Space Travel : A Symposium Introduction BY COLONEL PAUL A. CAMPBELL, USAF (MC), Chairman Many of us here today are of the opinion extra-atmospheric flight. Possibly that will that extra atmospheric flight--space flight, insoluble, and if they can--within the frame- if you please--is now entering the realm work of security--make predictions. of the feasible. We have on our program I am certain one of these problems will be Percent 130,000 99.7 120,000 99.5/8 110,000 99.1/4 100,000 190,000 90,000 '31,235 98.5 60,000 ,0,49 r 96 7,6 70,000 / 93 3/4 60,000 ,,I,~ ~,0'~6 --50,445 50,000 87 I/2 40,000 . ,4E,,0 75 30,000 f J 20,000; /20p,0 50 lO,OOO 0 J' I f 1905 1910 1915 1920 1925 1930 1935 1946 1945 1950 1955 1960 1965 Fig. 1. Graph showing man's altitude achievements plotted chronologically by years and the percentage of atmosphere penetrated. The broken line represents un- confirmed records reported in the press. today a group of experts representing vari- to attain agreement as to what constitutes ous disciplines. Their contributions toward be answered today. our goal can be questioned by no one. They To start off, I would like to show two have been asked to discuss the present state diagrams (Figs. 1 and 2) showing evidence of the art in their line of endeavor, prob- of man's approach toward space. The first lems which are soluble and those which are is the time-worn graph of altitude achieve- ment plotted chronologically. Note the This symposium was presented on May 8, 1957 at the 28th annual meeting of the Aero break-through produced by the advent of Medical Association, Denver, Colorado. rocket propulsion. The dotted lines repre- Dr. Campbell is special assistant for med- sent that portion of the achievements which ical research to the commander, Air Force Office of Scientific Research, Washington, have been reported at times in various news D.C. media but have never been confirmed. OCTOBER, 1957 479 SPA.CE TRAVEL---CAMPBELL The second diagram represents the same American Aviation, Los Angeles, will set us chronological graph of altitude achieve- straight on some of the quite serious human ments but plotted in terms of per cent of problems. mass of atmosphere penetrated. Note the Commander George W. Hoover, USN, Percent loo I jp." -? 90 jl v 00 ~ r 70 / 00 5O / 40 20 10 0 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 Fig. 2. The penetration of the atmosphere plotted according to year of achievement. The broken line represents unconfirmed records reported in the press. smooth asymptotic progress, and also that Office of Naval Research, Washington, D. tile sudden break tel)resented by advent of C., has chosen the subject, "What Instru- rocket propulsion has ironed out. Note, mentation Will Be Required." please, that the most rapid progress if one A. M. Mayo, chief equipment and safety uses this parameter took place in the early research engineer of the Douglas Aircraft days of aviation. That is a little defla- Company, El Segundo, California, will cover tionary. However, we shall hear many of survival aspects of space travel. the answers today from the members of Dr. J~ohn P. Hagen, Naval Research Lab- our symposium. oratory, Washington, D. C., will describe Konrad K. Dannenberg, director, Tech- the space travel implication of the Vanguard nical Liaison Group, Army Ballistic Mis- project.* siles Agency, will tell us how the "Pro- As a fitting conclusion of this series of pulsion Engineer Views Space Travel." discussions, Dr. Hubertus Strughold of the Professor Walter Orr Roberts, High Al- School of Aviation Medicine, Randolph Air titude Observatory, of the University of Force Base, Texas, will discuss the question, Colorado, will discuss "The Astronomer's "What are the Possibilities of an Inhabitable Views." Extra-Terrestrial Environment Reachable Dr. Heinz Haber of the University of from the Earth?" California, Los Angeles, will comment on "The Astrophysicist's Views." *Dr. Hagen was not present to read the Scott Crossfleld, test pilot for North report included in this symposium--E~IToR. 480 ~VIATION ~V~EDICINE The Propulsion Engineer's Views BY KONRAD K. DANNENBERG The purpose of this presentation is to that air molecules at the 250 mile peak al- analyze the status of existing-propulsion titude of the Wac Corporal are so rare that systems and their usefulness for extra-at- there was less air than is present in the best mospheric flight. First, a definition of the vacuum tubes. Today's knowledge can pro- extra-atmospheric portion of flight would vide marl with the transportation to venture be in place. Ninety-nine per cent of the into space right now. total air is contained within a 50-mile shell, and this coincides with the upper border of STATE OF THE ART the stratosphere. However, there is still Calculations have shown that conven- noticeable air resistance at this altitude tional power plants can do the job. New especially on high speed bodies, such as power sources should presently be viewed meteors and rocket ships. Not until 120 as possible improvements but are not a miles are exceeded is the atmosphere so thin necessity. Today's designs for solar and that it no longer offers detectable resistance nuclear power generators are very heavy to a traveling object, thus defining the mini- and, therefore, inefficient. It is generally mum altitude of manned space flight for expected that a 21-pound satellite will take short-lived satellites. to its orbit in late 1957 or early 1958. Im- The region beyond 120 miles is called the proved designs will permit several hundred exosphere. It has been demonstrated that pounds to be thrown into the orbit and rockets can move through it at great speeds. should follow shortly. In the early 1960s The lower border of the exosphere was we should be able to accelerate several reached by high altitude firings of single- thousand pounds to a velocity which would stage V-2 rockets in Germany in 1944 and permit any desired orbit, the altitudes of in the United States in 1948. More recently which will be determined by the satellite's a Viking rocket rose to approximately 160 specific mission. miles. A Wac Corporal launched as a For example, as an assembly point for second-stage from a V-2, reached a peak al- manned space ships, Dr. yon Braun pro- titude of 250 miles in 1949, thus traveling poses a celestial route 1,075 miles above the well within the exosphere. Newspapers late earth. Such a satellite would complete a trip in 1956 reported another flight of a multi- around the earth every two hours, which is stage rocket. Unconfirmed reports claimed desirable for observational purposes. It a peak altitude of about 600 miles which would orbit well beyond the atmosphere, and would then extend well into the upper re- would provide an excellent stepping stone gions of the exosphere. The precise borders for further progress into space. Vehicles of this outer atmospheric layer are un- taking off from such a satellite to go to the known at present. It simply "thins out" moon and to neighboring planets would need until there are no nitrogen or oxygen mole- only small power plants because the weight cules left. It is believed by many to extend of the ship does not need to be lifted off up to 700 or 800 miles. the earth's surface. Thrust ratings lower Propulsion units, for all practical pur- than the ship's weight are normal. It can, poses, encounter physical conditions of ex- therefore, be said that once propulsion prob- tra-atmospheric fl igh t when traveling lems of manned spaceships to extra-atmos- through the exosphere. It should be noted pheric orbits have been solved, there should be no major obstacle hindering the propul- Mr. Dannenberg is director of the tech- sion engineer to step into lunar space, or nical liaison group of the U. S. Army Bal- listic Missile Agency, Redstone Arsenal, even into the adjacent interplanetary space Alabama. of our two neighboring planets. OCTOBr.R, 1957 481 PROPULSION ENGINEER'S VIEWS--DANNENBERG ENERGY PROBLEMS quate, if one is willing to limit travel to the adjacent interplanetary space. The vast difference in energy level be- tween the earth's surface and space creates SPECIFIC IMPULSE the primary problem. To leave the gravity The "specific impulse" tells us how much field of the earth permanently with an thrust is obtained while consuming one escape velocity of 7 miles per second pound of propellant per second. A high would require 14.9 Kcal/g, whereas to orbit specific impulse is, therefore, desirable be- at an altitude of 140 miles at a circular cause it results in a smaller rocket having velocity of almost 5 miles per second only the same operational capabilities. However, 7.6 Kcal/g. would be required. Energy the specific impulse is not the only criteria levels presently of interest are in this span, for the desirability of a propellant. High We have a number of fuels which yield the density, for instance, permits one to carry desired amounff of energy; however, they the same amount of energy in a smaller have to be used with oxygen or another propellant and tank package. Very dense- oxidizer. This in turn cuts approximately in propellants may even result in decreased half the yield per gram of mass. Further- dimensions and weight of the rocket en- more, we must package our propellants in gines.