* Stunt would break altitude record and the sound barrier
* Not clear how long launch window will remain open
* Fragile balloon cannot handle strong winds
(Adds background) By Irene Klotz
Oct 9 (Reuters) - Plans for an Austrian daredevil to skydivefrom a balloon 23 miles (37 km) over the New Mexico desert wereon hold on Tuesday due to winds, but his team said thedeath-defying stunt could still happen later in the day.
Felix Baumgartner, a 43-year-old helicopter pilot, hot-airballoonist and professional skydiver, would break a longstandingaltitude record and the sound barrier if the jump goes forward.
Weather will be key. Baumgartner's team issued a statementearly Tuesday morning saying the launch of the massive butfragile helium balloon that would carry him to an altitude of120,000 feet (36,576 meters) above Roswell, New Mexico, had beendelayed until at least 9:30 a.m. EDT (1330 GMT).
The delay was prompted by winds at about 700 feet (213meters) above the launch site, the team said.
It was not immediately clear how long the window for thepossible launch would remain open but it takes about 2.5 to 3hours to reach 120,000 feet.
The 30-million-cubic-foot (850,000-cubic-meter) plasticballoon, which is about one-tenth the thickness of a Ziploc bag,cannot handle winds greater than 6 miles per hour (9.7 km perhour). The balloon will carry a specially made space capsulewhere Baumgartner will spend the ride into the stratosphere.
Baumgartner hopes to break the current record of 102,800feet (31,333 meters) for the highest-altitude freefall, amilestone set in 1960 by U.S. Air Force Colonel Joe Kittinger.
By jumping from 120,000 feet (36,576 meters) Baumgartnerwill also break the sound barrier. With virtually no air tocushion his fall, he is expected to reach the speed of sound,which is 690 mph (1,110 kph) at that altitude, after about 35seconds of freefall.
He will stay supersonic for nearly a minute and shouldfreefall for a total of 5 minutes and 35 seconds.
When Baumgartner jumps from the capsule, the position of hisbody will be crucial, since there is no air for him to movearound in. If he falls in a way that puts him into a rapid spin,Baumgartner could pass out and risk damaging his eyes, brain andcardiovascular system.
Baumgartner's safety gear includes a custom spacesuit toprotect him from the low pressure and the extreme cold.Temperatures are expected to be as low as about minus-70 degreesFahrenheit (minus-57 degrees Celsius.)
The near-vacuum puts him at risk of ebullism, a potentiallylethal condition in which fluids in the body turn to gas and theblood literally boils. Severe lung damage could occur withinminutes.
Helicopters equipped with newly developed instruments totreat lung damage will be standing by during Baumgartner'sskydive.
"What we're doing here is not just a record attempt. It's aflight test program," project adviser Jonathan Clark, a medicaldoctor and former NASA flight surgeon, told reporters during anews conference on Monday.
Among those interested in the spacesuit research arecommercial companies developing spaceships for passenger travel.The research could help people survive a high-altitude accident.
Clark's wife, shuttle Columbia astronaut Laurel Clark, diedalong with six crewmates when the spaceship broke apart overTexas on Feb. 1, 2003, as it headed for a landing in Florida.
Baumgartner's jump is sponsored by Red Bull, which will bewebcasting the event live at redbullstratos.com
(Editing by Tom Brown and Doina Chiacu)
Keywords: USA SPACE/SKYDIVE