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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Aggregat | 2/5 | https://en.wikipedia.org/wiki/Aggregat | reference | science, encyclopedia | 2026-05-05T13:25:58.892208+00:00 | kb-cron |
== A3 (1935–1937) == Development of the A3 can be traced at least to February 1935 when Major Ernst Ritter von Horstig sent General der Artillerie Karl Becker a budget of almost half a million marks for the construction of two new test stands at Kummersdorf. Included were mobile test rigs, small locomotives, and office and storage space. The A3 plans called for a rocket with an inertial guidance system and a 15 kN (3,300 lb) thrust engine. In March 1936, Generaloberst Werner von Fritsch witnessed a static firing of an A3 engine at Kummersdorf, and was sufficiently impressed to lend his support to the rocket program. Like the earlier A1 and A2 rockets, the A3 used a pressure-fed propellant system, and the same liquid oxygen and 75% ethanol mixture as the earlier designs. It generated its 14.7 kN (3,300 lb) for 45 seconds. It used a three-gyroscope system to deflect tungsten alloy jet vanes. The design was finished in early 1936 and further modifications that made the rocket stable at supersonic velocities were finalized later that year. The shape of the rocket was based on the 8-mm rifle bullet, in anticipation of supersonic flight. The rocket was 6.7 metres (22 ft) in length, 0.70 metres (2.3 ft) feet in diameter, and weighed 750 kg (1,650 lb) when fueled. Fins were included, for "arrow stability", structurally anchored by an antenna ring. The stabilized platform used a pitch gyro and a yaw gyro, connected to pneumatic servos, which stabilized the platform along the pitch and yaw axes. Electrical carriages on the platform acted as integrating accelerometers. These signals were mixed with those from the SG-33 system, to drive the molybdenum-tungsten jet vane control servomotors. The SG-33 was fixed to the rocket, not the stabilized platform, and used three rate gyros to sense roll, pitch and yaw deviations. Two of the jet vanes rotated in the same direction for pitch and yaw control, and in opposite directions for roll control. The guidance and control system was designed by Fritz Mueller, based on Johannes Maria Boykow's ideas, the technical director of Kreiselgeräte GmbH ("Gyro Instruments Limited"). The A3 engine was a scaled-up version of the A2, but with a mushroom-shaped injector at the top of the combustion chamber, based on a design by Walter Riedel. Ethanol was sprayed upwards to mix with the oxygen sprayed downward from jets at the top of the chamber. This increased efficiency and generated higher temperatures. This was the first of the Aggregat rockets to be launched from the Peenemünde area. As part of Operation Lighthouse the first A3 was launched on 4 December 1937, but suffered problems with premature parachute deployment and engine failure, and crashed close to the takeoff point. The second launch on 6 December 1937 suffered similar problems. The parachute was disabled in the third and fourth rockets launched on 8 and 11 December 1937, but these, too, experienced engine failures, though the lack of parachute drag allowed them to crash further from the launch site. They reached altitudes between 760 and 910 metres (2,500 and 3,000 ft), before falling into the sea. According to another source, one A3 reached a maximum downrange of 12 km (7.5 mi) and maximum altitude of 18 km (11 mi). With each launch a failure, von Braun and Dornberger looked for the cause. At first there was some thought of an electrostatic charge that prematurely set off the parachute, but this was largely disproved. Ultimately, the failures were attributed to the inadequate design of the rocket's experimental inertial guidance system and minor instabilities in the body and fin design. The control system was found to be unable to keep the rocket from turning with a wind greater than 3.7 metres per second (12 ft/s). The stable platform gyros were limited to a 30 degree range of motion, and when the platform tumbled, the parachutes deployed. The jet vanes needed to move faster, and have a larger control force, to stop the rolling. The fins were redesigned in the A5, when it was realized an expanding jet plume as the rocket gained altitude, would have destroyed the A3 fin stabilizing antenna ring. After this unsuccessful series of launches, the A3 was abandoned and A4 work postponed, while work on the A5 commenced. According to Dornberger, the A3 "...had not been equipped to take any payload. It was a purely experimental missile." Similarly, the A5 was to be "for research purposes only."
=== Specifications === Length: 6.74 m (22 ft 1 in) Diameter: 0.68 m (2 ft 3 in) Finspan: 0.93 m (3 ft 1 in) Launch mass: 748 kg (1,649 lb) Fuel: Ethanol and liquid oxygen Liftoff thrust: 14.7 kN