On Dec. 10, 1954, John Stapp, a U.S. Air Force flight surgeon and researcher, hopped into an experimental decelerator sled. It would be his last ride in the sled, testing the limits of gravitational forces on the human body as it accelerates and decelerates. He reached a speed of 632 miles per hour that day, experiencing 46.2 g. It was then the most ever experienced by a human and it made Col. John Stapp “The Fastest Man on Earth.”
Stapp, his Air Force colleagues and other researchers in the field were experimenting with the physical effects of gravitational forces on the human body for myriad reasons. First and foremost, the jet engine was a relatively new technology, and was being improved all the time. The Cold War was in full swing. Competition with the Soviet Union and the communist bloc was essential for maintaining American air supremacy in a potential conflict. Most importantly, however, man was beginning to slip the surly bonds of earth via rocket.
At the end of World War II, the newly-formed Air Force began testing the limits of powered flight. Consistent technological breakthroughs in manned flight meant that we needed to know just what effects the technology would have on the men who were flying the new technology. Then-Capt. John Stapp, an Air Force doctor who once had dreams of being a pediatrician, instead became aviation’s self-made guinea pig. He tested how men could function at high altitudes, including the extreme cold, the lack of air and even the possibility of decompression sickness from pressure changes. Not content to experiment on some poor airman, he volunteered himself.
The case of the ejection seat was no different. Physicists, doctors and engineers needed to know what happened to a person during both rapid acceleration and rapid deceleration – and deceleration meant testing for what could happen in an aircraft crash. When Stapp joined the Aero Med Lab, it was widely believed that 18 g was the maximum a human body could withstand. Accident reports made during World War II directly contradicted this assumption.
Air Force engineers built a rocket sled to test the gravitational forces on real human bodies, aircraft seats and protective harnesses. The 2000-foot long track with a series of hydraulic brakes at the end was dubbed the “Gee Whiz,” and could slow the sled from 150 miles per hour to half that in a fraction of a second. This reproduced the gravitational forces experienced during aircraft crashes.
The test subject was supposed to be a dummy named Oscar Eightball. On the first tests, the brakes failed, sending Oscar and the sled into the desert. When they figured out the braking system, the first operational test sent Oscar, secured in just a seatbelt, through one-inch canopy glass at 30 g-forces, shredding the glass (and the dummy’s face) like it was a paper bag. After 35 shocking tests, the sled was ready for a manned test. Not only did Stapp test it on himself first, he personally performed more of the harness tests than any other human subject.
By 1948, Stapp had already survived more than 18 g. His limit after 16 tests was, in fact, a whopping 35. He wasn’t immune, either. The tests tore out dental fillings, cracked ribs and broke bones. He reportedly reset bones on his way back to his office after test runs.
As Stapp ran his tests, neither the Aero Med Lab nor the Air Force knew he was gathering data by testing on himself. When they found out, he was warned to stop using humans, himself included, and was promoted to major in the hopes that he might actually listen. The data he gathered was used to create new air transport procedures, replace harnesses and develop a side-saddle harness for paratroopers.
He would need to go faster if he was going to make real progress. Pilots were breaking the sound barrier by then and Stapp needed to expand his testing. At Holloman Air Force Base in New Mexico, he began using a sled system that was once used to test missiles. For his 29th and final test run, the sled would go transonic, 0.9 Mach, and Stapp would endure the most g-forces of any human so far, protected by only a helmet and visor. The sled shot off like a bullet – faster than a bullet, actually – subjecting Stapp to 20 g at 632 miles per hour. The brakes stopped the sled in a fraction of a second.
When ambulance crews got to Stapp, he was not only alive, he was reportedly smiling. His eyes were filled with blood but it was only temporary. He’d proven that a pilot could eject at 40,000 feet while flying 1.6 Mach.
After Stapp’s ride to become the “Fastest Man on Earth” came to an end, the colonel himself still believed that the human body could withstand more. The Air Force refused to let him test his theory, of course. He told reporters the gravitational force on his head felt like the forcible removal of a tooth – a sensation he felt in his eyes. But he had no lasting medical issues associated with the experiments. He was correct about the body withstanding more force. In 2003, race car driver Kenny Brack felt the highest horizontal g-forces by a human being ever, when a crash propelled him to 214 g at Texas Motor Speedway.