Sonic Wind and “The Fastest Man On Earth”

In 1954, John Stapp rode a rocket sled to over 600mph and became “The Fastest Man on Earth”.

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Sonic Wind rocket sled on display at the Space History Museum in Alamogordo

During the First World War, airmen were not provided with parachutes to escape if their plane was shot down. French and British Generals thought that their pilots would give in to cowardice and abandon their aircraft too quickly. In the Second World War, on the other hand, parachutes were standard for all aircrew, and “hitting the silk” saved countless thousands of lives.

But by the end of the war, piston-engined fighters were already exceeding 400mph, and the new jet engines would be breaking the sound barrier within a short time. These kind of speeds made jumping out of the cockpit with a parachute virtually impossible: if the fearsome slipstream did not tear you apart, you would almost certainly strike the tail of your own airplane and be killed. A better way had to be found for aircrews in ever-faster jets.

The obvious solution was an ejection seat, which could be pushed clear of the crippled plane by a small rocket motor before deploying a parachute. But this raised questions for which there was no data to provide an answer. Could a human body withstand the sort of g-forces that a rocket-accelerated ejection seat would need to produce? What about the sudden deceleration when the parachute opened? Or the even larger deceleration that would happen if the pilot crash-landed without ejecting? The only way to get any answers would be through actual testing.

The task fell to Air Force flight surgeon John Paul Stapp. Stapp had already done some groundbreaking work on the effects of pure oxygen on pilots at high altitude. Now, he was assigned the task of determining what sort of g-forces a human body could stand without breaking. (Conventional medical opinion at the time was that a human body could not withstand anything higher than 18 g’s.)

The assignment took him to Muroc Air Base (now Edwards Air Base) in California, where the Army had already set up a 2,000-foot-long metal rail and a sled for testing the acceleration of captured German V-1 rockets. Stapp added four solid-fuel rockets with a total of 20,000 pounds of thrust to a new sled (dubbed the “Gee Whiz”) that could ride along the track and then be stopped by a series of brakes installed at the end. The first few dozen test runs were made using an anthropomorphic crash dummy nicknamed “Oscar Eightball”. On his first run, Oscar’s restraining straps failed and he was catapulted across the desert sands at several hundred miles per hour.

Then Stapp began doing test runs, building up gradually from 100mph to 200mph. He reached and passed the supposed 18-g limit with no ill effect, eventually reaching 35 g’s. In all, Stapp and seven other volunteers made a total of 74 runs on the contraption, reaching speeds of over 300 miles per hour—with Stapp breaking his wrist twice during test runs. But this apparatus, he realized, was not enough. He needed higher accelerations and faster speeds.

So in 1953, Stapp and his team were sent to Holloman Air Force Base near Alamogordo NM and allowed to build a new rig, adopting a 3500-feet track that had been used to test the Snark missile. Stapp built a new sled, dubbed “Sonic Wind”, with nine solid-fuel rockets producing a total thrust of 40,000 pounds. On the bottom of the sled was a metal scoop which, upon reaching the end of the track, would be immersed in a series of water pans that would quickly decelerate it and bring it to a stop. Stapp, knowing how dangerous it was, would be the only person to ride in it.

His first test was in March 1954. With just six of the rockets being ignited, the Sonic Wind moved down the track at 421mph, a new land speed record. Stapp was subjected to a force of 22 g’s. A whole series of test runs followed, reaching speeds up to 500mph.

In December 1954, it was decided to do a run with all nine rockets igniting. It was enormously dangerous. Stapp had to be tightly confined inside his cockpit so his arms would not flail around in the wind, and a mouthguard would prevent his teeth from being shattered.

When the rockets were fired, it took the sled five seconds to reach a speed of 632mph—almost the speed of sound. At the end of the track, the sled was slammed to a halt in just 1.4 seconds. Stapp had been subjected to over 40 g’s—the equivalent of hitting a brick wall at 120mph. He had broken both wrists, cracked several ribs, and had burst all the blood vessels in his eyes (leaving him temporarily blind). But he had survived.

After recovering, Stapp was making plans to add even more rocket engines to the Sonic Wind, hoping to push it to supersonic speeds of over 1,000mph. But the Air Force cancelled any further tests. They had already learned what they wanted to know—a pilot was physically capable of ejecting at altitude and at speed, and could also potentially survive crash-landings at much higher speeds than previously thought. Based on Stapp’s work, new ejection seats appeared with modified restraints.

Stapp, meanwhile, had become a media darling. Dubbed “The Fastest Man On Earth”, he was featured in magazines, had a Hollywood movie made about him, and was featured in an episode of the TV show “This Is Your Life”. He went on to run an automobile safety lab, using crash dummies to test seatbelts. Seemingly unaffected by the battering he had taken in his high-speed tests, Stapp died in 1999 at the ripe old age of 89.

The Sonic Wind sled is now on display at the New Mexico Museum of Space History in Alamogordo.