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Aviation History
1951
1951 - 1240.PDF
FLIGHT, 29 June 1951 Fig. 16. The U.S. submarine "Carbonero" launching a guided missile. Such vessels operating "flying bombs" and short-range rockets could seriously menace the United States. They would also be effective "command posts" for controlling missiles over long range. The air defence rockets we are developing today are simple devices compared with the type of missiles envisaged. A rocket capable of catching and destroying another rocket will be larger, faster and longer ranging, its control system more sensitive and rapid in response. A radar system will be required to detect the oncoming enemy missile before it reaches the peak of its trajectory and to trigger off the intercepting rocket. In the same way that a command system will represent the course of bomber and missile and guide the latter to its objective, so will tracking radar follow the course of each rocket and, in conjunction with a computer, aim the defending missile. When it is close enough to the invader, it will be detonated by a radio-fuse. In case it carries an atomic warhead, the incoming missile must be halted as far from its objective as possible. When it is considered that the A-4 rocket was in flight for only five minutes during the whole time from launch to impact, the magnitude of the problem can be appreciated. And, of course, several missiles will probably have to be dealt with simultaneously. Rocket missiles capable of high accelerations, and a guidance system to produce the necessary split-second response, are fore- most requirements. Indeed, all the most difficult problems met in the development of rockets capable of intercepting bombers are magnified many times—exactly how many we can only properly judge when we come to tackle them. In the opinion of the writer, the Americans have made a valuable start by conducting high- altitude research and thereby gaining experience with large rockets. How they began in 1946 with adapted German A-4 rockets and built up their high-altitude programme is well known, and it is in many ways unfortunate that British research was not allowed to follow similar lines. Considerable stores of A-4 equipment fell into, our hands after the surrender, and much useful work was under- taken by the Army at Cuxhaven, using German personnel, to rebuild damaged rockets and to provide complete servicing and launching facilities. In fact, what might have been the basis of a firm research foundation was built up within the space of a few months, but apart from a critical report on the accuracy of long- range rockets (which in the tests had been aimed at targets in the sea) and a 40-minute film,* there appear to have been few material results. So much has already been written about the A-4 rocket, particularly by the late W. G. A. Perring in his paper, A Critical Review of German Long-range Rocket Development (Journal of the Royal Aeronautical Society, July, 1946)9 that nothing need be added here. Not so widely known are the methods proposed for extending the range of the A-4, first by the simple addition of wings (the A-9) and secondly by means of wings and a powerful rocket booster (the A-9/A-10). Although it was later intended to employ a heavier fuel load, lighter construction and an improved propulsion unit, the proto- type A-9 (Fig. 17) was essentially an A-4 with swept-back wings and enlarged aerodynamic control surfaces. Preliminary work on the application of wings to rockets had previously been carried out with the A-5, the small (25ft long) prototype of the A-4, which developed a thrust of 3,300 lb for 45 sec. The addition of 75 sq ft of horizontal wing surface would not have converted the A-4 into a rocket aircraft. Take-off was precisely the same as for the A-4 in that the vehicle rose vertically before being eased into a 45-deg angle of climb. At the time of power cut-off (after about 60 sec), the wings would have no effect in the highly rarified atmosphere in which the rocket moved and it would then follow a ballistic trajectory. On the downward leg of the curve, however, air density would build up sufficiently for the vehicle to regain control (by virtue of its gyro-controlled aero- dynamic surfaces) and to be pulled out of its dive. Whereas at take-off the rocket weighed 12.8 tons, it now weighed about four tons and could operate efficiently as a supersonic glider. * "The German A-4 Rocket," Crown Film Unit. It was estimated that with the same A-4 type warhead, the bombardment range would have been increased from approxi- mately 190 miles to approximately 370 miles, a distance which could be covered in 17 minutes. There is, of course, one big disadvantage in using winged rockets offensively in that, in order to obtain protracted flight, the approach velocity "on target" at the end of a slowly decelerated glide will probably be subsonic. The interception problem is thereby greatly eased. Only one or two examples of the winged rocket were produced. In tests made during the winter of 1944-45, a first firing was unsuccessful because of premature power cut-off. The second A-9 operated satisfactorily, however, climbing under perfect control, and it was only after cut-off that the weapon started to rumble. Irregularity in the flight path at this time was accepted, because once the motor closed down the gas-vanes acting in the nozzle could no longer control the rocket, and the atmosphere was too tenuous for the aerodynamic surfaces to be of any use. However, the missile possessed "arrow stability" and, upon falling back into denser air, would regain the correct flight attitude. In an attempt to improve the all-round stability characteristics, the project was passed to the Volkenrode establishment for a detailed aerodynamic study to determine a wing configuration with minimum travel of the centre of pressure over the whole speed range. A delta-wing layout was eventually chosen, but the war ended before development could proceed. The delta-wing A-9 is bound up with another, more ambitious project known as the A-9/A-10 (Fig. 18): its object was nothing short of extending the range of the delta-rocket, launched from Europe, to the Atlantic seaboard of the United States. The technique of launching one rocket from another in flight, as was proposed here, is known as the "step" principle. Several steps can be employed which drop off as soon as they exhaust their fuel and impart their impulse to the steps ahead. In this way, no dead-weight in the form of tanks, motors and rocket structure is carried a moment longer than necessary. An example of a step- rocket employing solid fuel is seen in Fig. 19. It was used on a limited scale by the Germans in the closing months of the war from Zwolle in Holland against Antwerp and, for a warhead of 88 lb, it had a range of approximately 140 miles. Fig. 17. The second— and only successful— A-9 on the launching table at Peenemunde, December, 1944.
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