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 depressurised before popping open the hatch. 

Mr Isaacman emerged first, joining a small elite group of spacewalkers who until now had included only professional astronauts from a dozen countries.

"Back at home, we all have a lot of work to do. But from here, it sure looks like a perfect world," said Isaacman.

The commercial spacewalk was the main focus of the five-day flight financed by Mr Isaacman and Elon Musk's company, and the culmination of years of development geared toward settling Mars and other planets.

All four on board donned SpaceX's new spacewalking suits to protect themselves from the harsh vacuum. 

They launched on Tuesday from Florida, rocketing farther from Earth than anyone since NASA's moon walkers. 

The orbit was reduced by half — 740 kilometers — for the spacewalk.

This first spacewalking test, expected to last about two hours, involved more stretching than walking. The plan called for Mr Isaacman to 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.

After about 15 minutes outside, Mr Isaacman was replaced by SpaceX engineer Sarah Gillis to go through the same motions.

Each had 3.6-meter 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.

More and more wealthy passengers are plunking down huge sums for rides aboard private rockets to experience a few minutes of weightlessness. 

Other have spent tens of millions to stay in space for days or even weeks. Space experts and risk analysts say it's inevitable that some will seek the thrill of spacewalking, deemed one of the most dangerous parts of spaceflight after launch and re-entry but also the most soul-stirring.

This operation was planned down to the minute with little room for error. Trying out new spacesuits from a spacecraft new to spacewalking added to the risk. So did the fact that the entire capsule was exposed to the vacuum of space.

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

Mr 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 kicked it off in 1965, followed a few months later by NASA's Ed White.

AP