71k +FISSION FISSION FISSIONisr

si 40 0 0 144.67 Figure 12-17.Example of a multiplying chain reaction.

Deuterium, then, is an effective source ofcontainer is vaporized by the reaction; this is energy, provided it can be made to fuse at all.suitable for a weapon. To achieve fusion, a very high value of kinetic Fusion weapons, then, are really fission- energy must be expended in forcing any twofusion weapons, in which fission occurs first deuterium nuclei to unite. In laboratory experi-and acts to trigger the still greater fusion ments, artificial acceleration of nuclear par-reaction.Because heat provides the kinetic ticles has produced enough energy to initiateenergy necessary for their functioning,fusion small-scale fusion reactions. Mechanical ac-weaponsare sometimescalled THERMO- celeration of particles, however, is not feasible NUCLEAR weapons. in nuclear weapons, nor is itItdaptable to in- FUSION AND FISSION COMPARED.Both dustrial energy production. fusion and fission liberate nuclear energy. The two reactions differ in several respects. Thus far, heat has proved to be the only form One aspect, the means of initiation, has al- of kinetic energy capable of initiating a fusionready been discussed.Fission results when reaction large enough to have practical appli-a supercritical mass of suitable heavy material cations. Temperatures comparable to that ofis rapidly formed.The reaction occurs auto- the sunmillions of degrees Centigradearematically as soon as the free neutrons, al- required. A. multiplying fission chain reactionready present in the fissionable material, are produces these temperatures. Naturally thesupplied with a large enough number of atoms

. 288 292 . Chapter 12FUNDAMENTALS OF NUCLEAR PHYSICS

to support the process. Fusion does notoccurstruction,therefore, is possible with fusion automatically; it must be initiated by theap- weapons. plication of extremely high kineticenergy to Fission produces a large number of RADIO- suitablelight substancesnamely, deuteriumACTIVE PRODUCTSgammarays, nuclear par- and tritium. ticles, and isotopes of various middle-weight There is a practical limit to the size ofaelements. Some isotopes decay in a short fission weapon and, therefore, to the amount oftime.Others have a long half life and canre- energy that can be released by this reaction.main dangerous for a comparatively long tim. If- a weapon contains more thana limited num- A few long -lived isotopes, including strontium vu, ber of subcritical masses of fissionablema-tend, if they enter the body at all, to become terial, it becomes unsafe to handle andtrans-lodged in the bones.There they can cause port. No such limit is placed on the amountradiation damage over a period ofyears. Fus- of heavy hydrogen a fusionweapon can contain; ion, on the other hand, has tritium as its only this weapon may be as large as the availableradioactive product, and the tritium is itself launching devices permit. Much greater de-fused with deuterium to produce stable helium.

293 289 CHAPTER 13 PRINCIPLES OF NUCLEAR WEAPONS AND THEIR HANDLING

INTRODUCTION critical condition until certain sequential steps have been accomplished; this ensures that there SCOPE can be no spontaneous nuclear detonation. The importance of the critical mass must be em- This chapter will discuss hypothetical fissionphasized.It is this inherent feature of the nu- and fusion weapons, and will make some com-clear weapon which makes its operation unique parisons between the twotypes. The classifi-among weapons. In fact, it is the requirement cation of this publication prevents the descrip-that criticality must first be attained that makes tion of specific mark and mods of nuclearthe nuclear weapon the safest weapon in the weapons, but a general description willbe given. The emphasis will be on underlying principles,nation's defense stockpile. rather than on design details and operational In this course it is neither desirable nor sequenCes. permissible to cover all the details of nuclear Like the assembled weapons, the fuzes and However, some basic knowledge of other nonnuclear parts of nuclear weapons willweapons. be covered without reference to specific Servicehow they operate is considered essential. The design. essentials for a practical nuclear weapon con- The latter coition of this chapter will discusssist of the following: the basic organization of the nuclear weapons a. A sufficient quantity of fissionable ma- field, and some of the problems related to theterial to produce the desired energy release. use and handling of nuclear weapons. This material is in a subcritical state prior to the firing sequence of the weapon. IMPORTANCE b. Asystemforbringingthese sub- The Navy has a wide variety of officer billets.critical masses to supercriticality at the desired Many of these billets are indirectly related totime. weaponry. All present officer billets, however, c. Conventional requirements for any weapon are concerned with security, safety, defensivewhich would include a power source, fuzing and measures, and, whenever necessary, disasterfiring circuits, a means of control, and monitor- relief. AU of these officer responsibilities areing. graver and more complex, now that nuclear d. Safety and sating devices. warfare has become a part of the Navy. Whether or not he expects ever to be directly in charge As in conventional weapons, nuclear weapons of any phase of the nuclear weapons program,require fuzing devices to detonate them. These every young officer needs such information asfuzing devices consist of: Barometric pressure he will find in this chapter and in other non-switchessometimes called Hams; internal classified summaries. timers, toth electric and mechanical; sensing radars. hydrostatic pressure switches, com- FISSION WEAPONS monly called hydrostats; and contact crystals. Some weapons have more than one type of fuzing GENERAL REQUIREMENTS built into them and, therefore, have a fuzing option. The control crystals may be used as a It must be remembered that the nuclearbackup device to preclude the possibility of a material in a nuclear weapon is always in a Sub.'.dud weapon.

290 .294 Chapter 13PRINCIPLES OF NUCLEAR WEAPONSAND THEIR HANDLING

Fissionable Material much as a tennis ball bounces froma solid object. This also increases the efficiency of the As mentioned.in chapter 12, .fissionablema-weapon. terial for use in nuclear weapons consistsof suitable isotope of uranium or plutonium.WhenAchieving Criticality a mass of one of these isotopessupercritical in size and shapeis very rapidly formed,a high The means of achieving criticality depends, order multiplying chain reaction automaticallyamong other things, upon the total mass of fis- begins.If the design features of theweaponstanable material present. If there is just enough permit this reaction to continue,a powerfulmass present to produce a sustaining chain explosion will result. reaction, it is said to be a critical mass. If less If the design features do not favora rapidlymass were present, a subcritical mass which multiplying chain reaction, the fission willpro-will only maintain a nonsustaining chain reaction duce only a low order explosion; theweapon mayresults. A multiplying chain reaction issup- even be a complete dud. In view of thetremen-ported by a supercritical mass. dous cost of fissionable materials and the mili- Some of the means used to increase criticality tary importance of the targets at which fissionare: weapons are directed, it is important that these 1. Purifying the material chemically to weapons perform reliably. This section coversdecrease the possibility of capture. Some of the practical problemsthat have been 2. Enrichment of the fissionable material; met and resolved by the designers of fissionfor example, increasing the amount of uranium weapons. 235 compared to uranium 238. 3. Surrounding thematerial with a high density material which will reflect escaping Confining the Reaction neutrons back into the material. 4. Increasing the density of the fissionable The presence of stray neutrons in the atmos-material, which also reduces the escape prob- phere makes it impossible to preventa chainability. reaction in a supercritical mass of fissionable 5. Using shapes with a minimum surfale- material. It is necessary that, before detonation to-volume ratio to reduce kieutronescape (a the weapon not contain any fissionable materialsphere would be ideal). thatis as large as the criticalmass for the There is one other method that is used to given conditions. In order for an explosion tosome extent.This is by bringing two sub- occur, the material must then be made super-critical masses together, thereby increasing the critical within a very short time.Extremesurface-to-volume ratio. rapidityis necessary, because if the chain reaction were to be initiated by stray neutronsGUN PRINCIPLE before the fissionablematerial reached its most compact form, a relatively weak explosion One of the methods by which subcritical would occur. fissionable material can be brought to criticality is used in GUN type nuclear weapons (fig. 13-1). Obviously a nuclear reaction cannot becon-In this type two separated subcriticalmasses tained for very long. Yet this reaction must beare brought together to make a supercritical confined until it has gained so much momentummass.Essentially this is attaining criticality that it will produce an explosion of maximumby increasing the quantity of fissionablema- power. terial. One way to confine the fission reaction would The two subcritical masses of activema- be to use a high density material to provideterial are separated sufficiently so that there is inertia, which would delay expansion of the ex- no possibility of a chain reaction developing; and ploding material. This material acts like thehence no nuclear detonation. At the desired familiar TAMPER in blasting operations. Ininstant, two: events take place. First, the two addition to its primary function of confining thesubcritical. masses are brought together ina nuclear reaction during its early stages, thevery short interval of time to form a super- tamper also acts as a REFLECTOR from whichcritical mass. This is accomplished bymeans neutrons, bounce back into the reactingmassof firing conventional propellants which shoot

291 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS.

In this type of nuclear weapon, criticality is not achieved by adding more material, but by squeez- SUBCRITICAL ACTIVE ing the subcritical mass into a smaller volume MATERIAL TARGET SUBCRITICAL ACTIVE MATERIAL PROJECTILE by means of tremendous pressure.This in- PROPELLANT creases the density and thus the criticality of the 1 fissionable mass. The pressure applied to squeeze uranium or plutonium into a smaller volume is developed by detonating high explo- 131708 in such a way that the pressure wave GUN BARREL moves inward.In other words, by implosion. NEUTRON REFLECTOR It is important to note that for a full scale TAMPER nuclear detonation to take place, the implosion 144.68 wave must move inward from all directions. To Figure 13-1.Idealized gun type weapon. ensure this happening, a number of detonators are imbedded in the high explosive and all must detonate at the same instant. the subcritical projectile mass through a type of When the explosive is detonated, a smooth gun barrel into and in contact with a subcriticalshock wave moves inward against the sphere target mass.When these two masses reachof active material, striking it with equal force supercriticality, a nuclear detonation results.at all points. As a result of this compression, Second, by surrounding the target mass with athe materialis increased in density and a suitable tamper, it reflects neutrons back intomultiplying chain reaction automatically begins. the active material, increasing the reaction, and holds the active material together just a little longer, so that the enormous pressure built NEUTRON SOURCES up increases the effectiveness of the explosion. A question may arise as to the origin of the IMPLOSION PRINCIPLE first generation of free neutrons in a fission weapon. Another method by which suberitical masses One neutron source is the uranium or plu- can be brought to criticality is the basic designtonium as originally assembled in the weapon. of the implosion type nuclear weapon (fig.13-2). Even in subcritical masses, these radioactive

AIRCRAFT INFLIGHT I MONITORING 9 CONT.

ACTIVE SAFING DE- FUZING ATERIAL VICES BAROS PULLOUT RADARS SWITCHES INTERVAL POWER FIRING SUPPLY SAFE TIMERS DEVICES BATTERIES SEPARATION HYDROSTATS DEVICES CONTACT SAFING RELAYS

144.69 Figure 134.Idealized implosion type weapon. 296 292 Chapter 13PRINCIPLES OF NUCLEAR WEAPONSAND THEIR HANDLING

substances undergo a small amount ofspon- (for the sake of simplicity)we can regard as the taneous fission that results in the release oftarget; the other is in the nucleus thatwe can free neutrons. regard as the projectile. The projectile nucleus The designer of nuclearweapons, however, must be impelled with enough kineticenergy to wishes to be absolutely certain thatan abundancepierce the nucleus of the target, in spite of the of neutrons will be available foruse as soon asrepulsive forces that act between the twopro- the mass becomes supercritical. Thereforehetons or sets of protons. places in or near the fissionable materiala The energy requirements do not have to be special capsule called the INITIATOR. guessed; for the various combinations of target This capsule contains two substances. Oneand projectile nuclei, they can be computed by could be a reliable alpha emitter suchas po- standard formulas of nuclear physics. When lonium or radium; the other .7 light element suchthe United States began in earnest to develop as beryllium. When the light element is bom-a nuclear weapon, the fusion reaction was barded with an alpha particle, neutronsareruled out as being unlikely of achievement,on emitted.The capsule is carefully designed toa practical scale, by any means available to prevent any premature neutron development. man. After fission detonationshad been The same mechanical impulse that formstheachieved and their effects had been studied, supercritical mass shatters the initiator andhowever, the physicists began to suspect that makes emitted neutrons available to startthethe thermal energy released by a fissionre- multiplying chain reaction. action might possibly be adequate to starta fusion detonation. A fissionexplosionreproducesbriefly FUSION WEAPONS and in small space intensities of light and heat comparable to those in the sun. A fusion PRELIMINARY explosion does still more; it duplicatesa part of the actual process by which thesun and As explained in chapter 12, nuclearenergy OTHER stars produce their light and heat. is released not only by the splitting ofheavyThis process is not a chemical burningre- nuclei (the fission reaction) but also bythe action; it is a nuclear fusion reaction in which joining of light nuclei to form heavierones (thefour nuclei of simple hydrogen becomeone fusion reaction). nucleus of stable helium, with a conversion of FUSIONABLE MATERIAL is the material mass to radiant energy.The next article will with low atomic numbers which produces nuclear summarize the solar cycle. energy by the fusion of nuclei. Thelow number SOLAR FUSION CYCLE.Man has atomic nuclei have lower binding energies than reproducedon small scale under laboratory uranium or plutonium. Upon hearing thisconditionsthe six-stage process by which, statement for the first time, one might questionaccording to the currently accepted theory, quite justifiably why fusionweapons were notthe sun "burns hydrogen as fuel." Theprocess developed first. The reasonsare several; butinvolves carbon, which undergoes a series of the main reason is the amount of initiatingtransmutations asitcaptures one proton energy required. (hydrogen nucleus) after another, then suddenly emits all the captured hydrogen (now fused into Energy Requirements a single helium nucleus) and regains its original identity. Figure 13-3 shows the sun'scon- tinuously repeated cycle. Neutrons, the particles used in producing In the first stage simple carbon (C12) fuses large-scale fission reactions,possess the ad-with hydrogen (Hi), with an accompanyingre- vantages of electrical neutrality.To causelease of radiant energy representing themass fission, a free neutron has to pierce the bindinglost in the fusion. A similar fusion and release energy of a heavy nucleus that is already inof energy take place in the third and fourth unstable equilibrium, but it does not have tostages. In the second and again in the fifth overcome any electrostatic repulsion. stage, the constantly growing nucleus emitsa When two light nuclei fuse to forma heavierpositive electron; this means, in each instance, element, at least two mutually repellant protonsthat an excess negative charge remainson the are involved. One proton is in the nucleus thatnucleus and, in effect, converts a captured 297 293 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS proton to a neutron by counterbalancing itssimply a helium nucleus.The carbon has positive charge. merely acted as a catalyzing agent to briig In the sixth and final stage a fourth protonfour hydrogen nuclei together and hasten their is captured.If the previous pattern were fol-fusion into heliuni. This is the cycle by which, lowed, the growing nucleus would emit energyfor its millions of years of existence, the sun and become simple oxygen (016); but thishas been heating and lighting our solar system. doesn't happen.Instead, the nucleus becomesThe astrophysicists estimate that enough Irv- violently excited and emits all four of thedrogen remains to keep the cycle going for ten captured particles, thus regaining its originalbillion more years. identity as simple carbon. By the time of emission, the four captured FUSIONABLE MATERIALS protons (two of which, as already noted, have CHOICE.In the sun, then., hydrogen and been converted to neutrons) have achievedcarbon nuclei take part in a revolving, self- identity as an alpha particle, which is, of course,perpetuating process in which carbon becomes

+0,osX

4446

Z... r + RADIATION Iv pROTON .460... 0 us 1 air"" -Itio 1N. 0 e. p ROTOI + rn 4. ALPHA n ft. 0 k-,. ,-A7fici""rob.

33.278 Figure 13-3.Fusion in the sun.

294 .298 Chapter 13PRINCIPLES OF NUCLEAR WEAPONSAND THEIR HANDLING

nitrogen and oxygen isotopes, and then reverts(millions of degrees) and are referred toas to carbon when alp the captured hydrogenfusesthermonuclear processes; thy, c i!:e term "Ther- into helium. In designing the first fusionmonuclear Weapon," or TN weapon, the physicists decided against trying to reproduce the carbon-hydrogen cycle. Fusion Sequence The reason was a practical one.Through not complex, the carbon, nitrogen, andoxygen The first explosive reaction in a TNweapon nuclei involved in this cycle have higherbind-is the detonation of a conventional high explosive ing energies than the two hydrpgen isotopesor the burning of a conventional propellant. As deuterium. (1H) and tritium (111'3).Since thea result, the mass of uranium or plutonium problem of supplying adequate initiatingenergybecomes supercritical, and fissionbegins. When was known to be difficult at best, it seemedthe temperature becomes high. enough, fusion of wise to choose the simplest reagents possible.the deuterium (or deuterium and tritium) :mato The reagents must have both neutrons andpro-begins. Aa the fusion reaction progresses and tons;this requirement ruled outordinarythe heat intensifies, other nuclear reactionsmay hydrogen, but not deuterium and tritium. take place.The liberated neutrons may cause PRACTICAL FUSIONREACTIONS. Asfissions that would not likely occur k lower mentioned briefly in chapter 12, two deuteriumtemperatures. In general, the energy released nuclei can fuse ineither of two ways, asin the explosion of a thermonuclearweapon follows: originates in roughly equal amountsfrom fission 3 and fusion processes. H2+ H1+H 1 1H I.-1 1 energy, and 2. 2 1H+ 1H 3+ neutron + energy. WEAPON COMPARISONS SIZE A fusion weapon can, then, be basedon deuterium.The tritium produced in one of the two possible deuterium fusion reactions is the When you studied ene,;::..e.ert*...k types of radioactive hydrogen isotope identifiedas H3weapons in use now and in the 'recent. past, you in figure 12-5.It does not become an endfound that the yield of fission weaponswas in product, but rather enters into the fusionre-the kiloton range, while that of fusionweapons action by combining with deuterium,as follows:was in the megaton range. A fusion bomb can be many times more powerful thana fission bomb. A fieision bomb is limited in size be- H2+ 3-0-He4 1 1 2 + neutron + energy. cause the nuclear material must be no greater than the subcritical size.It would not be safe to handle or store if the amount of fissionable In the fusion weapon, then as in thesun material in it were greater.. hydrogen becomes helium, with a release of Fusion weapons are not limited in thisway. energy. It is no harder to detonate a large amountof As a fusion reaction progresses and theheatdeuterium or deuterium-tritium than a small intwusifies, other nuclear reactionsmay (andamount; neither is it more susceptible toac- sometimes do) take place.It is possible, forcidental detonation. example, for the neutrons liberated during Through experimentation, physicists have fusion to cause various fissions that would befound means for controlling the fusion reaction unlikely to occur at lowrr temperatures. on a small scale. Further development of their Because it is usable from the beginning oftechniques may make it possible touse the the fusion process, tritium as well asdeuteriumfusion reaction for nuclear power. may be included in the payload of a fusion weapon. YIELDS FUSION WEAPON C AARACTERISTICS The power of a nuclear weapon is expressed Nuclear fusion reactions can be broughtin terms of energy release (or yield) when it about only by means of very high temperaturesexplodes compared to the energy liberated.by the r 299 295 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS explgsion of trinitrotoluene (TNT).Thus, a The forerunner of current radar type fuzes 1-kiloton nuclear weapon is one which produceswas the proximity (for VT) projectile fuze of the same amount of energy in an explosion asWorld War II. Because recent years have seen does 1-kiloton (or 1,000 tons)of TNT. Similarly,many improvements in electronic equipment, a 1-megaton weapon would have the energyradar type fuzes are likely to. be used exten- equivalent of 1 million tons (or 1,000 kilotons) sively in the future. of TNT. The earliest nuclear bombs, such as BAROMETRIC TYPE.As the reader will those dropped over Japan in 1945, releasedrecall from earlier studies in basic sciences, roughly the same quantity of energy as 20,000the atmosphere exerts pressure.Like water tons (or 20 kilotons) of TNT. Since that time,pressure, atmospheric pressure increases with much more powerful nuclear weapons, withdepth. The barometric switch (familiarly called energy yields in the megaton range, have beerthe BARO) is a fuzing device that responds to developed. The nuclear detonations in tests carried outa predetermined value of atmospheric pressure. by the United States have ranged from ap- The barometricinitiatingdevice has no proximately 0.1 kiloton (in Nevada tests) to 15exact counterpart in older bomb type weapons. megatons (in the Bikini tests). It corresponds roughly, however to the conventional hydrostats that areusedin underwater ordnance. FUZING TECHNIQUES TIMER.Mechanical timing devices, representing various applications of the clock prin- INTRODUCTION ciple, are used in many conventional projectiles, bombs, nd mines. Not all of these older clock In the hypothetical nuclear weapons de-mechanisms are used to cause firing at a scribed in this chapter, a conventional explo-preselected instant. Some are used, instead, to sive reaction always acts as the trigger. Thisprevent firing from occurring before a given is followed by the fission and finally (if ar-instant; these timers are associated with impact ranged for) the fusion reactions. Actually, then,of influence devices that initiate the actual firing. the problem of fuzing a nuclear weapon is similar In an aircraft-launched nuclear weapon, of to the problem of fuzing conventional bombcourse, safety delays are vitally important to type or gun type ammunition. The techniquesprotect the launching craft and personnel. A may be somewhat more sophisticated, but thetimer can be designed to provide these delays, essential fuzecomponentsarming system,and also to close the firing circuit when the detonator, safety arrangements, and so onarebomb has fallen a selected distance below the all present. launching altitude. The dropping speeds of the A nuclear weapon may be designed to explodevarious types of nuclear bombs are known; in the air, at the surface of the ground or water,therefore the dropping distance is easily con- or below one or the other of these surfaces.verted to an equivalent time interval. These considerations affect the choice of a fuze. FUZING FOR SURFACE BURST FUZING FOR AIR BURST Heavy blast damage to a target area is A nuclear weapon, like a conventional one, frequently the most effective means of gainingmay be designed to burst at the surface of the a military objective. As chapter_ 14 will ex-ground or water. An impact fuze, in which the plain, a nuclear detonation in the air above ashock of landing causes one operating com- targetproduceswidespread blasteffect.ponent (or group of components) to move with Several types of fuzes can be used to initiaterespect to another, is used for surface bursts. a detonation at a selected altitude. If a delayed explosion is desired, an impact RADAR TYPE. A fuze maybe constructed tofuze may contain a timing device that prevents operate much like a small radar:14ft may trans-the detonation from occurringimmediately mit,receive, and compare electromagneticupon impact: A heavy weapon, falling from a pulses, and may fire when the signal (or com-high altitude, will penetrate some types of soil bination of signals) meets specific built-inand may even bury itself. A delayed-action requirements. . fuse permits this burial to take place.

NO 296 Chapter 13 PRINCIPLES OF NUCLEAR WEAPONSAND THEIR HANDLING

FUZING FOR UNDERWATER BURST consists of a normally open switch thatwill not close until specific requirements have been Nuclear weapons, like conventionalones,met. Similar but not identical electricalin- are capable of underwater detonation by hydro-terrupters are used in nuclearweapons. static fuzes.Timing devices can also be used to produce underwater detonations. PRACTICAL WEAPON TYPES SAFETY DEVICES The active materials and other highlycrit- Because of the high destructive capacityofical substances used in nuclearweapons are in all nuclear weapons, the fuzes used inthemlimited supply as well as beingvery expensive. must have positive protection againstaccidentalTherefore, a policy of attempting to makethe or premature arming. Certain types of safetyfewest number of weapons cover as widea range arrangements and accessories have performedof military applications as possible hasbeen reliably in conventionalweapons.With adap-pursued in the development ofour nuclear tations and refinements, similar safetydevicesweapons stockpile. This capability is achieved are usable in nuclear weapons. by planned interchangeability, and correlationof ARMING WIRES.The arming wirehas longnuclear weapons design with concurrent planning been familiar to naval aviators. Thiswire isand development of delivery vehicles. Bymeans threaded through a fuze to keepa movable com-of conversion components, bombscan be con- ponent from taking its armed position. Duringverted to warheads, and warheads to bombs. In launching, the fuzes (or equivalent devices)addition, by means of adaption kits, nuclearwar- are freed from the arming wires. heads can be made compatible withrockets, In conventional aircraft bombsa delaytorpedoes, missiles and depth bombs. period, providen by a windmill typevane and a gear train, keeps the fuze from becoming BOMBS armed immediately after the armingwire has been removed. In the safe interval, theplant- Since' the aircraft was the only practical ing craft escapes from the dangerzone. delivery vehicle for large weapons during World OTHER SAFETY FEATURES.Inertia,asWar II, bombs were the first nuclearweapons to the reader will recall from basic physics,isbe placed in stockpile. A bomb isa stockpile the natural tendency of a material object Ofstorage configuration of an aircraft-delivered, stationary) to resist being set in motionandfree-fall,or retarded-fallnuclear weapon. (if moving) to resist any changein the directionMajor components and nuclear componentsinte- or' speed of motion.In weapons, the force ofgrally contained in the basic assemblyare con- inertia can be utilized to produce a safety delaysidered to be a part of the bomb. A bomb isa by retarding the relative motionbetween twomajor assembly designated by a mk-mod-alt components. system and stockpiled as a complete entity of During the acceleration ofa projectile in aone or more packages. Additional majorassem- gun barrel, inertia tends to force all parts ofblies such as fuze, firing set, radar,power the fuze mechanism toward therear.Thissupply, and nuclear components maybe required manifestatwa of inertiacalled SETBACKinto constitute a complete nuclear gunnerycan be used to delay arming. Simi- weapon. larly, in several types of mine accessoriesand components, inertia is used either to prevent MISSILE WARHEADS an undesired action or to cause a desiredone. Some fuzing arrangementsfornuclear Almost as soon as fissionweapons had been weapons ude inertia as a means of achievingaproved practical, the thought ofa guided missile safety delay. with a nuclear explosive charge beganto inter- Electrical arrangements constitute anotherest the ordnance engineers. Since thattime, all means of assuring safety before and duringof the armed services have developedreliable launching, and for a selected perititl thereafter.missiles capable of delivering nuclear payloads. Nearly all naval mines, for example,are A nuclear warhead normally consistsof a assembled and planted With several breaksinhigh explosive system, nuclear system,elec- the battery-to-detonator circuit.Each breaktrical circuitry, and the mounting hardware.

29/ PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

A check of unclassified sources indicates theATOMIC DEMOLITION MUNITIONS following missiles as having a nuclear capability: The Navy's Polaris, Asroc, Subroc, Taloa, and ADMs are nuclear warheads adapted for use Terrier; the Army's Davy Crockett, Pershing,as emplaced demolition charges that canbe used Sergeant, Little John, and the Nike-Hercules;to destroy bridges, power stations, etc. and the Air Force's Atlas, Matador, Minuteman, Titan, Bomarc, and Genie. GUIDED MISSILES OTHER APPLICATIONS There are several different types of guided missiles, for different applications, just as Projectile there are different types of launching systems, from the short range Terrier to the intermediate The Army-has developed a nuclear projectilerange Polaris, and the long range Atlas. Most that can be fired successfully from artilleryof the guided missiles now in stockpile are howitzers. adapted for conventional as well as nuclear warfare. Underwater Weapons Safety is again of prime importance; a selfdestruct package is an integral part of the The Astor is a submarine-launched torpedowarhead, to protect friendly personnel in case capable of carrying a nuclear warhead.Thethe missile goes off course, or fails in its Navy also has developed a surface ship-launchedintended mission. rocket propelled weapon called ASROC, which In the Polaris missile system, a submerged may use a conventional torpedo or a nuclearsubmarine is, in effect, the launching platform depth charge as a warhead. for a deterrent or retaliatory missile. When used for this purpose, the submarine has many advantages. Nuclear propulsion and improved DELIVERY SYSTEMS AND TECHNIQUES design have given the submarine a ranging power and a degree of maneuverability that would have AIRCRAFT seemed fantastic as recently as World War II.

The usual advantages and disadvantages ofUNDERWATER ORDNANCE conventional aircraft bombing missions apply equally to missions involving nuclear weapons. The airplane is swift and maneuverable; it can One of our newer weapons used the con- penetrate far into enemy territory. ventional torpedo tube as a launching platform. Because of the large blast damage of nuclearSubroc is a guided missile used for antisub- bombs, the crew must be protected from thismarine warfare.It is launched from a sub- damage once the bomb is dropped. One way tomerged torpedo tube, programmed through the accomplish this could be to insert a timingair to reenter the water for a submarine kill. mechanism in the bomb to provide a safe separa- It provides ranges greatly in excess of present tion time. Another method would be to providetorpedo ranges. the bomb with a drag parachute to slow the bomb until a safe separation distance has been reached. This is described as a retarded-fallbomb. Both SAFETY AND SECURITY of these methods allow the aircraft to reach a point of safety prior to bomb detonation. SAFETY PRECAUTIONS In nuclear weapons, three main classes of GUNS components are subject to specific safety precautions.One class is the conventional high

As was previously.stated in chapter 12, theexplosive or propelling charge. A second gun is used by the Army and Merit', Corps toclass is the complement of mechanical and fire nuclear projectiles at long ranges: Eitherelectrical devices that provide for handling, a proximity fuze or timer can be used AOarming, and firing.The third and final class detonate this weapon. is the nuclear material.

298 .; 2 Chapter 13PRINCIPLES OF NUCLEARWEAPONS AND THEIR HANDLING

Conventional Explosives detonation of a nuclear weapon, there isstill a dangerous radiation hazard, unlessproper As was explained previously, highexplosives,safety procedures are followed. Uranium and propellants, and detonators are intergal partsinplutonium may become dispersedas small the construction of nuclearweapons. Due to theparticles as a result of impactor detonation of presence of these explosive hazards, the dangerthe high explosives, oras fumes if a fire from fire or an accidental detonation isalwaysoccurs. present, just as with conventional ammunition. The Department of Defense and the U.S. High-explosive safety criteria developedforAtomic Energy Commission havespecially conventional weapons are equally applicabletotrained personnel prepared to dealwith all nuclear weapons, whetheror not any nuclear material is present. aspects of accidents involving nuclearweapons. For example, our Explosive OrdnanceDisposal school trains in all phases of high explosive Electrical and Mechanical Components recovery or disposal in case of an accident, and only trained personnel are authorized forthis In addition to high explosive hazardstheretask. are also electrical and mechanical safety aspects of nuclear weapons. The same adherenceto SECURITY established safety criteria must prevailwith respect to the handling and testing of electrical, Nuclear weapons, because of their strategic electronic, and mechanical components ofnu-importance, vulnerability to sabotage, public clear weapons.The same precautions usedsafety considerations, and political implications, with high voltage, condensers, etc.,are also ap-require greater protection than theirsecurity plicable to nuclear ordnance.Similarly, con-classification alone would warrant. ventional mechanical safety precautionsin con- To prevent the possibility of accidentalor nection with handtools, power tools, chainhoists,deliberate launching or releasing ofa nuclear dollies, etc., equally apply. weapon, there has been established a "two man" rule.This is that a minimum of twopersons Nuclear Weapons Publications have access to nuclear weapons, each capable of detectingincorrect or unauthorized pro- These are publications promulgated by thecedure in the task being performed. Joint Atomic Weapons Publications System. Only properly cleared personnel whohave Generally, all such publicationsare assignedneed for access to a nuclear weapon,or who an AEC-DASA number; those publications whichhave a need to enter a space containingnuclear bear upon the Navy have in additiona NAVYweapons will be allowed entry to thesespaces. SWOP designation for Navy Special WeaponsOnly personnel of demonstratedreliability and Ordnance Publication. stability will be assigned to this type of duty. Publications include, for nuclearweapons and related equipment:General information or Definitions (4-), Reports (5 -), Safety (204,As- ELEMENTS OF ORGANIZATION sembly (35 -), and Maintenance (40-) seriesof publications, For example, NAVY SWOP 20-1 PRELIMINARY is a publication on explosive safety. When the secrets of nuclearenergy were Nuclear Components unlocked by the discoveries of scientists,men high in government realized that strictlegal All personnel assigned to work with fis-control must be enacted.The Atomic Energy sionable or fusionable materials must receiveAct of 1948 established the legalmeans for special training in the handling, storage, andcontrol and development of nuclearenergy and accounting methods peculiar to these materials.the materials involved.This act was later Prior to such training they mustpossess atamended by the Atomic Energy Act of 1954to least a secret clearance bassi on atackgroundextend controls over the expanding investigation. research and use of nuclear energy, and toexpedite Although nuclear weapons are designed to research and development in this field forpeace- prevent a nuclear yield in case ofan accidentalful as well as military purposes. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

ATOMIC ENERGY COMMISSION energy programs as directed by the Secretary of Defense. The Atomic Energy Commission (AEC) took The Director, DASA, is a military officer over control of all nuclear material from theof three starrank appointed by the Secretary Manhattan Engineer District in 1946. The AECof Defense, upon recommendation by the Joint has outright ownership of all fissionable andChiefs of Staff. Normally the assignment as fusionable material in the United States, and ofDirector, DASA, is rotated among the military all production facilities except those used forservices. special research which are not adequate for production of nuclear materials in amounts suf-Training ficient for use in nuclear weapons. The AEC is composed of five members, one DASA supplies training courses to fulfill the of whom is designated as chairman. These mem-requirements of the military departments for bers are appointed by the President of thetechnically qualified personnel in the fields of United States, with the advice and consent ofnuclear weapons assembly, maintenance, nu- the Senate. clear hazards, safety, and emergency dem- The Joint Committee on Atomic Energy isolition of weapons; and other fields that deal a congressional standing committee composedwith specific technical aspects of the overall of nine Senators and nine Representatives.nuclear weapons program. Team training of This committee makes continuing studies of thenuclear weapons assembly teams is usually activities of the AEC and atomic energy. accomplished at the Nuclear Weapons Train- The Military Liaison Committee is com-ing Centers for naval personnel. posed of a civilian chairman (assistant to the Secretary of Defense for Atomic Energy) andTechnical Services two representatives each from the departments DASA provides technical information and of the Navy, Army, and Air Force. This com-advice that is requested by the Services in mittee advises and consults with the AEC onconnection with their operation of assigned all matters that it believes relate to militarystorage sites, transportation, and other basic applications of nuclear weapons or nuclearlogistics functions required in support of forces energy, including development, manufacture assigned to the commanders of unified and use, and storage of nuclear weapons,andspecified commands. DASA prepares and sub- allocationofspecial nuclear material formits to the Joint Chiefs of Staff for review military research, and the control of information relating to the manufacture or use of nu-and approval, integrated full-scale weapons clear weapons.The chairman of the Militaryeffects test programs, and provides technical Liaison Committee is appointedby the Presidentliaison and assistance for operational evaluation with the advice and consent of the Senate. tests of weapons system involving nuclear The Division of Military Application directsdetonations that have been approved by the the research, development, production, testing,Services. custody, and storage readiness assurance of nuclear weapons.It manages related AECSTORAGE SITES installations and communities, and assists in These are installations maintained for the maintaining liaison between the AEC" and thestorageofnuclearweaponsmaterial and Department of Defense.The Director of theancillary equipment where storage inspection, division is a member of the Armed Forces onstorage monitoring, assembly, or retrofit (or active duty. any combination of these) may be performed. DEFENSE ATOMIC SUPPORT AGENCY National Stockpile Site The Defense Atomic Support Agency (RASA) This is an installation located within the is the designated agency of the Department of,,,continental United States which has facilities Defense.It provides support to the Secretaryfor storage, storage inspection, assembly, and of Defense, the Joint Chiefs of Staff, and theauthorized modification of nuclear and non- military departments in matters concerningnuclear components of nuclear weapons. Weap- nuclear weapons testing and such other nuclearons stored at a. National Stockpile Site are Chapter 13PRINCIPLES OF NUCLEAR WEAPONSAND THEIR HANDLING normally in the custody of AEC. The instal- STORAGE CONFIGURATIONS lation is jointly operated and occupied by AEC and DASA. Stockpile Storage

Operational Storage Site This is storage of weapon major assemblies in a disassembled state.Generally, each of these assemblies is packaged and sealed inan These sites have the same functionas NSSEI individual container. except that they are jointly occupied and operated by AEC and one of the Services. Operational Storage Operational storage is any storage condition Service Storage Facility occurring in the stockpile-to-target sequence following removal of the weapon components This is a service-operated and controlledfrom stockpile packages for partial assembly. site, located within the continental United States, which has the capability for storage and partial Nonready Storage or complete storage monitoring of nonnuclear This is storage of nuclear weapons thatare components. It may also havethis capability forpartially assembled, or in an unpackagedcon- nuclear components. dition which will require more assembly and testing than when in a ready storage condition. Shipi as Sites Nonready storage is used to reduce assembly time from that required for a stockpilecon- dition, to conserve storage space, or afford There are two classes of ships equipped greater ease of handling. to store nuclear weapons. Theseare classed as combatant ships and support ships. Ready Storage Combatant ships, have the capability for Ready storage is storage of a nuclear weapon delivering a nuclear weapon to a target byin a partially assembled and tested condition means of aircraft or missiles. These ships maywhich will permit completion of assembly inthe have a full or partial capability for storageshortest time possible. inspection, maintenance, monitoring, andas- sembly of nuclear and nonnuclear components. Assembled Storage Support ships, such as ABs and AKAs, have This is storage of nuclear weapons ina facilities for the storage and transport ofspecific condition of operational storage and nuclear weapons and for performing partialcompletely assembled, or less thosecom- storage monitoring.Weapons are stored inponents that are to be assembled at the time of either stockpile storage or nonready storage. loading Or during delivery to the target.

ALV

fr. 5... 301 14.41.4' 10;;* - 1 CHAPTER 14

-r EFFECTS OF NUCLEAR WEAPONS

INTRODUCTION that Can be expected, and will mention defensive measures. PRELIMINARY Whenever a new weapon is proposed, two COMPARISONS questions arise.First, what can this weapon do for us in combat? Second, if the enemy usesCONVENTIONAL REACTION the weapon against us, what defensive action can we take? The answers to these questions are A conventional explosion is a chemical reac- seldom simple, even when the weapon is a "con-tion.An initiating impulseusually heat or ventional" type.For nuclear weapons, theshockis applied to a substance whose molecules answers are complicated by two major factors:contain oxygen, carbon, and hydrogen in abun- (1) the explosion is a very large one; and (2) thedance. When initiated, explosive substances explosion is accompanied, and often followed asoxidize (burn) much more rapidly than ordinary well, by ionizing radiation. combustible materials. HIGH explosives (the When these two facts first became publicsubstances used as the burster charge in con- knowledge, a certain amount of hysteria wasventional bomb-type ammunition) are said to inevitable.Hysteria still characterizes muchdetonate rather than to burn in the usual sense. of the popular thinking about nuclear weapons.The detonation propagates itself as an intense Unbiased information, honestly faced and an-shock wave, followed immediately by a release alyzed, is an antidote to hysteria. A great dealof energy in the form of intense heat. of information on the effects of nuclear weapons During this almost instantaneous process, the has now been made available in unclassifiedoriginal moleucles break up and their atoms Government publications.The data for theserecombine to form more stable compounds.Only publications have come from two main sourcesthe electrons in the outermost shells of the the World War II detonations over Japan and theatoms are involved in molecule formation, and a postwar testing program. comparatively small amount of energy is suf- Out of the wealth of available informationficient to free the atoms from one molecular forthis chapter endeavors to summarize the detailsmation and recombine them in another. The con- that are most likely to be useful to a juniorversion of mass to energy in this process is officer.Regardless of specialty, every officersmall. has cause to be familiar with the effects of Most of the energy of heat is converted to nuclear explosions. energy of motion that bursts the container and sends a blast wave through the air, or a shock wave through the earth (or water).It is 4 primarily this blast or shock wave that causes The brief second section of this chapter willdamage. reviewand, wherenecessary, amplifythe However, the amount and type of damage can major comparisons and contrasts between con- be modified bra number of considerations. There ventional and nuclear weapons. The body ofinclude (but are not necessarily limited to) the the chapter will analyze the effects of severaltype and amount of the explosive subietance, the possible types of nuclear explosions. Con- strength of the target, and the distance between cluding sections will analyze the types of damagethe target and the point of detonation. Frequently

302 Chapter 14EFFECTS OF NUCLEAR WEAPONS

the target is shattered; sometimes itis ignitedclass byitself'.Because nuclear radiation immediately. More frequently, fire damage to thecannot ordinarily be discerned byany of the target occurs (if at all) as a secondary result offive senses, and beca ase theaverage person shock damage to fuel systems, stowedex-has a vague and partially erroneous idea of the plosives, or power lines. If the target isa ship,phenomenon, this asnelofa nuclear it may sink because it has been damagedbeyondexplosioneven more than the heavy blast and its capacity for rapid repair; or itmay remainshock damageis a possible source for panic. waterborne but be unfit for combat. . The next section will deacribe the several A successful conventional detonationis likelymajor classes of nuclear explosions, and will to kill or injure at leasta few personnel. Somesummarize the effects of each on a targetarea. fatalities or casualties occur immediatelyand are unavoidable. Still others occur as a result of secondary effects.Their causes may be NUCLEAR EXPLOSIONS falling or flying objects, short circuits,fire, flooding, or other resulting manifestations ofDISTRIBUTION OF ENERGY explosive violenCe.A taut ship or station endeavors to keep secondary casualties toa When anuclearexplosionoccurs, the minimum. This can be accomplished withstrength of its blast or shock wavepressures enlightened foresight, training, and discipline.is tremendously greater than from a chemical The explosive force, detonation velocity,explosive (compared per unit weight ofex- sensitivity, and other properties of militaryex-plosive). It also radiates an enormous amountof plosives vary for different types but allarethermal energy (heat). The nuclear radiation measured in terms of TNT. released into the atmosphere is a more ominous aspect of the event. NUCLEAR REACTION Figure 14-1 shows how energy isdistributed in a representative nuclear explosion. About 85 percent of the total energy appears firstas The forces binding the atomic nucleus to-intense heat. Almost immediately a consider- gether are vastly stronger than the forcesable part of this heat is converted to blastor binding atoms into a molecule. To break theseshock; the remaining thermal energy moves forces, a comparatively large amount of matterradially outward as heat and visible light. must be converted to energy. A nuclear explosive reaction, likea conventional one, is characterized by intense heat and a heavy wave of blast or shock. Theheat is many times higher than in a conventional BLAST AHD THERMAL "KM 32/6 \0110111.1131%.- IMAT/13" explosion; the shock wave, in addition to being 35% stronger, moves more slowly and coversa much greater area.If all or even part of a nuclear explosion takes place in the air, winds ofa high velocity are generated. Secondary effectsfalling and flying objects, damaged pipelines and wiring systems, and firesare more numerous and extreme than after a conventional explosion. Unavoidable casualties may be numerous. Unhappily,other casualties, some of which could be avoided by using elementary knowledge and taking simple pr3cautions, are liable to be very numerous. In these respects a nuclear explosion differs from a conventional one in depeikmore than in kind.In another respectthe certainty ofcon- comitant nuclear radiation and the possibility 5.166 orprobabilityofresidualradioative Figure 14-1.A typical nuclearenergy contaminationthe nuclear explosion is in a distribution graph. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Some 5 percent of the total energy appears The three parts of figure 14-2 show what immediately as invisible but extremely powerfulhappens during thefirst 11seconds after nuclear radiationalpha particles, beta par-detonation. ticles, gamma rays, and neutrons.This is An air burst is defined as one in which the called initial (nuclear) radiation. The residualweapon is exploded in the air at an altitude nuclear radiation occurs over a long time; itbelow 100,000 feet, but at such a height that is produced by the decay of the numerousthe fireball (at roughly maximum brilliance in radioactive isotopes that are formed by fis-its later stages) does not touch the surface of sion reaction. the earth.In a 1-megaton weapon the fireball In nuclear fusionreactions, theactualmay grow to nearly 5,800feet (1.1 miles)across. quantity of energy liberated for a given mass If the explosion takes place about 100,000 of material depends on the particular isotopefeet altitude, it is a high-altitude burst. The (or isotopes) involved. fireball characteristics are different because of the low-density air. The fraction of the explosion yield received Very soon atter the nuclear weapon is trig- as thermal energy at a distance from the burstgered, a rapidly multiplying nuclear reaction point depends on the nature of the weapon andvaporizes all parts of the weapon and its con- particularly on the environment of the ex-tainer.The reacting matter appears as an plosion.For a detonation in the atmosphereextremely hot and brilliant fireball resembling a below about 100,000 feet altitude, it ranges from about 30 to 40 percent.At higher altitudessmall sun. The fireball radiates heat, light, and where there is less air, the proportion of ther-nuclear emissions. mal energy is increased, and the proportion of fission energy converted to blast is decreased.Blast Damage At the other extreme, in an explosion com- The reaction causes a blast wave (the primary pletely confined under the earth, there wouldshock front) to move outward from the fireball. be no escape of thermal radiation. The air immediately behind this front acts as a The 15 percent allotted to nuclear radiationterribly violent wind.In the first portion of infigure 14-1 is appropriate for a fissionfigure 14-2 the blast wave has not yet reached weapon. In a thermonuclear (fusion) device, inGROUND ZERO (the point directly below the which only about half of the total energy arisesdetonation point). The light rays and the equally from fission, the residual radiation carries onlyswift gamma rays, however, have done so. about 5 portent of the energy released in the When the primary blast wave (incident wave) explosion. In contrast to thermal radiation, thestrikes ground zero with an impact like that of quantity of nuclear radiation is independenta tremendous hammer, a swond or REFLECTED of the height of burst. However, the attenuationblast wave begins to move, upward and outward of the initial nuclear radiation is determined byfrom ground. zero.The second part of figure the total at of air through which it travels,14-2 shows the reflected wave. At points on the and the dispersion of the radiation productssurface, the impact of the two waves is felt also varies with the height of the explosion.simultaneously. This is true also, for practical Other factors, such as wind, also affect thepurposes, of points ABOVE the surface in the dispersion of radioactive particles. vicinity of ground zero. At points somewhat farther out, suchPi and PR in figure 14-3,3, however, an object above REPRESENTATIVE AM BURST the surface, such as the top of a tall smokestack or a television tower, would receive two distinct As chapter 13 mentionedflin air burst overblows.It would be struck first by the incident a target is frequently the most efficient meanswave moving radially outward from the fireball of accomplishing a military objective. Aand, diortly thereafter, by the reflected wave 1-megaton detonation (equivalent in destructivemoving radially outward from ground zero. power to a milliontonsatTNrhasbeen selected Ap one goes farther out from ground zero, for study in this article. For a weapon of lowerhowever, the angular distance between the In- yield, the distance and the time intervals wouldcident verve and the reflected wave decreases.. be starter; fur a more powerful weapon, theyIn attar words, the two waves are moving more wild be longer. nearly in the same direction. Also, the reflected

304 Chapter 14EFFECTS OF NUCLEAR WEAPONS

NUCLEAR AND THERMAL RADIATIONS AFTER 1.8 SECONDS FIkEBALL

PRIMARY SHOCK (OR BLAST) FRONT GROUND ZERO

NUCLEAR AND THERMAL RADIATIONS PRIMARY SHOCK (OR BLAST) FRONT

AFTER 4.6 SECONDS REFLECTED SHOCK (OR BLAST) FRONT

'OVERBEGINNING OF MACH FRONT PRESSURE 16 PSI)

AFTER 11 SECONDS

100.32-.34 Figure 14-2. Three abates in thee development ofa 1-megaton air burst at 6,500 feet height. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

INCIDENT WAVE (0

REFLECTED TRIPLE WAVE (R) POINT

plI pill f pi PIV GROUND ZERO 5.189 Figure 14-3.Formation of the Mach front. wave tends to move faster, since the incidentstem has moved outward about 3 miles from wave has compressed the air through which itground zero.The overpressure is about 8 will move. At some point between Int and Pinpounds per square inch, and the wind is blowing in figure 4-13, the two waves begin to be felt asat 180 miles per hour.This is the situation a single strong shock, not only at the surfaceshown in the third part of figure 14-2. (as before) but above it as well.This point By the end of 3'7 seconds, however, sig- marks the beginning of the MACH FRONT. Fornificant changes have taken place, as shown in the explosion shown in figure 14-2, the over-figure 14-4.The overpressure has dropped to pressure (excess over normal atmospherica single pound per square inch, and the velocity pressure) of the Mach front at its poht of originof the wind behind the Mach stem is merely is 16 pounds per square inch. 40 miles per hour. The fireball has ceased to As the combined waves more further fromradiate much heat, but is still emitting gamma ground zero, the Mach front elongates itself,rays given off by the decay of various short- forming the Mach STEM, shown extending almostlived :radioactive isotopes formed during the vertically from points Piii and ply in figurefission reaction. This is an example of residual 14-3.An airplane or a tall object locatedradiation, as distinguished from the initial ABOVE the triple point at the upper end of theradiation given off as an immediate result of the Mach stem will. feel two separate blast waves.explosion. An object BELOW the triple point will feel the Though it no longer glows, the fireball is combined blast waves as a single perwerfulblow.still very hot.It rises swiftly, like a hot-gas The Mach effect is one reason for the long-rangeballoon, sucking air inward and upward after it. shattering power of a nuclear air burst. This suction phase of the buret creates strong Behind the primary shock wave and, afterwinds, opposite in direction to the Mach wind. its formation, behind the Mach totem, a strong,Near ground zero these AF'rENWINDS pull up- 1 swift wind blows almost horizontally outwardward a large amount of surface dirt plus much from ground zero.In its destructive power,of the lighter debris from buildings dudteredby this wind is like a concentrated, short-livedthe blast.This windborne material forms the hurricane. stem -4r water column of the mushroom cloud While the Mach front is being formed, thethat is 'characteristic of a nuclear air burst. In fireball is still radiating large amounts Of heat,figure 14-4 the cloud has begun to form. light, and nuclear emissions. By the end of 11 Within the second minute after a 1- megaton secontls, for a 1-megaton explosion, the Machdetonation, the top of the mushroom cloud is

306 Chapter 14EFFECTS OF NUCLEAR WEAPONS

NUCLEAR RADIATION - PRIMARY RATE OF RISE e SHOCK (OR 233 MPH -711, a,. BLAST) FRONT am% kft(ik,. HOT, GASEOUS BOMB RESIDUE REFLECTED SHOCK (OR BLAST) FRONT

MUSHROOM STEM (CENTER COLUMN)

MACH FRONT (OVERPRESSURE 1 PSI)-

AFTERWINDS WIND VELOCITY 4) MPH

2 1 0 1 2 3 S 6 7 I 9 MILES

100.35 Figure 14.4. Development of mushroom cloud and theMach front after a 1-megaton air burst.

about 7 miles in the air. The afterwindsareof these will, in time, be borne earthwardon blowing inward toward ground zero at about 200raindrops, fog droplets, or dust particles; or miles per hour. they may descend by their own weight.This returning radioactive material 'constitutes the Radiation Hazard fallout that is a peculiar hazard of nuclearexplosions. The mushroom cloud consists mainly of The fallout from a high air burstmay be vaporised fission products and other bombcarried great distances by wind drift, to become residues, plus some of the lighter materiala serious threat. Strontium-90 and cesium-137 carried up through the center column. Theare radioisotopes with long half-lives that have fission products, of course,are highly radio- drifted over large areas of the earth as delayed 'active. . fallout.They get into food and water and thus After 10 minutesthe mushroom cloud isabout are a biological hazard. These tiny radioactive IS miles inthe air and has spread out con-particles are carried in a jetstream of moving siderably. In time, normal winds dispersetheair that circles the earth at the edge of the cloud, thus sipreSdingits over awidetropopause, and are brought to earth by rain or area and dilutIngtheft. snow or by gradual fallout. A rise in the Because some Of theradioactive !lesionstrontium-90 count in milk in the United States products have veryshort half - lies, the tOtalmay be a confirmation of a nuclear detonation radiation tatsard,-is cOnAmitedeellesisingby,over Siberia.Fallout from some of the other decay all Well as by dispersal. It does not types of bursts, however, is a major hazard in completely vanish, however. Fission productsthe more immediate area of the burst. with Wog half-lives, and ,diminishing quantities The studentshouldclearly understand that of those with short halt- lives, remain. Bolea nonfissiOned water droplet or dust particle

307 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS does not itself become radioactive by acting ason preferred methods of construction and ma- a vehicle for a radioactive isotope. All it doesterials to use for shelters. These aspects are is to convey this product of the original explosiondiscussed later in this chapter. from the upper atmosphere to someplace where Becauseitis particularly destructive of it may possibly be picked up by a living organism.structures and equipment (and because of minimized radioactive after effects), an airburst In considering a bomb of greater or lesserabove a target area is likely to be a preferred yield than a megaton, the order and nature ofmethod of nuclear attack.Other classes of the events in an airburst will beas outlined inbursts are possible, however.It is therefore this article but the statistical values will benecessary to notice how each compares with an different. air burst. An air burst, then, produces intense heat (thermal) radiation, initial nuclear radiation from the fireball, residual nuclear radiationSURFACE BURSTS from the fission products in the mushroom cloud, great changes in atmospheric pressure, If an air detonation takes place at every low and strong, high-velocity winds, first away fromaltitude, part of, the fireball, in its rapidly ground zero and later toward it.At and neargrowing early stages, touches the surface of ground zero, any or all of the primary effectsground or water. This type of nuclear explosion are fatal to personnel.The combination ofis defined as a surface burst. pressure and wind destroys all light buildings, The intense heat of. the fireball vaporizes a and possibly all buildings whatsoever. large amount of soil' or water. This vaporized (but ordinarily not fissioned) extraneous material remains in the fireball as it rises.In Personnel Protection addition, the suction phase of the exploSion carries much more debris into mushroom stem Beyond the area of total immediate de- (center column) than would be expected in an air struction, blast and wind damage are still heavy.burst (fig. 14-5). Firesresulting either from the initial heat radiation or from various secondary causes soon reach dangerous proportions. Unprotected personnel may be killed or injured by radiation, by falling buildings, by blows or lacerations from falling or windborne objects, or by secondary fires. Many in underground shelters, and many above ground who have learned and applied elementary defense procedures, can sevethem- selves or, if injured, can be saved by well- drilled rescue teams. The human body is much more tolerant of short-term overpressure than even the strongest buildings are.It is the secondary effects of overpressurecrumbling walls and flying glass, for examplethat cause most injuries.The appalling casualties in the Japanese bombings were due in large measure to tha twin elements of complete surprise and unpreparedness. Many thousands of lives could have been saved had the people been alerted and trained in self-protection in the event of nuclear attack.Extensive and intensive studies of all aspects of those bombings have shown quite clearly how to protect yourself. Various types of buildings and shelters havebeentestad during 5.47 our nuclear weapons tests, and from these Figure 14-5.Formation of dirt cloud in studies recommendations have been published surface burst.

308 Chapter 14EFFECTS OF NUCLEAR WEAPONS

As the fireball cools, the vaporizedforeigntransmitted by the blast wave passingover the material condenses into minute particlesin thesurface. Cracks appear in the soil at varying mushroom cloud. The heavier debris im-distances from the crater, the size anddistance mediately falls back fairlynear the point ofof the cracks depending on the size of theex- burst; the lighter particlesmay remain airborneplosion, distance from the surface, type and for a long time.Radioactive fission productscondition of soil. may cling to any or all of thenon- fissioned The effects of underground shockfrom a particles. The surface burst, therefore,carriesnuclear explosion have been compared toan a much greater threat of hazardous radioactiveearthquake of moderate intensity.There are fallout than an air burst does. Though thesignificant differences, but those inthe business danger from the fallout of heavyparticles isof detecting nuclear explosions in otherareas greatest near the target (where damagefrom cannot always be sure if an earthquakeor a other causes is also severe)the airbornelighternuclear explosion caused the seismicwave particles may seriously contaminate wideareas.recorded on their instruments. In the test at Bikini atoll in 1954,substantial Except in the region close to groundzero, contamination spread over anarea of over 7,000where destruction would be virtually complete, square miles. Fallout can continueeven afterthe effects of blast, thermal radiation, and the cloud can no longer beseen. initial nuclear radiation will be lessextensive It is estimated, for example, thata 1-megatonthan for an air burst of similar size. However, bomb, exploded on the surface of theocean, would early fallout may be a very serious hazard convert about 20,000 tons of water tovapor. Atover a large area. a high altitude, this water vapor would condense into droplets like those inan ordinary cloud,SUBSURFACE BURSTS with the serious difference thatmany droplets would be vehicles for radioactive fissionpro- If a nuclear explosion occurs under such ducts. By the time these contaminateddropletsconditions that its center is beneath the ground fall as rain, they might oe hundreds ofmiles fromor under the surface of the water, it is classed the point of detonation. as a subsurface burst. Since some of the effects If any significant portion of thefireballof underground bursts and underwater burstsare touches land, a crater remains to markthe sitesimilar, they can be considered togetheras sub- of the explosion.The crater is formed partlysurface burst effects.In a subsurface burst, by vaporization of the soil and partlyby up-most of the shock energy of the explosionap- draft into the center column during thesuctionpears as underground or underwater shock, but phase. An observer at a distancecan recognizea certain proportion (which is less the greater a surface burst over land by the dirty color ofthe depth of the burst) escapes and produces the mushroom center column and cloud. air blast. Much of the thermal radiation and of The size of the crater willvary with the sizethe initial nuclear radiation will be absorbed of the bomb, the height at which itwas exploded,within a short distance of the explosion; The and the character and condition ofthe soil.energy of the absorbed radiations will merely Studies made following test explosionshaveheat the ground or the water. Some of the yielded information on the size, shape,andthermal and nuclear radiations willescape, depth of a crater to be expected froma par-varying with the depth of the explosion, but the ticular size bomb in a particular type andcon- intensities will be less than in an air burst. dition of soil (rocky, sandy, wet, dry),and However, the residual radiationsare of con- scalar tables have been compiled forpre-siderable significance since large quantities of dicting effects. earth or water in the vicinity of the explosion A varying portion of the kineticenergy of awill be contaminated with radioactive fission surface burst goes into ground shock similarproducts.If the burst is near the surfaceso to that produced by a penetrating high-explosivethat the fireball actually breaks through,the bomb. This shock aids the atmosphericover-amount of fallout will be about the sameas in a pressure in demolishing buildings near thesurface burst.If the burst is deep enough so point of burst. that none of the fireballemerges from the Beyond the immediate area of the crater,surface yet quantities of dirt (or water)are the ground shock transmitted through the earththrown up as a column into the air, much of the is usually small compared with the shockrock, soil, and large debris (or water) will fall

309 kari.a PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS back in the immediate area, but finer particlesvery deep detonation may fail to produce a will be carried aloft and Al descend later asspray dome.) fallout, perhaps far from the area. When the radioactive fireball (or gas bubble) Many subsurface tests of nuclear devicestouches the surface, the hot gases are violently have been made, for weapon use and for pos-expelled into the atmosphere, drawing up with sible commercial uses, such as blaiting outthem a hollow column (sometimes described as ground to build a tunnel, or a canal, or toa PLUME, or a CHIMNEY) of water. The com- deepen a harbor, or open a mine. A large bodyplex pressure relationships sometimes cause of data has been collected, studied, analyzed,water droplets to form a "Wilson" condensation and charted, so that effects of explosions of di-cloud about the hollow column. The cloud for- ferent sizes, different depths, and under variedmation reproduces, on a large scale, the con- conditions can be predicted%vith considerableditions in the laboratory cloud chamber. The accuracy. Wilson cloud remains only for a second or two, and is not radioactive. The radioactive contents of the bubble are vented through the hollow Underwater Bursts column and may form a cauliflowershaped cloud at the top (fig. 14-6). A nuclear underwater burst is defined as SHALLOW UNDER WATER BURST.Figure one whose origin is beneath the surface a14-6 shows three characteristic steps in a body of water. Most of the energy of the under-typical underwater burst. (Baker test at Bikini water burst appears as underwater shock, butatoll in 1946a 20-kiloton weapon was used in a certain proportion (dependent on the depth)comparatively shallow water.) Part A of the may escape and produce air blast. illustration shows. conditions 2 seconds after A "true" underwater burst is one in whichdetonation.Notice that the shock wave that the detonation and the formation of the com-surrounded the fireball in the water has become plete fireball both occur below the surface of the a blast wave in the air, surrounding the Wilson water.The fireball is in the form of a greatcloud. bubble.Because it is subject to hydrostatic . Twelve seconds after detonation, as shown pressure, the bubble is believed to be smallerin part B of figure 14-6, the water column has than fOr a bomb of comparable yield detonated inreached a height of about 3,300 feet. (An esti- the air. As the -rising bubble touches the sur-mated million tons of water were raised in the face,its glow disappears, because the gases.column in the Baker test.) The fission products expand and cool when they meet the lesserventing through the center of the column have resistance of the air. begun to condense into an atomic cloud resem- While it is still under the surface, the fire-bling a giant cauliflower. ball (or gas bubble) generates a shock wave, The cauliflower cloud is strongly radioactive, much as a fireball in the air generates a blastbut is too high to be a serious threat to ship- wave. A later paragraph will ment ion Some of theboard personnel at this time. A much greater peculiarities and military uses of this shockimmediate threat is the BASE SURGE that has wave.The peak overpressure does not fall offbegun to form around the lower end of the hollow asrapidly with distance as in air, but thecolumn. The base surge consists of radioactive duration of the shock wave is shorter than inmist from the contaminated water in the hollow air. column, which is now dropping backward due Two phenomena give advance warning that the to gravity.The base surge spreads radially fireball from an underwater: detonation is ap-outward, giving the appearance of a doughnut- proaching the surface.: First a rapidly expand- shaped cloud on the surface of the water. ing: white circle, called the SLICK, appears on the surface. The slick is compoSed of countless By this time, too, large water waves have droplets.. asurface 'water that have .been -tossedbegun to form andmove,outward from the base up by the. advancing' shock wave. At the center of the holloW column. of the slick, .a dome of water' and' spray rises, By /the twentieth second after detonation, con- directly over the detonation 'point. ditions are as shown in the third part of figure Neither the slick .nor. the,spray dome :con-14-6. The base surge is growing higher as it taint; -any ,radloaCtive ' matter,. They are -fore- moves outward. Large quantities of contaminated

runners of the true 'explosion phenomena.. . (A water, the MASS1NE WATER FALLOUT, beginto Chapter 14EFFECTS OF NUCLEARWEAPONS

HOT, GASEOUS I BOMB RESIDUES AFTER 2 I SHOCK FRONT SECONDS , , CONDENSATION (WILSON) CLOUD

HOLLOW WATER COLUMN I WATER PRESSURE WATER LEVEL (SHOCK WAVE) I yatf.s.2.4 4:47.::::::':::EK::::::K:::::::::::::::::0,::. "4 CRATER I WATER BOTTOM

I I

1 CAULIFLOWER CLOUD I OP.. AM el.e NUCLEAR RADIATION

COLUMN 3300 FEET IN DIAMETER

AFTER 12 WALL 500 FEET THICK SECONDS BASE SURGE FORMING (VELOCITY 120 KNOTS)

FIRST WAVE (HEIGHT 176 FEET) tt 595 UMW 1.4

CAULIFLOWER CLOUD

NUCLEAR RADIATION ,--

WATER FALLING FROM CLOUD (VELOCITY 50 FPS)

COLUMN GROWING MORE AFTER -20 SL ENDER SECONDS BASE SURGE STILL FORMING (VELOCITY 90 KNOTS)

WAVE;HEIGHT 106 FEET

MILES 1 1K 2 3

Figure 14-6.Three stages in the development ofa 100-kiloton shallow 5.163 underwater nuclear burst. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS pour down from the mushroom cloud. The direction. The base surge may extend downwind hollow column is continuously shrinking. for several miles. An underwater detonation at greater depth A minute after detonation, the hollow columnmay fail to produce any of the phenomena shown is much lower and the ring of outward-rushingin figures 14-6 and 14-7. Instead, the hot gas base surge much higher.Contaminated waterbubble may break into a large number of small and spray from the cauliflower c1ev.1 encirclebubbles as it rises through the water. When the the hollow column.Water waves continue tosmall bubbles reach the surface, they maybreak form and move outward. The first wave hasinto radioactive froth, perhaps with a thin layer traveled almost a mile from the column. In theof contaminated mist above it.' The mist is not Bikini lagoon tests, beaches were inundated, aslikely to create a large fallout problem, but far away as 11 miles, some to twice the depthdangerous amounts of the radioactive foam may of the approaching wave, far more than hadbeenbe washed against surface vessels or even anticipated. against the shore. Two and a half minutes after detonation, During any type of underwater nuclear ex- figure 14-7, the central column has been com-plosion, all or a great percentage of the radiant pletely replaced by a radioactive mist or cloudheat is absorbed by the water. Many of the first that extends downward to the surface of theneutrons and gamma rays are also absorbed. water. The base surge, still forming an outward- When and if the bubble reaches the surface and moving ring around the central cloud, has liftedbursts however the various fission products slightly. It appears, therefore, as a low-hangingarestill emitting rays and beta particles. cloud from which radioactively contaminated The hollow column, the cauliflower cloud, and rain is pouring. This rain is hazardous to sur-the base surge all contain large numbers of face vessels in its path. radioactive particles. The fallout (or rainout) of Though diffusion and the natural decay ofthese particles is liable to be the most serious isotopes with short half-lives have reduced thedanger to surface ships and shore installations intensity of the nuclear radiation given forthBEYOND the region of heavy shock (and blast). by the central cloud, the level of radiation isIt is important, therefore that naval officers in still dangerously high. general should have knowledge of decontamina- Eventually, the central 'cloud and the basetion procedures (as well as other damage control surge mingle and are carried off in the downwindand first aid procedures).

NUCLEAR RADIATION

07F...101

MIST OR. BASE SURGE CLOUD (VELOCITY 18 KNOTS)

RAINOUT PRODUCES CLEARING AT BASE

SURFACE WAVES /;///4"44r177;7-1--..1 18 FEET HIGH

MIL E4 1 it 5.164 Figure 14- 7. Conditions 2.5 minutes after a 100-kiloton shallow underwater nuclear burst.

3121 - Chapter 14EFFECTS OF NUCLEAR WEAPONS

DEEP UNDERWATER BURST.As observed in the WAHOO shot in 1958, deep underwater bursts do not produce an airborne radioactive cloud. The visible phenomena produced by this shot, which was 500 feet underwater,are shown in figure 14-8. No fireball could beseen, but a spray dome (fig. 14-8A) formed above thesurface of the water. The hot steam andgas burst through this and formed multiple plumes (fig. 14-8B) in all directions. As the plumescollapsed, a base surge (fig. 14-8C) formed, extending for a distance of about 2 1/2 miles downwind and 100.46 upward about 1,000 feet. The radioactivitywas Figure 14-8B.Plume after 11.7 seconds. associated with the base surge. The residual nuclear radiation was slight. In a deep underwater burst,very little of the energy escapes as air blast, but is absorbed by the water and produces a much greater shock wave than does a shallow burst. The peakoverpressure does not fall off as rapidly in wateras in air, therefore the shockwave can damage ships at considerable distances from the burst. At 3,000 feet from a 100-kiloton deepwater burst the peak overpressure is 2,700poundsper square inch, compared to only a few poundsper square inch in an air burst. 100.4'7 Underground Bursts Figure 14-8C.Base surge 45 seconds after explosion. When the fireball is formed below thesurface of the soil, the hot pressurized gas within it is mingled with bomb residues and vaporizedearly stages.Figure 14-9A shows conditions earth. Upon breaking through the surface, thetwo seconds after a 100-kiloton shallow under- expanding gases throw up a hollow, outward-ground burst.In addition to the phenomena flaring column consisting of earth debris mingledshown in the drawing, this type of detonation with fission products. produCes a ground shock resembling a small SHALLOW UNDERGROUND BURSTS.As inearthquake, except that it occurs nearer the a shallow underwater burst, a hemisphericalsurface. blast front surrounds the hollow column in its Inrising, the hollow column producesa throwout of contaminated debris..The lighter products of the explosion form a radioactive cloud about the upper part of the column. By the end of 9 seconds, as shown in figure 14-9B, the expandiqg cloud is still givingoff hazardous amounts 'bf radiation. Some of the heavier fragments in the throwout are falling back to the earth. Forty-five seconds after detonation (fig. 14-9C) the throwout is rapidly falling tothe ground. It can be expected that finer dust particles from the hollow column will forma ring of base surge, much like the mistsurge 100.45 that characterizes a shallow underwater burst. Figure 14-8A.Spray dome 5.3 seconds The dust particles in. the base surgeare heavily after explosion. contaminated, with nuclear byproducts.

313 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS rises toward the cloud and moves ahead of it in the downward direction.Thus, radioactive particles can be carried downwind for consider- HOT OASES, BOOB RESIDUE, AND DEBRIS able distances, seriously contaminating a large RADIOACTIVE CLOUD MOT VAPORS AND EARTH PARTIa.te area. It is estimated that a 1-megaton shallow OMT AIR 0101 FRONT underground burst would blow into air some ten 1111! million tons of soil and rock. The area around the crater would be heavily contaminated, and the fallout of lighter particles might be hazardous over a great distance. As a general rule, the thermal radiation will AFTER 9 SECONDS be almost completely absorbed by the soil material, so it represents no significant hazard. B The shock wave produced by the rapid expansion of the bubble of hot, high-pressure gages initiates a shock wave in the earth similar in some ways to an earthquake of moderate intensity.Theoretically, the disturbance should be equal in all directions, distinguishing it from an earthquake,in which there are slipping movements. However, this is not always true and it is not always possible todistinguish between earthquakes and underground nuclear explosions by the recordings made by seismo- graphs. The formation of a crater by surface burst is shown in figure 14-9E. Similar deformation of the earth takes place in an underground burst. The size of each damage zone varies with the type and condition of the soil, the size of the

MILES detonation, and the depth of the detonation, but 2 the types of damageare similar. Immediately beneath the visible or apparent crater are two more or less distinct zones, the rupture zone and the plastic zone. In the rupture zone, there are innumerable radial cracks in the earth or rock. Below that is the plastic zone, in which there are no actual cracks visible but the earth is permanently defornied and greatly compressed. In rock, the plastic zone will be much smaller than in soil. The cavity formed by the 5.165 explosion is the true crater, but the visible or Figure 14-9.Development of a 100-kilotonapparent crater may besmaller because of the 3.4 shallow underground burst:A. Two. secondsfallback of debris.- after detonation;B. Nine seconds after det- The crater produced by a shallow under- onation; C. After 45 seconds; D. After 4 1/2ground burst is deeper and wider than the one minutes; E. Formation of crater. produced by a surface burst of equivalent yield. A 100-KT surface burst would produce a carter After a few minutes, as shown in figure 580 feet- in diameter and 80feet in dry soil, while 14-9D, the central column loses. its separate aAaindlar burst 50 feet below 'the surface would identity. The lightest particles from the column produce a crater 720 feet in diameter and 120 have now .become part of the radioactive cloud..feet deep. This cloud spreads out, especially in the down- Mathematicalformulas,have been prepared, wind direction:If A base surge has formed, it with corrections for different factors such as

314- Chapter 14EFFECTS OF NUCLEAR WEAPONS

type of soil, so the expected cratersize can beshock decreases with increasing altitude anda computed for any size weapon. larger proportion is in the form of thermal . DEEP UNDERGROUND EXPLOSIONS.Oneradiation.However, the fraction of explosion of the purposes of testing nuclearweapons deepenergy emitted as nuclear radiation is not af- underground is to prevent contaminationof thefected by altitude.The radiation can travel air and the countryside. A numberof nuclearfaster and farther in the thin air but will beso test explosions have been carriedout at variouswidely scattered in the stratosphere thatthere depths underground. Various soilcharacter-is little danger from the initial nuclearradiation istics, particularly the moisture content,affectfrom a high altitude burst. The residualradi- the result. The data from the testsindicate that,ation that reaches the earth can bevery wide- in general, a scaled depth of 500 feetor more isspread. necessary to contain the radioactivity below the earth's surface. By scaled depthwe mean scaled Much of the thermal radiation will also be according to the strength of the explosion. Inthedissipated by the time it reaches the earth,so LOGAN shot (5-KT), for example,the actualthe effect is negligible. The blastwave set up depth of rock and earthcover was 830 feet, butby the explosion travels faster and farther in the scaled depth was computedas 512 feet. Thethe low-density air, but by the time itreaches formula for computing the scaleddepth is:the earth, the overpressure and blast fronthas died down to a small amount, sono damage 500 W 0.3 results. The difference in the fireball isstartling. where W is the explosion energy yield in kilotonsThe speed with which it develops,rises, and TNT equivalent.This formula applies if thespreads to tremendous size is fantastic. The overburden (rock and soil cover) is of drysoilfireball from the 1-megaton TEAK burstin the and loose rock. If the overburden is solidrock,Pacific could be clearly seen for the result is multiplied by 0.8. over 700 miles. It appeared as a large red luminoussphere (fig. When the fireball does not break thesurface14-10), and within seconds, of the earth, all the radiation and the a brilliant aurora radiantappeared from the bottom of the fireballand energy is retained in the earth. A year after thepurple streamers were seen to spread toward RAINIER shot, nearly all theenergy was stillthe north.The aurora was observed ata retained in the immediatearea of the explosion, distance 2,000 miles from the detonation, which took place in a 6-by 6-by 7-foot chamberthough the fireball could not beseen there. 790 feet below the surface ina type of rock called tuff. The explosion enlarged thespace to a cavern with a 62-foot radius, and melted the rock to a depth of four inches. Theroof of the cavern caved in, but radioactivity was not spread to the surface beyond the cave-in.Most of the radiation was retained in the molten rock,which congealed to glass. The shock caused seismic signals several hundred milesaway. A 1.7 kiloton nuclear device was detonated inthe RAINIER shot.

HIGH ALTITUDE BURSTS A high-altitude burst is definedas one in which the explosion takes place atan altitude in excess of 100,000 feet. Above this level, the air density is so low that the interactionof the weapon energy with the Surroundingiis markedly , ,100.38 different from that at lower altitudes, and variesFigure 14-10.Fireballandred luminous spher- with the altitude.The fireball characteristics ical wave formed after theTEAK high-altitude are different at high altitudes. The fraction. of shot. The photograph wastaken at Hawaii, 780 the energy of fission .converted into blast and miles from the explosion. 619 315

'. t. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

The extreme brightnessof thefireballis EFFECTS OF NUCLEAR EXPLOSIONS capable of producing effects on the eyes at great distances. The effects of nuclear explosions may be The TEAK shot was made at an altitude ofclassed as immediate and delayed effects. nearly 50 miles, and the ORANGE shot wasThose which occur within a few minutes after made at an altitude of about 27 miles. The ef-the explosion include air blast, ground or under- fects of the denser air in the ORANGE shot werewater shock,thermal radiation, and initial clearly shown in the smaller size and lesserradiation. The delayed effects are chiefly speed of the fireball and the diminished aurora.those of radiation from fallout and neutron- induced radioactivity, but fires caused by ef- Effect On Radio and Radar fects of blast and shock may be considered Commnications delayed effects. 'DAMAGE CRITERIA The detonations caused widespread disturbances in the ionosphere which affected theBasic Graph propagation of radio waves and other electromagnetic radiations of relatively long wave- In assessing the damage caused by any lengths. The TEAK and ORANGE shots disrupted explosionwhether "conventional" or nuclear radio communications in the very-low-frequencyitis convenient to represent the various in- range at distances over 3,000 miles from ex-tensities or damage, and the areas subjected plosion,.Other frequencies were affected forto each intensity, as a series of concentric different lengths of time and different distances.circles about the detonation point.See figure The disturbances caused by the initial radiation14-11. can be continued by the fallout radiation. This Of course figure 14-11 is a simplified and may occur hours after the detonation, continuinggeneralized graph. To show the data gathered the communications blackout for many hours.from the study of any particular explosion, this The effects on radar are similar if the signalgraph will have to be modified in one or several must pass through the ionosphere. Interferenceways.For a nuclear explosion, the several with search and tracking radars in weaponskinds of damage, and their separate or combined systems can be important, even critical. effects on equipment and personnel, are so varied From observations of the high-altitude testthat a series of graphs oftenbecomes necessary shots, some charts have been prepared to showto tell the story. the effects on electromagnetic radiations used in radio and radar.Factors that influence the effectsinclude moisture content of the air, density, of the air, wavelength used-by the radio or radar, height of the burst, energy yield of the burst, location of the radio or radar station with relation to the burst, and anumber of other factors.With so many variables affecting the fi result, it is difficult to -predict just what will happen to the communications of a 'particular installation. Although. we have spoken of electromagnetic disturbances in 'connection with high altitude burst, no matter where the burst occurs ,there are, inevitably some disturbances. A 'somewhat sianilar ,explosiVeTexcited occurrence in nature is lightning.The technical aspects of effects on radio 'and radar are not completely understood, but a reasonably accurate picture of ef-jA fects of the btirit on electromagnetic signals can be computed' from the facts revealed by 100.49 tests of nuclear devices. Figure 14-11. Zones of damage by an explosion. - 316 A, 320 Chapter 14EFFECTS OF NUCLEARWEAPONS

It may be desirable, also,to show a larger granted.In a nuclear explosion at number of damage intensitiesthan the four or below indicated in figure 14-11. the surface, nothing withinor near the fireball In will be salvageable.With an air burst (except actual practice thereare no lines ofa very high one), ground zero and demarcation betweenone damage area and a greater or another. lesser area surrounding itcan be considered Furthermore, the damageareas willcompletely demolished.For a nuclear weapon seldom be perfect circles;sometimes theyof any type, the area of TOTAL will vary greatly from thecircular form, ex- destruction is cept on the opensea. many times larger than for a conventional Winds, geographicalweapon of comparablesize. Figure 14-12 features, and other factorscan deflect the con-illustrates graphically the damage tours of the areasa great deal. Nevertheless, areas for for preliminary considerations, the different effects of nuclearexplosions com- figure 14-11 ispared with explosion of conventionalchemical a useful tool for defense andrecovery planning. explosives. Damage Areas The size of the areas withinwhich various degrees of destruction may be expecteddepend primarily upon the energy yieldof the explosion In- any effective explosionof bomb typeand the conditions of the ammunition, there is a large burst, that is, air or small area aboutburst, surface burst, etc.,and the height or the point of burst wheretotal destruction ofdepth of the burst. equipment and personnel must The topography and the be taken forweather also affect the size of theareas.

NUCLEAR CHEMICALS A OVERPRESSURE OVERPRESSURE

5 MILES 50/YDS.

2ds 2 psi

B DRAG OR WIND DRAG OR DYNAMIC DYNAMIC PRESSURE VELOCITY PRESSURE WINDVELOCITY 'MILE 9.a 10Y' \ , \ \ /'....,Hrri-

C THERMAL RADIATION.T THERMAL RADIATION 1 ...-. e \% SECONDARY foT .11 l'EACTION NEGLIGIBLE INITIAL v..) ,ii) .1 IN COMPARISON TO NUCLEAR BLAST) REACTION %....' / . ,... -..o" B NUCLEAR RADIATION NUCLEAR RADIATION

/tiVW.`:: 0%::% - vt;40%,`,0;::::40; -0,,,e. N% NONE :%%0UWPZZ:NZ% t . -, - 144.70 Figure 14-12.Comparison ofcharacteristics effects of nuclearvs. chemical explosion) (assuming equal weight of explosive).

317 '.;,,. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS The general conclusions concerning ex-duty, even in this area, would be to watch for pected effects of nuclear explosions on various fires and get them under control. targets are based on a combination of theoret- This chapter will not go into details about ical analysis with data obtained from actual"atomic defense" or "disaster control." As a nuclear explosions, both in Japan and at various junior officer you will receive further indoc- test sites, as well as from laboratory studies. trination in fundamental procedures and will be While no exact prediction of the effect on specific assigned a definite responsibility for some part types ofstructures can be made, the con- of the total program of your ship or station. clusions are considered to be most represent- SHIP DAMAGE. The various degrees of ship ative for the situations that might be encountered damage that may result from nuclear detonations in actual target complexes. are grouped into damage categories. These are DAMAGE ZONES ASHORE.In the area im- standard Navy definitions that apply to surface mediately surrounding ground zero (zone A, vessels.Each category is defined to describe fig.14-11), destruction is usually total; no the extent of impairment or loss of operational personnel or ordinary buildings have muchcapability through material damage. chance of survival.In the Japanese bombings, ) Sunk.That degree of damage which results although some earthquake-resistant buildingsih Tarof the ship due to uncontrollable flooding were not demolished, the interiors were de- or loss of longitudinal strength. stroyed and all people in them were killed or Immobilized.That degree of damage to the died soon afterward from radiation received. mar pThYMrion equipment or its vital auxiliary Zone B, the area of severe or heavy damage, machinery which precludes maintaining steer- is about three times as large as zone A. In thisage way. Repairs at sea are impossible; salvage area personnel injuries and damage to buildings or own destruction required. would be severe, but not complete. Many build- I Severe Damage.That degree of damage ings, much equipment, and many persons wouldwrucn renders the ship barely capable of making be lost, either within afew seconds after detona- headway to the nearest facility either afloat or tion or as a result of secondary phenomena. ashore.The military efficiency of the ship is Some buildings and equipment, and some peoplenear zero.Loss of the ghip is imminent in as well,might sufferonly minor primaryfollowup attack. AO - 1,6-010 &Wide- damage.The final number of casualties in the 4 Severe Topside Damage.That degree o heavy damage area would depend, in part, on thedamaiiMToplariftrucrurd, armament, equip- speed, level-headedness, ingenuity, and coop- ment, and appurtenances which destroys or seri- eration displayed by disaster-recovery person-ously impairs the offensive aspects of military nel, and all personnel in the area, as well as on efficiency. Retirement from action at or near full previous preparation for the emergency. power however, is possible.Restoration re- The C. zone is a still larger circular belt ofquires availability of a repair facility. lesser damage surrounding the B zone.. In the r Damage. That degree of damage zone of MODERATE damage, there would, ofto some vital ship control equipment or offensive course, be some heavy damage to light equip-armament which prevents the ship from effec- ment and structures. There would also be sometively carrying out her assigned mission. Out- fatalities and severe casualties to personnel. side assistance is required to restore casualty. Some persons, however, would be unharmed, and Ship is capable of retirement and has reasonable many would be able to do useful work aftercapability for self-defense. receiving simple first aid. The great problems IsOcArAtellamage.,That degree of damage 4 would be (1) to prevent panic and (2)to utilize allthat is within the capability of the ship's force able-bodied (and mentally or emotionally com-to restore to an extent which willpermit limited petent) personnel in damage control and disaster offensive employment of theship.Repair recovery.At a shore station, fire fightingfacilities are required to restore full military (possibly with severely damaged equipment) capability. would be vitally necessary. Light Dam That degree of damage that Within the zone of SLIGHT4damage, the mainis1 VithlrrtreTmmeaiate capability of the ship's problems would be to prevenipanic, to ascertainforce to restore at sea and which will restore that previously trained teams and. groups arefull military capability. functioning properly, and to make such adapta- In modern naval formations, the most ships tions as are ordered by higher authority. Onewould probably be in the damage-survival area.

318 22, Chapter 14EFFECTS OF NUCLEAR WEAPONS The non-nuclear effects occur very quicklyinblow. After the peak, the atmosphericpressure seconds to minutes after theburst.Of these, at the given point gradually drops themechanicaleffectscan cause damage back to normal. throughout the ship, but the thermal Shortly afterward, the pressure is reducedbelow radiationnormal by the suction phase of the explosion.The can cause damage only to the surfaceexposed directly to the radiation. The drop below normal is neveras great as the types of damageprevious rise above it; but it, too,can cause and modes of destructionor damage are de-damage. scribed in succeeding paragraphs.The conclusions reached about damage Massive, comparatively low buildingsof to ships arereinforced concrete, and lowmasonry buildings based on the observations oftests with nuclear devices. strengthened by heavy steel skeletons,are the Effects on shore structureswereonly structures likely to withstand 15or more determined by studies of theresults of thepsi (pounds per square inch) of peakoverpres- Japanese bombings and of the testsmade at thesure without severe damage. Nevada test site and at Eniwetok. Light wood Structures oformasonry buildingstypical living different materials and of differentconstructionaccommodationsreceivemoderate damage were placed at varied distances in eachof thefrom 2 to 3 psi overpressure. Howfar this several tests. Effects on personnelwere studied following the Japanese amount of overpressure is from groundzero bombings. depends on the height and theenergy of the burst. AM BLAST In Japan, nearly everything at closerange, except structures and smokestacks ofreinforced concrete, was destroyed. Telephone poleswere As already mentioned,an air burst of asnapped off at ground level; largegas storage nuclear weapon above a target hastremendoustanks were ruptured and collapsedby the crush- destructive capability and thereforegreat mil-ing action of the blast wave. itary usefulness. Fora short distance from the fireball, the blast damage from Naval vessels are constructed to withstand a surface burstbattle shock and constant poundingfrom the may be even greater, but the effectiverange tends to be shorter. Blast damage waves. Peak overpressures of 5 psi causelight can also stemdamage to most types of surfaceships, while from shallow subsurface bursts. overpressures required for severe damage vary The primary difference in blasteffects fromfrom 25 psi for destroyers to 40 psi forheavy a nuclear explosion and from high explosivesiscruisers.A ship's boilers, uptakes, andven- one of magnitude; the nuclear explosionpro-tilation system are especiallyvulnerable to duces many times the damage of thehigh ex-overpressur e. plosive.Another important difference is in the Some tanks and other heavy-duty shoreequip- blast wave (fig. 14-12). Ina nuclear explosion, ment have withstood 20 to 30 psi. the combination of high peakoverpressure, high Strangely enough, the human body has been wind (or dynamic) pressure, andlonger durationknown to stand short-term of the positive (compression) overpressures up to phase of the blist100 psi without severe or permanentdamage. wave results in mass distortion of buildings,The sharpness of the rise and the lengthof time similar to that produced by earthquakesand under pressure make a difference. hurricanes. Laboratory and field studies with animals Blast damage from a nuclear explosionreallyindicate that a peakoverpressure of 35 pounds has two distinct causes. Onecause lathe over-per square inch (if the rise time is short) witha pressure that has already been defined andpositive phase duration of 400 milliseconds (0.4 described. The other cause is the dragexerted by the nuclear windstorm. second) can cause death in human beings.The direct blast effect was not specificallyrecog- nized as a cause of fatality in Japan, butit no Overpressure Damage doubt was a significantcause of death in a laege number of those who received additionallethal injuries from thermal and nuclear radiations, A given point in space is subjectedto peakflying debris, falling walls, and fire.It was im- overpressure when the primary blastwave (or,pftsible to assign the specificcause of death of in the Mach region, the Mach wave)strikes it.those who were in the This is the time when a structure zone of greatest damage. or vehicle isBeyond that zone, many must have diedbecause most liable to collapse, as though froma hardof the complete disruption of medicalservices. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Of those who survived, lung hemorrhage wasgraphs, and charts may be found in the refer- reported, but other injuries usually complicated ences cited in the bibliography. the picture.Ruptured eardrums were more Drag, rather than overpressure, is the blast common. Temporary loss of consciousness was phenomenon that seriously threatens the many reported by some who survived with no other personnel who might otherwise suffer only slight apparent serious injuries. injuries.The winds of a nuclear explosion can Direct blast injuries that result in early impel heavy or sharp objects with tremendous death are air (emboli) in the arteries, lungforce, thus converting everyday materials into damage, and heart injury which cause death deadly weapons. A man who has survived peak upon even slight activity after injury; variousoverpressure intact may leave cover too soon, bone fractures, severing of major blood ves-only to be killed by a brickbat hurled against Yti sels, violent impact, and others. As pointed outhis temple, or a glass splinter driven into or above, it was impossible to determine incidencethrough his body. This is "missile hazard." of specific injuries or specific overpressures in Table 14-1 and figure 14-13 given some in- the Japanese cases. Direct blast injuries havedication of the relationships between overpres- been caused by conventional explosives, but the sure, wind velocity and dynamic pressure(drag situationisdifferent because of the shortforce).Dynamic pressure is a function of the duration of the positive pressure phase in con- wind velocity and the density of air behind the ventional explosions, which may be from about 1 shock front. Like the peak shock overprtcrure, to 15 milliseconds. the peak dynamic pressure decreases with increasing distance from the explosion center, although at a different rate, as can be seen in Drag Damage the illustration.(The dynamic pressure decreases more rapidly than does the shock over- Damage from a nuclear air burst is causedpressure.) by static pressure variations, wind (or dynamic) For the purpose of this orientation, let it be pressure, and flying objects. Most of the damage said that certain structures are more sus- to structures is caused by the positive phase ofceptible to damage by the drag forces in- the pressures; however, there are some struc-herent with air blast, while others are more tures which suffer greater damage from thesensitive to shock overpressure. The material dynamic pressure.Pressure produced on aused in the construction is only one of the building as a result of overpressure is knownfactors influencing the effects of the blast force. as ."diffraction loading."The air pressure bends or "diffracts" around the structure so that the structure is eventually engulfed by the blast wave, and approximately the,same pressure is exerted on the side walls and the roof. Forces produced on structures as a result of dynamic pressure are known as "drag loading."This type of loading is caused by the :'E transient winds behind the blast wave front, and they push and pull or drag the structure down. An air burst is characterized by violent winds blowing radially outward from ground.zero and, VINEEnsuma a short time later, by afterwinds blowing inward. The 'drag of. these winds is particularly destructive to lightweight walls, and to tall objects such YNAMIC PRESSURE as antennas and flagpoles. .Power lines, bridge AMBIENT vulnerable ARRIVAL spans, and parked vehicles are also TIME to drag. ,. ..Tables have been compiled to .show thetypeei of. buildings, structures, -and,.eqtdpment most 100.31 often affected:by each.type of. pressure,and.theFigure 14-13.Variation of overpressure and type:and extent of damage suffered. Such tables, dynamic,pressure with time at a fixed location. 424 ' .." -

Chapter 14EFFECTS OF NUCLEAR WEAPONS

Table 14 -1.. Overpressure, Dynamic Pressure,Ground Shock and Wind Velocity in Air at Sea Level for an Ideal Shock Front As has already been mentioned, ground shock resembles a small earthquake, except that it P"'" originates much nearer the surface. Peak Peak Maximum Ground shock is a threat to land-based per- over- dynamic wind sonnel, because it can demolish or damage un- pressure pressure velocity derground shelters.In the bomb crater, of (psi) (psi) (+ad) Movjcourse, these would be totally destroyed. For a short distance beyond the actual crater, the 72 80 1170 zone of total destruction would continue. Beyond 50 40 940 that would be a zone of heavy damage consisting 30 16 670 of severe distortion and partial collapse. 20 8 470 The effects of underground shock tend to fall 10 2 290 off rapidly, however. Too, when shock ceases to 5 0.7 160 be severe, effects from it become almost neg- 2 0.1 70 ligible. In a subsurface burst, if any part of the fireball breaks through the surface, the blast damage above ground is likely to be more ex- The method of construction, size and shape oftensive than the shock damage below it. the building, and orientation with relation to the Buried utility pipelines would be destroyed blast are some of the other factors in the dam-within the crater and would be damaged at age resulting. distances up to three times the radius of the .Considerable information on the effects ofcrater.Near the crater, the pipes themselves blast on. different types of structures was ob- would rupture. Farther out, the joints, especially tained in tests at the Nevada Test Site, wherebetween horizontal pipes and risers, would tend different types of residential structures wereto rupture. constructed for the purposes of the test. Fallout Well constructed tunnels and subways, par- shelters were built into many of. the basementsticularly in granite bedrock, are resistant to un- of these test structures, and provided invaluablederground shock. Complete demolition would be information needed for recommendations on con- likely to occur only within or near the bomb struction of fallout shelters. crater. As might be expected, the severity of ground NuclearHigh Explosive Comparison shock is related directly to the size of the detonation. However, other factors are involved. Although the blast effects of nuclear and con- The type and condition of the soil, the material ventional explosives were compared in the begin- and type of construction of the underground ning of this chapter, an additional differencestructures, and the orientation of the structures between the two should be pointed out here. Thewith relation to the explosion all influence the combination of very high peak overpressures,type and extent of damage. Shallow buried together with the much longer duration of thestructures and utility pipes beyond the crater positive, phase of the. blast wave froni nuclearand rupture and plastic deformation zones are explosion:4 results in "mass distortion" oflikely to suffer more damage from the air blast buildings and structuressimilar to that causedloading than from ground shock. Structuresthat by earthquakes.. An ordinary explosion will are partly above ground and partlybelow ground usually. 'damage only part of a large- building,will, of course, also be affectedbythe direct air but the nuclear blast can surround and destroyblast. it entirely. Underwater Shock SHOCK .,A shOck wave formed under the surface of the When all or part of the fireball strikes or iswater behaies much like a similar wave in air. formed, below the surface, a shock front in theSince water is a denser fluid than air, thevalues earth (or water) corresponds to the blast frontof normal pressure and overpressure are cor- in the air. respondingly higher.The reduction after peak PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS overpressure is more gradual than in air. Onat least weaken the hull. Second, it may distort, the other hand, the duration of the shock waverupture. or break loose any of the various ship's in water is shorter than in air. comr yuents or installations.Piping, shafting, The velocity of sound in water under normal-%air vents, and boiler brickwork are Tiusceptible conditions is nearly a mile per second, almostto damage. Platforms supporting heavy equip- five times as great as in air.When the peakment may be weakened or thrown out of proper pressure is high, the velocity of the shock wavealignment. Light objects may be thrown about so is greater than the normal velocity of sound.violently that they become a serious threat to The rate of motion of the shock front becomespersonnel. Electronic, fire control, and guided less at' lower overpressures and ultimately ap-missile equipment is likely to be rendered in- proaches that of sound, as it does in air. operative, at least temporarily. The damage to The shock wave in water may produce aequipment appears to be related to the peak reflected wave by strildng the bottom or anyvelocity imparted to the equipment by the shock rigid submerged object. If conditions wave. The damage to the hull of the ship is favorable, the primary wave and the reflected)related to the energy per unit area of the shock wave may fuse to produce a phenomenon com-wave, evaluated up to a time corresponding to parable to the Mach front in air. the surface cutoff time at a characteristic depth. When the shock wave touches the upper (orIn the Bikini underwater test, light interior air) surface of the water, apeculiar phenomenonequipment, especially electronic equipment, was occurs. Because air is lighter and less resistantdamaged at ranges considerably beyond the limit than water, the wave reflected back from the of hull damage. contact point is a RAREFACTION (or suction) Part of the shock energy of a shallow under- wave. When the Parerfaetten-wave reaches anywater burst is transmitted through the surface given point below the surface, a sharp pressure as a shock (or blast) wave of air. This air blast reduction, called CUTOFF, occurs. This neg-caused some damage to ship superstructures in ative pressure phOrts me short duration. Thethe tests. time interval between the arrival of the direct shock wave at a particular location (or target) in In the effects just mentioned, an underwater the water and that of the cutoff, signaling the ar-nuclear burst is similar to a conventional mine rival of the reflected wave, depends upon theor depth charge.The major difference lies in depth of burst, the depth of the target, and thethe extended damage radius of the nuclear wea- distance from the burst point to the target. Ifpon. The nature and extent of damage sustained the underwater target (ship bottom) is close toby a surface vessel from underwater shock will the surface, then the time elapsing between thedepend upon the depth of the burst, yield, depth arrival of the two shock fronts will be small andof water, range, the ship type, whether it is op- the cutoff will occur soon after the arrival oferating or riding at anchor, and its orientation the shock front. This may result in a decreasewith respect to the position of the explosion. In vessels underway, machinery will probably suf- 4 in the extent of damage sustained by the target. fer somewhat more damage than those at anchor. One phenomenon tends to neutralize the other, Underwater structures such as harbor instal- thus reducing the damaging power of the explo-lations, are damaged by the shock wave. In the sion.For shallowly submerged targets, there- Bikini test, the floor of the lagoon was drastically fore, nuclear weapons may not always be fully altered by the explosion. effective. The primary shock wave of an underwater From studies of the underwater burst at nuclear explosion strikes the target ship or other Bikini, charts have been prepared to show the object with a sudden violent blow. Inthis actionextent of the various effects of such an ex- a nuclear weapon resembles a conventional oneplosion at different depths and distances. Some with one significant difference. The conventional70 ships of different types were placed in and weapon, dedivers its blow at a single point or over near the test area. Figure 14-14 shows the ex- a comparatively small area, while the nuclearterior damage to one of them.Analysis and explosion acts simultaneously over a large areaevaluation of the damage produced much valuable with all encompassing force. information on the effects of underwater bursts, Underwater shock damages a vessel in oneand, conversely, ideas on how to .prevent or (or both) of two ways. First, it may rupture or minimize damage. ins 322 I . Chapter 14EFFECTS OF NUCLEAR WEAPONS

t;t4i-r,,r

5.49 Figure 14-14.Flight deck of carrier Independenceafter test at Bikini. Blast pressure entered the hangar deck from the side, through rupturing ofside curtains. Flight deck was bulged upward whereas hanger deck below was dished downward.

THERMAL RADIATION ever, the larger the yield of the weapon, the longer will be the PERIOD of luminosity. Within Description this seven-tenths of a millisecond from time of detonation, the fireball of al-megatonweapon Within a few milliseconds after the detona-will have reached a diameter of 440 feet. The tion of a nuclear weapon, intensely hot gases, atfireball increases to maximum diameter of abut tremendously high pressures, rapidly forma7200 feet at plus 10 seconds.It is then r33ing highly luminous mass known as the "fireball"at the rate of approximately 200 mph. Aftera or "ball of fire." At about seven-tenths of aminute, the ball of fire has cooled to an extent millisecond, the fireball from a 1-megatonthat it is no longer visible. nuclear weapon would appear to be more than The nuclear explosion has often been com- 30 times as bright as the sun at noon toan 'ob-pared to the conventional high explosive deto- server 60 miles away.Although the size ofnation in that, except for the yield and nuclear the fireball will vary with the bombenergy,radiation involved, they can be considered the luminosity does not vary greatly.How-similar.When referring to thermal effects,

23 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS this can be a poor comparison because of thebursts below 50,000 feet.(In high altitude very large proportion of energy released asbursts there is only one thermal radiation pulse. ) thermal radiation by a typical nuclear explo-In a 1-megaton nuclear explosion, the first sion. As was illustrated in figure 14-1, overpulse lasts for about a tenth of a second. The one-third of the energy of a typical nucleartemperatures are very high, and much of the explosion manifests itself in the form of thermalradiation is in the ultraviolet region.The radiation.Too, the temperatures involved in asituation with regard to the second pulse is nuclear explosion are much higher than withquite different. This pulse may last for several conventional explosives. seconds and it carries about 99% of the total Thermal radiation travels with the speed offtermal radiation energy of the nuclear ex- light, so that the time elapsing between itsplosion. The temperatures are lower thaninthe emission from the ball of fire and its arrivalfirst pulse, and most of the rays reaching the at a target a few miles away, is quite insignif-earth are visible or infrared (invisible) light. icant. It is this radiation that is main cause of skin zlichlikethajouLikenrabadiatesburns suffered by exposed individuals up to 12 ultraviolet (short wave length) as well as via;miles or more, and of eye effects at even ble and infrared (long_ wave leogthi rayq... Duegreater distances from a 1-megaton explosion. to certain phenomena associated with the ab-The warmth may be felt as far away as 75 miles. sorption of thermal radiation by the air inSince thermal radiation is largely stopped by front of the expanding fireball, the SURFACEordinary opaque materials, buildings and cloth- temperature undergoes a curious change. Whileing can provide protection. The radiation from the interior temperature of the fireball fallsthe second pulse can cause fires to start at :14 steadily, the surface temperature decreasesconsiderable distances from the burst. This more rapidly for a small fraction of a second,difference between the injury ranges of thermal then it increases again for a somewhat longerradiation and the other effects mentioned be- time, after which it falls continuously.Incomes more marked with increasing nuclear other words, there are effectively two surface- weapon yield.. temperature pulses,-the first of very short The most important physical effects of the duration, the second lasting for a relatively longhigh temperatures resulting from the absorption period of time (fig. 14-15).These surface-of thermal radiation are: burning of the skin and temperature pulies correspond to the pulses ofscorching, charring, and possible ignition of thermal energy radiated from the fireball incombustible organic substances such as wood, fabrics, and paper. Thin or porous materials, such as lightweight fabrics, newspaper, dried grass, and dried rotted wood, will flame when exposed to sufficient thermal radiation (with adequate oxygen supply). '11.9 1- 6 6>7 Effects on People Zn6. 111 Thermal radiation can be the cause of flash Mg4 burns or flame burns. Flash burns are directly S 3. caused by the radiant energy of the fireball. 1.1Wo 2 Flame burns are distinguished from flashburns g in that they are caused by fire, no matter what the origin. Flame burns occur as a secondary 0 result of thermal radiation, for example, those 2 3 4 8 6 7 8 9 10 II 12 TIME AFTER EXPLOSION resulting from the fires started by thermal (RELATIVE SCALE) radiation. The very large number of flash burns was 100.37 one of the most striking facts about the nuclear Figure 14-15.--Emission of thermal radiationbombing of Japan in World War II.It has been in two pulses in an air burst. estimated that 20 to 30 percent of the fatal

324 '328 Chapter 14EFFECTS OF NUCLEAR WEAPONS

casualties at Hiroshima and Nagasakiwere dueconditions (clouds, smoke, moisture content), to flash burns,as distinct from flame burns.and the atmospheric pressre. Though significant,it should be realized that Figure 14-16 in included to shoW theranges these illustrated resultswere magnified be-for moderate first-, second-, and third-degree cause the atmosphere was very clear and theburns from nuclear explosions.The graph is summer clothing worn was light and scanty. computed assuming a typical air burst with clear Moderately large doses of ultravioletra-atmospheric conditions prevailing. For atypical diation can produce painful blisters. Evensmallsurface burst, the distances would need to be doses can cause reddening of the skin.How scaled down to about BO per cent of those stated. ever, in most circumstances, the first pulse of If the detonation takes place at high altitude thermal radiation is not a significanthazard aswhere the air pressure is quite low, the situation far as skin burns are concerned. is different.If the atmosphere is hazy the Perhaps the most seriousconsequence ofdistances shown on the chart may be too great. thermal radiation is its ability to produceseriousThey are certainly too large if there isa sub- burn injury to personnel at longranges. stantial cloud layer of smoke below the point of burst. Conventionally, burns are classifiedaccording to their severity, in termsof degree (or depth) of injury.In first-degree burns there is only redness of the skin. A moderate sunburn is an example of a first-degree burn. ID.000 . Healing should occur without specialtreatment and there will be no scar formation. 10.000 A Second degree burnsare deeper, more severe, and are characterized by the formation 4.0 1 or blisters. A severe sunburn is an example of AIIIIrgi a second-degree burn. In third-degree burns, the full thicknessof the skin is destroyed.'Unless skin grafting 1.000 techniques are employed, there will 'bescar WMlir formation at the site of the injury. The extent of the area of skin which has been burned is also important. Thus,a first degree burn over the entire body may bemore severe iii than a third degree burn to one spot. The larger 100 rim.' the area burned, the more likely is theappear- ance of ''symptoms involving the whole. body. Further, .thereare certain critical, local regions, such as the hands where almostany Fir degree of burn will incapacitate the individual. Inother words, allpersons exposed to thermal radiation from' a nuclear explosion within a range in which theenergy received is sufficient to cause second-degree (at least) flash burns, will be potential casualties. Some will be protected to, some extent againstthermal radiation and may not be incapacitated.

. . ... 0.2 0.i. 4 From information available,calculations 0.7 10 7 have been made' of the thermal radiation neces- SLANT NCE PEON EXPLOSION NEM sary to produce each degree of btirn. Differences in skin pigmentation'cluie variations butan 5.174 average : used. Other 'variations thatare in.'. Figure 14-16.Ranges for first- second- and eluded in ',the computations are the size of the third degree burns as a function of totalenergy burst,- the height of the burst,' the atmospheric yield. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Eye Damage Effects Upon Materials Another danger of a nuclear explosion is its When thermal radiation strikes any material possible affect on the eyes. Thermal radiationor object, part may be reflected, part will be can cause both retinal burns and flash blindness.absorbed, and the remainder if any, will pass The first pulse of thermal radiation, whichthrough and ultimately strike other materials. seldom causes skin burns, is, however, capableIt is the radiation absorbed that produces the of producing retinal burns (permanentermanent or tem-heat damage suffered by the material. The nature porary effects on the eyes), especially in in-of the material and its color deter mine the extent dividuals who happen to b e looking in the directionor amount of absorptimi of the radiantheat. of the explosion. Numerous cases of flash blind- Tables have been compiled showing the ness (temporary) were found among the Japanese,radiant exposure required to ignite different but only one case of retinal injury was reported.types of fabrics, household materials, and forest This is because of the more or less remotefuels.Table 14-2 lists some of the materials chance that an individual will be looldngdirectlyand the approximate number of thermal calories at the ball of fire.The chance of temp araryper square centimeter required to produce the "flash blindness" or "dazzle," due to theburning or charring effect. The chart in figure flooding of the eye with brilliant light was much14-17 shows the thermal energy received at more prevalent than retinal burns. Flashblind-various slant ranges from different size weapons. The figures given are not absolute, since ness is of a temporary nature and vision is, regained within a comparatively short time.different conditions of the atmosphere cause However, flash blindness is of military signif-variations in the amount of thermal energy icance, since it may extend to 2 or 3 hours. reaching a certain point. The graph assumes a Because of the focusing action of the lens ofreasonably clear state of atmosphere, that is, the eye, enough energy can be collected toa visibility of 10 miles or more. produce a burn on the retina at such distance from a nuclear explosion that the thermal radiation intensity is too small to produce a skin Table 14-2 burn. As a result of accidental exposures during nuclear tests, a few retinal burns have been experienced at a distance of .10 miles for the Approx. caljcm2 explosion of a 20-KT weapon. It isbelieved that required: under suitable conditions, suchburns might have Effects resulted at even greater distance. Retinalburns 1 KT100 KT10 MT occur so soon after the explosion that reflex actionssuch as blinking and contraction of theSecond-degree bare eyepupil, giveonly limited protection. In all in- skin burn 4 5 9 stances, there will be at least a temporary lossNewspaper ignition 3 5 9 of visual acuity, but the ultimate effect willWhite pine charring 10 18 32 depend on the severity of the burn and on itsArmy khaki summer location on the retina. uniform destruction 18 31 56 .4 Navy white uniform Eye damage is greater under nighttime con- destruction 34 60 109 ditions. Intests,with rabbits and a high altitude .burst of 1-megaton, chorioretinal burns occurred at slant ranges up to 345 miles. No Thermal energies are expressed in calories measurements were made beyond that range, soper unit areasquare centimeter. Note that it is not known how far away retinal burns mightthe amount of energy required for burning, have occurred. Although there are differencescharring, etc., varies inversely with the yield between human and rabbit eyes and the dataof the nuclear weapon. This is because of the have not been extrapolated for human eyes; it israte, at which the energy is delivered.For a believed that a 1-megaton high-altitude burstgiven total amount of thermal energy received endangers the eyes of human beings atdistancesby each unit area of exposed material, the greater than 200 miles, and possibly as far as thedamage will be greater if the energy is de- eye can see. livered rapidly than if it is delivered slowly. Chapter 14EFFECTS OF NUCLEAR WEAPONS

This means that in order to produce thesame thermal effect in a given material, thetotal amount of thermal energy (per unit area)re- 20 ceived must be larger fora nuclear explosion 10"nil of high yield than forone of lower yield, because the energy is deliveredover a longer 71 period of time, i.e. more slowly, in the former ,era case. 17 Unless scattered, thermal radiation travels in straight lines like ordinary light. Forthis 1U reason any solid, opaque material, such asa 4 bulwark, gun shield, hill, or tree, betweena given object and the fireball will actas a SHIELD 4/ArilII and thus provide protection from directthermal 9 radiation. 200 4..,,, .,,7 These effects were seen inJapan in theareas looKill beyond the areas of complete destruction. The sides of telephone posts facing the blastwere charred and blackened while the opposite side 4 a ) was unharmed.. The same effect was seenon other materials and objects. liril The chart in figure 14-17 may be used to 107 estimate the distance at which specific materials mo NW. rffi are likely to,be ignited by a certain size nuclear 111 burst. For example, how far froma .1-megaton MS burst can you expect 'ignition of household items EWA such as. oilYdustmopa, oily rags, and crumpled newspapers?The average radiantexposure re- tiiiMi.111 quired for -ignition of such items is 5 calories per square. centimeter (5cal/sq..cm). On the SLANT RANGE FROM EXPLOSION (MILES) chart, follow the line for 1 mt. until it intersects 100.83 the slant line for 5 cal/sq.cm., which you'llfindFigure 14-17.Slant ranges for specifiedex- is 11 miles. On an average clear day, fires will posures as function of energy yield of the be started by absorption of thermal radiation in explosion. the materials named. Under other conditions, this distance is decreased. Fires that are caused directly by thermalbuildings, the nature of the terrain, the weather radiation are called primary fires. Secondaryconditions, and the adequacy of the defense. fires are due to other causes, for which the When a large area is burning simultaneously, blastis respoasiblev such as upset stoves,the phenomenon known as "fire storm"may broken gas. and fuel lines and electrical shortdevelop. Individual fires merge intoone gigantic circuits.The evidence from Hiroshima -andinferno. As a result of the huge masses of hot Nagasaki indicated that the great. majority ofair and gases rising from the fire, air is sucked fires were secondary in origin. Even thoughin with great force. Strong winds consequently few fires may be started by the radiant heatblow from outside toward the center of thearea from a surface.' burst, there will be many fireson fire.The effect is similar to the draft that of the secondary type due indirctly to the blastsucks up a chimney under which a fire is burning, daniage. except that it is on a much larger scale. Every- thing combustible in the area is burned. A fire FIRE STORM.No matter what the im- storm, is not produced only by a nuclear exposion mediate. cause, a nuclear burst over a built-upnor does it necessarily follow one. A fire storm area willresultin many fires burning simul-can be caused by an earthquake that results in taneously over a wide area. Once the fires havemany "secondary" fires (San Francisco), or started, the chances' of their spreading willfrom a forest fire, or incendiary bombs. The depend on the combustibility and closeness of thegreat Chicago fire, started by Mrs. O'Leary's PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS cow, became a fire storm.The incidence of fire storms is dependent on the conditions existing at the time of the fire.Although many fires were started in Nagasaki by the explosion, there was no definite fire storm because the winds blew the fire toward a thinly populated narrow valley where there was little material to feed the fire. RESISTANCE OF MATERIALS TO BURNING.Highly reflecting and transparent substances do not absorb much of the thermal radiation and so are relatively resistant to its effects.A thin material will often transmit a large proportion of the radiation striking it, and thus escape serious damage. A dark fabric will absorb a much larger proportion of thermal radiation than will the same kind of fabric that is white.However, a light-colored material which blackens (or chars) readily in the early stages of exposure to thermal radiation will, behave essentially as a dark material regardless of its original color. Some bizarre skin burns were seen among the Japanese population. The pattern of the dress fabric was burned into the skin, with the deepest burns matching the dark stripes or pattern of the fabric. Thick organic materials, such as plastics, heavy fabrics, and wood more than 1/2 inch thick, char but do not burn.Dense smoke, even jets of flame may be emitted, but the material does not sustain ignition. This type of behavior is illustrated in the photographs takenFigure 14-18.Effects of thermal radiation on of a white-painted wood frame house during one white-painted exterior of wood frame house: of the nuclear tests in Nevada. As figure 14-18A A. Almost immediately after explosion; B. Ef- indicates, at virtually the instant of the explosion, fects as seen about 2 seconds later. the house became covered with thick black smoke, and no sign of flame. Very shortly thereafter, but before the arrival of the blastas important a part in attenuating thermal radia- wave, the smoke ceased, as indicated in figuretion as was once suspected. When visibility is 14 -18B.The white paint coat reflected part ofin excess of 2 miles (light haze or clearer), the the thermal radiation and reduced the chance oftotal amount of thermal radiation received will fire. Presumably because the heat was partiallybe essentially the same as that on an "excep- conducted away from the surface, the tempera-tionally clear" day (visibility more than 30 ture was not high enough during the short ef- miles). This is because any decrease in direct fective radiation pulse for the wood to ignite;radiation is largely compensated for by an in- however,thincombustiblematerial wouldcrease in scattered radiation. probably burst into flame at the same location. When visibility is less than 2 miles because of rain, fog, or dense industrial smoke, there will be a definite decrease in radiant energy Range of Thermal Radiation (thermal) received at any specified distance. CLOUDS can also affect the amount of ra- ATMOSPHERIC CONDITIONS also play a partdiant, energy received. For example, if an ex- in the amount of thermal radiation received byplosion occurs about a cloud layer, there will a particular object. However, they do not playbe considerable attenuation at ground level.

328 832 Chapter 14EFFECTS OF NUCLEAR WEAPONS

Conversely, should an explosionoccur beneathoff during the first minute by the radioactive acloud layer, some of the radiation whichfission produ w the rising cloud.In that would normally have been lost tospace will befirst minute themounts of gamma radiation scattered back to earth. from the explos n and from induced activity Artificial white (chemical) SMOKEcan beare about equal. used to attenuate thermal radiation, for it acts Some alpha and beta particles are also like fog in this respect. A dense smokescreenemitted, but these have such short ranges and between the point of burst anda given targetlittle penetrating power that theyare not a source can reduce thermal radiation to as littleasof danger in that first minute. Alpha particles one-tenth of the amount which would otherwisecan travel only 1 to 3 inches in air before being have been received at the target.However, stopped; beta particles can go several hundred there is not likely to be time to throwup antimes farther, but even with their greater speed, effective smoke screen incase of a nuclearthey cannot penetrate a sheet of aluminummore explosion. than a few millimeters thick. It is the highly The effective range of thermal radiationisinjurious nature and long range ofgamma rays greater in open terrain and at sea, where thereand neutrons that makes them sucha significant is no protection from the radiant heat,than inaspect of nuclear explosions. built-up areas, where much of the radiation is RESIDUAL RADIATION is that emitted after obstructed. The Bikini tests indicated thatapproximately one minute from the instant ofa thermal radiation would not bean appreciable nuclear explosion.This radiation originates factor in producing damage atsea, since themainly from the bomb residues; that is, from the exposed portions of naval vesselsare prac-fission products and, to a lesser extent, from the tically fireproof. However, this does not excludeuranium and/or plutonium which has escaped the possibility of secondary fires involvingsuch fission.Additionally, the residues will usually combustibles as gasoline or explosives wherecontain some radionuclides as a result of there has been extensive blast damage. "neutron capture" by other weapon materials. Still another source of residual nuclear radiation NUCLEAR RADIATION is the activity induced by neutrons captured in various elements present in the explosion en- It has been previously pointed out that 15vironment. per cent of the total energy yield of a typical All of the nuclear radiation discussed thus nuclear weapon is distributed in the form offar in this section is the result of fissionre- nuclear radiations (fig. 14-1).Let us explore actions. Neutrons are the only significant further what this radiation consists of, how itnuclearradiations produced in pure fusion occurs, and what its dangers are. reactions.Thus, it can be seen that for ex- In any nuclear explosion there isan initialplosionsin which bothfission and fusion flux of radiations consisting mainly ofgamma (thermonuclear) processes occur, thepropor- rays and neutrons.Both of these (especiallytions of specific radiations will differ from gamma radiation) travel great distances throughthose of typical fission explosions.However, the air, and can penetrate great thicknesses offor present purposes, the differencemay be material.Remaining within the fireballaredisregarded.Since gamma rays and neutrons fission products and unfissioned bomb material. cause similar type injury to humans, the com- These fission products and unfissionedbombbined effect may be considered, although the material are also radioactive, and emitgamma relative biological effectiveness (RBE) ofneu- rays and beta particles. This emission of betatrons is much greater than that of gammarays. particles and gamma rays from the radioactive substance is a gradual process, and its hazard Fallout therefore remains over a significant period of time. As the height of burst ofa nuclear ex- INITIAL NUCLEAR RADIATION is arbi-plosion occurs nearer the surface of the earth trarily defined as that radiation emitted within(or sea), larger and larger proportionsof the (approximately) the first minute after theex- earth (or water) enter the fireball and arefuzed plosion. Initial nuclear radiation includes those or vaporized. When sufficient cooling has oc- neutrons and gamma rays given off almost in- curred, the fission products become incorpor- stantaneously, as well as the gamma rays given ated ith the earth particles as a result of the 333329 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS condensation of the vaporized products into fuzed particles of earth, etc. As the violent disturbance due to the explosion of the nuclear )0 , i u weapon subsides, these contaminated particles fall gradually back to the earth. This effect is referred to as the FALLOUT. The extent and 80 nature of the fallout can .range between wide extremesdependent on the energy yield and design of the bomb, the height of the explosion, 60 the nature of the surface beneath the point of burst, and the meteorological conditions. Inthe case of an AIR BURST occurring at an appre- 40 ciable distance above the earth's surface, sothat no large amounts of dirt (or water) are sucked into the cloud, the inherent radiation will be 20 widely dispersed. On the other hand, a nuclear explosion occurring at or near the earth's i surface can result in SEVERE contamination by 2 4 6 6 10 i the radioactive fallout. TIME AFTER EXPLOSION HOURS) It should be understood that fallout is a 144.71 gradual phenomenon extending over a period ofFigure 14-19.Rate of decay of fission products time.There can be considerable fallout many after a nuclear explosion (activity rated as100 hours after the surface detonation of a nuclear at 1 hour after detonation). weapon, and many miles away.Additionally, there is a phenomenon called WORLDWIDE or delayed FALLOUT which may continue for years after a nuclear explosion. Fallout that occurs Fallout and Type of Burst within 24 hours of a nuclear explosion is referred to as LOCAL or early FALLOUT. Contamination of the earth's surface with radioactivematerialresults from neutron RADIOACTIVE DECAtFission products, activityafter a nuclear explosion and from which make up the greatest hazard in residual The amount of contamination and its radiation, are initially very radioactive. How- fallout. ever, this activity falls off at a fairly rapid ratedistribution vary with the factors previously as the result of decay. Figure 14-19 shows the stated. exponential rate of decay of fission products The cloud of a thermonuclear explosionrises after a nuclear explosion. rapidly to the highest levels of the atmosphere and spreads over hundreds of square miles in the The mixture of radioisotopes present after a first hours. During this time the particles are nuclear explosion is so complex it is impossible being acted upon by the winds, including those up to represent the decay as a whole in terms of to 60,000 or 80,000 feet, which may vary greatly half-life, as eachradioisotope has its own in direction and velocity at different heights. definite half-life, ranging from a fraction of aParticle size will affect the rate of fall and as second to a million years. The chart presentsthe material descends through the rain cloud a fairly simple formula for calculating the ap-bearing levels, the fallout may be slightly ac- proximate decrease in total radiation intensitycelerated by rain or snow. The fallout may or in relation to time. The residual radioactivity may not be visible, but in any case, it can be for the fission products at 1 hour after nuclear detected with radiac equipment. Falling dust or detonation is taken as 100 and the subsequent decrease with time is indicated by the curve. ash, if visible, probably willbe radioactive. . At 7 hours after the explosion, fbr example, AIR BURST.The RADIOLOGICAL EF- the fission product activity will have decreased FECTS from a typical AIR BURST are com- to one-tenth (10 percent) of its amount at 1 hour. pletely overshadowed by the effects of blast and After 2 days, the activity would have decreased thermal radiation. An exception to this would to about 1 percent of the 1-hour value. be a "low" air burst of a high yield weapon

334 33! Chapter 14EFFECTS OF NUCLEAR WEAPONS

where there would be extensive inducedradio-the total residual radioactivity will bedeposited activity in the vicinity of groundzero. Raditt-on the ground within a few hundred miles of the logicaleffects might also be ofsome con-explosion. The remainder of the activity will sequence to those persons shielded from theremain suspended for a long period of timeas primary causes of casualties, andto thosewith an air burst. beyond the areas of serious blast andthermal The intensity of the radioactivity isvery damage. high immediately after the burst, but decays SURFACE BURST.A surface burstnuclearrapidly.Therefore, since not much time will explosion presents an entirely differentpicture.have elapsed, the particles reaching the ground With a surface burst,even though the inducednear the burst will be highly radioactive, while activity will be considerable, the activityof thethose which are carried a long distance will FALLOUT will be of much greaterconse-have lost much of their radioactivity before quence. they alight. The surface burst causes large amountsof Although the areas seriously affectedby earth (water), dust, and debris to betaken upheat and blast of thermonuclearweapons are into the fireball in its early stages. Heretheylarge, they are small when compared to the are fuzed or vaporized and become intimatelyarea of residualradiation haZard produced mixed withthe fission products and otherby fallout.Because of many uncertainties, bomb residues. As a result there isformed,especially of wind direction and velocity at upon cooling, a tremendous number of smalldifferent heights,it is impossible to apply a particles contaminated to some distancebelowstandard fallout pattern to all detonations. An their surfaces with radioactive matter.Inidealized fallout pattern has been prepared and addition, there are considerable quantitiesofa commanding officer can adjust the outlines pieces and particles, coveringa range of sizesaccording to whatever information is available from large lumps to fine dust, to thesurfacesto him at the time and plan his defenses for the of which fission productsare more or lessarea expected to receive fallout. Such knowledge firmly attached. would include information on wind and weather The larger (heavier) pieces, whichwillconditions in the area, the topography of thearea, include a great deal of contaminated materialand location and nature of naturalor manmade scoured and thrown out of the crater, willnotshelters. be carried up into the mushroom cloud,but As a general rule, the pattern of contamina- will descend from the column. Providedthetion will be as illustrated in figure 14-20.It wind is not excessive, these large particles,asbecomes an elongated cigar-shapedarea ex., they fall, will form a roughly circular patterntending downwind from the point of burst.Of around ground zero (though the circle willbecourse this pattern will vary with the wind somewhat eccentric as the result ofany wind).velocities and directions at all altitudes between Most of this heavier material referred toabovethe ground and the height of the atomiccloud. will descend within an hour orso. The actual fallout assumesa somewhat ir- The smaller particles present in the atomicregular shape, such as that shown in figure cloud' will be carried up to a height of several14-21, which was from a 43-KT shot. miles, and may spread out some distance in Note that the areas downwindare not im- the mushroom cloud before they beginto de-mediately contaminated.Rather, most of the scend. The actual time taken to return to thedownwind area will not be seriously contaminated earth, and the horizontal distance traveled,until hours after the explosion. Foran example will depend upon the original height attained, (fig. 14-20), a location 22 miles downwindwill the size. of the particles, and upon the wind inhave a DOSE RATE of about 10 roentgens/hour the upper atmosphere. one hour after the detonation. At 2 hours, the The fraction of the total radioactivity ofthedose rate has increased to 1000 r/hr. bomb residues that appears in the falloutde-at 18 hours, it is down to roughly 80 r/hr. The pends upon the extent to which the fireballincrease in dose from 1 to 2 hoursmeans that touches the surface.Thus, thoPprciportion offallout wai not complete at 1 hour after theex- available activity increases as the height ofplosion.With respect to the ACCUMULATED the burst decreases and more of the fireballDOSE received, at one hour after detonation,the comes in contact with the earth (or water). In100-mile point will not have receivedany ap- the case of a "contact burst,"some 50% ofpreciable radiation because the fallout has only 83..5. 331, , PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

UNDERGROUND BURST.The extent of residual radiation accompanying an underground burst will depend primarily on the depth of 200 1 RAIR burst and the weapon yield.With regards to 100 initial radiation, it is either nonapparent or in- 180 consequential by comparison to the residual 170 radiation.

110 If the explosion occurs at sufficient depth below the surface, essentially none of the bomb .. 100 residues and neutron-induced radioactive ma- 140 terials will escape to the atmosphere. There 130 will be no appreciable fallout. On the other hand, if the burst is near the 110 surface so that the ball of fire actually breaks 8 100 through, the consequences as regards fallout 00 will not vary greatly from those of a surface burst. Oth9r circumstances being more or less equal, the 4intamination in the crater area following an underground burst will be about the same as for a surface explosion of equal fission yield.However, the total contaminated area for a shallowunderground burst will be ;! greater because of the larger amount of fission 10 100 products present in the fallout. 1000 3000 UNDERWATER BURSTS.Radiological effects of UNDER WATER BURSTS closely parallel 4-1-1-1-1 11-1-11 those of underground origin.The base surge, 10 10 20 SO 10 0 10 20 2010 0 10 20 consisting of a contaminated cloud or mist of '4, DISTANCE FROM GROUND ZERO (MILES) small water droplets also has a parallel in the 1 ROM 4 HOURS 18 HOURS underground phenomena.During the first 15 minutes, the base surge is a source of con- 100.89 Figure 14-20.Dose-rate contours from earlytamination,ut the radiation intensity declines fallout at 1, 6, and 18 hours after a surfacerapidly. The total amount of radiation from the burst with 1-megaton fission yield (15 mphbase surge and "rain-out" from the atomic cloud varies with the size and type of burst, the ..1 effective'wind speed). depth of the water, and other factors.In the BAKER test at Bikini, the early dose rate of the .4 base surge was 100,000 roentgens per hour. started to arrive. While at the end of 8 hours,From a deep underwater burst there would be no the total dose has reached over 3000 roentgens.airborne cloud and consequently no fallout or In general then, at any given location, at arainout. As a general rule, the base surge is distance from a surface burst, some timeexpected to present a considerable radioactive '0_, elapses before the fall out arrives. Time of ar-hazard for a distance of several miles, especially rival and amount of radiation vary with the sizedownwind. The parts of the ship that are ex- and type of burst, the wind, and other conditions.posed to the base surge can absorb a great deal ,Pit Although the example given above is for theof radioactivity. surface burst of a high fission yield, 1-megaton An important difference between an under- nuclear weapon, the fallout phenomena .asso-water burst and one occurring underground, is ciated with a low fission yield weapon are es-that the radioactivity remaining in the water is -Is sentially the same except for differences ingradually dispersed, whereas that in the ground degree.Thus, a high energy fission yield ex-is not. Therefore, as a result of diffusion of the plosion will mean a larger area contaminated tovarious bomb residues, mixing with large a more serious extent than would a low fissionvolumes of water outside the contaminated area yield weapon. and the natural decay, the radiation intensity of ...336 332 Chapter 14EFFECTS OF NUCLEAR WEAPONS

conventional explosions.For this reason, the subject of RADIATION INJURY will be discussed here in more detail. The harmful effects of radiationappear to be due to the ionization (and excitation)produced in the cells that makeup living tissue. As a result of ionization,some of the constit- uents that are essential to normalfunctioning are damaged or destroyed. Some of the products formed may act as cell poisons.Addi- tionally, the living cells are frequently unable to undergo mitosis, so that normalcell re- placement is inhibited. The effects of nuclear radiationson living organisms depend not only on the total dose, that is, on the amount absorbed, but alsoon the rate of absorption, i.e., on whetherit is ACUTE or CHRONIC.In an acute exposure, 0 20 40 the whole radiation dose is received ina rela- MILES tively short period of time.It has somewhat arbitrarily been defined as that dosereceived 100.88during a 24-hour period.Delayed radiations, Figure 14-21.Early fallout dose-ratecontourslike those which may be received from fission from the TURK shot at the NevadaTest Site. products, persist over a longer period of time and this type of exposure is of the chronictype. thr water in which a nuclear explosionhas oc- The distinction between acute andchronic ctorfed will decrease fairly rapidly.Additiona-exposure lies in the fact that, if the dose rate is ally, fission products will settle to thebottom ofnot too high,the body can achieve partial the body of the water, thus greatlyattenuatingrecovery from some of the consequences of the the radiological hazards. nuclear radiations while still exposed. In ad- The radiation hazard therefore ismuch lessdition to the above, the percent of bodyexposure than the same amount of falloutover land. Thehas significance. If follows then, thatwhereas a radioactive water will be transported by prevail-person would die as the result of acute exposure ing currents, and if the currentsare known, theof 1000 reins whole-body radiation, hewould radioactive areas ca be charted and avoided.probably suffer no noticeable external effects Distilled water made from lightlycon-if the dose were spread overa period of 30 years. taminated sea water is perfectly safe todrink. The injury caused by a particular doseof This is because the radioactive materialremainsradiation will depend upon the extent andpart behind in the residual scale and brineof theof the body that is exposed. Differentportions distillation process. However, the ship'sevap-of the body show different sensitivitiesto orators must be secured while the ship isinionizing radiations, and thereare variations in significantlycontaminated waters, to avoidthe degree of sensitivity among individuals.The carrying dangerous contamination into the ship'sage and the physical condition of the person also interior.Also, it would be extremely difficultinfluence the result. .Since practically allthe to decontaminate the evaporator andkeep con-information we have on the effects of radiation tamination from reaching the water tanks.Iton humans is from the 'Japanese bombings, the should also be emphasized thatmere boiling ofinfluence of other injuries is hard to separate water is of no value as regards the removal offrom radiation injuries. Largenumbers of radioactivity. Japanese were exposed to doses ofradiation ranging from insignificant to fatal. Theresults Radiation Injury were complicated by. other injuries, shock, and lack of medical attention, andmany of the deaths As the student will recall from chapter 12,were probably due-to a combination of injuries. the injurious effects of nuclear radiationre-By combining the information availablefrom the resents a phenomenon completely absent inJapanese bombings with informationgatheredon PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS accidentally exposed persons and studies ofof acute radiation will die.It is believed that animals exposed at test sites, tables have beenprompt medical treatment (care) would reduce compiled to show the effects of acute radiationthis percentage. Everyone receiving 1000 r. or of different amounts. more would die within two or three weeks, if not ACUTE RADIATION INJURY. Table 14-3sooner, in spite of the best medical care. shows expected effects of acute whole-body A further matter of note is that the sooner radiation doses.Notice that the table beginsthe symptoms of radiation sickness appear after with 150 roentgens; no noticeable effects areexposure, the more serious the consequence will expected below that amount.Changes maybe. Additionally, there is a latent period between nevertheless be occurring in theblood. Perhapsthe first symptoms of radiation exposure and the most' striking and characteristic biologicala further condition of sickness. consequence of exposure to whole-body nuclear The clinical effects of radiation listed in the radiation are the changes in the blood and thetable are those noted in the Japanese population, blood-forming organs. The effects may not bewhere preexisting conditions were an unknown seen at once, but the loss of the ability to flightfactor and little actual data recording was done infections may result in death. For those whountil 2 weeks after the explosions.The most survive, recovery may take months or evenaccurate data are from the cases of radiation years.Careful charting of the course of bloodexposurein the Marshall Islands test, but changes in Japanese victims and those in the200 r. was the limit for the exposure there. Marshall Islands has furnished reliable data on LATE EFFECTS OF RADIATION.If a per- these phases of radiation exposure. son survives the acute effects of radiation, later It has been estimated that approximately 50effects may show up years later.These percent of the persons subjected to 450 roentgenseffects,like the acute ones, are caused by

Table 14-3. General Nature of Radiation Sickness. (Acute exposure)

Time after Acute doses received over a large area of body exposure 150-300 r 300-500 r 500-600 r First week Nausea and vomiting Nausea and vomiting Nausea and vomiting on first day. on first day. on first day; Otherwise, no diarrhea, vomit- definite symptoms. ing. Second week No definite symptoms. Loss of hair, loss of Inflammation of appetitie, gen- mouth and throat, eral sick feeling. fever, rapid weight loss, mortality rate about 90 percent. Later effects Loss of hair, loss of Fever, inflammation appetite, general of mouth and throat, sick feeling, sore pallor, skin throat, pallor, skin hemorrhage, hemorrhage, diarrhea; diarrhea, nose moderate weight.loss, bleed, rapid weight ultimate recovery. loss, mortality . likely in abapnce of rate of 50 percent complications. Mor- at 450 r. tality rate of 3 percent

at 200 r. . Chapter 14EFFECTS OF NUCLEAR WEAPONS

changes in the cells and tissues arisingfromblood changes and damage to the blood-forming the exposure.The replacing cells may not becells in the marrow of the bones proceedunseen quite normal. and may be advanced before detected. One of the effects mentionedpreviously is The hazards of fallout are external and that of cataracts.These are attributed to theinternal.The contaminated particles of the initial nuclear radiation at the timeof the ex-early fallout cause "beta burns" if they contact plosion, chiefly by fast neutrons, whichcausebare skin or skin protected by light clothing. lens opacities more frequently thangammaWhere fallout is heavy, the whole bodymay be radiation. exposed to beta particles.The effects were It is still too early to makea definite state-studies in the Marshall Island test explosion. ment about the effect of radiationon the lifeThe natives did not realize the significanceof span. At present there is no definite proof thatthe ash-like dust falling on them about 5 hours whole-body radiation exposure hastensaging.after the detonation.The itching and burning An increase in the incidenceof leukemiasensation experienced at the time subsided and cases was shown among the inhabitants ofdisappeared, but 2 or3 weeks later, skin Hiroshima and Nagasaki, but thetotal numberlesions, dark colored patches, and epilation of cases definitely associated withradiation ex-began to appear among the exposed population. posure is not large and there is stillsomeDiscoloration of nails was attributed togamma uncertainty about interpretation of the statistics.radiation. The skin lesions healed and the hair A twofold to fourfold increasein neoplasticregrew in a matterof6 months, but the disease (abnormal marked growths,i.e., tumors,studies of platelets and red blood cells showed cancers) was found in the Hiroshimapopulationthey continued to be lower than normal 5 and '7 but a similar study of Nagasaki showedno suchyears after the exposure.This indicates that relationship. Studies are being continuedon therepair of the bone marrow injurywas not relationship of cancer incidence toradiationcomplete. exposure. Internal hazard from fallout occurs when One of the most publicized resultsof radia-radioactive particles are consumed with food tion is that of sterility. Study of the Japaneseand water, or are inhaled. The nose isa good cities shows that the sterility is temporary.filter, so there is not so much dangerfrom To produce permanent sterility,a large radia-inhalation of early fallout, most of which is too tion dose is required, which is likelyto becoarse for inhalation.It is also possible for fatal.Among pregnant women exposed, thereradioactive material to get inside the body was a marked increase in stillbirths and deaththrough cuts or other wounds in which the of newborn infants.The surviving childrenskin is broken.(Alpha particles cannot pene- showed a greater frequency of mentalretarda-trate unbroken skin.) tion. Children conceived after the nuclear Even a very small quantity of radioactive exposures did not show an increase in abnorm- materialin the body can do considerable alities.Thus, the fear of effects on futuredamage, and the injury is continuousas long generations has not been substantiated, althoughas the material is in the body. The organ most experiments with fruit flies and animals showedaffected is determined by the type of radioactive increased mutations. material.Iodine, for example, tends to con- INJURY FROM FALLOUT AND RESIDUALcentrate in the thyroid gland.The fission RADIATION.A few radiation phenomena,suchproducts strontium and barium are depositedin as genetic effects, apparently depend primarilythecalcifyingtissue of bone.Cerium and upon the total dose received and to a lesser,plutonium also are "bone seekers." Theyare extent on the rate of delivery.The injurypotentially very hazardous because they injure caused to the germ cells under certaincondi-the sensitive bone marrow wheremany blood tions appears to be cumulative. In the majoritycells are produced. The damage to the blood- of instances however, the biological effectof aforming tissue thus result's in a reduction in given total dose of radiation decreasesas thethe number of blood cells andso affects the rate of exposure decreases. whole body adversely.The damage may not The effects of residual radiitionare thebecome apparent for some time. The primary same as for initial radiation, but not with suchhazard of inhaled plutonium is in thelungs dramatic onset.The symptoms develop grad-and bronchial lymph nodes. Uraniumcauses ually as the radiation dose accumulates.Thedamage to the kidneys but only asa heavy 335 339 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS metal poison (similar to lead poisoning), notto get beyond the reach of the effects, or to because of its radioactivity. provide protection against them within their The short-term hazard of early fallout in-radii of damage. gested by the natives of the Marshall Islands was small.The long-term hazard of delayed SHIPBOARD PROTECTIVE MEASURES fallout is another matter. The most important radioaCtive isotopes are probably cesium-137 The naval forces afloat have a distinct and strontium-90.As explained earlier, theadvantage in that they are readily dispersible. delayed fallout can spread to remote parts ofIn addition to this, the ships of the Navy are the globe and can contaminate water, milk, andso designed that they are comparatively re- food.Cesium-137 has a radioactive half-lifesistant to the blast (and/or shock) and the of 30.5 years and emits gamma rays as itthermal effects of nuclear weapons.Too, the decays.Strontium-90 has a radioactive half-features built into Navy ships for protection life of 27.7 years and emits only beta particlesagainst gas attack provide some measure of of fairly low energy, but once it gets into theprotection against radiation hazards. skeleton it stays there a long time.Experi- Both long- and short-range preparation go ments with animals indicate that the effectsinto proper readiness of Navy ships.Strict may be anemia, bone necrosis, cancer, andspecifications are set for the designers and possibly leukemia. builders in order that the ships are as resis- As a result of the nuclear test explosionstant as feasible to the effects of nuclear weap- in various countries, there has been an increaseons. Command action is taken to keep fire and in the strontium-90 content of the soil, plants,missile hazards minimized.Tactics include and the bones of animals and man.This in-such things as greater than normal dispersal, crease is worldwide and is not restricted tothe placing of all possible personnel under the areasin the vicinity of the test sites,cover, establishing the highest state of ma- although naturally it is higher there. terial readiness, and the activation of WATER The amount of carbon-14 in the troposphere WASHDOWN systems. has been increased by about 30 percent through After a nuclear explosion, the primary weapons testing.It will be a source of radia-problem is to keep and/or return the particu- tion for many generations, as its half-life islar ship to a maximum state of readiness by 5,760 years. preventing the avalanching casualties resulting from secondary effects, by restoring normal services or rigging alternate (or emergency) ATOMIC WARFARE DEFENSE services, attending to the wounded, conducting radiological surveys and decontaminating or GENERAL localizing as applicable, and by assessing the extent and nature of damage and restoring the .4; The effects of nuclear weapons .have beenunit as nearly as possible to its original given with considerable detail derived from condition. experience with nuclear detonations.But in Tactics included after a nuclear explosion , planning protection from the consequences ofwould include maneuvering to avoid, or to mini- a nuclear explosion, many uncertainties aremize the transit time through, any base surge, ;1 encountered.It is impossible to know in ad-fallout areas, or radioactive waters. vance where or when a weapon willbe detonated, Providing the maximum protection for the or what type it will be or its size. Nevertheless,men will often reduce the ship's immediate there are some basic principles which, if ap- operational capability (offensive and defensive). plied, can, give a measure of protection to aIt may become necessary for the commanding .4 large proportion of the population. officer to sacrifice personnel safety to preserve Foresightedness and an understanding of theship operational capability.In making his effects nuclear weapons will have greatdecision the CO must consider many factors, bearing on survival in event of nuclear warfare.some of which are:the mission of the ship, In general, there are two broad Categories ofthe estimated extent and duration of. the haz- protection that can be used to avoid the stunningardous environments, exposure guidance (how effects of nuclear weapons. They are DISTANCE long a man may be permitted to remain at a and SHIELDING. In other words, it is necessary.station in the contaminated area), rotation of

336 340 Chapter 14EFFECTS OF NUCLEARWEAPONS personnel, means of decontamination available, The area over which protectioncould be and protection available. Aship with a washdown system can prevent heavy effective in saving lives is roughly eightto ten contaminationtimes as large as that in which thechances of the ship surfaces if the systemis placed inof survival are small. operation before the nuclear explosion, It is in this possibly but evenlarge area that preplanning of protectivemeas- if that was not possible, the washdownsystemures is of the utmost importance. will reduce topside contaminationso decontamination teams can get to worksooner and men can be detailed to their stations forshortPROTECTIVE MEASURESINDIVIDUAL times, determined by the amount ofradioactivity ACTION present.The CO must know the actualor potential exposure hazards andthe counter- For an individual, in the event ofa surprise measure capabilities of his ship in order toattack, proper and immediate actioncan mean judge whether to continue,modify, or abortthe difference between life and death. the action and/or mission.If he has a good disaster control plan and has the From experience gained in bothnuclear and men trainedconventional explosions, there is littledoubt in their individual and team duties,the chances of survival and successful that as a general rule it ismore hazardous in mission are im-the open than inside a structure.In an emer- measurably increased.Not only. the CO, butgency, therefore, the best available shelter every officer on board ship andevery pettyshould be taken. officer and enlisted man has specific respon- Aboard ship, TAKE COVERshould be di- sibilities and duties to perform before,during, rected at the appropriate time for and after a nuclear explosion. those in exposed stations.Once properly shielded, and SHORE BASE PROTECTION other operations permitting, personnelshould take a position with knees flexed,and with a Ashore, the militarymust also plan tofirm grip on a substantial piece of the ship's disperse and/or providesuitable protection forstructure. personnel and material. This position should be held until The civil defensepassage of the blast and/or the shockwave. authorities should plan accordinglyfor the civilian population. Ashore, civil defense authorities (ormili- Much can be done towardstary, where they have jurisdiction)should have reducing blast and fire hazardsin existingdesignated structures. shelterareas and/orshelters. Shelters and shelterareas canSubways would providea good emergency shel- be provided. Dfsasar teamscan be organized and trained to kecp loases to ter; however these are found inonly a limited a minimum. number of cities. As an alternative,the base- Standards for slo--;Mr constructionhavebeenment of a building should be chosen.In this prepared by engineers with informationfromconne ction, a fire-resistant,reinforced- test buildings at test sites and fromthe resultsconcrete or steel frame structure is to bepre- foundin the Japanese bombings. Designsferred, since there is less likelihood ofa large have been prepared for both publicand privatedebris load on the floor above thebasement. shelters for various situations.The buildingEven basements of good buildingsare not, how- and stocking of shelters hasbeen sporadicever, an adequate substitute for a well designed chiefly because people believethat nothingshelter. can save you in a nuclear attack.It is true Should there not be any opportunityto take that there is little chance of survivalin thethe best shelter, alternate immediateaction zone of heavy damage around groundzero,will be necessary. The first indicationof an but the chances improve with distance.Justunexpected nuclear explosion (other thana sub- one quotation of statistics from the Japanesesurface explosion) would bea sudden increase results should be convincing. AtHiroshima,in the general illumination.It would be im- of approximately 3000 school studentswho were perative to avoid the instinctive tendency in the open and unshielded within to a mile oflook at the source of light, but ratherto do ground zero, about 90 percentwere dead oreverything possible to cover all exposedpor- missing after the explosion. In thesame zonetions of the body (anotherreason for proper were nearly 5000 students who were shieldedand suitable battle dress). Aperson inside a in one way or another; only 26percent of thembuilding should immediately fall were fatalities. prone and crawl behind a table or desk. This willprovide 341 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS a partial shield against splintered glass andPROTECTION FROM FALLOUT other flying missiles.No attempt should be Protection against the residual radioactivity made to get up until the blast wave has passed,present in LOCAL FALLOUT presents a number as indicated by the breaking of glass, crackingof difficult and involved problems.This is of plaster, and other signs of destruction. Thebecause the radioactive products are not nor- sound of the explosion also signifies the arrivalmally visible and require radiac equipment for of the blast wave. detection and measurement, and because of the A person caught in the open by the suddenwidespread and persistent character of the brightness due to . a nuclear explosion, shouldfallout, and too, because fallout prediction is drop to the ground, while curling up to shadeafunctionofcomplicatedmeteorological the arms, hands,neck, and face with theprocesses. clothed body.Although this action will haveFallout Prediction little effect against the initial nuclear radia- The fallout patterns charted after the various tion,it may help in reducing flash burns duenuclear tests have been used to prepare a to the thermal radiation. Of course, the degreeform to be used for predicting the area of of protection from thermal effects will varyfallout.It is called Radiological Fallout Fore- with the energy yield of the explosion. For ascasting (RADFO) and is made available to you will recall, low yield weapons expel alloperational commands. Before a nuclear attack, their thermal radiation in a short interval ofinformation will not be available on the location time, while the higher the yield, the longer theof the burst, type of burst, or yield of the thermal pulses of energy will last. Neverthe-weapon, and after the detonation it is expected less, there is nothing to be lost, and perhapsthat disruption of normal activities will prevent much to gain through such action. The curled-obtaining much real information about theburst. up position should be held until after the blastThe command will have information on the wave has passed. atmospheric wind structure, and with that in- Since eye injuries and skin burns fromformation, can plot a tentative fallout area thermal radiation can occur at great distanceswith the aid of the RADFO overlay (fig. 14-22). from the explosion, this type of avasive actionThe RADFO diagram is usually drawn in grease can be helpful over large areas.Ordinarypencil on a plastic sheet to be used as an sunglasses provide little or no protection ofoverlay on an appropriate map or chart. Var- the eyes against damage by thermal radiation.ious essential data are included in the legend The blink reflex is of doubtful help tithe personof the RADFO diagram. The legend also is facing the blast point, especially if theindicates the map scale or map identification thermal energy is released in one burst, asnumber for which it is drawn. Each command from lower energy weapons or those burst atrequests maps forits particular area and high altitudes (above 20 miles).Fortunately,keeps them on hand.The red outline marks most flash blindness is temporary. the area of high fallout expected from a low- yield weapon, and the black outline marks the If a shelter of some kind, no matter howhigh falloutarea for a high-yield weapon. minor, e.g. in a doorway, behind a tree, or inThe cross-hatched dot represents the point of a ditch or trench, can be reached within adetonation (surface zero).With the dot placed second, it may be possible to avoid a significantat the point of detonation (expected), the over- part of the initial nuclear radiation, as well aslay can be rotated in line with the winds at the thermal radiation. But shielding fromthe time, and it then outlines the approximate nuclear radiation requires considerable thick -area where the fallout can be expected.The ness of .material and this may not be availableship can be maneuvered to keep out of that in the open. By dropPing the the ground, somearea and the fallout preparations can be made little advantage may be provided by the groundaboard the ship. and surrounding objects. The complete description and instructions Putting out fires when they Se just startingfor use of the RADFO diagram are given in may be done by individuals in some instances.the United States Navy Radiological Fallout Every effort should be made to do this in orderManual, (1962), OPNAV INST P3441.3A. The to prevent large fires which may becomeactual fallout area will vary froin the RADFO uncontrollable. plot, but planning can be based on the pre- Chapter 14EFFECTS OFNUCLEAR WEAPONS

may affect vast areas, and thereforemay affect large numbers of people whomust have pro- RADFO'OVERLAY VALIDTIME II/1200Z tection for at least that periodof time. Anyone 12/0000Z acquainted with the daily traffic LOCATION SOR problems ac- MAP SCALE 1e160.000 companying the routine working daytransporta- tion in any large metropolitan area must realize. that attempting to evacuate thewhole population of a threatened areaupon short notice would result in a hopeless snarl.The alternative is to have prepared shelters,stocked with provisions, where large numbersof people can take refuge and remain perhaps forseveral days, or even weeks. Where approved sheltersare not available, even the basement of a frame housecan attenuate nuclear radiation bya factor of about 10. Greater reduction is possiblein large buildings or in shelters covered withseveral feet of earth.Three feet of earth willprovide a radiation attenuation factor in theneighborhood of 1000. Ships will have to depend onproper maneuvers, the GAS TIGHT ENVELOPE, waterwash down systems and decontaminationprocedures for protection. Ashore, the civildefense and/or military authorities must makeradiological surveys to ascertain the extent and natureof the contamination.Once this is known, it is. possible to take other correctiveactions, such as orderly evacuation of shelteredsurvivors and. decontamination ofessentialareas or equipments. Shifting winds and otherunknown Variables complicateany prediction of safe 100.90 evacuation routes. A petsonmay leave a com- Figure 14-22.Example offallout plot drawnparatively safe location and endup the loser with RAD PO overlayupon receipt of prediction for his effort. or warning message. Of the passive protectivemeasures that can be taken, shelter is the foremost.Complete liminary plot and earlyaction can be takenprotection for all people is hardlyfeasible, on that .basis.Plans can be made to minimizebut every Navy shore activity hasareas des- the hazards of fallout radiation,but they must ignated as shelter areas wherepeople are to go be flexible so theycan be adapted to theimmediately if a nuclear alarm is given.Evac- partiCular situation whichdevelops after- theuation routes are plannedso each person has an attack. assigned place to go incase there is .sufficient Group Protection advance warning so peoplecan get to designated Fallout gathering places.Know the location of the . from a surface burst can.Producemarked areas so, you can go to the assigned serious , contamination far beyondthe rangeone without hesitation when so ordered. of other effects suchas blasti shock thermal Civil Defense authorities radiation, and initial nuclear 'radiation.. have published Thepamphlets onhnethods of construction forhome quantity ;Of contaminated niatertg,produced by shelters. Family type shelters a surface ;burst of a megaton weaponwith a were widely fission used; In England dUring World 'WarII for rielii;is .;80., large that -the.tfallout,mayprotection against bombs, and. continue= arrive: in hazardoUs concentrations were.. a great up to "perhans `. 24 help ,in 'preventing casualties. &tenetshelters, hours' after the burst.. .It bUilt -according. to. Civil Defense.Standards to 339. 10 843 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS reduce the entrance of nuclear radiation, canuse on a stationary land target. Foranother be of inestimable help in case of nuclear attack.type of target, an attacking aircraft, for example, entirelydifferentcriteriaarenecessary. Protection Against Long-Range Fallout Should a nuclear-tipped misssile. be launched from the ship or should an air-to-air missile The radiation from long-range fallout is toobe used? Perhaps conventional antiaircraft fire attenuated to be harmful as external radiation.will take care of the situation. The officer in Its harm comes from ingestion, whether throughcommand must make the decision quickly. You inhalation, from drinking water, or food. Except can readily see that this is quite adifferent in cases of extreme overexposure, there is asituation from, say, the planned obliteration of latent period before signs and symptoms ofan enemy naval base. radiation illness appear. Radioactive material The actual mechanics of weapon selection within the body cannot be controlled by time,is a very complex operation. This operation distance, or shielding; it continues to affectis the function of relatively high echelons of the cells of the body until it hasbeen eliminatedcommand.The student should be aware that by natural processes or radioactive decay.there also are great moral and political issues Risk of exposure can be greatly reduced byinvolved in the use of nuclear weapons. For good housekeeping. Foods that might havethese reasons, the actual committing of nuclear received some of the radioactive fallout shouldweapons to use by our country is the respon- be thoroughly washed before using.Exposedsibility of the President of the United States. foods that cannot be washed should be disposedNotwithstanding, some generalized statements of. Cooking the foods or boiling the water does concerning the relative importance of various not reduce theradioactivity. A number ofeffects for different burst conditions is con- materials have been tested for possibilities assidered essential to a complete orientation in an agent to remove radioactive materials fromthe nuclear weapons subject area. the system. Various results have been re- The discussion following relates to the use ported. So far, none of the products so testedof nuclear weapons to achieve certain effects on have been accepted as useful for removingsurface targets, either land or sea. Most of radiation. Also, some materialshavebeentriedthe material damage caused by either an air for removal of radioactive fallout in milk.burst or a surface burst of a nuclear weapon This is another problem left to be solved byis. due mainly (directly or indirectly) to the 4 further research. shock or blast wave that accompanies the .1; explosion. In considering the destructive effect of a blast wave, one of the important char- 1 EMPLOYMENT OF NUCLEAR acteristics is the overpressure, that is, the WEAPONS EFFECT pressure above the normalatmospheric pressure. Other characteristics of theblast wave GENERAL that affect the degree of destruction are the dynamic pressure, duration, and time of arrival Many factors enter into the selection ofof the blast wave. the burst height (or depth) and yield of a particular weapon. Among these are fuzing lim- SURFACE BURST itations, type of target, available delivery systems, and the degree of damage desired. Since A SURFACE BURST will increase the range nuclear missiles, torpedoes, and depth bombsat which peak overpressures greater than about have become part of the arsenal, the aspects12 psi occur. It will reduce thermal radiation of weapon selection have been multiplied, received by ground targets compared to that Froni an EFFECTS 'standpoint, the basicreceived from an air burst at the tame slant Criteria Which goVern weapon Selection arerange and it will produce significant cratering peak blast Wave -OverpreSsure, .peak dynamicand ground shock. A peak overpressure of 12 presSure,. ''duration of ,the voiltive Wave. (ofpet will cause severe damage to all structures blast WOO, 'crater extent, thermal radiation,except those of ,reinforced-concrete, blast- initial nuclear radiation; residual filsionprOductresistant construction. It will also cause mod- fallOutOind indircedgroUtid contamination. ThiOse rate to severe damage to most military equip- criteria apply 'to the selection of: a WeapOn' toInents.. 844. 340 Chapter 14EFFECTS OF NUCLEARWEAPONS

Most naval ships operatingtoday will beburst is increased. Cratering, ground (orwater) immobilized when subjected to 20psi peakshock, and fallout contamination willincrease air overpressure. Five psi willcause lightwith the depth of burst up toa maximum (the damage to all naval andmercantile shipping.optimum depth depends on the effectbeing con- Light damage to naval shipsconsists of damagesidered) and then decrease.Maximum water to electronic, electrical, andmechanical equip-waves will be produced at a certain critical mentshowever, the shipsmay still be able todepth of burst. operate effectively. The surface burst will overdestroysome area. It is therefore not as economical (initsSCALING LAWS damage Capabilities)as an air burst. Conceiv- ably,therefore, the surface burstwould be used against resistant targetsor where as- The atomic bombs droppedon Japan are sured destruction is desirable. referred to as 20-KT bombsor nominal yield For weaker targets, whichare destroyed orweapons. The effects of those bombs have been damaged at relatively lowoverpressures orstudied and analyzed in all theiraspects, dynamic pressures, the heightof burst may beincluding their blast, thermal, andradiation raised to increase the damagearea, since theeffects. Since that time, tests of nuclearweapons required pressures will extend toa larger rangeof different sizes and types in variousenvi- than for a low air or surface burst. ronments have furnished much otherdata on While the terrain hassome effect on thethe effects of nuclear weapons. Fromstudies of blast wave, it is difficult to predict these effects, scaling laws have been formulated. the effectThe effects Of detonations of on the damage resulting. The fact thatthe weapons other than point of explosion cannot beseen from behindthe nominal 20-KT bombcan be calculated by a MI does not mean that the blast effectswillmeans of these simple scaling laws. not be felt. Blast wavescan easily bend around Although the laws are only ofan approximate obstructions, and multiple reflectionsbetweennature, they do provide a roughmeans of buildings and streets might increasethe over-comparing the effects of differentenergy re- pressure and dynamic pressure. leases. Scaling laws are applied to eachof the The LOCAL FALLOUT associatedwith aeffects of nuclear detonationsblast,thermal, surface burst is a very significantfactor inand radiation effects. nuclear weapons selection. In the case of blast effects, thescaling law states that the distance froman explosion at which any specifiedoverpressure is reached AIR BURST is proportional to the cube root ofthe energy released. For a 20401 burst, thelimit of An AIR BURST will increasethe groundsevere damage occurs in the region of 7-psi range at which overpressures of about 10psioverpressure, about 1 mile from groundzero. or less are obtained; maximize areas at whichComputing with the scaling formula,an over- significant thermal radiation is receivedon thepressure zone of 7 psi would be 1.3 miles from ground; and eliminate local falloutcontami-ground zero with a 40-KT bomb.Note that nation. Windowpane breakage is associatedwiththe damage limit is not twiceas great as for 0.5 psi overpressure, whilesevere damagea 20-KT bomb. To double the limit ofsevere to wood frame housesoccurs with 3 psi,damage, the amount of explosive wouldhave to and to reinforced-concrete buildingswith ap-be increased 8 times. proximately 10 psi. With regard to overall damageand casualties, the area affected by theburst is important. The area of the burst ispropor- SUBSURFACE BURST tional to the square of the radius;therefore theeffective area of blast damage ispro - With a SUBSURFACE BURST, peakairportional to two-thirds of theenergy release. overpressure, thermal radiation, and initialIf the effective area fora 20-KT bomb is 4 nuclear radiation decreaSe square miles it is 8.4 square mileb fora40-KT as the depth of thebomb.

341 ri :4845 . 1 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

The amount of thermal energy reaching aweapon increases. For example, a 100-KT bomb point at a given distance from the explosion will produce 120 times the nuclear radiation that will be directly proportional to the total energya I-KT bomb will produce; a 500-KT bomb will release of the bomb. If the thermal energyproduce 1,000-KT (1MT) weapon will produce from a 20-KT bomb is 41/2 calories per square1,000 times the amount of nuclear radiation; and centimeter at 3,000 yards from ground zero,a 1,000-KT (1MT) weapon will produce 2,100 from a 40-KT bomb it would be 9 calories pertimes as much. square centimeter. The same proportional in- The altitude of the burst affects the results, crease holds true for the immediate nuclearand the factor of height must be included to radiation. However, this proportion is reason-modify the calculations with the scaling laws. ably accurate only up to 40-KT bombs. ForCurves have been drawn to represent many higher energy releases, the proportion of initialconditions of burst. Figure 14-23 accumulates nuclear radiation to the energy of the bomb be-certain cardinal damage criteria for air burst comes greater and greater as the yield of theexplosions.

I 20poo 1r vzII I.ill I1 II . . 10,000 ... . 7D00 .... . 4000 . . 200 . Ip0 700. . .. . 40 . N q .

2 2 I . . 0 hira ; . O I. g4

I° 2 1 9 - ae au 1 -

. s1 .

. I II 11 . .-. A st 0.2. OA0.71.0 2 4 7 10 20 40 70100 DISTANCE FROM GROUND ZERO (MILES) 144.72 Figure 14 -23.- Limiting distances from ground zero at which various effects are produced in an. air -burst. .;

.346 342 BIBLIOGRAPHY FOR NUCLEAR WEAPONSORIENTATION

Glasstone, S., ed., The Effects of NuclearWeapons, U. S. Atomic Energy Commission, Washington, D. C. 1962;730 pp. Glasstone,S., Sourcebook on Atomic Energy,(U;U), Van Nostrand Company, Inc., 1958. Lapp, R. E. and H. L. Andrews,Nuclear Radiation Physics, Prentice- Hall, NiYork, 1963, 531pp. Behrens, C. F., Atomic Medicine, T.Nelson and Sone, 1949, 416pp. Saenger, E. L., editor, MedicalAspects of Radiation Accidents, U. S. Atomic .Energy Commission,Washington, b. C., 1963, 357pp. Principles of Radiation andContamination Control, NavShips 250-341-3 Vol. 1, Radsafe for Everybody. 1959.70 pp. Vol. 2, Procedures and GuidelinesRelating to Nuclear Weapons Effects, 1960, 340 pp. Vol. 3, Technical Information Relatingto Nuclear Weapons Effects, 1960, 154 pp. Atomic Energy Deskbook, (U;U),Government Printing Office, 1963. Basic Nuclear and Radiation Physics,(U;U), Atomic Weapons Training Group, FC DMA, Albuquerque, NewMexico. Fowler J. M. (ed.), Fallout, AStudy of Supeitombs, Strontium-90, Survival, and Basic Books, Inc., New York, 1960. . *Bethel H. Asp et al., Blast Wave,Los Alamos Scientific Laboratory, Los Alamos, New Mexico, March 27, 1958,LA-2000. *American Society of Civil Engineers,Design of Structures to Resist Nuclear Weapons Effects, ASCE Manual ofEngineering Practice No. 42, ASCE, New York, 1961. *Johnston, B. G., Damage to Commercialand Industrial Buildings Exposed to Nuclear Effects, FederalCivil Defense Administration, February 1956, WT-1189.

*These publications May be obtainedfor a small charge from the Office of Technical Services U+ S. Department of Commerce, Washington, D. C. These are only a sampling of the publications available tothe interested student. 341 343 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

*Johnson, G. W., and C. E. Violet, Phenomenology of Contained Nuclear Explosions, University of California, Lawrence Radiation Laboratory, Livermore, California, December 1958, UCRL 5124 Rev. 1. Disaster Control, (Ashore and Afloat), NavPers 10899-A, 1984, Govern- ment Printing Office, 359 pp. Officer Correspondence Courses Nuclear Ordnance, NavPers 10411. 5 assignments; 7points (Confidential- Restricted data). Nuclear Physics, NavPers 10901-B. 8 assignments; 32 points. Radiological Defense, NavPers 10771-B.12 assignments; 18 points.

*These publications maebe obtained for a small charge from the Office of TechniCal Bervicest t1. 8. Department of Commerce, Washhigton, D. C.

Thetie' are :only small sampling of .thEr publications .available to the interested student. 544 APPENDIX A

TABLE OF ATOMIC WEIGHTSAND BIBLIOGRAPHY (The atomic weight columnrepresents the mass of the most stable AU of the known elements isotope of the element. are included. Oxygen 16 is used as the basicelement. ) TABLE OF ATOMIC WEIGHTS Z ELEMENT A MASS Z ELEMENT A MASS 0 o/e/o 0 0.00055 35 Br 80 0 79.94401 0in/1 1 1.00899 36 Kr 84 83.93806 1 1/P/1 1 1.00759 37 Rb 88 85.93852 1 H 1 1.00814 38 Sr 88 2 87.93375 2/a/4 4 4.00277 39 Y 89 88.93408 2 He 4 4.00387 40 Zr 92 91.93382 3 Li 8 6.01703 41 Nb 93 92.93526 4 Be 9 9.01505 42 Mo 96 5 95.93490 B 10 10.01612 43 Tc 99 6 C 98.93951 12 12.00380 44 Ru 102 7 N 101.96341 14 14.00752 45 Rh 103 8 102.93790 0 18 16.00000 46 Pd 107 9 106.93895 F 19 19.00445 47 Ag 108 10 107.93895 Ne 20 20.00050 48 Cd 113 11 112.94028 Na 23 22.99705 49 In 115 12 114.94050 Mg 25 24.99375 50 Sn 119 13 118.94100 Al 27 26.99008 51 Sb 122 14 121.94368 Si 29 28.98566 52 Te 128 15 127.94610 P 31 30.98356 53 I 129 16 S 128.94575 33 32.98189 54 Xe 132 131.94600 17 Cl 38 35.97969 55 Cs 18 03 132.94720 Ar 40 59.97505 56 Ba 138 19 K 137.94870 40 39.97665 57 La 139 20 188.94950 Ca 41 40.97523 58 Ce 141 21 140.95172 Sc 45 44.97007 59 Pr 141 22 140.95110 ti 48 47.96312 60 Nd 144 23 143.95493 V 51 50.96004 61 Pm 148 24 145.95895 Cr 53 52.95746 62 Sm 150 25 149.96340 Mn 55 54.95540 63 Eu 152 26 152.00000 Fe 56 55.95264 64 Gd 158 27 159.97342 Co 59 58.95194 65 Tb 180 28 Ni 159.97775 60 59.94984 66 Dy 163 162.50000 29 Cu 84 63.99934 67 Ho 30 165 164.98110 Zn 86.; 65.94694 68 ,Er 188 31 Ga 167.98392 70 69.94814 69 Tm 169 168.94000 32 Ge .73 72.94645 70 Yb 33 174 173.98075 As 75 74.95440 71 Lu 175 34 Se 174.99737 79 78.94858 72 Hf 179 178.50000 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Z ELEMENT A MASS Z ELEMENT A MASS

73 Ta 180 180.00220 88 Eta 226 226.09600 74 W 183 183.00530 89 Ac 227 227.09888 75 Re 186 186.01070 90 111 232 232.11080 76 Os 190 190.01740 91 Pa 232 232.11118 77 Ir 192 192.02470 92 U 238 238.12522 78 Pt 195 195.02640 93 Nip 237 237.12220 79 Au 197 197.02748 94 Pu 244 244.14065 80 Hg 200 200.03191 95 Am 243 243.13748 81 Ti 204 204.03768 96 Cm 245 245.14209 82 Pb 207 207.04058 97 Bk 249 249.15252 83 Ea 209 209.04579 98 CI 249 249.15252 84 Po 210 210.04850 99 E 244 244.14780 85 Al 212 212.05693 100 Fm 252 252.16163 86 Rs 222 222.08690 101 Mid 256 258.17383 87 Fr 223 223.08960 102 No 263 263.00000 APPENDIX B

GLOSSARY

INTRODUCTION combustion in the exhaust jet ofa turbojet engine (aft or to the rear of the turbine). This glossary is intendedas a convenience for the student. It explains briefly AGC.An abbreviation forautomatic gain those tech-control. A circuit arrangement thatautomat- nical terms used in this textbookwith which the student should be ically maintains the output amplitude(sound acquainted in order tolevel in audio receivers) essentiallyconstant, comprehend the subject matter. Theexpla-despite variations in inputsignal strength. nations are not exhaustive. Theytake up only those senses or applications of AIRSPEED, TRUE.Calibrated airspeed each term thatcorrected for altitude effects, i.e.,pressure and the text is actually concernedwith, and do nottemperature, and for compressibility attempt general exp effects /andions of them. For morewhere high speeds are concerned. Notto be information on item in the glossary, theconfused with ground speed. student should consult the indextolocate AMBIENT CONDITIONS. Environmental further discuision in the text ofthis book.conditions; may pertain topresure, temperature, For more general and completeinformation etc. the student should consult a good technical ANGLE, DRIFT.The horizontalangle be- dictionary or encyclopedia, an engineeringhand- book, or an engineering tween the longitudinal axis ofan aircraft or or physics text. missile and its path relative to theground. ACCELEROMETER.An instrumentthat ANGLE, ELEVATION.Anglebetween the measures one or more components of theac-horizontal and a line froman observer to an celerations of a vehicle. elevated object. ACQUISITION.The process of acquiringa ANGLE, FLIGHT PATH.Theanglebetween target by radar;the initial contact withathe flight path of an aircraft selected or desired target prior or missile and to lock-on.the horizontal. Sometimes called FLIGHTPLAN ACTIVE MATERIAL..- Fissionable material,SLOPE. such as plutonium (N233), uranium (U235), or the ANGLE, GLIDING.The anglebetween the thorium.derived uranium isotope U233,whichflight path during a glide anda horizontal is capable of supporting afissionchainreaction.axis fixed relative to the earth. In the military field of atomic energy, the term ANGLE OF ATTACK.The anglebetween a refers to the nuclear components ofatomic weapons exclusive reference line fixed with respect .toan air- of the natural uraniumframe and the apparent relative flowline of parts. the air. AERODYNAMICS.The science thatdeals ANGLE OF ATTACK, ABSOLUTE.The with the motion of air and othergases andangle of attack of an airfoil,measured from with the forces acting on bodiesmoving throughthe attitude of zero lift: these gases. ANGLE OF ATTACK, CRITICAL.. -The AFC:An abbreviation for automaticfre-angle of attack at which the flowabout the quency control. A circuit that maintainsac-airfoil changes abruptly,as evidenced by ab- curate freipienCy control. rupt changes in the lift and drag. AFTEROURNIM-1. Thesharacterititicof ANODE.A positive electrode;the plate of some rocket motors to burn IOWA:1y forsomea vacuum tube. time afterthe Math burning andthrust has ANTENNA. A device whichradiates r-f ceaSedi ga The process of fuelinjection andpower ihto space in the form of electromagnetic

047 351 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS energy. It also provides a means of receptionmeasuresatmospheric pressure,withouta of electromagnetic energy. switch attachment or connection. ANTISUBMARINE TOR PED0.A BASELINE.A line joining a master and submarine-launched, long-range, high-speed,slave station in a Loran system. wire-guided, deep-diving, wakeless torpedo cap- BEAT FREQUENCY.A signal which re- able to carrying a nuclear warhead for use insults when two signals of different frequencies antisubmarine and antisurface ship operations.are applied 'to a nonlinear circuit.The beat- Also known as Astor. ing together of the signal results in a signal APOGEE.The pointat which a missilewhich has a frequency equal to the difference trajectory or a satellite orbit is farthest fromof the two applied frequencies.

the _.center.-of_ the gravitational field of the BETA (P) PARTICLE (BETA RAY).One controlling body (the earth) or bodies. of the particles which can be emitted by a ASTRONAUTICS.The science of travelingradioactive atomic nucleus. It has a mass of through space or sending missiles or guidedabout 1/1837 that of a proton. The negatively vehicles into space. charged beta particleis identical with the ATHODYD.A ramjet; an abbreviation forordinary electron, while the positively charged Aero-THermODYnamic Duct. type(position)differs from the electron in ATTITUDE.The position of an aircraft orhaving equal but opposite electrical properties missile as determined by the inclination ofThe emission of an electron entails the change its axes to some frame of reference. If notof a neutron into a proton inside the nucleus. otherwise specified, this frame of referenceThe emission of a positron is similarly asis fixed with respect to the earth. sociated with the change of a proton to a neu- AUDIO FREQUENCY.A frequency whichtron.Beta particles have no independent ex- can be detected as sound by the human ear.istence outside the nucleus, but are created The audio frequency range is normally under-at the instant of emission. stoodtoextend from 20 to 20,000 cycles BINARY NUMBER SYSTEM.A number sys- per second. tem, which uses two symbols (usually 0 and AUTOSYN.A Bendix-Marine trade name1) and has two as its radix (the fundamental for a synchro, derived from the words AUTO-number), just as the decimal system uses ten matically SYNchronous. See "synchro." Alsosymbols (0,1,2, 3, etc.), and has ten as its called Selsyn. radix. The system is widely used in electronic AZIMUTH.The angular measurement in acomputation where electrical connections can horizontal plane and in a clockwise directionbe used to represent the binary conditions, such at a point oriented to north. as, an open relay means 0, a closed relay BAND-PASS FILTER.A circuit designedmeans 1. to pass, with nearly equal response, all cur- BIPROPE LLANT.A rocket propellant made rents having frequencies within a definite band,up of two separate ingredients which are sep- and to reduce the amplitudes of currents ofarately fed to the combustion chamber.

all frequencies outside that band. .. BOLOMETER.-1. A very sensitive type BANDWIDTH.The number of cycles, kil-of metallic resistance thermometer, used for ocycles,or megacycles expressing the dif-measurements of thermal radiation. 2. In

ference between the . lowest and highest fre-electronics a small resistive element capable quencies of a portion of the frequency spectrum;ofdissipating microwavepower, using the heat for example, .a TV or radio station channelso developed to effect a change in its resist- assignment. ance, thus serving as an indicator* commonly BANG-BANG CONTROL.On-off control inused as a detector in low- andmedium-level

which controlsurfaces are ordered . eitherpower measurement. "full-over". or to .the neutral position. Also BOOSTER. .-1. A high-explosive element calledflip -flopcontrol and flicker control.sufficiently sensitive so as to be actuated by BARD. A. pressure-sensitive device (es-small explosive elements in a fuze or primer sentially a pressure,altimeter) used in someand powerful enough to cause detonation of weapons to actuate circuits. The term is athe main explosivefilling. 2. An auxiliary contraction of "barometric switch," sometimesor. -initial propulsion system which travels with referred .,to as a "baroSwitCh.". Not to bea misdile or aircraft and which may or may confused with barometer, an instrument whichnot separate from the patent craft when its

.352 348 Appendix BGLOSSARY impulse has been delivered. A booster systemin, and directly contribute to thepropagation may contain or consist of oneor more units.of the process. Specifically,a fission chain BREEDING (NUCLEAR).Aprocess whereby a fissionable nuclear reaction, where the energy liberatedor par- species is used as aticles produced (fission products)by the fis- source of neutrons to producemore nuclei of its own kind. This is the sion of an atom cause the fission ofother function of a breederatomic nuclei, which in turn propagatethe nuclear reactor (atomic pile),which, by trans-fission reaction in the samemanner. mutation, produces a greaternumber of fissionable atoms than the numberof parent CHUGGING.Intermittent burning ofa pro- atoms consumed. pellant which results in low frequencypressure BUBBLE.The fireball formed inan under-oscillations. Also called chuffing. water nuclear explosion, whichcontains hot CIRCUIT BREAKER.Anelectromagnetic or gases and vapors. It expands and burstsafterthermal device that opensa circuit when the reaching the surface of. the water. current in the circuit exceedsa predetermined BURTON METHOD (BURTONING).Name amount. sometimes given to the yard andstay method CIRCULAR ERROR PROBABILITY (CEP). of handling a cargo. A methodof replenishmentThe radius of a circle aboutthe aiming point at sea wherein a winchon each ship provideswithi' which there is a 50 percentprobability power and the single whips from thewinchesof hitting. Also called CircularProbable Error are shackled together. Aldo,a method of rig- (CPE). It describesthe hitting accuracy ofa ging tackles so that twosources of powerguided missile or an artillery shell. are used. COAXIAL CAB LE.A transmissionline con- CANARD.A type of airframehaving thesisting of two conductors concentricwith and stabilizing and control surfacesforward of theinsulated from each other. Thedielectric (in- main supporting surfaces, whilethe main lift-sulator) may be eithera solid or a gas. ing surfaces are rigidly attachedin the aftCoaxial cables are usedas transmission lines region of the body. for radio, radar, and televisionsignals. CAPACITOR.Two electrodesor sets of COLLECTOR.TOR. El Electrode ectrode in a velocity-mod- electrodes in the form ofplates, separatedulated vacuum tube on whichthe spent electron from each other byaninsulatingmaterial"bunches" are collected. Ina transistor, it is called thedielectric, and used to storean an electrode through which a priniaryflow of electric charge. carriers leaves the interelectroderegion. CARRIER.In electronics, thecarrier is COMPARATOR.A circuit whichcompares the basic r-f waveupon which other signals aretwo signals and indicates variancesbetween superimposed to transmit information. them. The circuit is also knownas an "add- CATHODE-RAY TUBE (CRT).Aspecialor-subtract" circuit. form of vacuum tube used in various electronic CONSOLE.A grouping of controls,indica- applications,e.g., as the picture tube ofators, and similar television receiver andas an oscilloscope electronic or mechanical tube. equipment, usually mounted ona large table- like or panel type equipment,used to monitor CENTRIFUGAL FORCE.A force causedby inertia exerted on a rotating obi readiness of and/or control specificfunctions ect in a directionof a system, such as missilecheckout, count- outward from the center of rotation. down, or launch operations. CENTRIPETAL..-Movinginward, or directed CONTINUOUS WAVE (C-W) RADAR.A inward, in a sense toward thecenter. systeth in whicha transmitter sends out a CHAFF .--Electromagnetic-ra d i at i o n re-continuous flow of r-fenergy to the target. flectors in the form ofnarrow metallic strips COSMIC RAYS.A highly of. variouslengths and frequencyresponses penetrating ra- used to create radar echoes diation apparently reaching theearth in all for confusion ofdirections from outerspace. Experimental ob- enemy radars. One type, calledyope or rope- chaff, consists of servations show that the cosmicrays entering .a ,roll of metallic foil orour atmosphererare composed almostentirely wire. of positively c'iarged CHAIN REACTION.In atomic nuclei. The general, any. self-intensity of the rays decreasesthrough col- sv:stainingprocess, whether liolecular ornu- lisions with other atomic particles clear, the products of which while passing are instrumentalthrough the atmosphere. . 353 949 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

CRITICAL MASS OR SIZE.The amount of DETECTOR.In electronics, the receiver fissionable material that will just support astage in which demodulation takes place, sep- spontaneous chain t eaction power level. Thisarating the modulation component from the is related to the Nrolume it occupies, or size.received signal. The mass of mo.'...crial -nay be referred to as DIE R GO LI C (NON-HYPERGOLIC). A crit, which, under 7. given set of conditions, isproperty of liquid propellants (oxidizer and of critical size. fuel) whereby they do not react spontaneously CRUCIFORM.- configuration in the formwhen brought into contact, butrequire an of a cross with 7.egs 90° apart. auxiliary ignition system to initiate combustion. CRYSTAL - CONTROLLED OSCILLATOR.. DISCRIMINATOR. --A device (in electronics) Ar orcillator, whose frequency is controlled toused to convert input frequency changes to a high degree (Vi accuracy by the use of a quartzproportional output voltages. For example, in crystal. Thfq frequency is dependent on thea radio receiver, the stage thatconverts the physical dimersions of the crystal, especiallyfrequency-modulated signals direct'' to audio- the Lickness. frequency signals. Cn.YSTAL ER.A device using certain DISTORTION. In electrl:.agneties,the properties of a ..lvystal. Cgermanium, silicon!produeCnn of an cntplat waveform which is not to mix two frequencleu. a t: trreproduction of the input waveform. CRYOTR3N.A device w ed for Switching,Distortion may consist of irregularities in making use of the fact that the superconductiveamplitude, frequency, or phase. transition depends on temperature as will as DITHER.A signal of controlled amplitude electromagnetic field. A straight wire is placeand frequency applied to the servomotor op- inside a coil of different material and cooled toerating a transfer valve. such that a transfer its superconductive temperature at whiel, avalve is constantly being "quivered" and can- very small voltage cause st persistent cur not stick at its nulled position. rent to flaw through the wire. If another cur- DOUBLER.In electronics, a frequency- rent gitteies through the coil, the turrotuidt.I.;multiplier circuit that doubles the input fre- :gnetic field causes the current in the wirequency. It is often used in missile transponder to cease. equipment. The transponder signal can thus DEAD RECKONING.--The process of ob-be distinguished from the ground transmitter taining an approximate position using a fix forsignalthatactivatedit, but can still be a a reference point and iten estimating the effectskno,m function of the original signal. of winds, , currents, etc. ELECTROMAGNETIC.Pertaining tothe combined electric and magnetic fields asso- DECIBEL..;-A unit expressing the magnitudeelated with radiation Or with movement of of a change in sound or electrical power level.changed particles.Electromagetic radiation One decibel (Ms) is approximately the amountincludes the entire range of radiations pro- that the power of a pure sine wave sound mustpagated by electric and magnetic fields, in-. be changed in order for the change to be justeluding x-vaysgama, ultraviolet, light, in- barely detectable by the average human ear.frared, heat,endnano rays. From the sharteat DECONTAMINATION.The process of re-wavelength (e,amma rays) to the longest radio moval of contaminating radioactive materialwaves, all ire.vel with the speed of light. from personnel, objects, structures, or anarea. ELECTRONICS.The blued field pertaining The problem of decontamination consists es-to the condrctioa of electricity icirotqh vacuum, sentially of reduction of the level of radio-gases, or semiconductors, and circuits as- activity,' chiefly by removal of the clingingsociated therownh. radioactive material, and thus reduction of EMISSIVITY.. -The rate at which the surface the hazard it imposes to a reasonably safeof a solid or a liquid emits electrons when limit. The term can also be applied to theadditional energy is impVied to the free elec- processes applied to biological or chemicaltrons in the material by the action of heat, agents. light, or other ruliant energy or by the impact DELAY CIRCUIT.A circuit Which delaysof other elect?ons on the surface. the starting of a waveform. ENVELOP. belectroniesl. The glass DEMODIYLATOR.A. device which derivesor metal houshig of a vacuum tube; 2. A infdrmation from a modulated waveform. ci.-.1-1,e drawn to pass through the peaks of a

350 054 oi 1 Appendix BGLOSSARY

graph showing the waveform ofa modulatedthe United States is 60 cyclesper second. radio-frequency carrier signal. In acoustics, the frequency representsthe EPILATION.Falling out of the hair.Casesnumber of sound waves passingany point of described in this textwere caused by exposurethe sound field per second. In lightor other to nuclear radiation. electromagnetic radiation, frequency is usually ESCAPE VELOCITY.The speednecessaryso enormous (500 million million per second to escape from the gravitational pullof a body.for yellowlight)that wavelengths or wave This is calculated at seven milesper second.numbers (reciprocal of wavelength measured A projectile accelerated from the earth'ssur-in cm) are ordinarily used instead. Radio face below this speed will graduallyreturnfrequencies are commonly given in thousands to earth (following a ballistic trajectory)be-of cycles (kilocycles) or millions ofcycles cause of the gravitational pull of the earth. (megacycles) per second. EXPLOSIVE TRAIN (Explosive Chain).In For example, 15 kc is understood tomean missile armament, a series ofexplosive el-15,000 cycles per second. A list of thefre- ements including primer detonator,andbooster,quency designations follows: arranged to per.'At warhead explosionto be initiated by relatively weak fuze signals. Very low vlf ...Below 30 kc FAIL-SAFE. A provision builtinto the Low 30 to 300 kc mechanism of a potentially hazardouspiece ofMedium mf 300 to 3,000 kc equipment which provides that the equipmentHigh hf ... 3,000 to 30,000 kc will remain safe to friendlyusers even though or 3-30mc it fails in its intendedpurpose. A projectileVery high vhf. 30,000 to 300,000 kc fuze which is armed viithan inertia setback or 30-300mc device so that it remains safe untilacceleratedUltrahigh uhf. 300,000 to 3,000,000 kc in firing is an example ofa fail-safe device. or 300-3000mc A missile destruct systemwhich operatesSuperhigh.shf. 3,000,000 to30,000,000 kc automatically upon discontinuance ofa control or 3,000-30,000mc signal is a fail -safe device. All nuclearweaponsExtremely have fail-safe appliances. high ehf. .30,000,000 to 300,000,000 kc FIX. -An accuratenavigationalposition or 30,000-300,000mc obtained by lines of bearingon fixed objects or celestial observations. FREQUENCY BAND.A chanel of frequen- FLASH DEPRESSANT.A compoundaddedcies associated with a modulated carrier. Mod- to solid propellants (usually thoseof granularern radars operate in the microwave region type) to reduce the intensityof the exhaust(shf). flame. FREQUENCY, CARRIER.The frequency of FLOWMETER. An instrumentused to meas-the unmodulated radio wave emanated froma uretheflowrateof a fluid in motion.radio, radar, or other type transmitter. In missile ,applications the rate of fuel flow FREQUENCY, SUBCARRIER.In telemeter- is an important matter in thefunctioning ofing, an intermediate frequency that is mod- the propulsive system. Simple mechanicalde-ulated by intelligence signals and, in turn, is vices often are not usable because ofhighlyused to modulate the radio carrier either alone corrosive fluids, or extremely cold fluidssuchor in conjunction with subcarriers on other as liquid oxygen. channels. F-M/C-W RADAR.A radar whichuses FUSE. A protectivedeviceinserted in frequency modulation and the pulse of continuousseries with a circuit. It contains a metalthat will wave energy for target tracking. Frequencymelt or break when current is increased beyond modulation is used. for determining targetspeed,a specific value for a definite period of time. while the continuous wave is used for determining FUZE.A device designed toinitiate a range. detonation of a. weapon under the conditions FREQUENCY.The number of completedesired, such as by impact, elapsed time, Cyclei per second existing in any form ofwaveproximity, or command. motion. In electricity, the frequency isthe GANGED DEVICE.Componentsso arranged number of complete alternationsper secondthat an adjustment made to one willcause the of an alternating current. The standardinsame adjustment to be made to all. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

GANTRY.A device used for erecting andSolid propellants that are hygroscopic must servicing largemissiles. The large, cranebe protected against moisture. typestructure travels on rails and can be IMPEDANCE. -The total opposition offered pushed away just before firing. to the flow of an alternating current. It may GATE.Anarrangement which permitsconsist of any combination of resistance, inradar signals to be received in a small selectedductive reactance, and capacitive reactance. fraction of the principal time interval. INDUCTANCE. The property of an electrical GATE. CIRCUIT.A circuit which passescircuit which tends to oppose any change of or amplifies a signal only on occurrenceofcurrent in the circuit. The symbol for in- a synchronizing signal. ductance is "L" and the unit of measure is GATING(CATHODE-RAY TUBE).Applyingthe "henry." a rectangular voltage to the grid orcathode INNER BODY.Any closed body, located in of a CRT to sensitize it during the sweep timea ramjet or other duct, around whichthe air only. taken into the diffuser or engine must flow. GHOSTS.False echo images on a radar- INNER LOOP.In guided missile control scope. systems, the feedback loop consisting of the GLIDE BOMB.A winged missile poweredcontrol system and missile aerodynamics, as by gravity. The wing loading is sohigh thatcontrasted to the outer loop, which consists itisincapable of flight at speeds of con-of the external guidance system kinematics. ventional bombardment aircraft.Such a mis- INTERVALOMETER.Any device that may sile must therefore be carried rather thanbe set so as to accomplish automatically a 2. towed to the point of release above the target.series of like actions, such as taking of aerial photographs, at a constant, predetermined in- GRAIN.A mass of solid propellant, cast orterval. extruded in a single piece or fOrmedby cement- ISOBAR. -One of two atoms or elements ing or pressing together smaller parts. having the same atomic weights or mass numbers GROUND C LUTTER. Unwanted radarbut different atomic numbers. echoes from terrain. Also called radar clutter. ISOMER, NUCLEAR.One of two or more GYROPILOT. A form of rudimentary deadnuclides having the same atomic number and reckoning guidance which automatically controlsthe same mass 'number but existing for meas- a missile in attitude and flight path. urable time intervals in different states.. The HEADING. The horizontal direction in whichstate of lowest energy is called the ground the missile ie pointed. state; all those of.higher energy are metastable HEAT ENGINE.An engine which convertsstates. The letter m added to the mass number heat energy into mechanical energy. in the symbol of the nuclide indicates it is HEAT SHIELD.A protective. shield. useda metastable isomer, asBr80m. JET STREAM.In 'meteorology, a narrow . to prevent destruction of a reentry subsystem by the heat generated in passing back into theband of high velocity wind in the upper tropo- atmosphere. . sphere or in the stratosphere. One is in the .-.. HEAVY WATER.Water in which the hy- northern hemisphere in the middle to northern drogen: of the water molecule consists entirelylatitudes,. and one is inthe southernhemisphere. of heavy hydrogen of mass two. It is used asThe velocity varies from 100 to 500 miles per a moderator in certain types of nuclear reactorshour. and was essential in the production of the In missiles, the jet stream is the stream first atomic bombs. of combustion products (exhaust gas,etc.) HOTSPOTS.-Regions in a contaminated area from a jet engine, rocket engine, or rocket in which the level of radioactive contaminationmotor.' Is- considerably higher than in neighboring JETTISON DEVICE.A mechanism for cast- ing loose or' dumping a missile from a ship or "regions. .. to be used in case of a misfire i.HYDROGEN. BOMB (or weapon).A termlauncher, sometimes" applied to miclear*eapons in whichor, similar mishap when there is danger of 'part of the explosive 'energy is obtained fromthe missile exploding on the ship. On a mis- nuclear'. fusion, .:(or . thermonuclear) reactions.sile, a jettison. device separates a section of ',1".HYGROSCOPIC.Descriptive of a, material the missile inflight, e.g., at staging of a which readily absorbs and retains moisture.ballistic missile. ..356 552 Appendix BGLOSSARY

JP-I, JP-2, JP-5, JP-6.Kerosene type jet MARGIN OF SAFETY.As used in missile fuels with different flash points and burningdesign, the percentage by which the ultimate characteristics. JP-5 is used almost exclu-strength of a member exceeds the design load. sively by Navy jets. MARRIAGE.The process ofuniting JP-3, JP-4.Jet fuels consisting of mix-physically the missile stages and all major tures of hydrocarbons but with different burn-subsystems. ing characteristics. JP-4 is the most commonly MEGOHM.A million ohms. used fuel for turbojets. MEMORY UNIT.A data storage device KILL PROBABILITY.A measure of thecontained in a computer. probability of destroying a target. MERIDIAN. A great circle on the earth that KNOT.A nautical mile (approx. 2,000 yd)passes through the poles. Longitude is meas- or 1.1516 statute miles per hour.It is not aured from the prime meridian, whichpasses measure of distance, but of speed. through Greenwich (near London), England. LAUNCH PHASE.That portion of the mis- MEV.Abbreviation for one million electron sile trajectory from takeoff through boostervolts, a unit of energy. burnout. For multistage missiles, it is the MICRO.A prefix meaning one- millionth. period from takeoff to first-stage burnout.-The abbreviation is the Greek lettermu, MICRON.One-millionth of a meter. 4 LAUNCHER, ZERO LENGTH.A launcher MICROSECOND.One-millionth of a second. that supports a missile in the desired attitude MICROSYN.A name applied toa small prior toignition, but which exercises neg-type. of synchro whose chief merit is that ligible control on the direction of the missile'sthere are not electrical connections to the rotor. travel after ignition. It can be used as an inductive potentiometer. LIMITER.In electronics, a circuit that MICROWAVES.Extremely shortradio limits the maximum positive or negative valueswaves that are not more than a few centimeters of a waveform to some predetermined amount.in wavelength. It is used in frequency modulated systems to MISFIRE.An unsuccessful attempt to start eliminate unwanted variations of amplitude ina rocket motor; usually but not always a case received waves. in which the igniter functions properly but the LORAN.Derived from LOng RAnge Nav-propellant does not ignite (or does ignite but igation. An electronic navigation system ingoes out). which two or more fixed transmitting stations MIXER.In electronics,. a stage in which utilize a pulse transmission technique. Air-two quantities are combined to obtain a third craft and surface vessels receiving the trans-quantity. The third quantity contains the in- mitted signals may determine ranges to thetelligence of the original inputs. Thosequan- stations and thereby establish the location oftities not further desired can be filtered out. I the receiver. MODERATOR.A material that slows neu- LOX.The commonly accepted abbreviationtrons. Used chiefly' in a nuclear reactor,or for liquid oxygen. The term originally denotedatomic pile. liquid oxygen explosives (L for liquid, 0 for MODULE.As used in the automation and oxygen, X for explosive). Gaseous oxygen is electronics field, a single assembly of parts and/ often abbreviated GOX. or components to form a larger component which MAGNETIC TAPE.A tape or ribbon ofmeets a functional requirement by performing any material impregnated or coated with mag- all of the resistive, inductiveand capaci- netic or other material on which informationtive functions of a vacuum tube circuit. may be placed in the form of magnetically As a combination of components withina polarized dots. One use is in missiles witha package, or so arranged that they are common preset or programmed flight path. to one mounting, that provide a complete function or functions necessary for subsystem.or MAGNETRON.A vacuum tubeoscillatorsystem operation. This type of arrangement containing two electrodes ire which the flowmakes field (shipboard) repair simply.a matter of electrons from cathode to anode is controlledof removing the malfunctioning module and by an r.externally applied magnetic field. It isputting a new one in its place. The defective used to generate microwaves (radar frequen-module is returned to the factory or other cies) with high output power. competent agency for repair.

353 357 ;,'. :.4 . PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

MOLECULE.The smallest particle of any NUCLEAR YIELDS.The energy released in substance that can exist free and still exhibitthe detonation of a nuclear weapon. Usually all the properties of the substance. measured in terms of the kilotons or megatons MONITORING.-1. The act of listening to,or trinitrotoluene (TNT) required to produce the reviewing, and/or recording enemy, one's own,same energy release.Yields are categorized or friendly forces' communications for theas: purpose of maintaining standards, improving communications, for reference or for enemy Very low...... lessthan 1 kiloton information. 2. The detecting and/or assessing Low . . .1 kiloton to 10 kilotons of known or suspected radioactive hazards, Medium.. over 10 kilotons to using radiation measuring instruments. 50 kilotons High . . over50 kilotons to MONOCOQUE.A type of airframe construc- 500 kilotons tion without framing which relies for its rigidity Very High ... over 500 kilotons. primarily upon the surface or skin; a shell- like structure. NUCLIDE.A general term referring to all MULTIPLEX. Denotesthesimultaneousnuclear species, both stable (about 270) and un- transmission of several functions over one linkstable (about 500), of the chemical elements, as without loss of detail of each function, such asdistinguished from the two or more nuclear amplitude, frequency, phase, or wave shape.species of a single chemical element, which are MULTIPLEXER.A device by which two orcalled isotopes.. Each species of atom is dis- more signals may be transmitted on the sametinguished by the constitution of its nucleus, carrier wave. which has a specified number of protons and MULTIVIBRATOR.A vacuum tube oscil-neutrons, and energy content. lator circuit whose output is essentially a square OSCILLOGRAM.The record produced by an wave. A practical application is its use as aoscillograph. sweep generator in TV or radar circuitry. OSCILLOGRAPHY. A recording instrument NAUTICAL MILE.A measure of distancefor making a graphic record of the instantaneous equal to one minute of arc on the earth's sur-values of a rapidly varying electric quantity as a face. function of time or some other quantity._ The United States has adopted the Inter- OSCILLOSCOPE.An instrument for show- national Nautical Mile equal to 1,852 meters oring, visually, graphical representations of the 6080.20 ft. an hour. See: Knot. waveforms encountered in electrical circuits. NOMINAL WEAPON.A nuclear weaponpro- OVERPRESSURE.The pressure resulting ducing a yield of approximately 20 kilotons.from the blast wave of an explosion.It is See: Nuclear yields. referred to as "positive" when it exceeds the NUCLEAR ACCIDENT.Any unplanned atmospheric pressure and "negative" during occurrence involving loss or destruction of, orthe passage of the wave, when resulting pres- serious damage to, nuclear weapons or theirsures are less than atmospheric pressure. It components which results in actual or potentialis usually expressed in pounds per square inch hazard to life or property. (psi) above the standard atmospheric pressure. NUCLEAR INCIDENT.An unexpected eventPeak overpressure is the maximum over- involving a nuclear weapon, facility, or com-pressure caused by a nuclear explosion at any ponent, resulting in any of the following but notgiven distance from ground zero. constituting a nuclear accident: a. an increase PARAMETER.An arbitrary constant, as in the possibility of explosion or radioactivedistinguished from a fixed or absolute constant: contamination; b. errors committed in assembly,e.g., missile gross weight. Any desired numer- testing, loading, or transportation of equipment,ical value may be given to a parameter. Mach and/or the malfunctioning of equipment andnumber is a characteristic parameter used in material which could lead to an unintentional computations in supersonic aerodynamics. operation of all or part of the weapon arming PASS BAND.(Of a filter).That band of ,and/or firing sequence, or could lead to a sub-frequencies which are passed with little attenu- stantial change in yield, or increased dud prob-ation. :--- ability; c. any act of God, unfavorable environ- PENTODE.A 5-element electron tube. ment or condition, resulting in damage to the PERIGEE.Point of orbit closest to the weapon, facility, or component. earth. The opposite is apogree, the highest point

058 354 Appendix BGLOSSARY

in the trajectory of a missile,or in a satellite PULSE LENGTH.The time durationof the orbit, the point that is thegreatest distancetransmission of the pulse of energy, usually from the center of the earth. measured in microseconds or in the equivalent PETECHIAE.A condition characterizedbydistance in yards, miles, etc. small spots on the skin.It is caused by the PULSE REPETITION RATE.(Also, Pulse escape of blood into the tissues. Repetition Frequency (PRF)).These terms PHOTON.A photon (or x-ray) isa quantumrefer to the repetition rate or frequency of the of electromagnetic radiation which hasa zeropulses transmitted by radar. PRR describes rest mass and an energy of h (Planck'scon-the number of pulses transmittedper unit of time. stant) tithes the frequency of theradiation. Pho- PURPURA.Medical term for a symptom tons are generated in collisionsbetween nucleicharacterized by the appearance of purple or electrons and inany other process in whichpatches on the skin and mucous membranes, due an electrically charged particle changes itsto hemorrhage in the fatty tissues beneath the momentum. Conversely, photons can be ab-akin. sorbed (i.e., annihilated)byany charged particle. QUANTUM.A discrete q uantity of radiative PIEZOELECTRIC EFFECT.The phenom-energy equal to the product of its frequency and enon exhibited by certain crystals of expansionPlanck's constant.The equation is E = hv. A along one axis and contraction alonganotherquantum of light energy is a photon. when subjected to an electrical field.Con- QUANTUM THEORY.The conceptthat versely, compression of certain crystalsgen- energy is radiated intermittently in units of erates an electrostatic voltageacross the crys-definite magnitude called QUANTA. tal. Piezoelectricity is only possible incrystal R-C CIRCUIT.An abbreviation for classes which do not possess a center ofsym-resistance-capacitance circuit.It is one of metry. the methods used to couple two electronic cir- PILE.A nuclear reactor.The term pilecuits together.Some of the characteristics comes from the first nuclear reactor whichwasof R-C coupling are wide frequencyresponse made by piling up graphite blocks andpieces ofand lower cost and size than that of transformer uranium and uranium oxide. or other inductive coupling systems. PIP.-.The indication on the CRTor a radar RADAR PICKET.Any ship, aircraft,or caused by the echo from an aircraftor othervehicle stationed at a distance from the forceor reflective object. Also called BLIP. Itmay beplace protected, for the purpose of increasing in the form of an inverted V ora spot of light.the radar detection range. PLANCK'S, CONSTANT (h).-TAuniversal RADARSCOPE. The visual cathode-ray tube constant of nature which relates theenergy of a(CRT) display used with a radar set. quantum of radiation to the frequencyof the RADIAC.A term devised to designatevar- oscillator which emitted it.It has the dimen-ious types of radiological measuring instruments sions of action (energy X time). or equipment. This term is derived from the PLASTICIZER.A material,that is addedtowords "RAdioactivity Detection, Indication, And a rocket propellant to increase plasticity, work-Computation," and is .normally usedas an ad- ability, or to extend physical properties. jective. POTENTIAL.The amount of charge heldby RADIATIONINTENSITY.Theradiation a body as compared to another point or body.dose rate at a given time and place. Itmay be Usually measured in volts. , . used coupled with a figure to denote the radiation PREAMPLIFIER. -.A stage at the input endof intensity used at a given number of hours after an amplifier-or receiver which increases.signala nuclear burst, e.g., RI3 is the radiation instrength. tensity 3 hours after the time of burst. PROPAGATION.Extending the action of; RADIATION SCATTERING.The diversion transmitting, carrying forward,as in space orof radiation (thermal, electromagnetic,or nu- time, through a medium, as the propagationof clear) from its original path asa result of sound or light waves. interactions or, collisions with atome, mole- PROPELLANT-WEIGHT RATIO.The ratiocules, or larger particles in the atmosphere of the weight of the propellant to the takeoffor other media between the source of radiation weight' of thormissile. This ratio is a measure(e.g., a nuclear explosion) anda point at some of the. efficiency of the missile configurationanddistance away. As a result of scattering, the miisile power Plant.' radiation (especially gamma rays and neutrons) 859 355 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS will be received at such a point from many SCALAR QUANTITY.Any quantity that can directions instead of only from the direction ofbe described by quantity alone, such astempera- the source. ture, in appropriate units.See also: Vector RADIO FREQUENCY (RF).Any frequencyquantity. of electrical energy capable of propagation into SEEBECK EFFECT.A thermocurrent, de- space.Radio frequencies normally are muchveloped or set in motion by heat; specifically an higher than sound-wave frequencies. electric current, in a heterogenous circuit, due RECTIFIERS. Devices used to change alter-to differences of temperature between the junc- nating current (a-c) to direct current (d-c).tions of substances of which the current is These may be vacuum tubes, semiconductorscomposed. A thermocouple produces a Seebeck such as germanium or silicon, dry-disc recti-effect; the two different metals in the junction fiers such as selenium and copper-oxide, andrespond at different rates. also certain types of crystals.A full-wave SERVOZINK.A power amplifier, usually rectifier circuit is one which utilizes both themechanical, by which signals at a low power level positive and the negative alternations of anare made to operate control surfaces requiring alternating current to produce a direct current.relatively large power inputs, e.g., a relay and REFLECTION INTERVAL, RADAR.Thea motor actuator. length of time required for a radar pulse to SHORAN.Derived from the words "SHOrt- travel from the source to the target and returnRAnge Navigation." A precise short-range to the source, taking the velocity of radionavigation system which uses the time of travel propagatiok to be equal to the velocity of light,of pulse-type transmission from two or more 2.998 x 10° to /sec or 299.8 m/s s. fixed stations to measure slant-range distance RELAY.In electronics, there are two re-from the stations. In conjunction witha suitable lated meanings.First, the relay may be ancomputer, is also used in precision bombing. electromechanical device which, when operated SLUG.A unit of mass.Mass in slugs is by an electrical signal, will cause contacts toalways obtained by dividing the weight in pounds make or break, thereby controlling one or more other electrical circuits.The solenoid is theby the acceleration of gravity, 32 ft per sect. basic mechanism of this type of relay. Second,Turned around, we may define unit force (the pound) as that force which, applied to a mass of ti the relay may be an electronic network to re-1 slug, will give it an acceleration of a foot per ceive and transmit information. There is usuallysecond per second. an amplification stage in the relay process. 4 RESISTOR.A circuit element whose chief SPEED OF SOUND.The speed at which characteristic is resistance to the flow of elec-sound travels through a given medium under tric current. . specified conditions. The speed of sound at sea RESONANCE.The condition existing in alevel in the International Standard Atmosphere series circuit in which the inductive and capa-is 1108 ft/second, 658 knots, 1215 Inn/hour. citive reactances cancel each other. Speeds are: sonic, subsonic, transonic, supersonic, hypersonic. REYNOLD's NUMBER.An abstract num- SPEEDGATE.The function of the speed- ber characteristic of the flown of a fluid in agate is to locate the target doppler signal and pipe or past an obstruction, used especially intrack it, and assist in guiding the missile on a testing of scale model airplanes (and missiles) in wind tunnels. It is the ratio of the productcollision course.It is a narrow band-pass of the density of the fluid, the flow velocity,filterthat sweeps the specified band of fre- and a characteristic linear dimension of thequencies to locate the signal. Itmay be called body under observation to the coefficient ofa gate, and the circuit a gate circuit. absolute viscosity: SQUIB.A small pyrotechnic device which may be used to fire the igniter in a missile Re PVLFrl booster rocket, or for some similar purpose. Not to be confused with a detonator, which ex- where Re is. Reynold's number,P is density ofplodes. fluid, Vie velocity of flow, L islinear dimension STAGING.Act of jettisoning, at a pre- of the body in the flow, and 14 is the coefficient ofdetermined flight time or trajectory point, cer- viscosity of the fluid. tain missile (orspicecraft) components Appendix B-GLOSSARY

(engines, tanks, booster equipment,stagingliquid propellant when agitated or pumped,and equipment, and !associated equipment) thatarewhich, by the addition of powdered metalsuch no longer needed. as aluminum, produces twice the thrust of other SUPERHETERODYNE.-The term "hetero-propellants. dyne" refers to two frequencies mixed (orbeat) TONE GENERATOR. -An electronicor together.The frequency mixing produces twomechanical device whose function is to generate beat frequencies whichare the sum and dif- a frequency in the audio range. ference between the two originalfrequencies. A superheterodyne receiver isone in which the TR BOX.-Common abbreviationfor incoming signal is mixed witha locally generatedTransmit-Receive switch or tube. This switch, signal to produce a predeterminedintermediateor tube, permits the use of a single antennaor frequency.The purpose of the superhetero-a radar for transmission and reception. The dyne receiver is to achieve betteramplification TR box prevents the absorption of thetrans- over a wide T-band of incoming signal frequen- mitted pulse into the receiver system,thereby cies than could be easily achieved withan RF protecting the receiver circuit from damage, amplifier. and also prevents the transmitter circuitsfrom SUPERREGENERATIVE SET .-A type of high absorbing any appreciable fraction of the reflec- frequency (VHF, UHF) receiver whichis ultra-ted echo signal. Also called Duplexer. sensitive.Advantages are extreme sensitivty, TRANSCEIVER.-A combination radio trans- simplicity, and reliability.Disadvantages are mitter and receiver in a single housingwith broadness of tuning (poor selectivity),and re- some of the electronic circuit componentsbeing radiation that can cause interferencein otherused dually for transmitting andreceiving. receiving equipment. TRANSPONDER.-A transmitter- receiver. SUSTAINER.-Apropulsionsystemthatcapable of accepting the challenge ofan inter- travels with and does not separatefrom therogator and automatically transmittingan ap- missile. The term is usually applied tosolidpropriate reply (to IFF). propellant rocket motors when usedas the prin- T'UBALLOY. -A colloquial term which refers cipal propulsion system, as distinguishedfromto natural uranium or to metal which iscom- an auxiliary motor or booster.However, itposed almost entirely of U-238.It is a con- sometimes denotes any missile stage exceptthe traction of "Tube Alloy,"a code name used booster. originally to mean naturally occurring uranium SWEAT (TRANSPIRATION) COOLING.- which is not easily fissioned. A technique for cooling combustionchambers or aerodynamically heated surfaces by forcing UMBILICAL CORD.-A cable fitted witha coolant through a porous wall. Film coolingat quick disconnect plug at the missile end, through the interface results. which missile equipment is controlled,moni- TERMINAL VELOCITY. -1. Hypothetical tored, and tested while the missileis still maximum speed a body could attain alonga spe- attached to the launcher. cified flight path under given conditions ofweight VECTOR.-A line used to representboth and thrust if diving through an unlimiteddis- direction and magnitude. tance in air ofspecified uniform density. VELOCITY.-Time rate of changeor dis- 2. Remaining speed of a projectile at thepoint placement.Velocity is a vector quantity. The in its downward path where it is levelwith the magnitude is expressed in units of length divided muzzle of the weapon. by time, and the direction is given relativeto THEODOLITE.-An optical instrument used some frame of reference, such as fixed axes og for measuring angles. the earth. TNT EQUNALENT.-Ameasure of the en- VERNIER.-A measuring device used forfine ergy release from a detonation of a nuclearand accurate measurement, consistingof a weapon, or from the explosion of a given quan- short scale made to slide along the divisionsof tity of fissionable or fusionable material,ina graduated instrument, to indicate parts of terms of the amount of TNT (trini4roluene)divisions. which would release the same amount'ofenergy when exploded. VERNIER ENGINE.-Rocket engine (usually liquid) used to adjust the final velocityof a long- THIXOTROPIC PROPELLANT. --A propelpi":range ballistic missile.The engines are also lant of gel-like consistency which flows likeany used to correct headingerrors. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

VIDEO. The term is applied to the frequencytances to the right or left (east or west) of the band of circuits by which visual signals arereference line are marked, especially on a map transmitted.The term "video" is also usedor chart. when speaking of a very wide band of frequen- Y-AXIS.A vertical axis in a system of cies, including and exceeding the audio bandrectangular coordinates; that line on which dis- of frequencies. tance above or below (north or south) the ref- WEATHERCOCK STABILITY.-1. An aero- erence line are marked, especially on a map, dynamic characteristic of a body which points itchart, or graph. into the relative wind.2. (Arrow stability) YAW.An angular displacement about the The partial derivatives of yawing and pitchingyaw axis of a missile. moments with respect to angles of attack inyaw ZENITH.The point in the celestial sphere and pitch. directly above the observer. X-AXIB.A horizontal axis in a system of ZERO-LIFT TRAJECTORY.A trajectory rectangular coordinates; that line on which dis-which is independent of aerodynamic lift.

862

..358 4.04 441 INDEX

AA problem, 258-260 Absolute temperature 70 Beam-rider guidance, 156, 181-204 Acceleration, 33, 231-238 application to Navy missiles, 181 Accelerometers, 161, 231-238 compared to command guidance, 181 Actuator units, missile control components, 181 systems, 132-144 launching station components,182 missile components, 182-184 Aerodynamic forces, 29 target, 184 Aerodynamics of supersonic missileflight,35 Ailerons, 40 limitations, 203 Air blast, 319 operation of, 196-203 Air burst, 296, 304, 341 control radar, 198 Aircraft missile systems, 265-267 one-radar system, 200-202 Air flow over a wing section, 29 stabilization, 199 Airfoils, 31 tracking radar, 197 Air Force missiles, 15-17 two-radar system, 202 Airframe, 51-54 principles of, 184-195 Airspeed transducers, 118 control and tracking radar Alpha radiation, 276 transmitters, 194 Altimeters, 117 guidance antennas, 184-188 over-the-horizon radar, 195 Amplifiers, 151-154 scanning, 189-194 Antennas, beam-rider guidance, 187 radar beam, 193 Army missiles14 Beam-rider trajectory, 48 Atmosphere, effect on missile flight,24 Beta radiation, 276 Atomic demolition munitions, 298 Bibliography for nuclearweapons Atomic Energy Commission, 300 orientation, 343 Atomic research, 268 Binding energy; mass defect, 282 Atomic structure, 270 Blast damage, 304 Atomic table, 269, 270 Blisters, 325 Atomic warfare defense, 338-340 Bolometer,, 212 Atomic weights and bibliography,345 Bombs, 297 Attitude control, 97 "Bone seekers", 335 Automatic sextant, 242 Boyle's law, 71 Auxiliary power supply, 51 Burns, radiation, 325 Auxiliary power supply unit, missile control systems, 101-105 Bursts, nuclear, 304, 331, 340 Campini, 7 Ballistic missiles, 229-231. Celestial-navigation guidance, 160 Ballistic trajectory, 48 Cerium, 335 Ballistite, 94 Cesium, 336 Barium, 335 Charles' law, 71 Barometrie switch, 296 Batteries used in guided missiles for :Chemical detectors, 214 Chemical versus nuclear reactions,275 awci/isuy power supply, 105 Chemical warheads, 58 359 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Choppers, 128 Cruciform, 45 Combination trajectory, 48 Cruisers, guided missile, 249-251 Combustion chamber, missile propulsion Damage from nuclear weapons,. 316-333 system, 74 areas, 317 Command guidance systems, 156, 169-180 ashore, 318 components, 169 blast, 319 definitions, 169 compared with chemical explosion, 317 functions, 171 drag, 320 future of, 179 eye damage, 326 3 launching station components, 176 nuclear radiation, 333 operation of, 170 ship damage, 318 command links, 170 shock, 321 information links, 170 thermal radiation, 324 purpose and applications, 169 zones, 318 transmitters, 172 Defense Atomic Support Agency, 300 types of, 172-180 Degressive burning, 93 hyperbolic, 173 Delivery systems and techniques, 298 radar command, 173, 178, 180 Destroyers, guided missile, 251-253 radio, 173-177 television, 172, 177 Diaphragm timers, 111 Command links, command Diffusers, 79 guidance systems, 170 Dirt cloid, 308 Composite guidance systems, 159, 228 Doppler homing equipment, 166 use in preset guidance system, 228 Doppler principle, 166-168 Computer, missile course, 176 Doppler radar, 168 Computer using specific velocity, 234 Drag, 32 Computing devices, missile control Drag damage, 320 systems, 97, 100, 123-129 Drag reduction, 44 function and requirements, 124 Ducted propulsion systems,. 80-86 operating principles, 128 Dummy warhead, 59 types of, 125-128 Earth's magnetic field, 164-166 Constant-dive-angle system for missiles, 239 Electrical control system, 133, 141 Control and tracking radar transmitter, Electrically damped accelerometer, 163 beam-rider guidance, 194 Electrical timers, 109 Control componentsand systems, 97-144 Electronic observation, command actuator units, '132-144 guidance systems, 170 auxiliary power supply unit, 101-105 Elevators, 40 computing devices, 123-129 Energy sources, missile control control action, types of, 100 systems, 101 control systeins, 100 Error signals, missile control controller units, 129-132 systems, 108 definitions, 97 Exercise warheads, 59 energy sources, 101 Exhaust nozzle, jet propulsion factors controlled, 99 systems, 74-78 methods of control, 99 Exhaust vanes, 42 missile-control servosystem, 105-108 Explosions, 303 pickoffs, 119-123 Eye injuries, 326 purpose and function, 98 reference devices, 108-113 Fallout, 330 sensor units, 113-119 Fallout,: protection from, 338 Controllers and actuators, 154 Feedback systems, _154 Control matrix, 159 Feed systems, liquid-fuel Control radar, beam-rider lockets, 88 guidance, 198 Fin designs, ,46 Coriolis force, 50 Fire storm, 327 1 360 4:. INDEX

Fission weapons, 290 location of components, 51, 52 Flash depressor, 94 payload, 57 Fleet ballistic missile, 2 propulsion systems, 51, 54 Formulas and laws, jet propulsion, 70-74 sectionalization of, 51 Fragmentation warheads, 56 telemetering systems, 64-68 Fuels, jet engine, 76 warheads, 51, 55-59 Fuel supply, missile propulsion Guided missiles, delivery systems systems, 76-78 and techniques, 298 Fusion weapons, 293-295 Guided missiles, introduction to, 1-23 Fuzes, guided missile, 59-64 after and during World War II, 10-12 Fuzing for surface burst, 296 classification of, 12 Fuzing techniques, 296 components of, 6 current U.S. service missiles, 14-23 Galcit, 95 Air Force missiles, 15-17 Gamma radiation, 277 Army, 14 Gas laws; jet propulsion systems, 71 Navy missiles, 17-23 Gas tight envelope, 339 designations, 12 Glossary, 347-358 Navy missile and rocket, 13 Goddard, Robert H., 7 guidance,' 4-6 Go lay detector, 212 systems, 9 Ground zero, 342 history of, 6 Guidance antennas, beam-rider, 184-188 propulsion systems, 6-9 Guidance systems, 145-168 purposes and uses of, 2-4 application of natural phenomena, 164-168 symbols, 13 Doppler principle, 166-168 types of, 4 earth's magnetic field, 164-166 weapons systems, 2 basic principles, 146 Guided missile ships and systems,249-267 components of,. 148 aircraft missile systems, 265-267 amplifiers, 151-154 mission of, 249 controllers and actuators, 154 submarine missile systems, 261-264 feedback systems, 154 surface ship missile systems, 254-260 reference units, 151 AA problem, 258-260 sensors, 148-151 phases of guidance, 146-148 missile logistics, 260 purpose and function of, 145 missile stowage, loading, and types of, 155-164 launching systems, 258 active, 221,. 222 Navy Tactical Data System, 260 organization of missile ships,254 beam rider, 156 Terrier (RIM) missile system, 255-258 celestial, 160 types of missile ships, 249-253 command, 156 cruisers, 249-251 homing, 205-224 destroyers, 251-253 inertial, 6, 160 submarines, 253 navigational, 231-248 Guns, 291, 298 optical, 170 passive, 159, 210-217 delivery techniques, 298 radar,185. radio, 173 Half life, principle of, 277 Half thickness, examples of, 278,279 television, 172, 177 Heading reference, 226 terrestrial,160 Heat barrier, 36 Guided missiles, components of,51-66 High altitude bursts, 315 airframe, 51-54 .t Homing guidance, 205-224 auxiliary power supply, 51_ active homing guidance, 221, 222 body configuralion, 53 basic principles, 205 control dystem, 51 interferometer, 222-224 guidance system, 51 passive homing system, 210-217

36177-A

ar PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Homing guidance (continued) Liquid-damped system, 162 basic principles of, 210-214 Liquid-fuel rockets, 88-92 infrared target detection, 217 Liquid propellants, 77 missile components, 214-217 Lobe formation of radar beam, 186 radio frequency, 217 Local fallout, 341 target characteristics, 214 Loran system, 157t semiactive, 218-221 Lorin, Rene, 7 trajectories, 207-210 Luminescent detectors, 213 lead angle or collision course, 208-210 pursuit homing, 207 Mach numbers and speed regions, 35 Hot-gas auxiliary system, 102 Magnetic forces, 50 Hybrid guidance, 160 Manometer accelerometer with Hybrid propulsion engine, 96 venturi damper, 163 Hydraulic actuators, missile, 133 Mass-energy, laws of, 281 Hydraulic-electrical control Matter, nature of, 269-275 system, 133 atomic structure, 270 Hydrodynamics, 46 atomic table, 269 Hyperbolic guidance system, 157, 173 chemical implications, 271 Hyperbolic trajectory, 48 chemical versus nuclear Hypersonic flight, 36 reactions, 275 electrical implications, 271 Ignition systems, missile propulsion electron shells,. 270 systems, 78 isotopes, 272 Illuminating warheads, 59 nuclear symbols, 272 Impact fuse, guided missiles, 60 stability, 273 Implosion weapon, 292 Mechanical digital indicator, 227 Inertial guidance, 6, 160 Mechanical. timers, 109 Information links, command guidance Missile configUration, effects of, 44-47 systems, 169, 170 Missile cpntrol components and Infrared portion of electromagnetic spectrum, systems, 97-144 passive homing system, 210 actuator units, 132-144 Infrared target detection, passive homing auxiliary power supply unit, 101-105 guidance system, 217 computing devices, 123-129 Injectors, missile propulsion function and requirements, 124 systems, 78 operating principles, 128 Initiator, 293 types of, 125-128 Mine cruciform, 45 control action, types of, 100 Intercontinental ballistic missile, 2 control systems, 100 Interferometer, homing guidance, 222-224 controller units, 129-132 Ionosphere, 26 electrical, 133, 141 Isotopes, 272 hydraulic, 133 hydraulic - electrical, 133 Jet, atmospheric, 44 pneumatic, 133, 137-141 Jet control, 42 pneumatic-electric, 141 Jet propulsion systems, 54, 69 definitions, 97 energy sources, 101 Launching station components, command factors controlled, 99 guidance systems, 176 methods of control, 99 Laws and formulas, missile propulsion missile-control servosystem, 105-108 systems, 70-74 pickoffs, 119-123 Lead angle course, 48, 208 purpose and function, 98 Lead homing, 159 reference devices, 108-113 Lift, 31 sensor units, 113-119 Lift and drag, 28 Missile course computer, 176 Lift effectiveness, 44 Missile dive attitude, 240

362

ty INDEX

Missile flight, factors affecting, 24-50 Missiles, components of, 51-88 aerodynamic forces, 29 airframe, 51-54 air flow over a wing section, 29 auxiliary power supply 51 effects of, 31-33 body configuration, 53 missile control, 33-35 control system, 51 terminology, 30 guidance system, 51 aerodynamics of supersonic location of components, 51, 52 missile flight, 35-47 payload, 57 control of supersonic missiles, 39-44 propulsion systems, 51, 54 heat barrier, 38 sectionalization of, 51 Mach numbers and speed telemetering systems, 64-88 regions, 35 warheads, 51, 55-59 missile configuration, 44-47 Missiles, current, U.S. service, 14-23 Reynolds number, 35 Air Force missiles, 15-17 shock wave, 36-39 Navy, 17-23 atmosphere, 24-26 Missiles, introduction to, 1-23 coriolis force, 50 after World War U, 12 forces acting on a flat surface in classification of, 12 an airstream, 28 components of, 8 gravity, 49 current U.S. service missiles, 14-23 lift and drag, 28 designations, 12 magnetic force, 50 during World War II, 10 Newton's law of motion, 27 guidance, 4-6 relativity of motion, 27 history of, 6 wind, 49 propulsion systems, 6-9 Missile plotting systeth, 177 purposes and uses of, 2-4 Missile propulsion systems, 69-98 symbols, 13 atmospheric jets, 80-86 types of, 4 pulsejet engines, 80-82 weapons systems, 2 ramjets, 84-86 Missile ships and systems, 249-267 turbojets, 82-84 aircraft missile systems, 265-267 basic laws and formulas, 70-74 mission of, 249 4. absolute pressure, 70 submarine missile systems, 261-264 absolute temperature, 70 surface ship missile systems, 254-280 application of, 72-74 types of missile ships, 249-253 gas laws, 71 Missile stowage, loading, and launching components of, 74-80 systems, 258 combustion chamber, 74 Missile tracking radar, 176 diffuier, .79 Missile warheads, 297 exhaust nozzle, 74-76 Motion, 27 fuel supply, 76-78 Motor timers, 109 ignition systems, 78 injectors 78 Mushroom cloud, 306 jet propulsion systems, Navigational guidance systems, 231-248 classification of, 69 automatic celestial navigation, 244 principles of, 70-74 celestial-ineitial system, 241-243 rocket moters,;,86-96 inertial guidance, 231-238 hybrid propulsion, 96 terminal inertial guidance liquid-fuel rockets, 88-92 systems, 238-241 nuclear-powered rockets, 95 terrestrial reference navigation,245-248 solid-fuel rockets, 92-95 Navy missiles, 13, 17-23 Missile receiver, beam-rider. and roc(cet designations, 13 guidance, 188 Navy Tactical Data System,260 Missile response, homing guidance Neutron radiation, 277 signals, 206 Neutron sources, 292 .36134 '. PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS

Newton's laws of motion, 27,73 underground, 332 Nitroglycerine, 94 comparisons, 302 Noise filters, 245 damage, 316 Nuclear and thermonuclear warheads, 59 eye darner; 326 Nuclear fission, 283-287 dirt cloud, 308 Nuclear particles, 273 employment of nuclear weapons Nuclear physics, fundamentals of, 268-289 effuc t, 340.342 atomic research preceding the bomb, 268 air burst, 341 atomic structure, 270 scaling laws, 34.1 chemical versus nuclear reactions, 275 .subsurface burst, 341 isotopes, 272 surface burst, 340 nature of matter, 269-275 explosions, 30F nuclear particles, 273 fallout, 329, 338-340 nuclear reactions, 281-289 fire storm, 327 binding energy; mass defect, 282 Mach front, 308 laws of mass-energy relationship, 281 protection of personnel, 308 nuclear fission, 283-287 radiation hazard, 307 nuclear fusion, 287-289 injury and sickness. 333 nuclear symbols, 272 radiation, nuclear, 329-336 objectives, 269 radiation, thermal, 323-329 radioactivity, 275-281 shock, P21 stability, 273-275 Nutating lobe, beam-rider guidance, 187 Nuclear-powered rockets, 95 Nutating waveguide, beam-rider Nuclear radiation, damage from, 333 guidance, 186 Nuclear reactions, 281-289 One-radar system, beam-rider Nuclear symbols, 272 guidance, 200-202 Nuclear weapons, 290-301 °pacifier, 94 Atomic Energy Commission, 300 Optical observation, command atomic demolition munitions, 298 guidance systems, 170 bombs, 297 Over-the-horizon radar, beam-rider comparison of, 295 . guidance, 195 Defense Atomic Support Agency, 300 Oxidizers, jet engine, 76 delivery systems and techniques, 298 fission weapons, 290 Payload, guided missiles, 57 fusion weapons, 293-295 Passive homing, 159; 210-217 fuzing techniques, 296 basic principles of, 210-214 guided missiles, 298 infrared target detection, 217 guns, 291, 298 missile components, 214-217 delivery techniques, 298 radio frequency, 217 implosion principle, 292 target characteristics, 214 importance of, 290 Photodetectors, 213 missile warheads, 297 Pickoffs, 119-123 neutron sources, 292 Piston type timers, 110 organization, 299 Plasticizer, 94 safety and security, 298 Plume, 313 Nuclear weapOns, bibliography for Plutonium, 335 orientation, 343 Pneumatic control system, 133, 137-141 Nuclear weapons, effects of, 302-342 electric, 141 air blast, 319 Pneumatic timers, 110 atomic warfare defense, '336-340 Polaris missile, 2, 263 bibliography for nuclear weapons Potentiometer pickoffs, 120 orientation, 343 Power plants, missile jet, 70 bursts, 304, 330, 340 Preset guidance system, 160, 225 air, 330 altimeters, 227 surface, 331 heading, 226

868384t v 1.7 INDEX

Preset guidance system (continued) Radiation, injury and sickness information set in the missile, 226 caused by, 333 length of flight, 227 RadiatiOn, nuclear, 329-336 use in composite systems, 228 bursts, types of, 330-333 Progressive burning, 93 fallout, 329 Propellants, 77 injury, 333-336 advanced, 95 shock, 321 and propulsion systems, 95 sickness, 334 charges, solid, 92 Radiation, thermal, 323-329 Propulsion systems, missile, 69-96 Bikini tests, 329 atomspheric jets, 80-86 effects on materials, 326-328 pulsejet engines, 80-82 effects on people, 324-326 ramjets, 84-86 burns and blisters, 325 turbojets, 82-84 eye damage, 326 basic laws and formulas, 70-74 fire storm, 327 absolute pressure, 70 range of, 328 absolute temperature, 70 Radiation warheads, 59 application of, 72-74 Radioactivity, 275-281 gas laws, 71 Radio and radar command guidance, 173 components of, 74-80 Radio command guidance system, 173 combustion chamber, 74 Radio command transmitter, command diffuser, 79 guidance systems, 174 exhaust nozzle, 74-76 Radio frequency passive homing fuel supply, 76-78 guidance, 217 ignition systems, 78 Radiotelemetering, 64 injectors, 78 Ramjets, missile propulsion jet propulsion systems, 69 systems, 84-86 principles of, 70-74 Receivers, command guidance rocket motors, 86-96 systems, 172 hybrid propulsion, 96 Reference devices, missile control liquid fuel rockets, 88-92 systems, 108-113 nuclear-powered rockets, 95 Relativity of motion, 27 solid-fuel rockets, 92-95 Residual radiation, 335 Protactinium, 268 Reynolds number, 35 Protection of personnel, 308 Rocket engine, jet propulsion Proximity fuzes, 61 systems, 70 Psychological warheads, 59 Rockets Pulse-Doppler radar, beam-rider designations, 13 guidance, 195 liquid fuel, 88 Pulsejetengines,80-82 motors, 86-96 Pursuit curve,8 nuclear-powered, 95 Pursuit homing, 159, 207 solid-fuel, 92 Rudders, 40 Radar-beacon, command guidance system, 179 Safety and security, nuclear Radar command guidance, weapons, 298 155, 173, 178, 180 Scaling laws, 341 Radar mapmatching, 246-248 Scanning, beam-rider Radar, missile tracking, 176 guidance, 189-194 Radar beam used in beam-rider Self-contained guidance systems, 160-164 'guidance, 184 Semiactive homing, 159, 218-221 Radar transmitters, control and tracking, 194 Sensor units Radiac circuit, 281 guidance system, 148-151 Radiation, beam rider guidance, 185 missile control system, 111-119 Radiation hazard, 307 Servomechanism, 100

1369 365 PRINCIPLES OF GUIDED MISSILES AND NUCLEAR WEAPONS Shaped-charge warhead, 57 Thermistors, 212 Shipboard protective measures, 336 Thorium, 268 Ship damage from nuclear weapons, 318 Thrust, 33 Shock caused by nuclear weapons, 321 Time delay fuse, 60 Shock wave, 36-40 Timers, mechanical, guided missile Shore base protection, 337 control system, 109 Sidewinder, 4 Timing devices, 296 Slick, 310 Tracking, guided missile, 9'7 Slot, 41 Tracking radar, beam-rider Solar fusion cycle, 293 guidance, 197 Solenoids, 130 Training warheads, 59 Solid-fuel rockets, 92-95 Trajectories, guided missile, 47-50 Sparrow missile system, 265 Transfer valve, 130 Spoiler, 41 Transmitters, command guidance Steller supervised inertial systems, 172 autonavigator, 242 Trinitrotoluene 296 Stratosphere, 26 Troposphere, 25 Strontium, 335 Turbines used in auxiliary power Submarine missile systems, 261-264 supply, 103 Submarines, guided missile, 253 Turbojets, 82-84 Subroc missile system, -264 Two-radar system, beam-rider Subsurface bursts, 309, 341 guidance, 202 Supersonic missiles, control Of,. 39-44 Surface iiirst, 308, 340 Ultraviolet radiation, 325 Surface ship missile systems, 254 Underground bursts, 313 Symbols, 13 Underwater bursts, 310 Undeiwater problem, 262 Tabs, .41 U.S. Service missiles, 14-23 Tail arrangements,. 45 Air Force, 15-17 Target, beam-rider guidance, 184 Navy, 17-23 Teak burst,' 315 Uranium, 268 Telemetering systems, missile °Uranium series, 276 propulsion, 64-68 Television guidance systeth, 172, 177 Vector control, 42 Terrestrial guidance system, 160 Velocity-daniping doppler, Terrier (RIM) missile:system, 255-259 radar, 168 Thermal radiation, 323-329 Vertical-dive system for Bikini tests, 329 missiles, 240 effects on materials, 326-328 Vibrators, .129

.effects on people, 324-326 burns and blisters, 325 Warhead, guided missile, 51,55-59

_ eye damage, 326 'Weapons, nuclear, 290-301 fire storm, 327 Whittle, Frank, 7 range of, 328 Thermal timers; 109 Zero-lift inertial system, 240

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