Thin Air, Big Mystery: Surviving High-Altitude Skydives

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Editor’s note: Today it was announced that on Oct. 8, Felix Baumgartner will ascend to 120,000 feet beneath his Red Bull Stratos balloon in a bid to beat Kittinger’s 52 year-old record.

In the late 1950s, pilots were pushing their aircraft to fly higher and faster as they readied to make the leap from atmospheric flight to spaceflight.

But there were a lot of unknowns with upper atmospheric supersonic flights. Would an aircraft be controllable flying Mach 3 at altitudes where there are just a handful of air molecules in a cubic foot? And more importantly, what would happen to the pilot? As one of the main organizations behind the push into space, the US Air Force was very interested in answering these questions.

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Because the air is so much thinner in the upper atmosphere, aircraft typically made supersonic flights — that is, flights in excess of the speed of sound — at high altitudes.

But there’s a problem with this flight plan. While it’s easier to fly supersonic in a thinner atmosphere, it’s harder to control an aircraft. The traditional control surfaces like ailerons on wings and tail rudders need air. They push against the atmosphere to change a plane’s direction in flight. Without enough air to push against, they’re pretty useless.

This presented a risk for pilots: aircraft were prone to tumbling, and pilots are prone to ejecting from tumbling aircraft. So came the question of what bailing out at high altitude would do to a pilot.

Early research into pilot ejection at high altitudes was done under the US Air Force’s Project High Dive. Dropping human dummies from high altitudes showed scientists that a body tended to fall in a prone position but rolled around its vertical axis up to 465 times a minute — from the pilot’s point of view it would be like rolling really fast down a hill but without the hill.

The kinds of g-forced the pilot would experience would almost certainly kill him, so the US Air Force needed to find a way of stabilizing a pilot’s fall from a high altitude bailout.

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Francis F. Beaupre came up with the system built around a series of parachutes that would deploy in sequence to stabilize the pilot. Here’s how the sequence was designed:

Right after bailing out, the pilot would pull a cord to release an 18-inch pilot parachute after a few seconds of delay. Once it was fully inflated, the pilot chute would pull out a 6-foot diameter stabilization parachute. Next would come the main parachute release. It would inflate partway until the pilot passed through 14,000 feet as measured by an aneroid barometer on his person. Passing this altitude would trigger full release of the 28-foot diameter main parachute. It would inflate fully, and he’d make a soft landing on Earth.

Beaupre’s stabilization parachute system worked at altitudes where jet aircraft were normally flying, but it needed to work higher. Aircraft like the X-15 were brushing the fringes of space, and they would need a safe way to bailout of the rocket plane just like pilots did from jet aircraft. So the Aeromedical Research Laboratory at Holloman Air Force Base began a series of high altitude parachute tests where pilots jumped from balloons. This was Project Excelsior.

Project Excelsior wasn’t a long term project. There were just three tests, but they were manned, most famously by then Captain Joseph W. Kittinger Jr.

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Kittinger made his highest jump, and set the still unbroken high altitude jump record, on the third and last jump of Project Excelsior. On Aug. 16, 1960, Kittinger lifted off from an old abandoned airstrip north of Tularosa, New Mexico in an open gondola; his pressure suit was his only defense from the harsh environment of near space. At the tests starting altitude of 102,800 feet, Kittinger had 99.2 percent of the atmosphere beneath him.

Then he jumped, and the Beaupre multistage parachute system worked perfectly. After a 13 second free fall, a 6-foot parachute opened and stabilized his fall — this is the one that prevented the spin dummies that had fallen before experienced. After another four minutes and 36 seconds he was down to about 17,500 feet where the main 28-foot parachute opened. He floated the rest of the way to Earth.

Image: Kittinger takes the plunge. Credit: US Air Force