SpaceX’s latest mission — a bold and risky trek into Earth’s Van Allen radiation belts by a four-person crew of civilians who will also aim to conduct the first commercial spacewalk — just took flight at 5:23 a.m. ET.

SpaceX is making another attempt to get Polaris Dawn — a risky mission that will send four civilians into the radiation belts and on a historic spacewalk — off the ground this week.

SpaceX has once again delayed the kickoff of its latest mission: a bold and risky trek into Earth’s Van Allen radiation belts by a four-person crew of civilians who will also aim to conduct the first commercial spacewalk.

Isaacman, Menon, Gillis and Poteet will spend five days aboard a SpaceX Crew Dragon capsule that will soar to altitudes higher than any human has traveled since NASA’s Apollo program ended in the 1970s.

SpaceX launched four astronauts into orbit Friday using a recycled rocket and capsule, the third crew flight in less than a year for Elon Musk’s rapidly expanding company.