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Aviation History
1945
1945 - 1785.PDF
264 FLIGHT SEPTEMBER 6TH, BOMBERS OR ROCKETS? V.2 would have if gravity and air drag were absent.) Using an atomic drive, we have suggested that the exhaust velocity might = 335 X 7,000 ft./sec. at least, since an atomic fuel should give not less than 335 times the exhaust velocity of an explosive fuel. = 2,350,000 ft./sec. at least. In other words, the mass ratio for the same range and payload i.e., for the same value of vo) as V.2 would be given by 8,3ooft./sec. Mo M = 1.004 at most, instead of 3.0 ! There would no longer be any argument about the " economy " of rocket projectiles—the fuel load required would \£ negligible (36 lb. instead of 8 tons !). To look at the matter in another, and even more striking, way, we can work out what final velocity our hypothetical rocket with atomic drive wpuld have if we gave it the same mass ratio as V.2. .,, . vo (ft./sec.) 2,350,000 ft./sec. 3.o » e 2,350,000 .'. vo = 1,760,000 m.p.h. This would be far more than sufficient, even after allowing for gravity and air drag, to fling the projectile to infinity ; 1,760,000 m.p.h. is vastly in excess of the escape velocity from this planet. Intermediate mass ratios between 3.0 and 1.004 would therefore give an atomic rocket any desired range. Any point on the earth's surface could be reached from any other point. Readers wilkno doubt be saying, " All that is all very well, but wbttt justification is there for the assumption that atomic energy could be used for reaction propulsion ? " The writer can make only the following answers, which he finds personally satisfying and can only hope others will, too. Sceptical Discoverers 1. Kvery time a new scientific discovery is made, it is curious that those who make it are often the most sceptical of its practical application to particular problems. Hertz first detected radio waves, but scoffed at the suggestion that they might ever be used for tele-communication. Only a few7 years ago, some of the very men who have now helped to produce the atomic bomb were deprecating suggestions that atomic energy would ever be released on anything but a laboratory scale. (It is well appreciated this is not a scientific argument, but it—and p*mt (2) below similarly— constitutes, 1 believe, a significant consideration. 2. All those who have ever considered the use of rocket propulsion for any duty have realised that they are dealing fundamentally with an energy problem, of obtaining suffi- cient stores of energy to accomplish the work required in a practical manner. The release of atomic energy unlocks for us the door to stores of power immeasurably greater than any we have known before. It is surely very improb- able that these two facts will never be associated, that the second will not provide the solution to the first. 3. Perhaps an atomic drive might be provided by the reaction from radiation pressure generated by the atomic explosion. Perhaps the reaction might be provided by a stream of minute sub-atomic particles travelling at immense velocities, giving a jet of very small mass^emd huge speed. This would have very low propulsive efficiency, except at incredible flight velocities, but that would not matter where such large energy stocks were available. In either case, the " jet" so generated would be even more deadly than the gas blast from a V.2 ; presumably the problem would reduce to making it uni-directional. Perhaps this might be achieved by some technique of using electric or magnetic fields surrounding the propulsive " nozzle " ; perhaps some of the energy of the atomic explosion could be used to provide these fields—rather as some of the gas energy is used in the turbine of a Whittle unit to drive the compressor, which is a necessary component of such present jet engines Perhaps the atomic explosion could be used to heat some 1* working fluid which would itself provide the propulsive jet Perhaps—very probably !—none of these things, but something else. Non-Military Possibilities of Rockets The uses of rocket projectiles for ultra-high speed ter- restial transportation, for providing stations for many purposes high above the earth's atmospheric limits, and for interplanetary travel, have been considered by many technicians. With atomic drive, all these Wellsian dreams would become practical of achievement. Whereas, so far, they have been bare technical possibilities, attainable only on a marginal basis of practicability due to the huge fuel loads required, they would then become what might be termed (for want of better words) commercial propositions. Anyone who feels disinclined to take seriously mention of such developments would do well to consider the advent of radar, jet propulsion, V.2 rockets, and finally, the atomic bomb, during the last short six years, to say nothing of the development of aviation itself since the Wrights first flew in 1903. The fascinating possibility last mentioned, namely, space. > flight, would be an achievement of outstanding moment, truly worthwhile in the real sense of that expression relative to man's development, and with the greatest practical and philosophical impact on his outlook. Its realisation depends essentially on imparting to a projectile with reasonable acceleration, a velocity termed the " velocity of liberation " or " escape velocity." Once a ship was moving with this speed (= 25,000 m.p.h. , it would never fall back to earth even after the motors ceased thrusting, but would travel outwards into space with ever diminishing, but always positive, velocity, free to be manoeuvred into the gravitational field of any other planetary body its crew desired to visit. After allowing for the effects of gravity, air drag while traversing the atmosphere, fuel reserve for manoeuvring, landing and return journey, one might very conservatively guess that an equivalent " required velocity at end of powered flight" might be as much as 100,000 m.p.h. instead of the bare 25,000 m.p.h. escape velocity. In other words, the fuel needed to do the actual job -required after allowing for these factors, could be assumed to be equivalent to that needed for the alternative task of imparting a v0 of 100,000 m.p.h., instead of 25,000 m.p.h., under conditions where these other factors were absent. (It could be shown that this is a very severe assumption). Reverting to the simple formula used earlier, we would then have : M 147,000•^-j- = e 2'35°.OO° f or an atomic-driven space ship = 1.065. i.e., the fuel weight would be only 6\ per cent, as much as the final landing weight of the ship. Even the most optirr^'^j of estimators ha-^ suggested that a fuel weight of many times the final landing weight would have been neres sary with the present types of chemical -fuelled rocket motors. As a concluding note, it is relevant to this article to quote a remark made some years ago by a friend of the writer who is now in the R.A.F. and who shares an interest in this absorbing subject. This man (one Fl./Lt, A. C. Clarke) then observed, " The release of atomic energy will make interplanetary travel not only possible but imperative." At the time, the wit of this epigrammatic remark seemed more to the point than its practical importance ;/t now that this situation is possibly reversed. SURPLUS R.G.A.F. AIRMEN'S helmets, gauntlets, bl ildd l N(E<|UlPI g gogfeleS a^4 ineifs"Tesrffier belts are included in a list oi .goadi* declared surplus by the R.C.A.F. and will be nationa%i distributed through whole- salers/By the War Asset!^QSigoraticfb. / There are 30,000 leath/r helmets, a»<TT5^|>o pairs o< gauntlets. About 20,000 belts!are to m^rgeased. Only new vflts are to be sold in Canana, the othergoing with clothing for relief in Europe.
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