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Aviation History
1951
1951 - 1327.PDF
FLIGHT EVOLUTION of the GUIDED MISSILE... The missile as finally developed had a length of 16ft, with a diameter of I2in, and a gross weight of 665 lb. Power was supplied by a.liquid-propellent rocket unit manufactured by the Aerojet Corporation which produced a thrust of 1,500 lb for 45 sec. A spontaneously combustible propellent combina- tion comprising nitric acid as an oxydizer and aniline as a fuel was employed, the latter being fed through a jacket sur- rounding the combustion chamber for the purpose of cooling prior to injection. Compressed-air instead of the more con- ventional nitrogen was used to displace the propellent to the motor. A modified naval rocket known as the Tiny Tim became the booster, changes being made in the nose shape and fins to suit its specialized task. The thrust was also increased— from 30,000 lb for one second to 50,000 lb for a little more than half a second. As this would drive the rocket 216ft, which was considered a prohibitive height for a launching tower, it was decided to use a 100-ft tower and, for the first time, to allow part of the burning period of the booster to take place in free flight. The WAC Corporal was test-fired at the White Sands Proving Grounds, New Mexico, during September and October 1945. Tracked by radar, the missile reached an alti- tude of approximately 43.5 miles in vertical flight. The sub- stantial increase in altitude over that originally planned was primarily the result of weight economies made as the design matured, and the added impulse provided by the Tiny Tim booster. In its initial tests, the WAC Corporal carried meteoro- logical instruments with an automatic parachute device allow- ing the nose cone to be detached in flight and recovered. Later, a radio-telemetering system was developed which enabled instrument readings to be transmitted directly from the rocket to ground receiving stations. High-altitude research with the A-4 (V-2) rocket (Fig. 21) began in 1946, after the U.S. Army Ordnance Department had completed plans to launch a series of captured rockets for military appraisal at White Sands. The possibility of improving the vehicle's utility by using the warhead space to carry recording equipment was discussed in January 1946, and the work of producing a suitable instrument compart- ment for the rocket was undertaken by the Naval Research Laboratory. The Johns Hopkins University Applied Physics Laboratory at Silver Springs, Md., was assigned to perform basic studies of the physics of the upper atmosphere and to provide the instrumentation. The A-4, as is now well known, is a self-launching rocket requiring no guiding tower or booster to assist it from the ground. It has a total length of 46ft and is 5ft 5m in diameter. The launching stand is merely a platform on which the rocket rests before the motor is set in operation. A total propellent load consisting of over 19,000 lb (alcohol and liquid oxygen) is carried and the motor has a firing time of approximately 60 sec. With a combustion chamber pres- sure of about 15 atmospheres at 2,500 deg C, the exhaust velocity is approximately 6,56oft/secj and the thrust is 28 tons. Acceleration rises to 6 g—with a velocity of 5,oooft/scc (3,400 m.p.h.)—just before burn-out, which occurs at an altitude of 100,000ft. Altitudes of between 65 and 114 miles have been attained with flight times averaging eight minutes> and periods of four to five minutes have thus been spent above the balloon limit. Launching of the missile is controlled from a block-house with 15-in reinforced-concrete walls, located 1,oooft from the firing point. This is the nerve centre for the entire opera- tion, where starting circuits for the rocket motor and instru- mentation all terminate. Communication is maintained between the block-house and all the observing and recording stations, which are disposed in various parts of the proving area. The instrument-head provides 19.6 cu ft of space for the various components of equipment, which are mounted in a "pyramid" frame with the smaller and lighter units at the top. From time to time, space has been made available in the after section of the rocket, and although high tempera- tures and vibration have been encountered due to the close proximity of the propulsion unit, components located there have usually been recovered from the impact wreckage in reasonably good condition. The work of tracking the A-4 rockets and recording the trajectory data is shared by the Ballistic Research Laboratory of the Aberdeen Proving Ground, the Signal Corps, and the New Mexico College of Agriculture and Mechanic Arts. Measurements made by the B.R.L. include position, velocity and acceleration (as functions of time), aspect, point of im- pact, and duration of flight. The Laboratory also provides time signals both on wire and radio communication channels for use by the various observers in co-ordinating measure- ments with the trajectory data. Radio, radar, photographic and visual equipment are used in making trajectory measure- ments. Although physical recovery of instruments after impact has proved useful, it has not been completely reliable, particu- larly in the early phases of the programme. For example, in the case of a rocket fired on May 10th, 1946, an intensive search of the impact crater and surrounding area failed to discover any part of the instrumentation. The need for re- cording data in flight and transmitting it directly to a ground receiving station was obvious; and the subsequent incorpora- tion of a radio telemetering system, developed by the Radio Sonde Section of the Naval Research Laboratory, placed an entirely new aspect on the experiments. The Laboratory's telemetering system was first installed in a rocket fired on July 30th, 1946. Briefly, it is a time- modulated system which delivers higher peak power at a lower average power consumption than a continuous carrier system. It operates at about 1,000 mc/s, a frequency high enough to penetrate the ionosphere. The data voltages de- rived from experimental equipment are converted into time intervals defined by voltage pulses, and these are transmitted from the rocket and received by ground stations which decode and record the data. Several methods, including recording on a moving strip of photographic paper and direct fuming of the meter panel, are used for recording the voltage data. . Instrumentation. Cone Fuel Tanks and. Propulsion Unit - Telemetering Transmitter Antennoe Receiving Antennae Fig. 11. General arrangement diagram of the Aerobee which, designed generally on the lines of the WAC Corporal, embodies greater stowage volume for instruments. The rocket is designed to reach an altitude of about 18 miles and a speed of 2,790 m.p.h.
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