SpaceX is expected to launch four civilian astronauts Friday on a five-day mission to extreme orbital altitude in order to conduct a series of experiments.The mission, which will launch from Kennedy Space Center, is the first of three planned spaceflights part of the Polaris program. Two of the four members on the flight are expected to leave their capsule and conduct a spacewalk, the first private citizens to do so. The Polaris Dawn crew will travel from Brevard County through portions of the Van Allen radiation belt in SpaceX's Crew Dragon capsule atop a Falcon 9 rocket.Here's everything you need to know about the historic mission taking off from Florida soon.What is the Polaris Dawn mission? The purpose of the Polaris Dawn mission is largely experimental, with the four-person crew expected to conduct a series of tests while in space.According to the Polaris program, the crew will be conducting scientific research designed to advance both human health on Earth and the understanding of human health during long-duration spaceflights like ones being planned in the future.With help from many educational institutions, the astronauts will do research expected to contribute to the understanding of decompression sickness, space radiation, Spaceflight Associated Neuro-Ocular Syndrome (SANS), and more.Additionally, the Polaris program says the crew will test Starlink laser-based communications in space and SpaceX's extravehicular activity (EVA) spacesuits.When will the Polaris Dawn mission launch?The Polaris Dawn mission was originally expected to launch on Monday, Aug. 26, then Tuesday, Aug. 27, then Wednesday Aug. 28. All three launches were scrubbed, and now, SpaceX is targeting this week for its launch.According to SpaceX, Aug. 26's launch was moved to Aug. 27 to allow more time for checks. However, that launch was then postponed because of "a ground-side helium leak on the quick disconnect umbilical." Unfavorable recovery weather cancelled both Aug. 28's targeted launch and Aug. 29's backup launch times.Now, FAA records show that Polaris Dawn is scheduled to launch on Friday, Sept. 6.Polaris Dawn, hence its name, is expected to launch in the early hours of the morning. According to the FAA, the launch window will open at 3:33 a.m.Who are the crew members for Polaris Dawn?The Polaris Dawn crew consists of four private citizens, one of which includes billionaire entrepreneur Jared Isaacman who is funding and organizing Polaris' partnership with SpaceX.Isaacman is the mission's commander and will be joined by three crew members. They are Scott Poteet, the mission pilot; Sarah Gillis, the mission specialist; and Anna Menon, the mission specialist and medical officer.SpaceX says this is the first human spaceflight for all the crew members except Isaacman, who previously flew to space as a commander of Inspiration4.