Amazon founder Jeff Bezos is preparing to fly to space on Tuesday on a rocket built by his private space company, Blue Origin.
If successful, he will make his mark on human space flight after more than two decades of work.
The July 20 launch, which will be broadcast live, is a demonstration of Mr Bezos's faith in the company's New Shepard rocket and in the experience he hopes to sell to customers in the future.
Founded in secret in 2000 — years before Sir Richard Branson or Elon Musk set up their rival private space businesses — with the aim of bringing down the cost of getting into space, Blue Origin has been shrouded in secrecy.
Space tourism was intended to be a large part of the business from the outset, but Mr Bezos, 57, has traditionally shied away from the kind of brash publicity stunts for which his rivals have become known.
It took 15 years before the company reached space with a rocket, and fellow billionaire Mr Musk once suggested Mr Bezos should focus more of his time on making Blue Origin a success.
Earlier this month, Mr Bezos officially stepped down as chief executive of Amazon, the sprawling e-commerce company that helped to make him the world's richest man, turning his attention to the budding space company he founded more than 20 years ago.
Now worth an estimated $210 billion, Mr Bezos has reportedly been selling a billion dollars in Amazon stock a year to fund Blue Origin, and hopes to one day help humans leave Earth to live in huge space colonies.
For the time being, however, Mr Bezos hopes the experience of suborbital space flight that Blue Origin wants to offer will prove a more compelling option than the ones soon to be available from his competitors.
Billionaire space race
Blue Origin's rocket is capable of soaring higher than Mr Branson's flight earlier this month, which peaked at an altitude of around 86km.
The company has often pointed out that Virgin Galactic's spaceplane is not able to cross the Karman line, which says space begins at 100km, sparking a debate over where the edge of space actually lies.
Blue Origin was criticised after it posted an image on Twitter comparing the two launch systems in the build-up to Mr Branson's pioneering first flight.
Mr Bezos's personal attachment to Blue Origin is clear. He is said to sign off emails with the company's motto: Gradatim Ferociter, Latin for “step by step, ferociously".
What is also evident is his long-standing obsession with space and space exploration.
“To see the Earth from space, it changes you, it changes your relationship with this planet, with humanity,” Mr Bezos said in a video last month, in which he announced that his brother Mark would also be on board the flight.
Aside from the Bezos brothers, the Blue Origin rocket will also be carrying Wally Funk, an aviation pioneer who was the first female head of the US Federal Aviation Agency and who, at the age of 82, will become the oldest person ever to fly to space.
The winning bidder of the public auction for the final seat, who is yet to be identified after paying $28 million, will be on a later flight, the company said.
In that seat instead will be 18-year-old physics student Oliver Daemen, Blue Origin announced on Thursday. If all goes to plan he will become the youngest person ever to fly to space.
Blue Origin's history is littered with references to the heroes of space exploration in the twentieth century.
Its two rockets, New Shepard and New Glenn, are both named after trailblazing US astronauts, and Mr Bezos's coming flight is due to blast off on the same date that Nasa's Apollo 11 mission to the Moon took off in 1969.
Standing 18.3 metres tall, the New Shepard is fully autonomous and reusable, and is designed to blast its six passengers to an altitude of more than 100km, with the capsule landing by parachute separately from the booster.
Early dreams of space
Born in New Mexico to a teenage mother, Jackie, Mr Bezos developed a love of innovation and computers from an early age.
His mother married a Cuban immigrant, Mike Bezos, who adopted Jackie's son after he turned four.
Mr Bezos started his first business, a children's education camp called the Dream Institute, with his girlfriend at the time, while they were still at high-school.
From an early age, Mr Bezos was already thinking about ambitious plans in space.
In 1982 the Miami Herald published a round-up of local high school valedictorian speeches, including the one given by a young Mr Bezos.
In it, the newspaper reported, he said he dreamt of opening orbital hotels and building space colonies.
″The whole idea is to preserve the Earth,” he was quoted as saying.
After studying computer science and electrical engineering at Princeton University, he went on to become the youngest senior vice president on Wall Street in 1990.
In 1994, he founded Amazon out of his garage and he became a billionaire five years later.