This weekend Austrian daredevil Felix Baumgartner plans to ride a balloon to the edge of space. Then, after reaching 120,000 feet, he'll jump into the unknown.

Only pressure chamber tests, computer modeling, and tales of a pilot who survived an emergency ejection at supersonic speeds offer Baumgartner, a professional BASE jumper, and his support team any measure of solace.

But a few things are certain. For a short time inside his pressurized spacesuit, Baumgartner will be the fastest man alive. Thirty seconds after leaping from a small capsule, in fact, he'll exceed the speed of sound in the thin upper atmosphere by traveling 690 mph. And if he safely parachutes to the ground between 12 and 15 minutes later, he'll walk away with at least four new world records: the highest skydive, the longest free fall, the first to reach supersonic speeds in free fall, and the highest manned balloon ride.