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Aviation History
1956
1956 - 1713.PDF
FLIGHT, 7 December 1956 MISSILES THAT THINK ... too slow. In the stirring days of the Battle of Britain, plotterswould hold telephones to their ears, watch cathode-ray tube faces and push counters about on maps. Today all data transmissionfrom the early-warning sets is entirely automatic, as is the whole process of feeding information to the second and third stages andto the missiles themselves. In fact, there are grounds for believing that there are air-defence systems already in being which candefend a country though "untouched by hand." Such a system has to be not only entirely reliable, but it hasto make a number of vital provisions which may not immediately be apparent. Some of these are: every target must be engagedby at least one SAM or AAM; the total defensive force must be properly distributed among the total raiding force; only justenough must be thrown at each target to ensure its destruction; no SAM tracking set must be able to lock on to a friendly fighter(and, by the same token, no AAM fighter must be able to shoot down either itself or another defending fighter). A further criticalfactor is that the raiding force must be assumed to bear nuclear weapons, any one of which could create destruction of unparalleledconsequence. For this reason every single attacker has to be not only destroyed, but destroyed before it can release what it maybe carrying. Means must therefore be provided to guard against unserviceability or any other failure in any part of the air-defencesystem. The missiles themselves must also be far more reliable than manned aircraft are at present. Statistical approaches areused in the development of weapons to ensure that such a require- ment will be met in practice. Statistical reliability study mightshow that a given target could be destroyed by 1.2 missiles—so in practice two would have to be fired. The Missile Itself. Some people, including the author, findguided missiles of intense interest. There is much that one can learn from them for, by the nature of things, they are at least onegeneration ahead of aircraft. Furthermore, their inbuilt intelli- gence is sometimes of a truly remarkable order and the develop-ment effort and workmanship which goes into them is altogether exceptional. It is only unfortunate that their reason d'etre isat present purely destructive—although missile development has greatly facilitated the design of upper-atmosphere research vehiclesand earth satellites. Basically, a missile is a synthesis of five or six factors. Theintangible factor of aerodynamics must be given full weight in the earlier stages of the design, the tangible aspects of structure, guidance and control, propulsion and warhead being the mainsub-divisions of the eventual missile. All these factors interact to a degree which surpasses that found in aircraft. Having fewtraditions, the missile designer is not deterred by a bizarre-looking creation; in fact, it is already clear that guided missiles accept morevariety in configuration than do aircraft. Aerodynamics. The majority of missiles are not purely ballisticrounds but fly with the aid of wings. (At Mach numbers greater than 4, however, it is practicable to generate sufficient lift fromthe body alone.) Few missile designs are influenced in any way by the requirements of subsonic flight; nearly all current weaponsaccelerate very rapidly to a high supersonic speed and maintain that speed for the remainder of their existence. It is thereforepossible to accept a wing loading several times greater than any admissible in aircraft and the wing can therefore be propor-tionately smaller (wing loading is determined by the worst com- bination of the maximum lateral acceleration required at topaltitude). Aerodynamic surfaces can be of truly supersonic profile. Elsewhere in this issue are recounted many of the factors whichhave to be considered by a missile designer. The author of that article makes it clear that although both birds and aircraft useonly one set of wings (placed substantially in the horizontal plane), missiles can manoeuvre far more effectively with two sets, mutuallyperpendicular. It normally makes little difference which part of the missile is uppermost and, in fact, some current designs aredeliberately arranged to spin slowly about their longitudinal axis. Structure. This is one of the few aspects of missile design uponwhich it is possible to comment at some length. We have, there- fore, reserved this factor as the basis of a special article entitled"Missile Design" on pages 885-889 in this issue. Guidance. There are many who would claim that the develop-ment of the guidance sysrem was, in most missiles, responsible for the expenditure of more man-hours than everything else puttogether. Although not always correct, this belief reflects the very considerable problems involved in making exceedingly com-plex and densely packed systems function with impeccable reli- ability, even when subjected to most adverse environmentalconditions. There are several types of guidance, which are cata- logued below under typical names. Direct Command Guidance (Fig. 1, p. 880). This is sometimesconsidered the most elementary form of guidance, since the missile itself has no power of "thinking" whatever. Instead it is steeredby instructions transmitted to it by any of several methods. Typical of the most elementary forms of command guidance is A Wellsian scene at Redstone Arsenal, a major centre of U.S. Army missile activity. A Jupiter A ballistic weapon is being mounted—by what must be the biggest crane in the missile business—on a vertical rig for night firing. For scale, the Jupiter A is 69ft from nose to tail.
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