The Red Bull Stratos "space jump" planned by Austrian skydiver Felix Baumgartner, 43, won't actually be from space. The Oct. 8 stunt takes aim at an altitude of almost 23 miles, or 120,000 feet (36 kilometers) — well short of the altitude where space begins, 62 miles, or 327,000 feet (100 km), above Earth. Higher jumps probably would require expensive rockets and specialized space-diving suits — not to mention a thriving commercial spaceflight industry with paying customers — to become a reality.

The limits of current technology are being pushed by Baumgartner's planned supersonic plunge — for instance, he will rely upon the largest balloon ever built for manned flight to carry him into the stratosphere. During his initial free fall in the near-vacuum conditions of the stratosphere, he will have relatively little control over steering and attitude.

Baumgartner will be wearing a pressure suit similar to what supersonic SR-71 Blackbird pilots once wore. At higher altitudes, however, "the suit stops needing to become a pressure suit and starts needing to become a small spacecraft," observes Jeff Feige, chief executive of spacesuit maker Orbital Outfitters.