Polaris Dawn’s spacewalk will be historic — and risky. Here’s everything to know.

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 on X. According to SpaceX, the livestream will start one hour before the spacewalk begins at 2:23 a.m. ET on Thursday. If you’re on the West Coast, that’s 11:23 p.m. PT 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.”

“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.

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.

“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 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.