An Austrian daredevil is gearing up to make the world's highest skydive, a daring leap from 23 miles
above Earth that promises to break more than one record if all goes according to plan.
Veteran skydiver Felix Baumgartner, 43, will make the jump on Tuesday (Oct. 9) at the earliest, thereby becoming the first person ever to freefall faster than the speed of sound. His skydive will also be the highest ever, superceding a record set in 1960 by U.S. Air Force Captain Joe Kittinger by more than 3 miles (5 kilometers).
A helium-filled balloon will lift Baumgartner, sitting inside a custom-built capsule, to an altitude of 120,000 feet (36,576 meters). At that altitude, which registers in the upper echelons of the stratosphere, the atmosphere is a mere inkling of its sea-level self, exerting a pressure less than 0.5 percent of its value near the ground. Even if gradually acclimated, humans cannot survive long above 26,000 feet without an oxygen tank, so a much loftier Baumgartner will definitely require supplemental oxygen.
When the skydiver steps out of his capsule and plunges into the void, he'll accelerate for approximately 30 seconds before reaching his peak speed, explained Michael Weissman, a physicist at the University of Illinois at Urbana-Champaign. Weissman estimates that Baumgartner's speed will max out just above the sea-level speed of sound, which is about 760 miles per hour
(1,225 kilometers per hour).