The four would-be citizen astronauts poised to ride a SpaceX rocket ship around the globe as the first all-civilian crew launched into orbit said on Tuesday they were eager for liftoff on the eve of their flight, feeling only "the good kind" of jitters.
The SpaceX fully automated Crew Dragon spacecraft will orbit Earth on a three-day trip, dubbed the Inspiration4 mission, with an entrepreneur, a childhood cancer survivor and two sweepstake winners on board.
"I was just worried that this moment would never come in my life. Let's get going, let's do it," said Sian Proctor, 51, a geoscience professor, artist and lifelong space enthusiast who was a 2009 finalist in NASA's astronaut candidate programme before she was cut.
Proctor also disclosed she and her flightmates received a telephone call from one of her personal heroes, former first lady Michelle Obama, wishing them well, an honour she said "would stay with me the rest of my life".
The spacecraft is due to take off from the Kennedy Space Centre in Florida at 8:02pm local time on Wednesday night - that's around 8am New Zealand time.
Once launched, it will soar to an altitude of 575 kilometres - just above where the Hubble Space Telescope currently sits.
The flight's benefactor said the mission "represents a new era for human space flight and exploration".
The crew members professed the utmost confidence in SpaceX, the private California-based rocket company founded by billionaire entrepreneur Elon Musk.
Bankrolled by a millionaire
The flight has a private benefactor - 38-year-old Jared Isaacman, an American entrepreneur who started the payment-processing company Shift4 Payments when he was 16.
Isaacman himself is a pilot, and he also founded the tactical aircraft training centre Draken International.
He believes space should be more accessible, and theorises that investing in space now will make it more affordable in the future.
"Because it's so expensive, space has been the exclusive domain of world superpowers and the elite that they select," he said.
"It just shouldn't stay that way."
The exact cost of the flight has not been disclosed, but a seat on the Crew Dragon spacecraft reportedly cost about $US75 million.
Separately, the flight is also serving as a fundraiser for St Jude Children's Research Hospital in Tennessee.
Isaacman is taking up one of the four seats, and offered the second seat to a woman who works at St Jude hospital as a physician's assistant.
Cancer survivor among astronauts
Hayley Arceneaux, 29, is set to become the youngest American to have flown into space, but she will also become the first person to wear a prosthesis in space.
She survived a bone cancer diagnosis at age 10, and much of her left thigh bone has been replaced with a titanium rod.
She now wears a prosthesis, and as such, her SpaceX capsule seat has been adjusted to accommodate her knee. She is excited about the mission.
"Any jitters are the good kind," she said. "I'm just waiting for tomorrow to get here."
The other two seats on the flight went to contest winners - Proctor, 51, who beat out 200 other entrants in a Shift4 Payments competition, and data engineer Chris Sembroski, 42, a former Air Force missileman.
What are they flying in?
The Inspiration4 crew will be in SpaceX's Crew Dragon spacecraft, which will detatch from the Falcon 9 rocket - a reusable rocket manufactured by SpaceX.
Sitting at 8.1 metres high and 4 metres in diameter, the Crew Dragon has two windows and a newly installed glass dome at the top of the capsule.
Privacy is at a minimum - there are no sleeping compartments or work stations, and a curtain covers the toilet.
Once in the air, the Inspiration4 crew will take blood samples and conduct other medical research.
On the menu will be cold pizza, and standard astronaut fare - think pre-packaged and freeze-dried foods.
While NASA isn't involved at all in SpaceX's first private flight, the mission will set off from a launch pad used by NASA crews.
It will also land in the Atlantic Ocean near the Florida coast, like its predecessors.
- ABC /Reuters