A billionaire stepped out for the first private spacewalk Thursday, teaming up with SpaceX on the daring endeavour hundreds of miles above Earth.

Tech entrepreneur Jared Isaacman and his crew waited until their capsule was depressurized before popping open the hatch. Isaacman was to be the first one out, aiming to join a small elite group of spacewalkers who until now had represented countries.

All four on board donned SpaceX's new spacewalking suits to protect themselves from the harsh vacuum. They launched on Tuesday from Cape Canaveral, Fla., rocketing farther from Earth than anyone since NASA's moonwalkers over 50 years ago. The orbit was reduced by half — to 737 kilometres — for the spacewalk.

[embed]https://www.youtube.com/watch?v=VjHzpOqu5iU[/embed]

The spacewalk was the main focus of the five-day flight, and the culmination of years of development geared toward settling Mars and other planets.

This first spacewalking test, expected to last about two hours, involved more stretching than walking. The plan called for Isaacman to emerge from the capsule but keep a hand or foot attached to it the whole time as he flexed his arms and legs to see how the new spacesuit would hold up. The hatch sported a walker-like structure for extra support.

Private expense unclear

After about 15 minutes outside, Isaacman was to be replaced by SpaceX engineer Sarah Gillis to go through the same motions. Each had 12-foot (3.6-metre) tethers but no intention of unfurling them or dangling at the end, unlike what happens at the International Space Station, where astronauts routinely float out to do repairs at a much lower orbit.

Scott (Kidd) Poteet, a former Air Force Thunderbird pilot, and SpaceX engineer Anna Menon were to stay strapped to their seats to monitor from inside. All four underwent intensive training before the trip.

Isaacman, 41, CEO and founder of the Shift4 credit card-processing company, has declined to disclose how much he invested in the flight. It was the first of three flights in a program he's dubbed Polaris; this one was called Polaris Dawn. For SpaceX's inaugural private flight in 2021, he took up contest winners and a cancer survivor.

Until Thursday, only 263 people had conducted a spacewalk, representing 12 countries. The Soviet Union's Alexei Leonov was the first, in 1965, followed a few months later by NASA's Ed White.

WATCH l Setting the stakes for big step in commercial space flight:

SpaceX launches risky commercial spacewalk mission

SpaceX has sent a crew of four civilian astronauts into space to venture the furthest humans have been since Apollo in 1972 and conduct the first commercial spacewalk.