John Paul Stapp (1910-1999), US aviation researcher, in a laboratory. Stapp pioneered the study of the effects of deceleration on humans. He gained a doctorate in biophysics and a degree in medicine before joining the US Air Force in 1944. From 1946 he worked on the deceleration project that was studying how pilots could survive crashes. The model seen here is of the human decelerator sled. This was mounted on rails and powered by rockets. 45 sets of powerful brakes supplied the deceleration forces required. The system began operating in 1947. By August 1948, several runs involving humans had been made. Dr Stapp was one of the most frequent volunteers. Forces of up to 45 G were achieved safely (1 G is the force of gravity at the Earth's surface). This work led to the design of improved safety harnesses for aircraft pilots.