The weather window for a launch opens between July and September, during which Baumgartner, 43, will attempt a world record breaking jump from a helium balloon at an altitude of 120,000 feet (36,576 metres), while simultaneously collecting valuable data for the advancement of medical science.

Dr. Clark, himself a former six-time Space Shuttle crew surgeon at NASA, said the team has studied every possible physical effect during all critical phases of the mission, especially the point at which Baumgartner’s body breaks the sound barrier and then rapidly decelerates to subsonic speeds as the atmosphere thickens.

Baumgartner will accelerate from standstill to nearly 700 mph (1,125 km/h) in about 30 seconds, according to the team’s calculations. The myriad of challenges associated with the project explains why the current record for the highest altitude freefall of 102,800 feet (31,333 metres) set by U.S. Air Force Colonel Joe Kittinger has remained unbroken for 52 years.

Pilot Felix Baumgartner. Photo: Jörg Mitter/Red Bull Content Pool

There are several critical phases during the ascent and freefall. At launch the wind must be no more than 2 to 4 miles per hour (3 to 6km/h) to enable the capsule and 55 storey-high balloon to lift off safely. However, during the first 1,000 feet (305 metres) of ascent, Baumgartner will be unable to perform an emergency exit as there will not be enough altitude for an emergency parachute deployment.

During the test jump from 71,581 feet (21,818 metres) in March 2012, Baumgartner passed through a level of the stratosphere where the temperature plunged to minus 68'C.

'Felix will experience the environment of near space at 120,000 feet. It’s the vacuum of space and the extreme cold so the reduced pressure requires that he wear a pressure suit to survive and protect him from the cold,' Dr. Clark said.

On the way up, beginning at around 63,000 feet (19,200 metres), Baumgartner will pass through the 'Armstrong Line', a point where the air pressure becomes so low that without the pressurization of a capsule or spacesuit, body fluids would vaporize, in other words start to 'boil' at normal body temperature.

Dr. Clark said: 'To visualize it, think about how soda in a bottle looks clear until you open it and release the pressure. Then the bubbles come out of the solution and rise to the top. That’s essentially what would be happening in Felix's blood and tissues if his life-support systems failed, and it can turn deadly very quickly.'

On the way down, Dr. Clark said the scientists have taken all possible measures to prevent Baumgartner from falling into an uncontrollable 'flat spin'.

'Flat spin is a genuine threat. The primary concerns during a flat spin are the eyes, the brain, and the cardiovascular system. If the center of rotation is in the upper part of the body, blood rushes toward the feet, which can cause a blackout. If the rotation is centered in the lower part of the body, blood rushes toward the head, potentially causing a condition called 'red out' with effects that can range from a feeling of pressure in the head to an ocular hemorrhage and intercranial hemorrhage (bleeding in the brain). The longer the spin lasts, the more dangerous it becomes.'

Medical Doctor Jonathan Clark. Photo: Jörg Mitter/Red Bull Content Pool

Baumgartner himself has spent several years studying the risks and preparing mentally and physically.

'Breaking the speed of sound in freefall is a pioneering effort and being a pioneer requires risk. I don’t have to put myself in danger to be happy. But I have to have a challenge. This is the ultimate skydive.'

His mentor Joe Kittinger, a retired U.S. Air Force colonel and current record holder, is also confident his protégé will succeed.

'I always tell Felix that he needs the 'Three Cs' – confidence in his team, confidence in his equipment and confidence in himself. At this stage, he’s got all that.'