German airmen were experiencing G-induced physiological effects as early as WWI, although no research on acceleration physiology was conducted at that time in Germany. This changed in 1931 with the studies of Heinz von Diringshofen, who gained experience with prolonged acceleration in flight. The first German centrifuge was constructed by the von Diringshofen brothers and was in operation at the Air Ministry's Aeromedical Research Institute in Berlin from 1935-1945. After WWII, Otto Gauer and Heinz Haher authored the paper "Man under Gravity-Free Conditions," paving the way to manned space exploration and demonstrating the change of research interest from the effects of multiple G forces to those of zero G.