Joe Skipper/Reuters A SpaceX Falcon 9 rocket lifts off with Polaris Dawn, a private human spaceflight mission with two crew members expected to attempt the first-ever private spacewalk, at the Kennedy Space Center in Cape Canaveral, Florida. Sept. 10, 2024. Show more SPACEWALK PLANNED FOR THIRD DAY The Polaris Dawn spacewalk is planned for the mission's third day at 700 km in altitude and will last about 20 minutes. SpaceX's Crew Dragon craft will slowly depressurize its entire cabin - it has no airlock like the ISS - and all four astronauts will rely on their slimmed-down, SpaceX-built spacesuits for oxygen. The first U.S. spacewalk was in 1965, aboard a Gemini capsule, and used a similar procedure to the one planned for Polaris Dawn: the capsule was depressurised, the hatch opened, and a spacesuited astronaut ventured outside on a tether. Jared Isaacman, 41, a pilot and the billionaire founder of electronic payment company Shift4, is bankrolling the Polaris mission, as he did for his Inspiration4 flight with SpaceX in 2021. He has declined to say how much he is paying for the missions, but they are likely to cost hundreds of millions of dollars. Joining him is mission pilot Scott Poteet, 50, a retired U.S. Air Force lieutenant colonel; and SpaceX employees Sarah Gillis, 30, and Anna Menon, 38, both senior engineers at the company. For the spacewalk, Isaacman and Gillis will exit the spacecraft tethered by an oxygen line while Poteet and Menon stay in the cabin. The mission is the first in Isaacman's private Polaris program that includes a follow-on Crew Dragon mission in the future, followed by a flight on SpaceX's Starship, a giant rocket the company has spent billions of dollars developing as a flagship moon and Mars vehicle. The four-person crew are effectively test subjects for an array of scientific experiments that will aim to shed light on how cosmic radiation and the vacuum of space affect the human body, adding to decades of studies on astronauts living aboard the ISS. Since the retirement of the Space Shuttle in 2011, NASA has relied heavily on the company and its Crew Dragon, which has flown nine astronaut missions to and from the ISS for the agency as the only U.S. crew-grade vehicle in operation. The company has previously flown four private missions: Isaacman's Inspiration4, and three private astronaut flights arranged by Houston-based mission broker Axiom Space. Boeing is struggling to develop a similar spacecraft, Starliner, that could rival Crew Dragon. But Starliner's latest NASA test mission that began in June - its first time flying a crew - left its astronauts on the ISS last week because of issues with its propulsion system. (Reporting by Joey Roulette in Washington and Gerry Doyle in Singapore; Editing by Sandra Maler and Alex Richardson) A SpaceX Falcon 9 rocket lifts off with Polaris Dawn, a private human spaceflight mission with two crew members expected to attempt the first-ever private spacewalk, at the Kennedy Space Center in Cape Canaveral, Florida. Sept. 10, 2024.  Joe Skipper/Reuters