On board the mission, called Polaris Dawn, is billionaire Jared Isaacman, who flew into orbit with SpaceX in 2021 and financed the flight and its development. Flying with him are two senior SpaceX engineers, Sarah Gillis and Anna Menon, as well as Isaacman’s friend and former Air Force pilot Scott “Kidd” Poteet.

The crew, flying in a modified SpaceX Crew Dragon spacecraft, is scheduled to launch on a Falcon 9 rocket from NASA’s Kennedy Space Center in Florida at 3:38 a.m. local time on August 27. SpaceX also has launch options at 5:23 a.m. or 7:09 a.m. If the mission is delayed, the company can also launch at the same times on August 28.

The defining moment of the mission is scheduled to occur on flight day three, when Isaacman and Gillis will emerge from an open hatch on their Crew Dragon spacecraft and each conduct a spacewalk. The two will go out individually for about 15 to 20 minutes each while tethered to the vehicle.

It’s unclear how SpaceX plans to incorporate spacewalks into future missions, but the company is keen to test the new capability.

“I think we’re really excited about where the company is going,” Gillis said in an interview before the launch. “This is obviously the first step, and this is a really important step.”

While only Gillis and Isaacman will exit the spacecraft, the entire crew will wear SpaceX’s new spacesuits, as the entire interior of the Crew Dragon will be exposed to the vacuum of space for the maneuver. The entire process, from venting the spacecraft’s atmosphere to resealing the vehicle, should take about two hours.

Although the primary focus of the mission is the spacewalk, Polaris Dawn plans to accomplish a number of secondary objectives and break some spaceflight records. During the first phase of flight, the Crew Dragon spacecraft will reach an altitude of 1,400 kilometers above Earth, the highest distance humans have flown since the Apollo astronauts landed on the moon. If the mission is successful, both Menon and Gillis will hold the record for women who have flown the farthest from Earth.

Because of the distance the crew will travel, they will be exposed to much higher levels of radiation than most astronauts on their way to the International Space Station in low Earth orbit. This will allow SpaceX to collect important research on how the space environment affects the human body.

In addition, SpaceX plans an in-flight demonstration of its Starlink service. A “plaser” mounted on the spacecraft will attempt to connect to Starlink internet satellites to test connectivity that future missions could use.

The entire Polaris Dawn mission is expected to last about five days before the crew returns to Earth and splashes down off the coast of Florida.