Jared Isaacman after his return from the Polaris Dawn mission.

Back on planet Earth a week after returning from space, Jared Isaacman is still catching up on sleep. “I think I just set a new record of sleep deprivation on this five-day mission," he chuckles in a phone call from his home in Allentown, Pennsylvania.

The fighter-jet-flying, space-traveling billionaire took part in a historic orbital mission called Polaris Dawn in mid-September, reaching a distance of 870 miles away from Earth—the highest Earth orbit any human has been to since NASA's Apollo 17 mission in 1972. On September 12, he also became the first ever private citizen to conduct a spacewalk—alongside crewmember Sarah Gillis, an engineer at Elon Musk’s SpaceX, which operated the mission and designed and built the brand new spacesuits that Isaacman and his three crew members wore.

"I did not expect it to feel the way it did. In my mind I had visualized every step and in the simulators we had done that choreography a hundred times," says Isaacman of his experience during the spacewalk, technically known as an extravehicular activity, or EVA. “I wasn't expecting all of the other senses to come together. It gets really cold, the adrenaline starts flying and then there's some physical exertion because that spacesuit, when it’s pressurized, is very rigid. You have all of that coming together plus the visual stimulus of seeing Earth like that, and it is quite overwhelming."

The spacewalk was scheduled to last for about two hours, but the whole process took only around 90 minutes. Isaacman and his crewmates spent two and a half years training for the mission, with three-quarters of that taking up about half of each month, while the remainder was nearly full-time preparation work. While only Isaacman and Gillis exited the vehicle—a........

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