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Previous chapter: Kummersdorf
During 1933, after months of experimentation with rocket engines attached to a static test bench in Kummersdorf, a fresh team of engineers led by Wernher von Braun, attempted to build its first complete rocket. In line with military secrecy, the rocket was designated Aggregat-1, or A-1 for short.
The A-1 rocket was apparently equipped with a 2B.2 engine, an intermediate design, which had emerged in the course of endless experimentation with the shape of the combustion chamber. As all other engines in the B-series, it was regeneratively cooled by its own fuel, which would flow through a special cooling jacket enveloping the combustion chamber. Both propellant components with a total mass of 85 pounds were forced into the combustion chamber by pressure from a nitrogen tank. In its turn, the combustion chamber was placed inside the fuel tank. According to some sources, such a design was dictated by the need to shorten the vehicle, but more likely it was another effort to prevent overheating of the combustion chamber. The concept was apparently first developed by Arthur Rudolph and Alfons Piesstch under contract with the army. (213)
From the outset, a spin stabilization, so familiar to the artillery engineers, was proposed to keep the rocket on course against the wind or uneven engine thrust. However unlike with an artillery shell or a solid-propellant missile, it would not be possible to spin the entire vehicle, since the resulting centrifugal force would press liquid propellants to the walls of the tanks leaving the engine dry. To solve the problem, Dornberger proposed to equip the rocket with an 85-pound rotating nose.
Von Braun subcontracted the development of a gyroscope to Kreiselgerate GMBH (Gyroscope Company). It was led by a charismatic Austrian naval officer Johannes Boykow, the author of numerous patents for gyroscopes, controlling torpedoes and naval firing control systems. When Von Braun first explained Boykow what kind of job he wanted his gyroscopes to do, he reportedly said, "I've been expecting a call like yours for many years and I've prepared for it." (296)
A three-phase current motor, which would be spun before launch up to 9,000 rotations per minute from a ground source, would then run on the inertia during the rocket's brief ascent. (315) If Von Braun accurately recorded his state of mind at the time, even more sophisticated flight control mechanisms were mulled, but had to wait for the A-1's successors. "Problems such as gyro controls, jet vanes, actuators, cut-off control, feed pumps, electromagnetic valves, turned over and over in my mind," he wrote about the events of 1932. (174)
Although some sources claim that the A-1 was destroyed on the launch pad, it never made it that far. Wernher von Braun described only a single attempt to fire the A-1 rocket. He did not elaborate when and where it happened, but did write that "within half a second of firing it burst into fragments. Delayed ignition detonated an explosive mixture which had accumulated in the combustion chamber." (174) From the lack of details about the expedition to the launch site and from the fact that the rocket's range was too long to fly within Kummersdorf's boundaries, it is clear that Von Braun was describing a static test of the complete A-1 rocket, rather than an actual launch attempt. Based on his statement that the A-1 "had taken six months to build," the mishap probably took place in the second half of 1933.
According to Von Braun, "a second A-1 with improved ignition might have flown well, but certain other factors called for a complete redesign." Developers realized that the rocket was "too nose heavy" in the words of Von Braun's boss Walter Dornberger. (296) The rocket's center of gravity turned out to be very far in front, thus not promising reliable stabilization. The problem could be alleviated by moving the gyroscope into the center of its body, between the fuel and oxidizer tanks. The new configuration was designated the A-2.
A-1 technical overview:
Next chapter: A-2
Writing, photography and illustrations: Anatoly Zak; Last update: October 10, 2008
Page editor: Alain Chabot; Last edit: October 5, 2008
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The combustion chamber of the 2B.2 engine, which likely powered the A-1 and A-2 rockets.