Polaris Dawn spacewalk: Watch live as SpaceX's commercial astronauts attempt mission's historic EVA

• SpaceX's Polaris Dawn mission is about to attempt the first-ever commercial spacewalk.
• Four people plan to don new spacesuits and open their Crew Dragon spaceship to the vacuum of space.

A billionaire-backed SpaceX mission is about to attempt a daring, first-of-its-kind feat.

On Thursday, four people currently orbiting Earth in a SpaceX Crew Dragon spaceship plan to don a set of brand-new spacesuits, open their spaceship's hatch to completely expose its interior to the vacuum of space, and attempt the first-ever commercial spacewalk.

Their week-long mission, called Polaris Dawn, is fully private with no NASA involvement — but it's no billionaire joyride. This spacewalk is a critical test of technical abilities that SpaceX will need to achieve Elon Musk's ultimate goal of building a city on Mars.

It's also a risky feat for all four Polaris Dawn crew members: Jared Isaacman, the mission's billionaire benefactor and commander; Anna Menon and Sarah Gillis, two SpaceX engineers; and Scott Poteet, a retired Air Force pilot who previously led strategy at Isaacman's company Shift4.

Even though only two will perform the spacewalk, the entire crew will be drifting in the vacuum of space, wearing new spacesuits that haven't been tested in-orbit yet. The stakes are high.

"I know that they take safety very seriously," Leroy Chiao, a retired NASA astronaut who has spent more than 36 hours on spacewalks and consulted for SpaceX on its Safety Advisory Panel for 12 years, told Business Insider in an email.

He added that SpaceX knows any mishap would "seriously impact" commercial human spaceflight, "if not kill it."

The Polaris program plans to livestream the spacewalk, most likely on X. Business Insider will post details here once they're available.

According to SpaceX, the spacewalk will begin at 2:23 a.m. ET on Thursday. If you're on the West Coast, that's 11:23 p.m. on Wednesday. SpaceX says there is also a backup opportunity on Friday.

"I'll be watching with great interest," Chiao said.

The Polaris Dawn spacewalk plan

The spacewalk procedure begins 48 hours before opening the Crew Dragon's hatch, with a "pre-breathe."

The two-day process should slowly decrease the pressure in the spaceship's cabin and eventually put the crew on 100% oxygen. That helps purge nitrogen from their blood and prevent a dangerous condition called "the bends."

This procedure is similar to one that astronauts on the International Space Station use before their spacewalks, although their pre-breathes only last a few hours because they do it in the confines of a small, contained airlock. Crew Dragon has no airlock, so the crew must balance the pressure in the entire cabin with the pressure in the spacesuits and give everyone's body an opportunity to adjust. Hence, a longer, 48-hour pre-breathe.

After the pre-breathe, the Polaris crew should don their spacesuits — the first SpaceX has ever designed for spacewalks. Each spacesuit will be connected to the spacecraft through an umbilical cord that will provide what the astronauts need to survive like power and air.

When the time finally comes, the crew plans to open their spaceship's hatch. Since there is no airlock, this will expose the entire cabin of the vehicle and its crew to the vacuum of space.

"You are taking on a lot of risk at that point," Isaacman said in a briefing on August 19.

"You're throwing away all the safety of your vehicle," he added.

Then, if all goes as planned, Isaacman and Gillis will leave the spacecraft to perform tests on their spacesuits, but they will always maintain contact with one of the many handrails added to the ship's exterior for this mission. The other two — Menon and Poteet — will stay inside providing support.

The risks and stakes are high

The Polaris Dawn spacewalk plan — no airlock, vehicle fully open to space — is not totally unprecedented. NASA's Gemini and Apollo programs did the same thing.

Abhi Tripathi, a former Dragon mission director at SpaceX, who now directs mission operations at UC Berkeley's Space Sciences Laboratory, told BI that the spaceship was designed "from the beginning" to withstand unplanned depressurization events.

Tripathi added that he doesn't see "any special risks" with the spacewalk. In fact, he admitted to feeling a bit of "FOMO and jealousy" seeing his former colleagues, Menon and Gillis, go to space.

What's more, SpaceX has spent two and a half years upgrading the Crew Dragon, testing it, and running simulations with the four crew members to prepare for this spacewalk.

Chiao also expressed confidence that the company has "thoroughly reviewed" its flight plans.

But trying anything new in space is risky. And there's a lot that's new in this plan: a 48-hour pre-breathe protocol, the spacesuits, the fact that a Crew Dragon spacewalk has never happened before, and the fact that all the crew members will be new to spacewalking.

Isaacman previously flew to space in 2021 on another Crew Dragon flight he commissioned. Poteet was the mission director for that flight, called Inspiration4. Menon and Gillis have provided ground support for multiple SpaceX missions. None of them have ever been in the actual vacuum of space before, though.

"They will be testing a new suit with people who have never done this before," Chiao said.

He added that depressurizing the entire cabin also adds risk for the two people remaining inside. They'll be wearing spacesuits, too, but it will still be a more precarious situation than sitting inside a sealed, pressurized, environmentally controlled spacecraft.

As with any space mission or spacewalk, there is also a risk that any of the millions of bits of space debris orbiting Earth could impact the spacecraft and endanger its crew.

Tripathi previously worked in flight reliability at SpaceX, a division which is now led by Bill Gerstenmaier, who previously spent four decades overseeing various human spaceflight programs at NASA.

"I feel very comfortable that there's maybe no better team in the world from a safety perspective than the folks that are trying to make sure every I is dotted and T's are crossed at SpaceX," Tripathi said.