CAPE CANAVERAL, FLORIDA (REUTERS)Entrepreneur Elon Musk's SpaceX is set to launch two American astronauts to the International Space Station on Wednesday (May 27) from Nasa's Kennedy Space Centre in Florida, ending the US space agency's nine-year hiatus in human spaceflight.
California-based SpaceX's Crew Dragon capsule carrying astronauts Doug Hurley and Bob Behnken and its Falcon 9 rocket is due to lift off at 4.33pm EDT (2033 GMT) on Wednesday from the same launch pad used by Nasa's last space shuttle mission in 2011.
President Donald Trump and Vice-President Mike Pence will view the launch in person, a White House spokesman said.
For Mr Musk, SpaceX and Nasa, a safe flight would mark a milestone in the quest to produce reusable spacecraft that can make space travel more affordable. Mr Musk is the founder and CEO of SpaceX and CEO of Tesla Inc.
"Bob and I've been working on this programme for five years, day in and day out," Mr Hurley, 53, said as he and Mr Behnken, 49, arrived at the Kennedy Space Centre from Houston the previous week."It's been a marathon in several ways, and that's what you'd expect to develop a human-rated space vehicle that can go to and from the International Space Station."
Nasa, hoping to stimulate a commercial space marketplace, awarded US$3.1 billion (S$4.41 billion) to SpaceX and US$4.5 billion to Boeing Co to develop dueling space capsules, experimenting with a contract model that allows the space agency to buy astronaut seats from both companies.
Boeing's CST-100 Starliner capsule is not expected to launch its first crew until 2021.
Nasa Administrator Jim Bridenstine declared the mission a"go" the previous week at Kennedy Space Centre after space agency and SpaceX officials convened for final engineering checks.
SpaceX successfully tested Crew Dragon without astronauts the previous year in its first orbital mission to the space station.
That vehicle was destroyed the following month during a ground test when one of the valves for its abort system burst, causing an explosion that triggered a nine-month engineering investigation that ended in January.