Billionaire American businessman Jeff Bezos and his three crewmates are engaging in a crash course of training in preparation for his company Blue Origin's inaugural flight to the edge of space.
The suborbital launch from a site in the high desert plains of West Texas marks a crucial test for Blue Origin's New Shepard spacecraft, an 18-metre tall and fully autonomous rocket-and-capsule combo that is central to plans by Bezos to tap a potentially lucrative space tourism market.
The 11-minute trip planned for Tuesday from the company's Launch Site One facility is set to include the oldest person ever to go to space - 82-year-old trailblazing female aviator Wally Funk - and the youngest - 18-year-old physics student Oliver Daemen.
Joining them for Blue Origin's launch will be Bezos, the founder and current executive chairman of Amazon.com, and his brother Mark Bezos.
The mission would represent the world's first unpiloted flight to space with an all-civilian crew. Blue Origin, which will have none of its staff astronauts or trained personnel onboard, expressed confidence at a briefing on Sunday.
"We are not currently working any open issues and New Shepard is ready to fly," Flight Director Steve Lanius said, adding that the weather forecast appeared favourable for the scheduled lift-off at 8am (11pm AEDT) on Tuesday.
New Shepard is due to launch nine days after rival Richard Branson's space tourism company, Virgin Galactic, successfully carried out a suborbital flight from New Mexico with the British billionaire inside its rocket plane.
Illustrating tensions in the high-stakes "billionaire space race," Blue Origin has described Virgin Galactic as falling short of the 62-mile-high-mark (100 kilometres) - called the Karman line - set by an international aeronautics body as defining the boundary between Earth's atmosphere and space.
The US space agency NASA and the US Air Force both define an astronaut as anyone who has flown higher than 80km, as Branson achieved with his flight.