Michael Neufeld - The Rocket and the Reich

When Wernher von Braun created Steinhoff’s new division, one effect was to reinforce the tendency toward an “everything-under-one-roof” facility in which corporate contracting was secondary. The new personnel in this area also contributed to the increasingly scientific tone at Peenemünde. Academically trained engineers from the technical universities took over more and more positions, in many cases overshadowing the mere handful of veterans from the early rocket groups, most of whom worked under Thiel. The center’s technical leadership came to be dominated by a remarkably homogeneous group of young diploma and doctor engineers, almost all of whom were born between 1904 and 1914. (The aerodynamicists were the only significant group who were scientists by training; von Braun also had a doctorate in physics but was really an engineer.)

The war only increased the predominance of the academic engineers. The enactment of a civilian draft and the pressure to speed up A-4 development allowed many new specialists to be called to Peenemünde. Personal connections—often through the network of university institutes created after the easing of secrecy restrictions in the autumn of 1939—were frequently the determining factor in who was drafted. (Political connections played no role.) That was one reason why individuals from the Technical University of Darmstadt came to be so prominent in Steinhoff’s division. Darmstadt was also dominant in university research for Peenemünde. Of 238 academic personnel working on contract for the program in January 1940, ninety-two were from Darmstadt. The next largest contractors were the Technical University of Dresden and the Institute for Oscillation Research (Berlin), with forty-five each. 52

Research in guidance and control occupied more university personnel than the other two key technologies combined. This pattern reflected the number of problems Peenemünde had yet to solve in September 1939 if it was to make a guided A-4 feasible. Determining the basic gyroscope and control system configuration was only half the battle. Much additional radio equipment was needed beyond that developed to stop the A-5’s engine manually and eject its parachute. The distances covered by the A-4 and the difficulty of recovering the vehicle meant that Peenemünde had to have a telemetry system that could send measurements to the ground instead of using a movie camera to record an oscilloscope screen, as was done with the A-5. A radio tracking system to measure velocity and position was also needed when the A-4 was out of sight. University institutes, particularly in Berlin and Dresden, made many contributions to the work. Of particular importance was the tracking system developed by Professor Wolman of Dresden. In its final form, it used a ground signal retransmitted by the A-4 to measure the velocity of the missile. Triangulation from multiple sites determined the trajectory. (Just as in the case of a siren, which is higher-pitched when coming toward one and lower going away, the direction and magnitude of the Doppler shift in frequency of the rocket’s signal allowed its velocity to be determined.) 53

University guidance research focused as well on a related problem: how to shut off the A-4’s engine at the proper time to give it the correct range to hit the target. Boykow had wanted to use some kind of integrating accelerometer, that is, a device that integrated the acceleration of the missile over time to measure the velocity. One of the fundamental problems of that approach is that a small error in measurement of acceleration is increased exponentially as it is integrated. In July 1939 Kreiselgeräte revived the idea by proposing a gyro suspended in such a way that it could function as an accelerometer. Under Fritz Müller’s leadership, the mechanism was developed into one of the primary means for determining the cutoff of the A-4. But in the fall of 1939 its potential for success was far from clear. 54

With access to university researchers much increased after the war began, von Braun and Steinhoff launched a number of competing projects. At Darmstadt, two institutes began to develop accelerometers based on other physical principles. Wolman at Dresden, meanwhile, was able in 1940–41 to create an alternative radio method derived from his tracking work. A transmitter/receiver behind the launch site and in line with the direction of firing could determine the velocity of the missile and send the signal to cut the engine off at the proper moment. The signal was transmitted from the ground, and the missile doubled the frequency and then retransmitted it. Ground equipment compared the original with the received signal and automatically sent the command when the A-4 had reached the correct velocity. The Wolman radio and Müller accelerometer methods became the two A-4 engine cutoff systems and thus were essential innovations for the success of that missile. 55

One final and critical piece was needed for the A-4, and it too emerged from Peenemünde’s growing involvement with electronics and radio. Soon after Steinhoff’s arrival, he decided that something had to be done about the effects of wind on accuracy. A wind blowing across the trajectory would push the missile sideways and thereby introduce a cross-range error at the target (see Figure 3.3). The planned guidance systems might successfully stabilize the vehicle and carry out the pitch program, but they could do nothing to detect horizontal movement away from the planned trajectory. Just before or after the September 1, 1939, attack on Poland, Steinhoff met with a member of the Air Ministry, who agreed to cooperate in the modification and improvement of Luftwaffe guide beams for navigation and bomber direction. In addition to the accuracy of the A-4, the difficult problem of guiding the descending glider missile was on the minds of the Peenemünders. Dornberger specifically mentioned in September and October the need to perfect a guide beam for that missile (later called the A-9) in justifying a request to the Luftwaffe for more test aircraft. The air service eventually lent Peenemünde-East three airplanes. 56

Steinhoff agreement’s with his Air Ministry colleague did not have much meaning, however. Neither the Luftwaffe nor corporate contractors had the manpower to shoulder the main burden of work during the war. Thus Steinhoff needed to build a guide beam section in his growing laboratory. How he did so is a good example of the role of personal connections in wartime recruiting. One night in October 1939 Helmut Hoelzer, an electrical engineer working at the electronics firm of Telefunken in Berlin, heard a noise under his window. He saw Steinhoff and Steuding, whom he knew from Darmstadt, plus a younger third man. They invited him out to a bar, and this third man, who was “whistling all the time,” tapping his foot to the band music, and looking at the women, asked Hoelzer mysterious questions about how to guide a flying body—without, however, indicating what kind of body. Hoelzer said he could not answer. Within two weeks he received a civilian draft notice to go to Peenemünde-East, about which he knew nothing, and the first person who met him was the third man: von Braun, technical director of the place at age twenty-seven. Hoelzer was put to work researching guide beams. 57

The one he finally developed, along with his staff, was derived from the blind-landing system of the electronics firm Lorenz. A transmitter 10 to 12 kilometers behind the launch site sent a signal alternately through two antennas a short distance apart. The missile could tell from the strength and character of the signals it received whether it was left or right of the line to the target and would steer its way back to the center. (Technically speaking, it was a guide-plane system, not a guide beam, since it did not control whether the missile was above or below the desired trajectory, only whether it was left or right.) Although this beam was simple in principle, the complications were considerable. A simple steering correction for the position relative to the guide plane would destabilize the missile. As the missile reached the center of the beam, the correction signal would go to zero, but it would still have the momentum to drift to the other side. The missile would then make a new correction in the other direction, with the result that each time the situation would get worse. Thus it was necessary that Hoelzer develop an electronic “mixing device” to calculate additional mathematical terms to modify the guide beam signal. 58