SpaceX is poised to launch four civilians into space in an historic mission from the Kennedy Space Centre.
It will be the first flight into space without a professional astronaut on board.
Instead, the fully automated Crew Dragon spacecraft mission – known as Inspiration4 – will carry an entrepreneur, a childhood cancer survivor and two sweepstake winners.
The mission will see the craft and crew orbit Earth on a three-day trip following blast off from Florida at 10am AEST.
The Crew Dragon spacecraft will reach an altitude of 575 kilometres, slightly higher where the Hubble Space Telescope currently sits.
A seat on board reportedly cost about $75 million, even though the exact figures have not been released.
One of those with a spot is entrepreneur Jared Isaacman, the 38-year-old American businessman who is also the flight's private benefactor.
He believes space should be more accessible.
"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."
Cancer survivor Hayley Arceneaux will become the first person to wear a prosthesis in space with most of her left thigh bone replaced with a titanium rod.
The seat she will be in has been adjusted to accommodate her knee.
And at just 29, Ms Arceneaux will become the youngest American to have flown into space.
The final two seats have gone to two people who won them in a competition.
They are geoscience professor and pilot Sian Proctor, 51, and data engineer Chris Sembroski, 42, a former Air Force missileman.
The crew has spent the past six months taking on a training regimen with SpaceX.
The three-day journey will see the quartet free-flying through Earth's orbit, whipping around the planet once every 90 minutes while the passengers float, buoyed by microgravity, and take in panoramic views of our home planet.
To cap off the journey, their spacecraft will dive back into the atmosphere for a fiery re-entry and splash down off the coast of Florida.
And yes, for all three days in space, the passengers will all have to share a special zero-gravity-friendly toilet located near the top of the capsule.
No showering will be available, and crew will all have to sleep in the same reclining seats they will ride in during launch.
This is far from the first time civilians have travelled to space. Though NASA has been averse to signing up non-astronauts for routine missions after the death of Christa McAuliffe, a New Hampshire school teacher who was killed in the Challenger disaster in 1986, a cohort of wealthy thrill-seekers paid their own way to the International Space Station in the 2000s through a company called Space Adventures.
American investment management billionaire Dennis Tito became the first to self-fund a trip in 2001 with his eight-day stay on the International Space Station, and six others came after him. They all booked rides alongside professional astronauts on Russian Soyuz spacecraft.
This mission, however, has been billed as the beginning of a new era of space travel in which average people, rather than government-selected astronauts and the occasional deep-pocketed adventurer, carry the mantle of space exploration.
– With CNN