The heart and soul of Kreiselgeräte was its technical director, Johannes Maria Boykow (1879–1935). Von Braun gives a striking description of the man:
Boykow was one of the strangest and most charming characters I have ever met. A former naval officer of the Imperial Austrian Navy, he had seen the whole world and knew how to spin a yarn. Before the First World War, he had quit the services to become a dramatic actor. Drafted back when the war broke out, he became a destroyer captain, a naval aviator and finally got in touch with torpedo development. And it was here that he ran into the problems of the gyroscope which were to concern him for the rest of his life. He acquired hundreds of patents and gradually became the [German] Navy’s No. 1 expert in gyro compasses and… fire control equipment. He was a true genius, but… he did not bother much about the mundane engineering phases of his inventions. His company’s design office often found it necessary to deviate considerably from his original ideas, and therefore the end products but vaguely resembled his initial proposals. Unfortunately, I found this out only after severe setbacks. When I first met Boykow, I was left spellbound by his analytic sharpness and imagination and, being a novice in the gyro field myself, I took everything he said for granted.
By October 1934 Boykow had begun designing what would become the A-3 guidance and control system. For the task he could draw on experiments with aircraft autopilots he had made independently of Kreiselgeräte. But he died not much more than a year later, leaving it to the company to complete.52
After preliminary laboratory experiments with stabilization in one axis, Kreiselgeräte assembled the first version of what it called the “Sg 33” in mid-1936. Its final form for the A-3 is illustrated in Figure 2.1. The Sg 33 had the function of simply holding the rocket to a vertical course, yet it was, in the end, too complicated for the technology of the time. Two gyros were to hold a stabilized platform horizontal. When the rocket tipped in pitch (nose backward or forward) or yaw (side to side) the corresponding gyro wheel, spinning at 20,000 rpm, would move (“precess”) at right angles, as the laws of physics dictate. This movement was sensed by electrical contacts, which in turn released nitrogen gas through small nozzles to push the platform back into place. (Unlike succeeding systems, the platform gyros had no direct influence on the attitude of the rocket.) Located on top of the platform were two devices to measure the movement of the rocket in a horizontal direction away from the initial vertical trajectory. The primitive accelerometers used little wagons on tracks to convert horizontal acceleration into a measurement of horizontal speed, which was then sent to the control system of the rocket. Under the platform were three “rate gyros.” Their function was to measure the rate at which the rocket was turning away from its specified direction, whether in pitch, yaw, or roll (turning around the longitudinal axis). The signals from the rate gyros were used to push the rocket back into its initial vertical attitude.53
The control forces commanded by the wagons and rate gyros were sent to “jet vanes” in the rocket exhaust, which deflected the direction of thrust—an idea anticipated by Oberth and other pioneers. (Goddard had already experimented in New Mexico with jet vanes and a less ambitious gyro system as early as 1932.) But it was no easy task finding materials that would withstand the fiery temperatures and erosion of a rocket exhaust. The Kummersdorf group were finally able to develop, in conjunction with a contractor, molybdenum and tungsten vanes that were at least adequate to the task, but only after hundreds of test failures. Those vanes were rotated by rods that came down from electrical servomotors in the guidance system at the top of the A-3.54
Also guiding the rocket were the long, narrow fins that gave it longitudinal stability or, to use the more picturesque German term, “arrow stability.” They ensured that, when the vehicle pitched or yawed around its center of gravity, the lift forces generated by the fins would tend to force the vehicle back to its original position—nose-on into the airflow—so it would have an inherent aerodynamic stability like an arrow. (In technical terms, the fins ensured that the rocket’s center of pressure was behind its center of gravity.) Finding the appropriate shape for the fins was another difficult task. The Luftwaffe alliance was helpful here, because in late 1935 the Technical Office was able to introduce von Braun to one of the handful of supersonic wind tunnel groups in the country, at the Technical University in Aachen, near the Dutch and Belgian borders. An assistant professor there, Dr. Rudolf Hermann, made the preliminary drag measurements that allowed a calculation of the performance of the rocket. He then worked on the fin form so that stability through the whole range from zero velocity to supersonic was assured.55
At the beginning of December 1937, a year later than von Braun’s 1935 estimate, four A-3s were finally ready for launch. They were not smalclass="underline" 6.5 m (22 ft) long and 0.7 m (2.3 ft) in diameter, with a fueled weight of 750 kg (1,650 lb). Each rocket carried registering instruments to measure either the heating of the skin through friction or atmospheric temperature and pressure during a parachute descent from a peak altitude of 20 km. The launch site was the Greifswalder Oie, the small island with high cliffs a few kilometers offshore from Peenemünde. Ironically, it was the same location Oberth had requested for the launching of his Frau im Mond rocket in 1929, only to be refused by the Prussian authorities because he might endanger the lighthouse there. In the Third Reich, however, a request from the military was not likely to be turned down.56
Converting the island proved to be a major task and expense for the Army, because about the only thing on the island, except for the lighthouse, was the combination farmhouse-guesthouse run by the island’s lessee. It was fortunate that a small-gauge railway had been left in place from the erection of the lighthouse, because there were no roads. When a liquid oxygen tanker truck was brought over to the island, the launch crew spent hours trying to pull it out of the mud. The Army New Construction Office built a dock, a launch bunker, a generator building, and temporary barracks. Telephone lines were strung to link the buildings. A large tent was put up in a wooded area for workspace. An ancient ferry was leased to haul the equipment from the mainland.57
Toward the end of November a select crew of about 120 individuals from Peenemünde and Berlin, headed by Dornberger, Zanssen, and von Braun, assembled on the island for “Operation Beacon.” Most were new to the launch business, as the rocket program had grown so much since the A-2s. Enthusiasm ran high, which was fortunate, because conditions were trying. The weather became miserable: It rained for days, which delayed the launches, and then it was bitterly cold. The wind threatened to tear the tent pegs right out of the ground. An “extraordinary plague of mice and rats” emerged to gnaw on the tar paper of the bunkers, so that constant tearing sounds could be heard, and rain seeped through after ten days. More ominously, the field mice showed a taste for cable insulation, causing short circuits. Technical delays in the launching tried the patience of the many high-level visitors and caused problems with the launch organization, because so much was on loan from other organizations—airplanes from the Luftwaffe, boats from the Navy, photo and measuring equipment from other branches of Ordnance.58