UPDATE 3-Daredevil set for supersonic skydive over New Mexico

* Launch now targeted for 1:15 p.m. EDT (1715 GMT

* Stunt would break altitude record and sound barrier

(Recasts with new launch time, details)

By Irene Klotz

Oct 9 (Reuters) - A n Austrian daredevil made last-minute preparations on Tuesday for a death-defying s kydive from a balloon 23 miles (37 km) over the New Mexico desert af ter delays due to winds earlier in the day.

Felix Baumgartner, a 43-year-old helicopter pilot, hot-air balloonist and professional skydiver, would break a longstanding altitude record and the sound barrier if the jump goes forward.7

Baumgartner's team said the launch of a massive but fragile helium balloon that would carry him u p t o 120,000 feet (36,576 meters) above Roswell, New Mexico, had been sc heduled for about 1:1 5 p.m . EDT (1715 GMT ).

The launch was delayed by about four hours b ecause of winds above the l aunch site, the team said in a statement.

After they died down Baumgartner, wearing a pressurized spacesuit, p repared t o climb into a specially made capsule that wou ld c arry him into the stratosphere.

"(The) countdown is officially back on," Sarah Anderson, a member of Baumgartner's launch team, told Reuters by e-mail.

If the launch proceeds it would take about 2.5 to 3 hours to reach 120,000 feet.

The 30-million-cubic-foot (850,000-cubic-meter) plastic balloon, which is about one-tenth the thickness of a Ziploc bag, cannot handle winds greater than 6 miles per hour (9.7 km per hour).

Baumgartner hopes to break the record of 102,800 feet (31,333 meters) for the highest-altitude freefall, a milestone set in 1960 by U.S. Air Force Colonel Joe Kittinger.

As he falls from 120,000 feet (36,576 meters) Baumgartner would also break the sound barrier. With virtually no air to resist his fall, he was expected to reach the speed of sound, which is 690 mph (1,110 kph) at that altitude, after about 35 seconds of freefall.

He would stay supersonic for nearly a minute and should freefall for a total of 5 minutes and 35 seconds.

When Baumgartner jumps from the capsule, the position of his body will be crucial, since there is no air for him to move around in. If he falls in a way that puts him into a rapid spin, Baumgartner could pass out and risk damaging his eyes, brain and cardiovascular system

Baumgartner's safety gear includes his custom spacesuit that will protect him from low pressure and the extreme cold. Temperatures are expected to be as low as about minus 70 degrees Fahrenheit (minus 57 degrees Celsius.)

The near-vacuum puts him at risk of ebullism, a potentially lethal condition in which fluids in the body turn to gas and the blood literally boils. Severe lung damage could occur within minutes.

Helicopters equipped with newly developed instruments to treat lung damage will be standing by during Baumgartner's skydive.

"What we're doing here is not just a record attempt. It's a flight test program," project adviser Jonathan Clark, a medical doctor and former NASA flight surgeon, told reporters during a news conference on Monday.

Among those interested in the spacesuit research are commercial companies developing spaceships for passenger travel. The research could help people survive a high-altitude accident.

Clark's wife, astronaut Laurel Clark, died along with six crewmates when the space shuttle Columbia broke apart over Texas on Feb. 1, 2003, as it headed for a landing in Florida.

(Editing by Tom Brown and David Storey)

((thomas.brown@thomsonreuters.com)(305 810 2688)(Reuters Messaging: thomas.brown.reuters.com@reuters.net))