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Aviation History
1956
1956 - 1718.PDF
882 FLIGHT, 7 December 1956 Many thousands of missiles have been made by the Santa Monica division of the Douglas Aircraft Company. This overhead conveyor line takes Nike Ajax weapons through final assembly. Compared with the picture on the left this view of a bay in the Chrysler plant in Detroit emphasizes that big missiles come in smaller numbers. These are warheads for Redstone (Jupiter A). Thoroughly covered in frost, this Canadian Velvet Glove air-to-air weapon is roughing it in the Westinghouse plant at Hamilton, Ontario, after a test at —100 deg F at a pressure equivalent to 95,000ft. Sole British guided weapon^ of which photographs may be published is the Fairey Fireflash. This fluorescent-red-painted example is seen on its transport and lifting (by manual screw-jacks) trolley. MISSILES THAT THINK . . . less, many components will invariably get hot enough to fry anegg or even melt solder. Air Pressure: Static pressure may drop from atmospheric to lessthan 1 lb/sq in in a period measured in seconds; and in three or four seconds the dynamic head may jump from zero to perhaps550 lb/sq in. In general, the missile accessory business parallels that whichsupports the development and production of aircraft. Each com- plete weapon contract is tied up between the purchaser or sponsor(the Ministry of Supply in Britain) and the main contractor. The latter—probably an aircraft or electronic firm with an appreciableexperience of such work—investigates the mathematics of the requirement and comes up with an initial design study. Prob-ably at a fairly early stage are the accessory manufacturers brought in. Each is given a fairly comprehensive specification underliningthe conditions under which their parts will operate, but it is unlikely that they will be told full details of the programme orany information not concerning them directly. The accessory maker must, however, say what his part will weigh and how bigit will be; and, having committed himself, he must adhere to his estimate, since redesign at a late stage may be disastrous in itsresults. Most careful attention must be paid to material specifications.Not only must every part be fully capable of standing up to the extremes of temperature and vibration, but all components mustbe mutually compatible—there must not, for example, be any trouble from differential rates of expansion. It may be possibleto evolve items from units originally designed for aircraft, but fundamental changes may be necessary. Mechanical strength mayneed to be increased, and the rigidity of movable or cantilever parts may need to be increased, to take the natural frequency outof the vibratory ranges experienced and thereby prevent resonance.To take a particularly simple case, it is frequently found that a simple potentiometer for a piloted aircraft can be made from what might be termed "traditional" materials. The windingcan be based on a plastic former, and if any turns have to be blanked off this can be done readily enough by attaching astrip of wire to the required turns with ordinary soft solder. For missile use several changes would have to be made to sucha unit. The former for the coil-winding would have to be of ceramic material, resistant to high temperatures. For the samereason, something would have to replace the soft solder; and any input or output wires would have to be insulated with glassbeads and not with rubber or other conventional substance. Even the potentiometer wiper-arm would have to be redesigned, andmade stronger—so that it could bear high accelerations—and stiffer—so that it could not resonate in sympathy with a missilenatural-frequency. Once the basic design appears to be correct, the standarddevelopment procedure can be applied. If the item is fairly com- plex six prototypes may be made and thoroughly proved, and asuitably modified unit may then be submitted to the prime con- tractor for full laboratory checking. Even if the component iseliminated through some failing, it may well find its way into the missile-system ground equipment (which is an even bigger fieldthan designing for missiles themselves, and one with a largely different set of problems).Power Systems. Nearly all the accessory power needed by a missile can be provided by any of four systems: stored electricity,air or gas bottles or gas from a slow-burning charge, ram-air or a self-contained source.Electrical accumulators provide power in the form in which much of it is required. A direct-current system can, in fact,supply direct pick-offs for telemetering signals. An a.c. system may be more miniaturized but output amplification may berequired. The accumulators are normally arranged in potted, shock-resistant banks, each cell having a very high capacity forits weight or bulk. A recent development is the self-activated, chemically-heated battery. A recent American example, weigh-ing 10 oz and fitting a 2in cube, gives 25 amp at 9 V; it has an established shelf life of a year. [Cont. on p. 883
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