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Aviation History
1951
1951 - 1451.PDF
"4 Evolution of the Guided Missile . . . sensibly, to take up an orbital path around it. The latter result would, of course, be more exacting in the control technique, but nevertheless infinitely more worthwhile as a scientific experiment. It may even be possible, with com- paratively light equipment, to transmit radio-pictures of the lunar surface back to the earth, including large areas which are hidden from our direct view. However, this interesting prospect is not likely to arise very early in the development of space-missiles, because of the heavier payload and the delicate control and telemetering techniques involved. In developing any study of space-flight, one is often confronted by questions which to the layman must seem the last word in logical contempt. How, for example, can we discuss so calmly a moon-flight extending 240,000 miles when the farthest we have so far been able to project a rocket is 242 miles? Clearly, to the uninformed, this does appear a most plausible argument. With space-flight, however, one must emphasize that, given unlimited time, it is not distance that matters but velocity, for a rocket that can attain a minimum of 7 miles/sec, will defeat the earth's gravity and never return. This velocity can effectively be built up by using a series of chemical step rockets. The booster steps jettison pro- gressively, contributing a high fraction of escape velocity to the small instrument rocket in the nose which achieves final release from the earth. Having served their purpose in building up velocity, the boosters drop back to the ground. Meanwhile, the final step will coast on across space without any further expenditure of energy. A paper by the American investigators Malina and Sumrnerfield has shown that escape velocity can be obtained by guided-missiles with any number of the available pro- pellents by proper choice of the number of steps. As an example, an acid-aniline rocket having a gross mass of 823,000 lb, and consisting of five steps, could project away from the earth a payload of 10 lb. Alternatively, an acid- aniline rocket having ten steps could produce the same result for a gross mass of 136,000 lb. In both these cases, the , - Structural wt. structural factor Structural ^t+propdlenn^.was taken as 0.20. Proportionately better initial take-off masses are derived in other selected cases using oxygen-ethanol and oxygen- hydrogen in which, incidentally, for the latter, the structural factor was increased to 0.33. The instrumental device proposed, which it was thought could be built within the 10 lb limit, was a small radar-beacon transmitter and an electrical pick-up for measuring a single quantity—cosmic ray intensity, for example. Radar signals could be sent to the rocket during flight by means of a ground transmitter similar to that which has already been used to reflect back echoes from the moon. The radar beacon in the rocket's final step is intended to "reflect" the signal back to the receiver on earth to provide data on the missile's trajec- tory. The values of cosmic ray intensity taken during flight could be incorporated in the return signal. This possibility alone puts an excellent case for the early development of extra-terrestrial missiles, and with the further prospect of a light solar-regenerator, converting solar heat to electrical energy in a continuous operating cycle, transmission between the rocket and the earth should be possible over much longer periods. First, however, must come the non-returning earth satellite vehicle, and useful information on radiation phenomena should be obtained by a similar system of transmission, to provide, for example, a check on the periodic rise and fall in the intensity of cosmic and ultra-violet radiations. Even the initial results will have much more than academic interest and indeed are likely to bring immediate benefits in the fields of electronics and meteorology. Finally, to take the case of an oxygen-hydrogen "escape" rocket with this same 10 lb payload, we find that with five steps the take-off mass reduces to 8,320 lb. This reduction FLIGHT Fig. 26. The ^close-orbit earth satellite rocket" described in this article. Constructed in three steps, with expendable tanks, the gross mass would be approximately 325,000 Ib, and the instrumental payload 110 Ib. in mass as compared with the acid-aniline five-step rocket (823,000 lb gross) emphasizes the importance of developing practical high-performance rocket systems, but it is nevertheless interesting to bear in mind that, with careful design, experiments of a unique and fundamental nature could be carried out in interplanetary space with present-day conventional propellents. It is, of course, Likely that such research vehicles will arise from the RAND studies, for once even the primary orbital vehicle is established, the step beyond that to a guided-missile capable of liberating itself completely from the earth is comparatively small. To obtain these deeper penetrations into space will require not only multiple-step rockets, but even more drastic tech- niques (such as expendable construction of the individual steps) where the projection of heavier payloads are involved. In a paper recently presented to the British Interplanetary Society by Messrs. A. M. Kunesch, A. E. Dixon and the present writer, a method of construction was outlined in which the forward portion of the rocket is broken down into separate tank stages which jettison progressively as propellent is consumed. Each stage consists of two half-cylindrical tank bays with integral structure, held together with explosive ties, which, on assembly, form an efficient hull. The tanks are pressure-balanced, permitting the use of light diaphragms for the backing panels. To afford some streamlining effect in the early part of the ascent and to provide a light method of jointing, since all the tanks are faced together axially, the separate stages have conical noses. End loads would mainly be transmitted through external jointed longerons to which the tank bays are directly anchored. In order to obtain a practical evaluation of the expendable- tank idea, a design study was made of a satellite rocket intended to reach its orbit between the altitudes of 600 and 700 miles. The rocket envisaged (Figs. 26 and 27 and Table III) is a three-step vehicle with the component rockets situated one within the other. In no case does the design exceed the limitations imposed by current engineering prac- tice, and the propellent is taken conventionally as liquid oxygen and alcohol. The conservative nature of this study is
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