The journey has been commissioned by Jared Iaacman, a US billionaire who made his fortune in tech and fighter jets and says he has been a space geek since he was a child. It is not clear how much he has paid for the journey.
But he has already offered three tickets to other members of the public. One of them will go to a healthcare worker from St Jude Children’s Research Hospital, who has already been selected for the mission, and another will go to a business owner who uses Shift4 payments, the credit card processing company that helped make Mr Isaacman rich.
And the fourth will be part of the plan to use the mission to raise $200 million for St Jude. Anyone who donates to the hospital during February will be entered into a lottery to win that seat.
"I truly want us to live in a world 50 or 100 years from now where people are jumping in their rockets like the Jetsons and there are families bouncing around on the moon with their kid in a spacesuit," said Mr Isaacman, who turns 38 next week.
"I also think if we are going to live in that world, we better conquer childhood cancer along the way."
He has bought an ad at the Super Bowl next weekend to publicise the mission, dubbed Inspiration4 and targeted for October.
Details of the ride in a SpaceX Dragon capsule are still being worked out, including the number of days the four will be in orbit after blasting off from Florida. The other passengers will be announced next month.
The trip is the latest private space travel announcement. Three businessmen are paying 55 million dollars each to fly to the International Space Station next January aboard a SpaceX Dragon, and a Japanese businessman has a deal with SpaceX to fly to the moon in a few years.
Mr Isaacman would not divulge how much he is paying SpaceX, except to say that the anticipated donation to St Jude "vastly exceeds the cost of the mission".
While a former Nasa astronaut will accompany the three businessmen, Mr Isaacman will serve as his own spacecraft commander.
The appeal, he said, is learning all about about SpaceX's Dragon and Falcon 9 rocket. While the capsules are designed to fly autonomously, a pilot can override the system in an emergency.
Mr Isaacman dropped out of high school when he was 16, then started a business in his parents' basement that became the genesis for Shift4.
He set a speed record flying around the world in 2009 while raising money for the Make-A-Wish programme, and later established Draken International, the world's largest private fleet of fighter jets.
His 100 million dollar commitment to St Jude in Memphis is the largest by a single individual and one of the largest overall.
"We're pinching ourselves every single day," said Rick Shadyac, president of St Jude's fundraising organisation.
Besides SpaceX training, Mr Isaacman intends to take his crew on a mountain expedition to mimic his most uncomfortable experience so far - camping on the side of a mountain in bitter winter conditions.
"We're all going to get to know each other... really well before launch," he said.
Additional reporting by Associated Press
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