Skydiver Felix Baumgartner set to break sound barrier

Baumgartner aims to open his parachute about 5,000ft
(1.5km) above the ground

The Austrian skydiver Felix Baumgartner will attempt to become the first human to break the sound barrier unaided by a vehicle.

He is going to jump out of a balloon at more than 120,000ft (36.5km) above Roswell, New Mexico.

In the near vacuum at that altitude, he should accelerate beyond about 690mph (1,110km/h) within 40 seconds.

If all goes well, he will open a parachute near the ground to land softly in the desert, 10 minutes later.

The 43-year-old adventurer - famous for jumping off skyscrapers - is under no illusions about the dangers he faces.

Where he is going, the air pressure is less than 2% of what it is at sea level, and it is impossible to breathe without an oxygen supply.

Others who have tried to break the existing records for the highest, fastest and longest freefalls have lost their lives in the process.

"If something goes wrong, the only thing that might help you is God," says Baumgartner.

"Because if you run out of luck, if you run out of skills, there is nothing left and you have to really hope he is not going to let you down."

Difficult wind conditions at Roswell airport mean that lift-off for the balloon will occur no earlier than 1130 local time (1730 GMT; 1830BST).

The absolute mark for the highest skydive is held by retired US Air Force Col Joe Kittinger.

He leapt from a balloon at an altitude of 102,800ft (31.3km) in August 1960.

Now an octogenarian, Kittinger is part of Baumgartner's team and will be the only voice talking to him over the radio during the two-and-a-half hour ascent and the 10-minute descent.

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