Conventional Missile Attacks Against Aircraft on Airfields and Aircraft Carriers

MEMORANDUM RM-4718-PR AIR FORCE DECLASSIFICATION OFFICE Classification Re'ained__------—.„. J A N U A R Y 1966 Classification Changed To: jp / Q l No Classified AF Equities \J ------—-

Refer To:______Reviewers Declassified from SECRET by the Air Force Declassification Office on 23 Oct 2018

CONVENTIONAL MISSILE ATTACKS AGAINST AIRCRAFT ON AIRFIELDS AND AIRCRAFT CARRIERS

J. G. H a m m e r an d W . R. E ls w ic k

PREPARED FOR: UNITED STATES AIR FORCE PROJECT RAND

7 ¿ e RJMD(fyyfotatca# SANTA MONICA • CALIFORNIA MEMORANDUM RM -4718-PR JANUARY 1966

CONVENTIONAL MISSILE ATTACKS AGAINST AIRCRAFT ON AIRFIELDS AND AIRCRAFT CARRIERS

J. G. H a m m e r an d W . R. E ls w ic k

This research is sponsored by the United States Air Force under Project RAND—Con tract No. AF 49(638)-1700—monitored by the Directorate of Operational Requirements and Development Plans, Deputy Chief of Staff, Research and Development. Hq USAF. Views or conclusions contained in this Memorandum should not be interpreted as representing the official opinion or policy of the United States Air Force.

■7& IUIIII) 1700 S r • Sant O N I C A l l F o R • 90406 -11-

Published by The Rand Corporltion — i i i —

PREFACE

This Memorandum considers the possibilities of specialized non nuclear b a llis tic missile attacks against U.S. airpower based on South Vietnam a irfield s and on board aircraft carriers operating in the vicin ity of the Gulf of Tonkin.

The subject should be of interest to those concerned with non nuclear weapon systems and their role in limited war situations. It is one phase of a general problem treated in Ref. 1. The authors wish to acknowledge the assistance of their colleagues M. B. Schaffer and D. B. Wilson.

Jones, W. M. , and J. R. Schlesinger, A Possible Soviet Deployment in Southeast Asia (U) (Short T it le ), The RAND Corporation, RM-4613-PR, October 1965

-V -

SUMMARY

A ballistic missile attack using warheads containing many small fragmentation bomblets is considered, with special application to the war in Vietnam. The aircraft on two U.S.-operated airfields in South Vietnam and a U.S. carrier in the vicin ity of Tonkin are used as the basis for evaluating the cost of such an attack in terms of numbers of fixed-payload missiles required and required total payload of bomblets. It is shown that large boosters adapted to short ranges could carry payloads large enough to damage exposed, parked aircraft.

- v i i -

CONTENTS

PREFACE...... i i i

SUMMARY ...... v

LIST OF FIGURES...... ix

Section I. INTRODUCTION ...... 1

I I o THE THREAT...... 3

I I I . UoS. TARGETS AT R IS K ...... 7

IV. RESULTS...... 13

Vo DISCUSSION OF PARAMETERS AND ASSUMPTIONS...... 22

VI. CONCLUSIONS...... 26

APPENDIX...... 29

REFERENCES 39

- ix -

FIGURES

Target areas at Da Nang ...... 8

Target areas at Bien Hoa ...... 9 Assumed target area to include carrier that has had time to steam a distance S ...... 11 Bomblet payload required against land targets and single shot missile delivery capabilities (0.7 coverage, 15 PK “ ° ' 7) ...... Bomblet payload required and achievable versus missile range (CEP = 600 ft ) ...... 19 Bomblet payload required and achievable versus missile range (CEP = 1500 f t ) ...... 20

Bomblet payload required and achievable versus missile range (CEP = 3000 f t ) ...... 21 Radius of equivalent circular target area versus carrier speed and missile range ...... 31

Required pattern area for 70 per cent coverage of area targets ...... 32

Effectiveness of bomblets against 3000-psi concrete .... 35 Perforation of homogeneous armor plate versus weight and L/D of bomblet ...... 36

-1-

I . INTRODUCTION

Because of the obvious constraints on the use of nuclear weapons, the question of using IRBMs and ICBMs with non-nuclear warheads has been examined many times in the past. The idea has usually been dis missed as impractical and inefficient. Analysts have usually thought in terms of long ranges, poor target intelligence, hard targets or large area targets, and a small unit payload of the order of 3000 to

7000 lb. Under this set of assumptions, target k i l l expectancy and economic payoff were usually quite low, and there was usually little payoff in refinement of guidance and reduction of CEP. As a conse quence, non-nuclear warheads associated with such systems have appeared to be ineffective. This study suggests that there is a situation where missiles armed with non-nuclear warheads may find application under certain conditions.

The war in Vietnam is different from any anticipated conflict, and the applicable tactics and techniques, or "ground rules," are not the same for both sides. Specifically, for example, while the use of missiles carrying non-nuclear warheads offers no particular advantage to the United States, such a system might be used effec tiv ely against U.S. and Government of South Vietnam (GVN) forces. The missiles could not only be used e ffectively , but for the purpose postulated in this study, could be a better choice in many respects than nuclear armed missiles. The Vietnamese situation presents the enemy with an unusually favorable set of circumstances:

1) Targets are lucrative; large numbers of unsheltered U.S. aircra ft are parked close together on hardsta.nd areas, especially during the rainy season, and on flig h t decks of aircraft carriers in the vicinity of Tonkin Gulf. 2) Firing ranges are short, 50 to 600 miles. Therefore, larger payloads can be lofted by IRBMs and ICBMs, and inertial guidance errors can be reduced. 3) Targets are compact: aircra ft parked on a ramp or flight deck rather than scattered about an airfield. Thus, improvements in missile guidance and lower CEPs would have decided value. -2-

4) The intelligence-firing cycle time is short compared to the time required for response or evacuation of a target area. A rtille ry spotting techniques may be possible against fixed targets.

It thus appears that one of the primary sources of U.S. techno logical superiority in Vietnam, combat airpower, presents an inviting, soft target that could be vulnerable to a special kind of non-nuclear attack. In the sections to follow are a description of the threat, the results together with a. discussion of parameters and assumptions and the conclusions of the analysis. The method of analysis and graphic displays of some of the relationships are presented in the

Appendix. -3 -

I I . THE THREAT

The weapon system with which this Memorandum is concerned is achievable with present technology by the United States--and presumably

by the Soviet Union--a.nd could pose a credible threat to the U.S.

position in South Vietnam. Of course the Soviets probably would not conceive of this exact system, and might not choose to use such a system, but it is important to recognize that the system appears to be appropriate for attack of such U.S. targets as areas of parked air

craft and carrier decks laden with aircraft. As we conceive of the weapon system, it would consist of a delivery vehicle (the missile booster), a payload package or reentry vehicle, and a. warhead containing many small fragmentation bomblets. At a pre

determined altitude over the target, the bomblets would be released to fa ll in a pattern of predetermined size. The number of bomblets in the pattern would be determined by the desired level of damage and by

the lethal radius of the individual bomblets against the type of tar get considered. As w ill be shown later, a respectable expected lethality can be achieved within a very large pattern of bomblets; and the entire pattern can be placed over one of the postulated targets with a high value of expected coverage. The seriousness of the threat posed by such a system seems to depend on (1) the U.S. vulnerability and (2) the objectives, capabilities, and ingenuity of our enemies. The first can be described; the second can be inferred to some extent.

U.S. land-based airpower in South Vietnam has been vulnerable to nany types of attack from the time aircra ft were fir s t employed against the Viet Cong, but the recent successful mortar attacks have sharply delineated this threat. Since then the United States has been guarding air bases with combinations of Marines, Hawk missiles, a rtille ry , para troopers, and interceptor aircraft. Presumably as a result of these measures, the conventional threats of sabotage, recoilless r if le fire, mortar fire, artillery fire and conventional air attack have been greatly reduced.

We have not attempted to determine the relative effectiveness of other types of sub-missiles. Data on the fragmentation types were more readily available. In the Gulf of Tonkin and the South China Sea, except for the early encounter with the North Vietnamese PT boats, our naval air units have operated with relative impunity. The presence of Russian trawlers in the vicinity offers no direct threat.

While certain types of threats can thus be discounted, there are few completely secure air bases in South Vietnam. Large numbers of aircraft have been moved in. Hardstand area on these bases is limited.

A ircraft are parked close together, especially during the monsoon season. I t has been reported that the A-ls have on occasion been so closely parked on the hardstands that the wings had to be folded.

These bases have become highly lucrative targets for ballistic missiles, against which there is currently no effective active or passive defense. As for the naval forces, it is reported that they have been so active that approximately one-half of a carrier's complement of aircraft would be found on the flig h t deck at any time. Carriers operating in or near the Gulf of Tonkin are of necessity close to possible b a llis tic missile launching sites within North Vietnam.

Although it certainly could be argued that parked aircraft pre sent an ideal target for a b a llis tic missile with a nuclear warhead, it seems doubtful that the Soviets or the Chinese would choose to launch such an attack against U.S. forces. However, could a success ful attack with some type of "acceptable" non-nuclear warhead be launched against the two or three main air bases and one or more of the carriers, the Communist forces might be tempted. A few large single-stage missiles could be moved by water or air into the Hanoi area and set up under forest cover during the rainy season or during other periods of inclement weather, thereby perhaps evading U.S. reconnaissance efforts. Although radio guidance sites are not necessary, the Soviets could survey and in stall such sites at any time. There is high ground near the coasts of both North Vietnam and Hainan where radar guidance sites could be installed in an attempt to maintain continuous contact with our carriers. Airborne radar or seaborne radar could also be employed.

The Soviets have a number of boosters that could be adapted to the task of lofting a large ordnance load the required distance of 300 -5 -

to 600 miles between Hanoi and the air bases at risk. I t would be even easier for them to fire the short ranges to reach U.S. carriers.

Both the single stage SS-4 and SS-5 could theoretically be modified to lo ft more than 12,000 to 24,000 lb over a 600-mile minimum-energy trajectory, while the two-stage SS-7 and SS-8 can with modification (2 3) propel more than 25,000 to 35,000 lb over the same distance. ’

Payloads intended for shorter ranges could be larger i f minimum-energy trajectories were used.

The economic tradeoff, missile costs versus U.S. aircraft damaged or destroyed, might well favor the attacker. Even allowing for siting- in shots, this could s t i l l be the case. Admittedly, the airfields themselves and the carriers would probably not be damaged; but such a missile attack could disrupt land-based air operations or force the carriers to operate from a distant location, much to the disadvantage of the United States. The propaganda payoff for the Soviets would, no doubt, be large. An unpredictable amount of collateral damage among the closely parked aircraft would enhance the payoff.

The Soviets have recently been unusually active in firin g b a llis tic • •, , (4) missiles over short ranges: Range Date (n mi)

April 8, 1964 440 July 18, 1964 510 August 12, 1964 515 October 10, 1964 481

October 16, 1964 507 October 29, 1964 480 January 30, 1965 309 March 5, 1965 300

March 13, 1965 312

But see Conclusions, p. 26. ^Morris, D. N., Charts for Determining the Characteristics of B a llis tic Trajectories in a Vacuum, The RAND Corporation, RM-3752-PR, April 1964. 3 Sharkey, E. H., The Rocket Performance Computer, The RAND Corporation, RM-2300-RC, December 8, 1958. ^Sino-Soviet Bloc Missile and Space Technology (U ), U.S. Army, Missile Command, Ml 1-65, January-March 1965 -6-

Further, from two to six multiple objects were reported in seven of the nine firings. The flights were either heavily instrumented or guided, as evidenced by the large number of telemeter channels. Mul tip le objects (10-16) have also been noted during recent SS-5 firings to 2,000 m iles. -7-

I I I . U.S. TARGETS AT RISK

Two air bases in South Vietnam and one aircra ft carrier are con

sidered as representative targets for the purposes of this study. In

each case the target is an area. Once the size, shape, and location of the area have been determined, there is no essential difference in the analyses of the land and sea targets since carrier movement is accounted for in the determination of area, as w ill be shown later.

Da Nang (Fig. 1), 330 n mi from Hanoi, has, in addition to the 10,000-ft (long) landing strip, a parking apron of approximately 1,920,000 sq ft that appears to be a rectangular area 600 ft by 3200 ft; this parking area w ill be designated as Target D-l. There is also an area containing old aircra ft revetments that appears to be about 3600 ft by 4500 ft; this area w ill be designated as Target D-2.

Bien Hoa. (Fig. 2), the second air base, is 600 n mi from Hanoi. It has a 10,000-ft runway and two parking aprons. The larger apron, designated as Target B-l, is about 1000 ft by 500 ft, while the smaller, designated as Target B-2, is 300 ft by 800 ft. These two target areas are close enough together to be considered as a single target for large patterns. This would give a target area of approxi mately 1200 ft by 1500 ft- On a ll these parking aprons normal precautions would or could be taken to disperse aircraft in various locations and configurations, making use of the entire hardstand area. Consequently, the entire parking apron or revetment area must be targeted rather than specific portions, as the real target objectives are the aircra ft themselves. Carrier a ircra ft have in recent months played an increasingly important role in the Vietnamese war. Elements of the American fleet, including carriers, are stationed in or near the Gulf of Tonkin. F ir ing ranges from the nearest point of land on North Vietnam to the position of the carriers are no greater than 50-200 mi.

Adapted from Ref. 5: A irfields and Seaplane Stations of the World (U), Vol. 25, U.S. Air Force, ACS/Intelligence -8-

Fig. 1— Target areas at Da Nang -9-

Fig. 2— Target areas at Bien Hoa -10-

If one of the carriers were selected as a target for the bomblet pattern and located with precision at the moment of missile firing, it would be possible for an attacker to define an area within which the carrier would have to be at the time of missile arrival. The size and location of this area, would be functions of the range at the time of firing and the extent of the possible maneuvers of the carrier dur ing the time of flig h t. Some time would of course be required for

transmittal of target data from observation points to missile site; and additional time would be required to program the missile. These time factors have not been considered in detail. I t has been assumed that by continuous observation and tracking of the carrier one could predict its course, speed and location at the time the missile was ready to fire, and then verify the predictions with a last-minute observation of the carrier. Since the carrier would not always main tain course and speed long enough to allow it s e lf to be targeted, many attempts and considerable patience would probably be required be

fore the best prediction could be made, but sooner or later it should be possible to target correctly. Airborne radar might be required.

Figure 3 is a representation of the maximum possible area within which an aircra ft carrier could be found i f it began evasive maneuvers at the time of missile firing. Position 0 is the location of the carrier at the instant of launch. I f the carrier maintained its speed, i t could follow any of the arrow paths shown. Each path has the length

S, the distance that a carrier making a given average speed could go during the time of missile fligh t. The enclosing circle shown in Fig. 3 therefore defines a circular target area that is a function of the carrier speed and its distance from the launch site (range). As examples of the numbers involved, an average carrier speed of 30 kn and a range of 100 mi would give a target area with a radius of 8000 ft, while a 20-kn speed at 100 mi would present a target radius of about 3600 ft. Such target areas would normally be considered too large for conventional warheads, but the possible use of small, scattered bomblets makes patterns of this size a consideration. In a ll probability a carrier would not be forewarned and there fore would not engage in evasive maneuvers. Also, it might continue -11-

n Original course of carrier

O is original carrier position. All arrows drawn from O have length S.

Fig.3— Assumed target area to include carrier that has had time to steam a distance S. -12-

into the wind in order to launch aircra ft even though under attack. The location predictive errors would then be measured in terms of hundreds of feet, and the effective target area would be smaller. -13-

IV. RESULTS

The results of the analysis are summarized in the tables and figures of this section. We assumed bomb lets weighing 0.63 lb would be used against exposed aircraft on parking ramps or carrier decks,

and bomb lets weighing 15 lb would be used against aircraft in NATO- type shelters. In each case these weights approach the minimum that

w ill accomplish the attack objective; larger weights would be less efficient. All results are based upon a target coverage of 0.70

and an expected kill (lethality) of 0.70 within the pattern. The product of these two values is taken to be the effectiveness of the attack. The parameter of interest is the required payload of bomb lets

for a given combination of target characteristics and missile delivery

CEP ." Table 1 shows as a function of the CEP the required payload in pounds to achieve a 0.49 effectiveness against aircraft exposed in the open or in open-top revetments. The targets are the four parking areas shown in Figs. 1 and 2. Reinforcing or collateral damage is accounted for in the value selected as the k ill radius and the definition of kill.

Table 1

REQUIRED PAYLOADS3 AGAINST EXPOSED AIRCRAFT OR AIRCRAFT IN (OPEN-TOP) REVETMENTS

PATTERN AREA FOR 0 .70 REQUIRED PAYLOAD FOR COVERAGE (f t 2) 0.7 LETHALITY WITHIN TARGET PATTERN (lb) AREA CEP CEP _ TARGET (f t 2) 600' 1500' 3000' 600' 1500' 3000' D-l 1.92xl06 5.6xl06 16 .0x10^ 52.0xl06 5,680 16,300 52,800 D-2 16.20xl06 20.0xl06 30.0xl06 65.0xl06 20,300 30,500 66,100 B-l 0.5xl06 2.6x10^ ll.OxlO6 42 .0x10^ 2,640 13,800 50,200 B-2 0.24x106 2.3xl06 11.5xl06 42 .OxlO6 2,340 12,500 50,200

3. In the tables and charts the values for payload are the total munitions weight.

For discussion, see Appendix, p. 29. See Sec. V (p. 22) for discussion. -14-

To interpret Table 1, for example, one reads for Target D-l (Da Nang apron) that a missile carrying 5680 lb of 0.63-lb bomb lets and having a CEP of 600 ft will k ill 70 per cent (on the average) of the unprotected aircraft parked in the area covered by the bomb let pattern. The effectiveness of the attack is 0.49, the product of the 0.70 coverage and the 0.70 lethality within the bomblet pattern. Figure 4 shows the same information with the four targets plotted for each of the three values of CEP on axes of range and payload. In addition, for reference, the payload capabilities of three Soviet delivery systems are shown: theoretical SS-4, the first stage of SS-7, and the first stage of SS-8. These payload capabilities were computed by assuming that it is possible to trade fuel for payload as the range is decreased, thereby permitting large payloads at the ranges of inter est in this study. The curve for the SS-4 is labeled "theoretical" since the missile is a one-stage vehicle, and it is not really possible to trade fuel for payload beyond a certain point because of the con straints of structural configuration. The SS-7 and SS-8, however, have two stages. The first-stage boosters would be able to transport a payload that would simply replace the second-stage vehicle and the normal reentry vehicle. The large payloads shown for short ranges would therefore be more feasible, and all of the targets appear to be vulnerable to a one-missile attack with a CEP of 600 ft. If the range-payload tradeoff were not considered, the unmodified SS-4 missile could carry a payload of about 3000 lb. The first stage of the SS-7 could carry a payload of about 25,000 lb. If these were taken as fixed payload capabilities and if more than one missile were used, the missile requirements for the land targets would be as shown in Table 2. Note the modest number of large payload (25,000-lb) missiles .

For discussion, see Appendix, p. 29. Payload (lb) 20

i.—BombletFig.4— payload required against land targets and ige ht isl delivery missile shot capabilitiessingle 07 coverage,(0.7 pK -15- 100 ag ( mi) (n Range

=0.7) 1000 -16-

Table 2

MISSILE PAYLOADS REQUIRED TO ACHIEVE A 0.49 KILL EFFECTIVENESS ON TARGET3

Number of 3,000-lb Payloads Number of 25,000-lb Payloads

CEP CEP

Target 600' 1500 ' 3000 ' 600' 15 00 1 3000' r—t Q 1 2 6 18 1 1 2 D-2 7 10 22 1 1+ 3 B-l 1 4 14 1 1 2 B-2 1 4 14 1 1 2 £ When target coverage is achieved by multiple payload packages; there are options both in the choice of aiming points within the target area and in the size of bomblet pattern produced by each payload package. No attempt has been made here to optimize these factors. The values are obtained by assuming each of the payload packages is aimed at the same point and that each has a bomblet pattern large enough for 0.70 target coverage. Their cumulative effect is to build up the necessary bomblet density.

Table 3 shows the effectiveness of 15-lb bomblets against the same target areas if the aircraft were inside NATO-type shelters. These shelters have a cover of both one-half inch of steel and a minimum of four feet of earth. The effective lethal radius of the 15-lb bomblets was taken as only 23 ft, despite their greatly increased weight over the 0.63-lb bomblets. This is because here the lethal radius is governed by the portion of the total shelter area in which a k ill is possible. The 15-lb bomblets can penetrate only a limited area of the shelter roof near the top of the arch; bomblets outside this area fa il to penetrate to the interior of the shelter and can do no significant damage. The effectiveness of NATO-type shelters can be appreciated by comparing the payloads required for each target with the same cases in Table 1. The payload requirement for a given level of k ill goes up by a factor of about 10.7. -17-

Table 3

REQUIRED PAYLOADS AGAINST AIRCRAFT IN NATO-TYPE SHELTERS3 (4 1 EARTH AND 1/2" STEEL) (PATTERN AREAS FOR 0.70 COVERAGE ARE THE SAME AS IN TABLE 1)

REQUIRED PAYLOAD FOR 0.7 LETHALITY WITHIN PATTERN (lb)

CEP

TARGET 600' 1500' 3000'

D-l 60,800 174,500 563,000 D-2 218,000 327,000 708,000 B-l 283,000 120,000 456,000 B-2 25,000 114,500 456,000

aFor discussion, see Appendix, p. 29.

Table 4 shows the results of the analysis for the effectiveness

against aircraft on a carrier. The difference in payloads required against a carrier taking evasive action and one maintaining course and speed is due to the different areas that must be targeted to achieve the 0.70 coverage.

Table 4

MISSILE PAYLOADS REQUIRED TO ACHIEVE 0.70 LETHALITY WITH 0.70 COVERAGE AGAINST CARRIER-BORNE AIRCRAFT

PAYLOAD (lb) REQUIRED IF PAYLOAD (lb) REQUIRED IF CARRIER IS TAKING EVASIVE CARRIER MAINTAINS COURSE RANGE ACTION AND SPEED IS 20 KNOTS AND SPEED TO CARRIEI CEP CEP (n mi) 600' 1500' 3000' 600' 1500' 3000'

50 14,200 25,100 62,000 2,450 13,100 51,300 100 28,500 38,800 76,000 2,450 13,100 51,300

150 43,800 53,000 91,000 2,450 13,100 51,300

200 5 7,600 66,100 106,000 2,450 13,100 51,300 -18-

Figures 5, 6, and 7 show the payloads required for aircraft on carrier decks at various ranges for the three values of CEP: 600 ft, 1500 ft, and 3000 ft. Also shown are the capabilities of the theo re tica l SS-4, the fir s t stage SS-7, and the fir s t stage SS-8. I f the carrier maneuvers during the time of flig h t of the missile, the area to be targeted must be larger, based on a pattern such as that shown in Fig. 3. I f the carrier maintains course and speed, the target area can be much smaller. We have assumed in the latter case that the target was a circular area of 1000-ft diameter.

For discussion, see Appendix, p. 29. Bomblet payload (lb) i.—Bomblet payloadFig.5— required and achievable range missile versus 10 CP =(CEP 600 ft) sie rne n mi) (n range issile M -19- 100 1000 Bomblet payload (lb) i.—Bomblet payloadFig.6— required and achievable missilerange versus 10

CP = 1500(CEP ft) sie rne n mi) (n range issile M -20- 100

1000 Bomblef payload (lb) i.—Bomblet payloadFig.7— required range and achievable missile versus 10

-21- sie rne n mi) (n range issile M ( CEP = 3000 ft) 100

1000 -22-

V. DISCUSSION OF PARAMETERS AND ASSUMPTIONS

The results tabulated in Sec. IV demonstrate the importance of a small CEP in keeping down the total required payload. This is be cause a small CEP permits a smaller bomblet pattern to achieve a given coverage. Against the airfield s in South Vietnam, the CEP could be extremely small. I t is believed that the guidance error could almost be removed by rela tively simple midflight guidance from ground stations along the route of the missile trajectory. This is within the present capability of Soviet technology and achievable in a practi cal sense because of Viet Cong holdings in South Vietnam. I t has been estimated that with this technique the guidance error could be reduced to the same order of magnitude as the error in establishing the loca tion of the ground control stations; in other words it could be as small as 50 ft. The reentry error, on the other hand, is independent of this kind of guidance; and it would remain as the dominant part of the total error. Its magnitude is estimated to be such that the total CEP could be as small as 600 ft. Terminal guidance has not been con sidered a possibility with present technology. The assumption of random bomblet distribution within the pattern sim plifies the analysis, and it might be realizable. For example, i f the missile reentry vehicle were spun about its axis at the proper altitude, the bomb lets could be thrown out by centrifugal force. Their radial velocity would be a function of the rotational speed and the storage location of the bomblet within the reentry vehicle. Another possibility would be the use of preset fins on the bomb lets. It does not seem unreasonable that a large number of bomblets (20,000 for example), scattered at high altitude, would be distributed in a fa irly random way throughout the pattern by the time they struck the earth.

A value of 0.70 has been used as a desirable value of target coverage by the bomblet pattern. For each combination of target area and CEP, there is a pattern size that w ill give the required 0.70 coverage. These pattern sizes appear feasible for the target areas and CEPs considered in this study. -23 -

The next important parameter is the lethality of the individual bomblets within the pattern. In this connection an effort has been made to determine the optimum weight of bomblet to achieve a given p .

These calculations are described in the Appendix. For a BLU-3/B type bomblet the optimum weight appears to be in the range of 0.6 to 0.9 lb. The optimum weight density for a p of 0.70 against parked aircraft K 2 appears to be sligh tly greater than one pound per 1000 ft of pattern.

As a nominal weight, we have chosen a 0.63-lb bomblet, and for a p of 2 K 0.70 we have used a weight density of 1.015 lb per 1000 ft of pattern. In using the concept of lethality, one should be aware of possible ambiguity in the definition of target damage. Several degrees of damage to exposed aircraft are defined in the literature, but these definitions are not precise unless the damage is total demolition. For our purpose, damage to exposed parked aircraft is taken to mean

immediate disablement, preventing any operational use of the aircraft without extensive, lengthy, and expensive repairs: in other words, a "runway k ill." Even with this definition, some conservatism is introduced since we are not concerned in this study with an isolated aircraft as a

target. Damage will be amplified because of the interacting effects of fires, explosions, and debris. In other words, to achieve a given k ill probability, bomblets used against an area containing closely- parked aircraft can be considered on the average to have a greater

effectiveness than if they were used against a single aircraft. In their presently considered configuration, the bomblets are not efficient penetrators. The penetrating ability is a function of the sectional pressure (weight/cross sectional area) of the bomblet and

its impact velocity. The sectional pressure for an e ffic ie n t frag mentation-type bomblet is quite low, a couple of pounds per square inch or less. At the same time, the achievable impact velocity w ill

not be very great. Some calculations, described further in the Appendix,

show that bomblets having an L/D of three, a sectional pressure of

three pounds per square inch, and a typical drag function w ill reach a terminal velocity of about 1000 ft/sec as they f a ll through the earth's atmosphere. Even with an L/D as high as eight, the bomblets' -24-

terminal velocity w ill not exceed around 1500 ft/sec. These are considered to be upper bounds to the impact velocities achievable.

A bomblet with given values of L/D, weight density, and impact velocity will have a penetrating capability that is a function of its weight. A one-pound bomblet with an L/D of three, weight density of 3 170 lb/ft , and impact velocity of 1100 ft/sec will perforate about

1/2" of armor plate. I t requires a six- to eight-pound bomblet to perforate 1" of armor plate, and a 30- to 60-lb bomblet to perforate

2" of armor plate. Increasing the weight of the bomblet does increase its penetrating capability, but it also decreases the number of bomblets in a given payload. A pattern of heavy bomb lets becomes too small to achieve good coverage of the area targeted.

In considering possible damage to the aircraft carriers, we note that those operating in the area include vessels of: the Essex class, which has a flig h t deck consisting of 3" of wood planking on a 5/8" steel plate; the Forrestal class, which has a flight deck consisting of a light coating over steel of 5/8" to 1"; the Midway class, which has a flig h t deck of more than 2" of steel. Because of this, the authors fee l that the m issile-delivered bomblet attack of the type being considered is no real threat to aircraft carriers themselves.

Similar reasoning makes the bomblet attack unattractive against hardened shelters on land. For example to perforate a thin steel structure with three or four feet of earth cover requires a bomblet of about 15 lb. Once again, this would reduce the number of bomb lets possible in a given payload to the point that the system would be ineffective in coverage. Currently, aircraft in Vietnam and other remoter areas are not sheltered. I f the proposed Department of Defense shelter program were carried out, an attack of the type we postulate would be ineffective against such sheltered aircraft. However, it is the authors' opinion that limited wars are apt to occur in remote areas where shelters have not been provided. If U.S. policy is to be prepared to resist aggression

For discussion, see Appendix, p. 29. -25 -

on virtu ally a worldwide basis, the chances are very good that our aircraft will not be operating from hardened shelters. On the other hand, i f conditions are such as to permit and encourage construction of hardened aircra ft shelters, i t w ill be because of a more serious threat than non-nuclear b a llis tic missiles. -26-

VI. CONCLUSIONS

In general, it appears credible that a successful ballistic missile attack with special non-nuclear warheads could be launched

from the vicinity of Hanoi against U.S. aircraft both on airfields in

South Vietnam and on aircraft carriers operating in the vicinity of the Gulf of Tonkin. The requisites for a successful attack are surprise, a small number of high-payload missiles, a small CEP, precise target location, and an adequate command and control system.

All the land targets, as well as carriers within a hundred-mile

range, appear vulnerable to a single-weapon, 600-ft CEP attack using the fir s t stage of the SS-7 or SS-8 as a delivery vehicle.

The SS-4 could theoretically carry a payload sufficient to achieve a 0.49 effectiveness against the smaller land targets and aircraft on close-in carriers. It is doubtful, however, that this theoretical payload capability could be realized without extensive redesign of

the missile.

I f the SS-4 were used without redesign, carrying only its nominal payload (based on an 1100-mi range) over these short ranges, a sizable number would be needed. The most d iffic u lt target, for example, would

be D-2 at Da Nang. As many as 22 missiles would be needed for 0.49

kill effectiveness if the CEP were 3000 ft. The easiest target, B-2 at Bien Hoa, would require only one missile for 0.49 k ill effectiveness with a CEP of 600 ft. Larger CEPs would increase the numbers of missiles required in a ll cases.

CEPs of 600 f t appear reasonable for the ranges in question, especially i f midcourse radio guidance were employed. A CEP of less than a few hundred feet may be d iffic u lt to achieve because of reentry and bomb let dispersal errors.

Revetments around land-based aircraft offer l i t t l e protection in the multibomb attack pattern because the angle of impact is essentially vertica l. Also, due to the small damage radius of the 0.63-lb bomblets, -27-

the presence of revetments is not c ritic a l since an impact outside the revetment would be too far away to damage aircraft anyway. The penetrating capability of bomblets against light roofs may be obtained at the expense of some optimization of effect. For a given total payload and pattern size and within practical limits, the k ill effectiveness improves with a larger number of smaller bomblets. The analysis indicates that for aircraft in the open the optimum bomb let size is a l i t t l e less than one pound. However, for aircraft in NATO-type shelters, a direct hit near the center of the shelter by a bomblet of 15 lb or more would be required to damage the aircraft. Also, at sea an attack against an aircraft carrier itself appears to be in effective unless much larger bomblets are used and some sort of target homing is employed. Targeting the carrierborne aircraft at ranges greater than about 70 miles may require airborne radar and/or seaborne radar.

Penetrating bomblets of high ballistic coefficient (W/C^A) are slender and achieve a small mean area of effectiveness per unit weight; hence, they are relatively in efficien t when compared to the coverage achievable by low density fragmentation bomblets of near optimum shape.

On the other hand, there may be no better way to drive a fragmentation warhead through the roof of a shelter or through a flig h t deck of an aircraft carrier. In this event the required ordnance load would be large . The shaped charge principle does not appear to be applicable in attacks of the type considered unless there can be appreciable follow- through fragmentation.

The missile should be looked upon as merely an ordnance delivery vehicle capable of a range-payload tradeoff. Non-nuclear payloads should be as large as the range and vehicle allow.

Although the weapon system considered here has immediate con nection with the war in Vietnam, a situation where the United States appears vulnerable to a bomblet attack, it is conceivable that in other situations the United States might find such a weapon system suitable for its own purposes. It would appear to be particularly -28-

effective for covering large, soft-target areas without overkill or undesirable collateral damage. Its versatility could be improved by adapting other types of bomblets so that they could be interchangeable with the fragmentation bomblets. For example, i t might be possible to deliver incendiary bomblets as well as fragmentation bomblets, which should also offer an improvement in collateral damage, especially when employed against "wet-wing" aircraft.

Aircraft with fuel tanks in their wings. -29-

Appendix

ANALYSIS

This section contains supplementary details of the analysis. In addition, a number of figures are included either to show their use as computational aids or for substantiation of statements made else where in the study. The parameter of interest is the required payload to achieve a given effectiveness against specific targets. The kill effectiveness was taken to be the product of the target coverage and the lethality within the pattern of bomblets. The locations of the land targets were assumed to be known within a negligible error. Similarly, the

location, course and speed of a carrier were assumed to be known with negligible error at the time of missile, firin g. Allowing for pos sible carrier movement during the time of flig h t, an area that would include the position of the carrier when the missile arrived was de fined as a target. With these assumptions, both the land and sea targets could be treated as known, stationary areas.

COVERAGE OF TARGET AREA

The probability of placing the bomblet pattern over the target area (target coverage) was then assumed to depend only on the shape and size of the target area and the CEP and size of the bomblet pat tern delivered. A value of 0.70 was used throughout as a desirable coverage, and a circular Gaussian distribution was assumed for the distance between the center of the target and the center of the bomblet pattern delivered. Mathematically, the coverage was taken to be the integral of a function that is the product of the probability of a certain miss distance times the target coverage at that miss distance. This was done by a graphical numerical approximation for a few cases to verify the applicability of extrapolating Nomogram 1 of Ref. 6 for

^Physical Vulnerability Handbook--Non-Nuclear Weapons (U ), Defense Intelligence Agency, PC 550/1-1-63, August 1963 -30-

rectangular targets. For circular targets data from Ref. 7 were used . The size of the target area at sea was determined from the assumed

carrier speed, an assumed minimum tactical turning diameter of 1000 yd,

and an assumed time of flig h t of the missile. The time of flig h t was

computed for the in itia l range, assuming minimum energy trajectories

in vacuum. Figure 8 shows the radius of the target area as a function of carrier speed and range from the missile launch site.

Figure 9 shows the required circular pattern area that the bomblets must cover to assure 0.70 coverage against various rectangular and circular target areas and values of CEP. This figure was used for both land and sea targets.

LETHALITY WITHIN THE PATTERN

Given the condition that the target area is covered by the bomb-

let pattern, there is a probability that an aircraft in the area w ill be killed. This probability, multiplied by the number of aircraft in the area, gives the expected number that w ill be k illed . For the purpose of this study, the basic criterion is that 70 per cent of the

aircraft within the pattern might be k illed . In other words, p K within the pattern is set at 0.70. The problem then becomes the determination of the least payload that would achieve a p^ of 0.70 within the pattern area.

For completely random distribution of n bomblets within the pattern, the probability that a single aircraft will be killed is

where lethal area of a bomb let

area of bomblet pattern

^Germond, H. H., The Circular Coverage Function, The RAND Corporation, RM-330, January 1950. Target radius (ft) Fig.8— Radius of equivalent circular target area versus versus area target circular equivalent of Radius Fig.8— 10 are sed n msie range missile and speed carrier M is s ile range ( n mi ) mi ( n range ile s is M 31 100

1000 -32-

OJ loO 10 100 a / C E P

Fig.9— Required pattern area for 70 per cent coverage of area targets -33-

For large values of n, this equation can be approximated by

In order to get a relationship between A and w (the weight of a bomb- JL> let) several computations were made using the Full Spray Lethal Area

Program applied to BLU-3/B type bombs. For variation in total mass of pellets from one-half to double that of the BLU-3/B, i t was found that for a constant charge-to-mass ratio the lethal area scaled with the non-parasitic weight of the bomblet. I f the parasitic weight is assumed to be constant and equal to about 10 per cent of the weight of the BLU-3/B, the following can be written

where w is the total weight of the bomblet and k is the scaling factor. 2 The above expression is based on a lethal area of 1750 f t for the BLU-3/B against parked aircraft and a scalable weight of 1.5 lb.

The scaling factor proved insensitive even to sizable variations in target size or composition. In fact, for such diverse targets as prone men, soft vehicles, and simulated aircraft, the scaling factor remained in the range 0.682 - 0.790. Substituting the expression for A^ in that for p^ and solving for n, one gets

AP ln (1_PK) n =

- 0.2 1750

The total payload is approximately In (l-p K) (1.5)' w WT = (n) (w) = ÎL 1750 (w - 0.2).

The value of w that makes W,^ a minimum can be found by setting

ôwt -— = 0. The minimum value of the ratio W /A can then be computed, ôw T P -34-

Performing the calculations with these values, these results were obtained:

Individual Target k Optimum w (lb) PK wt /ap ( lb/100° ffc2)

Simulated a/c „ 1/4" Al, 13 ft 0.682 0.70 0.630 1.015

Standing Man 0.790 0.70 0.953 1.135

Keeping in mind the limited input information and the approximate nature of these calculations, it was nevertheless fe lt that two useful conclusions might be made for the purpose of this study: 1) The most effective fragmentation bomb attack against parked aircraft within an area target would be made with a pattern of bomblets lighter than the BLU-3/B. I t appears that the bomb let weight would be under 1 lb, and perhaps as small as 0.63 lb. 2) An expected k ill of 0.7 for the aircraft within the pattern might be achieved with an average bomb let density approaching 1.015 lb 2 per 1000 ft of pattern.

AIRCRAFT IN NATO-TYPE SHELTERS

A different procedure was followed to obtain the payloads required against the NATO-type shelters. In this case the bomblet weight was dictated by the requirement that i t penetrate the steel and earth cover.

Figure 10 shows the bomblet weight required to perforate or penetrate various thicknesses of concrete and earth. It is based on information from Ref. 6, and assumes an L/D ratio of 3, an impact velocity of 3 1100 ft/sec, and a weight density of 175 lb/ft for the bomblet. Figure 11 shows the relationship between L/D and bomblet weight to perforate various thicknesses of armor plate. It is also taken from information in Ref. 6, and embodies the same assumptions as Fig. 10. On the basis of Fig. 11 the conclusion was made that the

0.63-lb bomblets offer no threat to aircraft carriers themselves. I t is doubtful that either the bomblets or their fragments would per forate more than 1/2 inch of steel plate. -35 -

Perforât on — v

— Pénétrât ion

10 Impact v e lo c ity =1100 ft//sec

Bomblet density = 175 lb/ft3

Length/ti iameter = 3

0 I I I I I I I I I____ 1____ L 10 20 30 40

Gross weight of bomblet (lb )

Fig. 10— Effectiveness of bomblets against 3000-psi concrete -36-

0 .7 1 2 3 4 5 10 20 30 40 50 100 200 300 400 Weight (lb)

Fig. 11— Perforation of homogeneous armor plate versus weight and L/D of bomblet -37-

The assumption that the impact velocity is no greater than 1100 ft/ sec can be supported by calculations of the terminal velocity of a bomblet in free fa ll through the earth's atmosphere. This was done using drag coefficien t vs. Mach number data from Ref. 8. For an L/D of 3 and a bomblet density of 175 lb/ft , the terminal velocity is about 1000 ft/

sec. For an L/D of 8, the terminal velocity is about 1460 ft/sec. The actual velocities are probably less than sonic.

BOOSTER PAYLOAD CAPABILITIES

The payload capabilities shown in Figs. 4-7 for the SS-4, SS-7, and SS-8 missiles were computed for minimum energy, vacuum trajectories. The estimated nominal ranges and payloads given in Ref. 4 were used as check points, and the weight inventory was adjusted to give the required combinations of fuel, structure, and payload corresponding to a given range. A specific impulse of 250 lb-sec/lb was used for a ll three boosters. This may be conservative for the SS-8; and it may very well be that the SS-8 capability equals or exceeds that of the SS-7 at short ranges.

Hoerner, S. F., Fluid Dynamic Drag, published by the author, 1965.

-39-

REFERENCES

1. Jones, W. M ., and J. R. Schlesinger, A Possible Soviet Deployment in Southeast Asia (U) (Short T i t l e ) , The RAND Corporation, RM-4613-PR, October 1965

2. Morris, D. N., Charts for Determining the Characteristics of Ballistic Trajectories in a Vacuum, The RAND Corporation, RM-3752-PR, April 1964,

3. Sharkey, E. H ., The Rocket Performance Computer, The RAND Corpor ation, RM-2300-RC, December 8, 1958.

4. Sino-Soviet Bloc Missile and Space Technology (U ), U. S. Army, Missile Command, Ml 1-65, January-March 1965

5. A irfield s and Seaplane Stations of the World (U ), Vol. 25, U. S. Air Force, ACS/Intelligence

6. Physical Vulnerability Handbook--Non-Nuclear Weapons (U ), Defense Intelligence Agency, PC 550/1-1-63, August 1963

7. Germond, H. H ., The Circular Coverage Function, The RAND Corpor ation, RM-330 , January 1950c

8. Hoerner, S. F., Fluid Dynamic Drag, published by the author, 1965.