ROSWELL, N.M. (AP) -- Extreme athlete Felix Baumgartner started preparations early Sunday for his attempt to be the first skydiver in history to break the sound barrier.
Before sunrise the former Austrian paratrooper's team began unpacking the 30 million cubic foot helium balloon to hoist the capsule that will carry him 23 miles up in the sky.
Early Sunday, mission control officials declared a "weather hold" until 8:15 a.m. MDT, and said that inflation of the balloon wouldn't begin until after that hold is lifted. Earlier, the launch team said they were aiming for the three-hour ascent to begin Sunday at 8 a.m.
The jump was postponed twice last week because of high winds.
If he succeeds in the death-defying feat, the man nicknamed "Fearless Felix" will break a 52-year-old altitude record by Joe Kittinger, who jumped from 19.5 miles and reached a speed of 614 mph, just under the sound barrier.
This attempt will be the end of a five-year road for Baumgartner, a record-setting high-altitude jumper. He already made two preparation jumps in the area, one in March from 15 miles high and on in July from 18 miles high. It will also be the end of his extreme altitude jumping career; he has promised this will be his final jump.
Coincidentally, Sunday also marks the 65th anniversary of U.S. test pilot Chuck Yeager successful attempt to become the first man to officially break the sound barrier aboard an airplane.
Baumgartner plans to travel faster than the speed of sound with only the benefit of a high-tech suit.
Dr. Jonathan Clark, Baumgartner's medical director, has told reporters he expects the pressurized spacesuit to protect him from the shock waves of breaking the sound barrier. If all goes well and he survives the jump, NASA could certify a new generation of spacesuits for protecting astronauts and provide an escape option from spacecraft at 120,000 feet, he said.
Any contact with the capsule on his exit could tear the pressurized suit. A rip could expose him to a lack of oxygen and temperatures as low as 70 degrees below zero. It could cause potentially lethal bubbles to form in his bodily fluids, a condition known as "boiling blood."
Clark is a NASA space shuttle crew surgeon who lost his wife, Laurel Clark, in the 2003 Columbia accident. No one knows what happens to a body when it breaks the sound barrier, Clark said.
Winds have to be under 2 MPH for Baumgartner to start his ascent to the stratosphere from this desert town better known as the site of a rumored UFO landing in 1947.
Jumping from more than three times the height of the average cruising altitude for jetliners, Baumgartner's expects to hit a speed of 690 mph or more before he activates his parachute at 9,500 feet above sea level, or about 5,000 feet above the ground in southeastern New Mexico. The total jump should take about 10 minutes.
The energy drink maker Red Bull, which is sponsoring the feat, has been promoting a live Internet stream of the event from nearly 30 cameras on the capsule, the ground and a helicopter. But organizers said there will be a 20-second delay in their broadcast of footage in case of a tragic accident.
After the jump, Baumgartner says he plans to settle down with his girlfriend and fly helicopters on mountain rescue and firefighting missions in the U.S. and Austria.