In 1954, Air Force physician John Stapp rode a rocket sled at 632 mph (1,017 km/h), enduring 46.2 g to test human deceleration limits. He suffered broken ribs, lost fillings, and temporary blindness but survived. His research led to major safety advances, including improved harnesses, ejection seats, and wind-blast survival tests at 570 mph (920 km/h). His work revolutionized aviation and crash safety, proving humans could withstand extreme forces.