Jeff Bezos, the world's richest person, is set to blast off on board his company Blue Origin's New Shepard launch vehicle for a suborbital flight as part of a history-making crew.
The American billionaire is due to fly at 11pm Tuesday AEST from a desert site in West Texas on an 11-minute voyage to the edge of space, nine days after Richard Branson was on board his competing space tourism company Virgin Galactic's successful inaugural suborbital flight from New Mexico.
Branson got to space first, but Bezos is due to fly higher - 100km for Blue Origin compared to 86km for Virgin Galactic - in what experts call the world's first unpiloted space flight with an all-civilian crew.
Amazon founder Bezos and his brother, private equity executive Mark Bezos, will be joined in the flight by two others.
Pioneering female aviator Wally Funk and recent high school graduate Oliver Daemen, 18, are set to become the oldest and youngest people to reach space.
"I am excited, but not anxious. We'll see how I feel when I'm strapped into my seat," Bezos said in an interview with Fox on Monday.
"We're ready. The vehicle's ready. This team is amazing. I feel very good about it. And I think my fellow crewmates feel good about it, too."
Funk was one of the so-called Mercury 13 group of women who trained to become NASA astronauts in the early 1960s but was passed over because of her gender.
Daemen, Blue Origin's first paying customer, is set to attend the University of Utrecht in the Netherlands to study physics and innovation management. His father heads investment management firm Somerset Capital Partners.
Barring technical or weather-related delays, New Shepard is due to blast off around 8am local time (11pm AEST) from Blue Origin's launch facility in rural Texas.
New Shepard is an 18-metre fully autonomous rocket-and-capsule combo that cannot be piloted from inside the spacecraft.
It is completely computer-flown and will have none of Blue Origin's staff astronauts or trained personnel onboard.
In contrast, Virgin Galactic used a space plane with a pair of pilots onboard.
New Shepard will hurtle at speeds upwards of 3540km/h to an altitude of about 100km, the so-called Karman line set by an international aeronautics body as defining the boundary between Earth's atmosphere and space.
During the flight, the crew will unbuckle for a few minutes of weightlessness and gaze back at the Earth's curvature through what Blue Origin calls the largest windows ever used in space travel.
Then, the capsule falls back to Earth under parachutes, using a last-minute retro-thrust system that expels a "pillow of air" for a soft landing at 1.6 km/h in the Texas desert.
Australian Associated Press