"You have to remember all the procedures," he said in an interview during testing for the jump. "You know you're in a really hostile environment. And you cannot think about anything else. You have to be focused. Otherwise, you're gonna die."

The balloon being used is light and translucent. The material is only .0008 of an inch thick, and it will change shape and size as it rises.

The pressurized helmet and suit, which restrict Baumgartner's mobility and together weigh 100 pounds, have been equipped with sensors and recorders to measure everything from his speed to his heart rate. Cameras on the ground and on the capsule will transmit live images of his attempt.

Baumgartner was not doing interviews leading up to the jump, but his performance coach, Andy Walshe, described him as mentally well-prepared.

"He knows that he's rehearsed it and knows what to do," Walshe said Sunday. "We want him in the right state of mind. We ask him to reflect on what he's done, what he's been through and what he's achieving for himself personally, so he can relax and focus."

The record for such a jump is currently held by Col. Joe Kittinger, who in 1960 jumped from 102,800 feet as part of a U.S. Air Force mission. More than 50 years later, Kittinger is a consultant and mentor for Baumgartner's effort.

Kittinger has also been giving Baumgartner advice on what to expect. For example, he described what it feels like to fall through space when there is so little air: "There's no way you can tell how fast you're going, because there's no visual cues."

Kittinger rejects any suggestion that he is jealous that Baumgartner is poised to beat his record.

"Oh no. I'm delighted," he told CNN recently. "He's advancing science, and he'll do a great job."