A supersonic jump, from 23 miles in the air

He has sky-dived across the English Channel. He once plunged into the black void of a 623-foot-deep cave, which he formerly considered the most difficult jump of his career.
But now Fearless Felix, as his fans call him, has something more difficult on the agenda: jumping from a helium balloon in the stratosphere at least 1,20,000 feet above Earth. Within about half a minute, he figures, he would be going 690 miles per hour and become the first skydiver to break the speed of sound. After a free fall lasting five and a half minutes, his parachute would open and land him 23 miles below the balloon.

At least, that’s the plan, although no one really knows what the shock wave will do to his body as it exceeds the speed of sound. The jump, expected sometime this year, would break one of the most venerable aerospace records. For half a century, no one has surpassed (one person died trying) the altitude record set by Joe Kittinger as part of an Air Force programme called Project Excelsior.

In 1960, Kittinger jumped from a balloon 1,02,800 feet above the New Mexico desert. Today, at 81, Kittinger is a retired colonel and part of a team working on Baumgartner’s jump.

More than three dozen veterans of NASA, the Air Force and the aerospace industry have been working for three years to plan the jump, build a balloon and pressurised capsule, and customise an astronaut’s suit for Baumgartner.

Baumgartner hopes to remain stable and conscious throughout his longer fall without relying on a drogue parachute. This stabilising technique would ordinarily be fairly easy for an expert like Baumgartner, 41, a former paratrooper in the Austrian Special Forces and a veteran of more than 2,500 jumps from planes, cliffs and assorted landmarks. But to survive the stratosphere’s near vacuum and frigid temperatures, he will need a sealed helmet and a pressurised suit.