(CNN) -- Skydiver Felix Baumgartner's next chance to attempt a record-breaking free fall from the stratosphere will be on Sunday.


With nothing but a space suit, helmet and parachute, Baumgartner is aiming to jump from a balloon at a higher altitude than anyone ever has -- 120,000 feet (about 23 miles), more than three times the cruising altitude of the average airliner.

The Austrian daredevil, dubbed "Fearless Felix," also hopes to be the first person to break the sound barrier without the protection of a vehicle. At that altitude, the thin air provides so little resistance that after just 40 seconds, he is expected to be free-falling faster than 690 miles an hour.

"He's prepared. He's done the hard work," his performance coach, Andy Walshe, told reporters last week.

On the day of the launch, "we wake him up at 2 a.m.," he said. "We're in a very prescribed routine at that point. Every moment -- what has to happen. That's what helps you keep your focus."

Project meteorologist Don Day said Saturday that weather conditions Sunday look favorable at ground level, but he is keeping an eye on the potential for stronger winds at higher altitudes -- including possible wind speeds exceeding 100 mph at the jet stream level.

Baumgartner almost made an attempt last Tuesday from his launch site in Roswell, New Mexico. But as he was waiting in his capsule for the giant helium balloon to finish inflating, a gust of wind twisted the balloon like a spinnaker, and ruined it.

"We had a few minutes of chaos and hell," said Art Thompson, the technical project director for the mission, after Tuesday's setback.

He said the failed attempt cost them a balloon worth several hundred thousand dollars, plus around $65,000 worth of helium. "This was, unfortunately, an extremely expensive dress rehearsal of what we want to do," he said.

But with a backup balloon on site -- and more helium as well -- the main question now is the weather.

After Tuesday's launch was scrubbed, Baumgartner tweeted, "We've made it so far, there's no way turning back."

Once the launch occurs, Baumgartner expects to spend two or three hours on the ascent in a capsule hanging from the helium balloon. Then he will open the hatch, climb out, jump off the step with a bunny hop, and form a crouched "delta" position to maximize his acceleration.

He plans to fall 115,000 feet in less than five minutes, then deploy a parachute for the final 5,000 feet to earth.

The attempt has serious risks. He and his team have practiced how he can avoid getting trapped in a dangerous "horizontal spin." His life will also depend on the integrity of his pressure suit, since temperatures could hit 70 degrees below zero Fahrenheit or lower, and the atmosphere will be so thin that his blood would vaporize if he were unprotected.

If he loses consciousness during the five-minute plunge, he will survive only if his parachute deploys automatically.

Another unknown: the effects on the body of breaking the sound barrier. While reaching such speeds can cause stress on an aircraft, planners for this jump believe there will be little effect on Baumgartner because he will be at an altitude at which there is so little air that shock waves are barely transmitted.

Baumgartner is an Austrian helicopter pilot and former soldier who has parachuted from such landmarks as the Petronas Towers in Malaysia and the Christ the Redeemer statue in Rio de Janeiro.

He has been preparing for his latest feat for five years -- both physically and mentally.

"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, one-tenth as thick as a sandwich bag, 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 at www.youtube.com/user/redbull.

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 on Baumgartner's effort, and will be the one from mission control who speaks to Baumgartner over the headset throughout the attempt.

After a test jump earlier this year, when the two lost communication with each other, Baumgartner told CNN he realized how much he relies on Kittinger as a mentor.

"Immediately you can feel how lonely you feel," Baumgartner said. "I wanted to hear the voice because I am so used to this. Every time we have been practicing on the ground, Joe was talking to me. So I am used to the voice, and [it] makes me feel safe."

Kittinger has also been giving Baumgartner advice on what to expect during his attempt. For example, he said, when you're at an altitude so high that you see the curvature of the earth, "there's no way you can tell how fast you're going, because there's no visual cues."

He also learned the importance of patience back when he was making jumps, Kittinger told reporters last week.

"On one occasion, I waited 30 days to launch a stratospheric balloon," he said.

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