Felix Baumgartner, 43, will plummet from a special balloon-hoisted capsule 23 miles (120,000 ft) in the air, wearing a pressurised suit. It is thought that he will reach speeds of up to 690mph before his parachute opens.

The diver is expected to land in the desert around Roswell, New Mexico - where an alien craft allegedly crashed to earth in 1947.

Baumgartner will ascend to the platform in a three-hour balloon flight, accompanied by a team of experts including a former NASA crew surgeon, leading space engineers and scientists and a 84-year-old retired US Air Force Colonel, who set a fistful of word records parachuting himself form 102,800 feet in 1960.

The jump height is three times the common cruising altitude of today's aircraft, and temperatures can be as low as -56 degrees Celsius. Oxygen is almost inexistent and air pressure is less than one per cent that of the Earth's surface.

Should the suit rip, experts say Baumgartner's skin could boil and his brain explode under the pressure, in front of a live audience of millions.

Despite the obvious risks, Baumgartner's Red Bull-sponsored Stratos team say they have every confidence in the mission, pointing out that they have been planning the jump for the last five years and the equipment has been tested to exhaustion.

"So many unknowns, but we have solutions to survive," Baumgartner said.

"I'm deleting any negative thoughts and focusing on what I have to do right now," the veteran diver tweeted.

Baumgartner's confidence is shared by his mum Eva, who has arrived at the launch base in Roswell to support her son.

"We have all waited for this to happen for so long. Felix's dream is becoming a reality," she said.

It is thought that Baumgartner will break the barrier about 40 seconds after jumping. The parachute will open about six minutes into the jump, around 5,000ft up.

The whole descent will last for 20 minutes and will be fully televised, with Baumgartner being followed by 35 cameras.

"We want to share that [the event] with the world. It's like landing on the moon. Why was that live?" Baumgartner asked Fox.

According to Red Bull Stratos, setting a new world record is not the only aim of the jump, as Baumgartner's "attempt to dare atmospheric limits" also "holds the potential to provide valuable medical and scientific research data for future pioneers."

After landing, Baumgartner, who in 2003 famously skydived across the English Channel flying with a carbon fibre wing, plans to retire to the safer occupation of mountain and fire fighting helicopter rescue.

"After this I'm going to retire because I've been successfully doing things for the last 25 years and I'm still alive," he said.

NASA Mexico