SpaceX’s risky next mission: The first private spacewalk

Two members of a four-person crew will conduct the walk, which is designed to test new spacesuits that the Elon Musk-backed company has developed.

The mission, called Polaris Dawn, is funded by Jared Isaacman, a technology billionaire who also paid for a flight with SpaceX completed about three years ago. Mission participants and SpaceX executives said the flight would help advance the company’s space-exploration aims, such as a human mission to Mars that has long animated Musk.

Polaris Dawn is slated to launch Tuesday from Kennedy Space Center in Florida. The spacewalk is scheduled to happen a couple of days later. Details on the walk’s timing will be released after the launch, a mission spokeswoman said.

Extravehicular activities, as spacewalks are formally called, have long been the domain of government astronauts working on official space agency projects. In 1965, a Soviet cosmonaut conducted the first, and American Ed White followed up a few months later on NASA’s Gemini 4 mission. Since then, NASA astronauts have donned agency suits to explore the moon, repair the Hubble telescope and maintain the International Space Station.

But spacewalks pose major risks for those conducting them, leaving astronauts enveloped in a device that must protect them against the vacuum of space, where debris flies by at around 17,000 miles an hour and temperatures can be extreme. In June, NASA said it ended a spacewalk at the ISS early after a water leak emerged in the suit worn by agency astronaut Tracy Dyson.

“You’re throwing away all the safety of your vehicle," Isaacman said during a recent briefing about the mission. “Your suit becomes your spaceship."

Pulling off the risky Polaris Dawn mission would mark a powerful first for SpaceX, which has carved out leading roles launching rockets, transporting crew for NASA and operating the Starlink satellite-communications network.

On Saturday, NASA said that in a later mission, SpaceX would help return two astronauts that have been parked at the International Space Station since early June. The astronauts, Barry Wilmore and Sunita Williams, have been unable to leave the ISS because of the space agency’s concerns about the Boeing vehicle that brought them there.

The coming Polaris Dawn mission, in addition to the spacewalk, will take astronauts farther into space than humans have reached in decades, according to a statement from the mission. While SpaceX has conducted other flights with civilians, there is little precedent, commercially or in terms of regulations, for private-astronaut missions.

Along with Isaacman, the other participants in the coming flight are Scott Poteet, a former Air Force pilot, and SpaceX operations engineers Sarah Gillis and Anna Menon.

All four will face challenges during the spacewalk, which is expected to take place while their Crew Dragon vehicle is orbiting Earth around 435 miles above sea level.

The spacecraft doesn’t have an airlock, so the crew will all put on their spacesuits and “vent" the vehicle, removing its pressure. Once that is complete, crew members will open a hatch on the Crew Dragon. Everyone, as well as the interior of the ship, will be exposed to the vacuum of space.

Isaacman and Gillis are slated to exit from the vehicle for around 15 to 20 minutes, a spokeswoman for the mission said. They will conduct various demonstrations to see how the suits perform. Neither will float freely from the vehicle; they will have their hands or feet connected to it at all times.

Since the mission was announced in February 2022, the four crew members’ training has included skydiving and spending time in a vacuum chamber at NASA’s Johnson Space Center in Houston. The quartet spent around 2,000 hours in a flight simulator and practiced getting used to symptoms associated with hypoxia, or when the body experiences lower levels of oxygen.

In parallel, SpaceX teams have been working to create the suits. They feature a new system to ensure joint mobility, a copper-and-tin visor that provides solar and heat protection and other technology, Gillis said during the recent briefing. She said SpaceX had conducted intensive testing of the Crew Dragon to prepare it for the vacuum of space and the suits.

The flight has objectives beyond the spacewalk, including a test of the Starlink satellite communications system and science experiments. It will deliver the crew to an orbit of 870 miles above Earth for a time, more than three times higher than the space station and the highest altitude of any crew since NASA’s Apollo moon missions decades ago.

In addition to Polaris Dawn, Isaacman is financially backing two future missions with SpaceX. The founder and chief executive of Shift4 Payments flew on the three-day Inspiration4 flight to low-Earth orbit with SpaceX in 2021. Isaacman has declined to discuss financial details related to the missions.

Private-astronaut flights are still a nascent market, and companies working on them have faced setbacks. A Japanese billionaire this summer canceled a future private-crew flight on Starship—a vehicle SpaceX is still developing—citing a lack of clarity about when the ship might be ready.

Jeff Bezos’ space company, Blue Origin, has conducted seven suborbital flights with people but paused flying those missions for more than a year to deal with a problem that emerged during an uncrewed flight in 2022.

Virgin Galactic, founded by Richard Branson to use a unique plane and spacecraft to take travelers to the edge of space, isn’t operating those missions as it works to develop new vehicles.

In addition to its work with Isaacman, SpaceX in 2022 and 2023 transported nongovernment astronauts to the ISS, on flights put together by Houston-based Axiom Space. SpaceX said in August that it would launch another private crew on a flight that would travel over the Earth’s polar regions.

Write to Micah Maidenberg at micah.maidenberg@wsj.com