Baumgartner's team has a plan for every contingency but one: If the balloon ruptures shortly after liftoff because of a gust of wind or something else, the capsule will come crashing down with him inside. He won't have time to blow the hatch and bail out.
"I have every expectation that he'll come through this successfully based on our analysis," Clark says, "but you know, it still is an unknown."
Kittinger leapt from an open gondola on Aug. 16, 1960, from an altitude of 19.5 miles and reached 614 mph, or Mach 0.9 — records that stand to this day. He was a captain in the Air Force, and the military's Excelsior project was a test bed for the nation's young space program.
Kittinger has been Baumgartner's mentor, signing on with this new project after decades of refusing others' requests.
Fearless Felix insists he would not attempt the jump if the odds were against him.
"I think they underestimate the skills of a skydiver," says Baumgartner, who has made more than 2,500 jumps from planes, helicopters, landmarks and skyscrapers, with no serious injuries.
If he makes it back in one piece, Baumgartner plans on settling down with his girlfriend and flying helicopters in the U.S. and Austria, performing mountain rescues and firefighting.
"After this," he promises, "I'm going to retire because I've been successfully doing things for the last 25 years and I'm still alive."
Red Bull Stratos: http://www.redbullstratos.com
National Museum of the U.S. Air Force: http://tinyurl.com/2dsnn6
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