If the wind blowing across the New Mexican desert drops, a 43-year-old Austrian will step out of a small silver capsule and attempt to make history.
If all goes to plan, Felix Baumgartner will jump from the largest helium-filled balloon ever built for manned flight and hurtle towards the earth from near the edge of space, 37 kilometres up. As he reaches a speed of 1110km/h he will deploy his parachute, becoming the first man to break the sound barrier in free fall.
Live: Watch Baumgartner's attempt
If it goes wrong — as Jonathan Clark, medical director on the Red Bull Stratos team, which has spent five years and undisclosed millions preparing the stunt, says cheerfully — "his skin will boil".
Baumgartner said in a recent interview that he "loves a challenge". The man who made his first parachute jump at 16 — the earliest his native Austria would permit it — and then joined the army to continue his training also hates being called an adrenalin junkie: "I like the planning."
Both Baumgartner and Red Bull Stratos determinedly describe the purpose of the project as "to advance scientific discoveries in aerospace for the benefit of mankind". It is also, as one commentator has said, one giant leap for publicity.
Despite years of planning and two previous test jumps — including one in July from just over 27,000 metres — with just five days to go the attempt was put back 24 hours due to forecasts of strong winds. A weekend dress rehearsal went well, and the forecast looks good for tomorrow.
Images of the team working around the clock from mission control in Roswell, New Mexico, look like preparations for a NASA space launch — and the team does include many former NASA scientists.
They also have the formidable 81-year-old current record holder, Joe Kittinger, on board. In 1960, as a US Air Force pilot, he jumped from a balloon at 31.3 kilometres up. Kittinger still flies planes and balloons, proclaiming "the sky is still my office". Although at least one man has died trying to break his record, he says he gets several phone calls a month from people who want to attempt the challenge.
Baumgartner will go up in a specially designed capsule wearing a space suit. When the moment comes to open the door, the pressure in the capsule will be switched off and the space suit's own system will take over — a moment, he has said, "when you can feel your body just does not want to be there".
Kittinger greeted him with a hug after the July test, but clearly thinks this is free fall for softies: "I went up in an open gondola, and Felix is going up in a very sophisticated space capsule ... He's going up in luxury, he's going up in a Cadillac by comparison with what we did 52 years ago."
Baumgartner has already racked up a string of records, including in 1999 jumping from the Petronas Towers in Kuala Lumpur, then the tallest buildings in the world. He also has the record for the lowest altitude jump, from the left hand of the giant statue of Christ the Redeemer in Rio de Janeiro in 2001.
In 2003 he became the first to skydive across the English Channel, using a carbon-fibre wing, and he has also jumped from a cliff into the Stygian depths of a cave in Croatia.
"I am that type of person who wants to enjoy life," Baugartner says. His mother does get a bit anxious about it all, he admits. She will be at Roswell to watch the attempt.
"She says, 'If something goes wrong, at least I can hold you in my hands one more time.' I really don't want to put my mum in that spot, and that means I really have to stay alive."
Guardian News & Media