Career
In October 1939, while working for the Telefunken electronics firm in Berlin, Hoelzer met with Ernst Steinhoff, Hermann Steuding, and Wernher von Braun regarding guide beams for a flying body. In late 1940 at Peenemünde, Hoelzer was head of the guide beam division (assistant Henry Otto Hirschler), which developed a guide-plane system which alternates a transmitted signal from two antennas a short distance apart, as well as a vacuum tube mixing device (German: Mischgerät) which corrected for momentum that would perturb an object that had been moved back on-track. By the Fall of 1941, Hoelzer"s "mixing device" was used to provide V-2 rocket rate measurement instead of rate gyros.
Then at the beginning of 1942, Hoelzer built an analog computer to calculate and simulate V-2 rocket trajectories Hoelzer"s team also developed the Messina telemetry system.
After evacuating Peenemünde for the Alpenfestung (Alpine Fortress), Hoelzer returned to Peenemünde via motorcycle to look for portions of his Doctor of Philosophy dissertation prior to surrendering to United States forces at the end of World World War World War II