SpaceX Polaris Dawn Spacewalk: How to Watch the Astronauts

Early Thursday morning, four private astronauts circling far above Earth will try something daring — let all the air out of their spacecraft.

That will be a prelude for two of the astronauts, who will then venture outside for the first commercial spacewalk ever, an event that is to be the highlight of the Polaris Dawn mission led by Jared Isaacman, a billionaire entrepreneur.

When is the spacewalk and how can I watch it?

The spacewalk is scheduled to begin at 2:23 a.m. Eastern time. SpaceX plans to broadcast live coverage starting one hour before the spacewalk begins.

If needed, a backup opportunity is available on Friday at the same time.

What will happen during the spacewalk?

Because there is no airlock in the SpaceX Crew Dragon spacecraft used for the flight, the only way to perform a spacewalk is to let all the air out of the spacecraft, and then open one of the hatches. That requires all four crew members to wear spacesuits.

NASA and Soviet astronauts conducted spacewalks in a similar manner in the 1960s.

As the Crew Dragon swings around Earth in an elliptical orbit that swings as close as 120 miles to the surface and as high as 460 miles, Mr. Isaacman and Sarah Gillis, a SpaceX engineer, will exit the capsule for about 15 to 20 minutes each.

They will pass through the hatch at the top of the Crew Dragon with the help of a handrail that SpaceX has named Skywalker, moving around carefully and deliberately. The two will not be outside the spacecraft at the same time.