Yet another billionaire entrepreneur is set to ride into space this week, strapped inside the capsule of a SpaceX rocketship, as part of an astro-tourist team poised to make history as the first all-civilian crew launched into earth orbit.
Jared Isaacman, the American founder and chief executive of ecommerce firm Shift4 Payments, will lead three fellow spaceflight novices on a trip expected to last three days from blast-off at Cape Canaveral, Florida, to splashdown in the Atlantic.
The 38-year-old tech mogul has plunked down an unspecified but presumably exorbitant sum to fellow billionaire and SpaceX owner Elon Musk to fly Isaacman and three specially selected travel mates into orbit aboard a SpaceX Crew Dragon capsule.
The crew vehicle is set for launch from NASA's Kennedy Space Center atop one of Musk's reusable Falcon 9 rockets, with a 24-hour targeted launch window that opens at 8pm US Eastern Daylight Time on Wednesday. That window will be narrowed, or possibly altered, a few days before, depending on weather.
Dubbed Inspiration4, the orbital outing was conceived by Isaacman primarily to raise awareness and support for one of his favourite causes, St. Jude Children's Research Hospital, a leading paediatric cancer centre. He has pledged $US100 million ($A136 million) personally to the institute.
But a successful mission would also help usher in a new era of commercial space tourism, with several companies vying for wealthy customers willing to pay a small fortune to experience the exhilaration of supersonic flight, weightlessness and the visual spectacle of space.
Setting acceptable levels of consumer risk in the inherently dangerous endeavour of rocket travel is also key, and raises a pointed question.
"Do you have to be both rich and brave to get on these flights right now?" said Sridhar Tayur, a professor of operations management and new business models at Carnegie Mellon University in Pittsburgh, in an interview with Reuters on Friday.
SpaceX is easily the most well-established player in the burgeoning constellation of commercial rocket ventures, having already launched numerous cargo payloads and astronauts to the International Space Station for NASA.
Rival companies Virgin Galactic and Blue Origin both recently celebrated their debut astro-tourism missions with their respective founding executives - billionaires Richard Branson and Jeff Bezos - each going along for the ride.
But those two high-profile flights were suborbital in scale, sending their crews of citizen astronauts to space and back in a matter of minutes.
The SpaceX flight is designed to carry its four passengers where no all-civilian crew has gone before - into Earth orbit.
There, they will circle the globe once every 90 minutes at more than 27,000km/h, or roughly 22 times the speed of sound. The target altitude is 575 kilometres, beyond the orbits of the International Space Station or even the Hubble Space Telescope.
Like Blue Origin, the 20-story-tall SpaceX launch vehicle and crew capsule will take off vertically from a launch pad on a flight directed entirely from the ground.
Branson's suborbital rocket plane, by contrast, had two highly trained pilots at the controls as it carried its four rear-seat passengers 80 kilometres high.
The Inspiration4 crew will have no part to play in operating their spacecraft, despite some largely honorary titles, though two members - Isaacman and geoscientist Sian Proctor - are licensed pilots.
Rounding out the crew are "chief medical officer" Hayley Arceneaux, 29, a bone cancer survivor turned St. Jude physicians' assistant, and mission "specialist" Chris Sembroski, 42, a US Air Force veteran and aerospace data engineer who won a seat in a sweepstake.
The four crewmates have spent the past five months undergoing rigorous preparations, including altitude fitness, centrifuge (G-force), microgravity and simulator training, emergency drills, classroom work and medical exams.