 In 1954, John Paul Stapp strapped himself to a rocket sled and shot across the desert. When the sled stopped, he pulled more than 40 Gs, that's more than 40 times the force of gravity. And it might not seem like it, but the test was done in the name of pilot safety. I'm Amy Shearer Tidal, and this week on Richard Space, we're talking about Sonic Wind No. 1. After the Second World War, technological advances were seeing airplanes flying higher and faster, breaking the sound barrier and reaching toward space. But humans weren't exactly getting any more robust. The higher planes flew, the harder they crashed, and that meant flying was an increasingly hazardous job for a pilot. For John Paul Stapp, the disparity between human frailty and advancing technology in the air presented a very interesting research opportunity. Just how much force could a pilot withstand during a crash? If designers knew this, they could design seats and restraints to keep airmen alive through more crashes. To this end, deceleration tests were Stapp's best ally. Stapp's method was simple. Add a rocket-powered sled down a track to mimic an airplane flying, then have it stop quite suddenly, the sudden deceleration mimicking a crash. Measuring what happened to his body would tell him what a pilot could and could not survive. Stapp's most famous sled run was his last. On December 10th, 1954, he was strapped into the forward-facing seat of a sled. His arms and legs were secured, he wore a helmet and had a bite block in his mouth. Behind the seat was a sled's propulsion unit consisting of nine solid-fueled rockets. Inside of him was 2,000 feet of track. Sitting underneath the final stretch of the track were a series of pools. A scoop on the underside of the sled would dig into the pools to stop it. Alongside the track were high-speed cameras ready to capture the test. In the air was Joe Kittenger in a T-33, ready to fly a photographer over the track at the moment the sled stopped. As soon as the clouds cleared, the test was on. The nine rockets rode to life with 40,000 pounds of thrust, and within five seconds Stapp had reached a top speed of 632 miles per hour. That's Mach 0.9. He tore along the track until the scoop on the underside of the sled hit the water. From that point, it only took 1.4 seconds for the sled to stop. The sudden deceleration hit Stapp with more than 40 Gs of force. For an instant, he weighed 6,800 pounds. That's the same deceleration in force that a driver would feel in a car traveling at 120 miles and then slamming into a brick wall. The extreme G-forces broke all the blood vessels in Stapp's eyes, cracked his ribs, broke his wrists, and affected his circulatory and respiratory systems. But he survived and almost immediately began planning his next run. He wanted to get the sled up to 1,000 miles per hour to break Mach 1, but the Air Force finally stepped in and put a stop to his self-testing. They knew that it was only a matter of time before he lost his life, and his life and research were too valuable to lose. For more on Stapp's rocket sled runs and what happened with his research, check out the latest article on vintage space over at Popsci. Leave your questions and comments below and for weekly vintage space video updates, don't forget to subscribe.