Skydiving at Mach 1.24

Roswell, New Mexico: A man fell to Earth from more than 24 miles high Sunday, becoming the first human to break the sound barrier under his own power - with some help from gravity.

The man, Felix Baumgartner, an Austrian daredevil, made the highest and fastest jump in history after ascending by a helium balloon to an altitude of 128,100 feet. As millions around the world experienced the vertiginous view from his capsule's camera, which showed a round blue world surrounded by the black of space, he stepped off into the void and plummeted for more than four minutes, reaching a maximum speed measured at 833.9 miles per hour, or Mach 1.24.

He broke altitude and speed records set half a century ago by Joe Kittinger, now 84, a retired Air Force colonel whose reassuring voice from mission control guided Mr Baumgartner through tense moments. Engineers considered aborting the mission when Mr Baumgartner's faceplate began fogging during the ascent, but he insisted on proceeding and made plans for doing the jump blind.

That proved unnecessary, but a new crisis occurred early in the jump when he began spinning out of control in the thin air of the stratosphere - the same problem that had nearly killed Mr Kittinger a half-century earlier. But as the atmosphere thickened, Mr Baumgartner managed to stop the spin and fall smoothly until he opened his parachute about a mile above the ground and landed smoothly in the New Mexico desert.

"It was harder than I expected," said Mr Baumgartner, a 43-year-old former Austrian paratrooper. "Trust me, when you stand up there on top of the world, you become so humble. It's not about breaking records any more. It's not about getting scientific data. It's all about coming home."

Mr Kittinger praised Mr Baumgartner's courage for proceeding with the mission and said that he had more than broken a record.

"He demonstrated that a man could survive in an extremely high altitude escape situation," Mr Kittinger said. "Future astronauts will wear the spacesuit that Felix test-jumped today."

Mr Baumgartner was backed by a NASA-style mission control operation at an airfield in Roswell that involved 300 people, including more than 70 engineers, scientists and physicians who have been working for five years on the project, called Red Bull Stratos, after the drink company that has financed it.

Besides aiming at records, the engineers and scientists on the Red Bull Stratos team have been gathering and publishing reams of data intended to help future pilots, astronauts and perhaps space tourists survive if they have to bail out.

"We're testing new spacesuits, escape concepts and treatment protocols for pressure loss at extreme altitudes," said the Red Bull Stratos medical director, Dr Jonathan Clark, who formerly oversaw the health of space shuttle crews at NASA. "There are so many things that could go wrong here that we're pushing the technical envelope."

While building the customized suit and capsule, the team of aerospace veterans had to contend with one crucial uncertainty: What happens to the human body when it breaks the sound barrier? There was also one major unexpected problem for Mr Baumgartner, known to his fans as Fearless Felix.

Although he had no trouble jumping off buildings and bridges, and soaring across the English Channel in a carbon-fibre wing, he found himself suffering panic attacks when forced to spend hours inside the pressurized suit and helmet. At one point in 2010, rather than take an endurance test in it, he went to an airport and fled the United States. With the help of a sports psychologist and other specialists, he learned techniques for dealing with the claustrophobia.

One of the techniques Mr Baumgartner developed was to stay busy throughout the ascent. He conversed steadily with Mr Kittinger, a former fighter pilot whose deep voice exuded the right stuff as he confidently went through a 40-item checklist rehearsing every move that Mr Baumgartner would make when it came time to leave the capsule.

When the actual moment came, Mr Kittinger said to him, "All right, step up on the exterior step. Start the cameras. And our guardian angel will take care of you now."

Mr Baumgartner stepped outside, saluted and made the jump right after delivering a message that was mostly garbled by radio static. Afterward, he repeated it: "I know the whole world is watching, and I wish the whole world could see what I see. Sometimes you have to go up really high to understand how small you really are."

Engineers forecast that Mr Baumgartner would reach a supersonic speed of 720 miles an hour by jumping from 120,000 feet, the altitude that they had promised to reach. But all along they had hoped the balloon would go even higher - and lead to an even faster fall, which did occur. As a result, even though he fell farther than Mr Kittinger did, his fall took less time: 4 minutes and 20 seconds, which was 16 seconds less than Mr Kittinger's.

Mr Baumgartner jumped from an altitude of 128,100 feet and landed in desert about 4,000 above sea level, so the jump from capsule to the ground covered about 23 and a half miles.

When Mr Baumgartner lost control of his body during the early part of the jump, he feared going into a flat spin that would send blood away from the centre of his body.

"At a certain R.P.M.," he said afterward, "there's only one way for blood to leave your body, and that's through your eyeballs. That means you're dead. That was what we feared most."

Because of the limited sensation inside his pressurized suit, he said recovering from a spin was much more difficult than during an ordinary dive.

"As a sky-diver, you can feel the air on your right shoulder and you immediately know what to do," he said. "Here you don't feel the air, so you have to wait until the air pushes you around. Then you think, 'Oh, it pushed me around clockwise - that means I have to do this.' "

Brian Utley of the FAI, the international federation that certifies aerospace records, calculated the height and speed of the jump by independently analysing data gathered on microchips in Mr Baumgartner's suit. After a thorough analysis of the data is made over the next several weeks, Mr Utley said, the precise official figures might be slightly different, but he had no doubt that Mr Baumgartner had set a supersonic speed record.

As the balloon rose in the sky, viewers from around the world went to YouTube to watch a live video stream from the capsule and mission control. By the time Mr Baumgartner made his leap into space, the audience grew to a peak of eight million.