The Dragon capsule's two men and two women will be going round and round the planet in an unusually high orbit - 100 miles (160 km) higher than the International Space Station - before splashing down off the Florida coast this weekend. It's SpaceX founder Elon Musk's first entry in the race for space tourism.
Isaacman, 38, made his fortune with a payment-processing company he started in his teens. He's the third billionaire to launch this summer, following the brief space-skimming flights by Virgin Galactic's Richard Branson and Blue Origin's Jeff Bezos in July.
He has pledged USD 100 million out of his own pocket to a hospital and is seeking another USD 100 million in donations. Arceneaux, a physician assistant, is the youngest American in space and the first person in space with a prosthesis, a titanium rod in her left leg.
"Someday NASA astronauts will be the exception, not the rule," said Cornell University's Mason Peck, an engineering professor who served as NASA's chief technologist nearly a decade ago.
