After jumping from a balloon at an altitude of 120,000 feet, Felix Baumgartner will likely become the first human to go faster than the speed of sound without being in an airplane, sources connected with the attempt said.
The attempt will take place later this year, Baumgartner said.
Vital to the success of the attempt will be a suit, similar to those worn by astronauts, which will maintain air pressure, protect him from freezing temperatures and deliver oxygen during his almost-five-minute free fall before his parachute opens.
Engineers have run tests with Baumgartner wearing the suit inside a pressure chamber recreating the conditions at 120,000 feet.
"The suit does its job," Baumgartner said.
Group Capt. David Gradwell, head of aviation medicine for Britain's Royal Air Force, said the attempt is a remarkable effort with significant challenges.
"[Baumgartner] will be falling very fast so he will have to be sure he remains stable so that he doesn't spin out of control," Gradwell told BBC News.
"He needs to see through the visor of his pressure helmet to see what's going on in order to operate his parachute properly and see that it has properly deployed."
If the attempt succeeds, it will beat a record set in 1960 by U.S. Air Force Capt. Joe Kittinger, who jumped from a balloon at 102,800 feet.
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