Extreme athlete Felix Baumgartner will leap from the stratosphere into the history books Sunday if all goes as planned in his mission to skydive from a balloon, 37 kilometres above New Mexico.
The 43-year-old Austrian will try to break a long-standing freefall record and the sound barrier after a three-hour ascent.
The jump from the edge of space was postponed on Monday and Tuesday because of unexpected winds, but the weather forecast is said to be favourable for his latest attempt.
The former military parachutist plans to ride a pressurized capsule carried aloft by a 55-storey, ultra-thin helium balloon launched from Roswell, N.M., before he jumps in a specially designed suit.
Baumgartner has been training for five years for the jump, during which he will be in freefall for some five minutes before opening a parachute at 5,000 feet above ground. The total jump should take about 10 minutes.
The current record for a high-altitude skydive was set in 1960 by Joe Kittinger, who jumped from a balloon flying at 31,333 metres (102,800 feet). Kittinger, a retired U.S. Air Force colonel, fell for four minutes and 36 seconds and reached a maximum speed of 988 km/h (614 m/h) before opening his parachute.
Baumgartner hopes to top that by exceeding 1,110 km/h (690 m/h) — the speed of sound at the targeted altitude — and freefalling for five minutes and 35 seconds.
To keep Baumagartner safe, a special suit was designed, similar to an astronaut's and meant to withstand extreme conditions.
Canadian space suit engineer Shane Jacobs spent the last three years building the pressurized suit.
Jacobs says one of the most dangerous things that skydivers at high altitudes face is going into a flat spin, in which the body rotates horizontally.
"This could create g-forces that can make you unconscious," he told CBC News.
"When he's jumping from such high altitude, even though he's a very experienced skydiver and he knows how to position his body when he normally skydives from low altitudes, the atmosphere is so thin, that there isn't enough atmospheric drag to really push against to control your body."
What Kittinger did when he jumped over 50 years ago, is he used a smaller drogue parachute, in addition to the main chute, to gain stability.Felix and for this mission we didn't want to nominally deploy a"For this mission we didn't want to nominally deploy a droge chute because we want Felix to be able to hopefully break the speed of sound. But should he not be able to control his body position, we have a system that he wears on his wrist that measures g-forces, and if they build up for a great amount of time it will automatically deploy the drogue chute, which will stabilize him and make sure the mission is successful," Jacobs said.
Dr. Jonathan Clark, Baumgartner's medical director, has told reporters he expects the pressurized spacesuit will protect him from the shock waves of breaking the sound barrier.