SpaceX to launch billionaire's private crew on historic Polaris Dawn mission

A crew of four private astronauts on Tuesday were in the final stages of preparation for a risky SpaceX mission to attempt the first-ever private spacewalk using the company's new spacesuits and a redesigned spacecraft.

A billionaire entrepreneur, a retired military fighter pilot and two SpaceX employees are poised to launch at 3:38am ET from the National Aeronautics and Space Administration's (Nasa) Kennedy Space Center in Florida, Reuters reported.

The crew is set to blast into space aboard SpaceX's Crew Dragon capsule, the spacecraft's fifth — and riskiest — private space mission so far.

An attempt to launch last month was postponed hours before liftoff over a small helium leak in ground equipment on SpaceX's launchpad.

Permitted to resume Falcon 9 flights, the Polaris mission is now set for a pre-dawn launch Tuesday, but with only a 40% chance of favourable weather, according to US Space Force launch weather modeling.

SpaceX has other launch opportunities Tuesday at 5:23am and 7:09am.

"Crew safety is absolutely paramount and this mission carries more risk than usual, as it will be the furthest humans have traveled from Earth since Apollo and the first commercial spacewalk!," Elon Musk, SpaceX's CEO, wrote about the mission last month on his social media site X.

Polaris Dawn mission

The SpaceX mission, called Polaris Dawn, will last about five days in an oval-shaped orbit that passes as close to Earth as 190-kilometre and as far as 1,400km, the farthest any humans will have traveled since the end of the US' Apollo moon program in 1972.

The spacewalk is planned for the mission's third day at 700km in altitude and will last around 20 minutes.

SpaceX's Crew Dragon craft will slowly depressurise its entire cabin — it has no airlock like the ISS — and all four astronauts will rely on their slimmed-down, SpaceX-built spacesuits for oxygen.

Jared Isaacman, 41, a pilot and the billionaire founder of electronic payment company Shift4, is bankrolling the Polaris mission but has declined to say how much he is paying for the missions. However, they are likely to cost hundreds of millions of dollars.

Joining him is mission pilot Scott Poteet, 50, a retired US Air Force lieutenant colonel; and SpaceX employees Sarah Gillis, 30, and Anna Menon, 38, both senior engineers at the company.

For the spacewalk, Isaacman and Gillis will exit the spacecraft tethered by an oxygen line while Poteet and Menon stay in the cabin.

The four-person crew are effectively test subjects for an array of scientific experiments that will aim to shed light on how cosmic radiation and the vacuum of space affect the human body, adding to decades of studies on astronauts living aboard the ISS.