A data engineer on the first all-civilian astronaut crew to reach orbit has made some spaceflight history, with a zero-gravity ukulele performance in a SpaceX capsule hundreds of kilometres above earth's surface.
Chris Sembroski, 42, a Lockheed Martin employee and US Air Force veteran, strummed a few chords for home-bound viewers during a 10-minute show-and-tell session on Friday by the four-member Inspiration4 team as they flew about 28,000km/h over Europe.
SpaceX, the rocket company owned by high-tech mogul and Tesla electric car maker chief Elon Musk, announced afterward that the crew was expected to return to earth on Saturday.
Splashdown is set for just after 7pm EDT (0900 on Sunday) off Florida's coast.
The astronauts spent much of their first 48 hours aloft schmoozing from space, including phone calls with family, friends and supporters such as Musk and Hollywood star Tom Cruise, mission officials said.
They also appeared by video link on the New York Stock Exchange on Friday for the ringing of the closing bell.
The crew's orbital appearance aboard the Crew Dragon capsule was live-streamed over the YouTube channel of SpaceX, which supplied the spacecraft, launched it from Florida and operated it from the company's suburban Los Angeles headquarters.
Billionaire Jared Isaacman, chief executive of the e-commerce firm Shift4 Payments, paid Musk an undisclosed sum for the flight - reported about $US200 million ($A274 million) by Time magazine - on what became SpaceX's inaugural astro-tourism flight.
Sembroski was not alone in demonstrating spaceflight pastimes.
Geoscientist and former NASA astronaut candidate Sian Proctor, 51, showed off a drawing she made while in orbit, and Hayley Arceneaux, 29, a physician assistant at St Jude Children's Research Center in Tennessee, where she was once a childhood cancer patient herself, twirled about the cabin to give viewers a feel for microgravity.
Inspiration4 blasted off on Wednesday from the Kennedy Space Center in Cape Canaveral atop a SpaceX Falcon 9 rocket. The crew capsule reached a cruising orbital altitude of more than 585 kilometres - higher than the International Space Station or Hubble Space Telescope, and the furthest any human has flown from earth since NASA's Apollo moon program ended in 1972.
The SpaceX launch marked a leap ahead of competitors Virgin Galactic and Blue Origin, which also offer rocket rides to customers willing to pay a small fortune.
Australian Associated Press