As early as 1945, service personnel realized the need for a comprehensive and controlled series of studies into the effects of deceleration on the human body. This led to fundamental concepts that could be applied to better safeguard aircraft occupants during a crash. The initial phase of the program, as set up by the Aero Medical Laboratory of the Wright
Air Development Center, was to develop equipment and instrumentation. This was so aircraft crashes might be simulated, and to study the strength factors of seats and harnesses. Human tolerance to the deceleration encountered in simulated aircraft crashes could also be simulated. The first run on the
rocket sled took place on 30 April 1947 with ballast. The sled ran off the tracks. The first human run took place the following December. Instrumentation on all the early runs was in the developmental stage, and it was not until August 1948 that it was adequate to begin recording. By August 1948, sixteen human runs had completed, all in the backward-facing position. Forward-facing runs started in August 1949. Most of the earlier tests ran to compare the standard Air Force harnesses with a series of modified harnesses. This was to determine which type gave the best protection to the pilot. By June 8, 1951, 74 human runs had been made on the decelerator, 19 with the subjects in the backward position, and 55 in the forward position. Stapp, one of the most frequent volunteers on the runs, sustained a fracture of his right wrist during the runs on two separate occasions, also broke ribs, lost fillings from his teeth and developed bleeding into his retinas that caused temporary vision loss; in one run he survived forces up to 38 g (
g-forces). Stapp's research on the decelerator had profound implications for both civilian and military aviation. For instance, the backward-facing seat concept, which was known before, was given great impetus by the crash research program. It proved beyond a doubt that this position was the safest for aircraft passengers and required little harness support, Stapp reached a speed of , which exceeded the land speed record and made him the fastest man on Earth. Stapp believed that the tolerance of humans to acceleration had not yet been reached in tests. He believed it is much greater than thought possible. He said "I felt a sensation in the eyes, somewhat like the extraction of a molar without anesthetic," but his survival without any permanent injuries supported the development of further safety technologies including the
ejection seat. Also developed by Stapp as an added safety measure was an improved version of the currently used
shoulder strap and lap belt. The new high-strength harness withstood 45.4 g (445 m/s²), compared to the 17 g (167 m/s²), which was the limit that could be tolerated with the old combination. Basically, the new pilot harness added an inverted "V" strap crossing the pilot's thighs added to the standard lap belt and shoulder straps. The leg and shoulder straps and the lap belt all fastened together at one point, and pressure was distributed evenly over the stronger body surfaces, rather than on the
solar plexus, as was the case with the old harness. == Wind-blast experiments ==