A crew of four private astronauts is gearing up for a daring SpaceX mission that includes the first-ever private spacewalk, utilizing the company’s newly designed spacesuits and a modified spacecraft. The team, composed of a billionaire entrepreneur, a retired fighter pilot, and two SpaceX engineers, is set to launch at 3:38 a.m. ET (0738 GMT) on Tuesday from NASA’s Kennedy Space Center in Florida. They will board SpaceX’s Crew Dragon capsule for the company’s fifth-and most hazardous-private space venture to date.

The mission, called Polaris Dawn, was initially delayed last month due to a small helium leak in ground equipment on the launchpad. Though SpaceX repaired the issue, further delays occurred when U.S. regulators grounded the Falcon 9 rocket following a booster recovery failure on an unrelated mission. With those problems resolved, the mission is now back on track, though there is only a 40% chance of favorable weather for the scheduled launch.

SpaceX CEO Elon Musk highlighted the heightened risks of this mission, noting that it would be the farthest humans have traveled from Earth since the Apollo era and the first commercial spacewalk. In the past, spacewalks were the domain of well-trained government astronauts, with over 270 spacewalks conducted on the International Space Station (ISS) since 2000, and 16 by Chinese astronauts on the Tiangong station.

Polaris Dawn’s five-day mission will see the Crew Dragon orbit between 190 km (118 miles) and 1,400 km (870 miles) from Earth—marking the furthest distance humans have traveled since the U.S. Apollo missions ended in 1972. On the third day, a spacewalk at 700 km altitude is planned, lasting approximately 20 minutes. Since the spacecraft lacks an airlock, the entire cabin will be depressurized, and the crew will rely on SpaceX’s custom spacesuits for oxygen.

Jared Isaacman, a 41-year-old billionaire and pilot, is financing the mission, as he did with the Inspiration 4 flight in 2021. Joining Isaacman are mission pilot Scott Poteet, a retired Air Force lieutenant colonel, and SpaceX engineers Sarah Gillis and Anna Menon. Poteet and Menon will stay inside the spacecraft while Isaacman and Gillis undertake the tethered spacewalk.

This mission is the first in Isaacman’s Polaris program, which will eventually include a future Crew Dragon mission and a flight aboard SpaceX’s Starship. The crew will also conduct experiments on how cosmic radiation and space’s vacuum affect the human body, contributing to the growing body of research from the ISS.