Record parachute jump attempt begins 36.5km above earth

The 41-year-old skydiver will test his limits facing temperatures far below zero, little oxygen and sudden changes in air pressure.

NEW YORK // Like a comic book hero, Felix Baumgartner plans to jump from a helium balloon at least 120,000 feet or 36.5km above the earth in a skydive likely to propel him 1,110 kilometres per hour and break the speed of sound.

If "Fearless Felix", as he is known to his fans, survives the jump planned for later this year somewhere over North America, he will break the world record of the highest parachute jump from a balloon at 31.3km and the longest and fastest free fall. Mr Baumgartner, a 41-year-old Austrian who is internationally renowned for his skydiving adventures, also hopes to provide scientific answers about the effects of supersonic travel on the human body as well as notch another world record.

"The effect on the human body of the transition from subsonic through transonic to supersonic velocity and back again are not known," he said in a press release. "This is just one of the things we hope to learn. Looking at the bigger picture, it's clear that we have a unique opportunity to support science in a very specific field. Maybe one day it will be possible to bring astronauts home safely from space if their equipment malfunctions."

Joe Kittinger, who is 81 and the holder of the current world record that he achieved for the US Air Force in 1960, is a consultant to the team behind Mr Baumgartner. He will hear Mr Kittinger's voice through a special helmet during the 23 minutes or so that it will take to descend to earth. "He was my childhood hero," said Mr Baumgartner. One person has died trying to break Mr Kittinger's 50-year-old record.

The risks are formidable even with the pressure suit and capsule that will contain Mr Baumgartner on his ascent by balloon. What is known is that he is likely to break the speed of sound within about half a minute of jumping and his parachute will open after a free fall lasting about five-and-a-half minutes. The speed of sound varies according to altitude and temperature and the Red Bull Stratos team sponsoring Mr Baumgartner estimates it at about 1,110 kmh at the predicted altitude of 30.48km.

"Known hazards at such altitudes include temperatures well below zero, an environment with too little oxygen to sustain human life, and the tendency to spin uncontrollably to the point of unconsciousness or worse," said an information sheet from the team. "Unpredictable factors compounding those dangers include sudden changes in air pressure and resulting instability in the 'transonic' zone [speeds approaching supersonic velocity], which in the mid-20th century caused aircraft to go out of control or break up and resulted in the concept of a sound 'barrier'."

Mr Baumgartner will wear a sealed helmet and a pressurised suit that inflates to three pounds per square inch or else his blood could "boil" with life-threatening vapour bubbles. He has practised stabilisation manoeuvres using the suit in a special wind tunnel in California. For the first 25 to 30 seconds of his flight, thin air will provide little resistance so he will not be able to adjust his position using air flow so he must "choreograph" his movements to step off the capsule in an optimal position. But the capsule will not be fixed rigidly to the balloon and can react to his motion.

Part of his training is practising this choreography. In the wind tunnel, he is also getting used to wearing the pressure suit and adjusting his arms and legs to achieved the optimal V shape for descent with his head first, arms and legs pointing backwards. He will also have a drogue or small parachute used to decelerate an object that is moving rapidly should he need to avert the potentially fatal tendency for falling objects to spin uncontrollably at high altitudes.

"What we're counting on is that, while the high altitude presents many challenges, the air will also be rarefied, so shock waves won't have the same detrimental, concussive effect as they would down low," said Dr Jonathan Clark, the team's medical director. "But ultimately, this mission is a test flight so we'll know a lot more afterwards than we'll know beforehand. We expect the unexpected." [e-mail]