Billionaire businessman Jared Isaacman becomes the first non-professional astronaut to walk in space
"Back at home we all have a lot of work to do, but from here Earth sure looks like a perfect world," he says as he steps out into space
Watch all the key moments here, including stunning views from Isaacman's helmet-cam 435 miles (700km) above Earth
Mission specialist Sarah Gillis followed Isaacman's spacewalk - they're now back in the spacecraft
Isaacman is bankrolling the Polaris Dawn mission which blasted off in SpaceX's Crew Dragon spaceship on Tuesday - they'll return to Earth on Saturday
Read more: Jared Isaacman, the private astronaut who began making his fortune aged 16
Watch the moment Isaacman steps out into space - from the camera mounted on his helmet
Jared Isaacman was conducting suit mobility tests while the spacecraft flew over Australia and Antarctica, SpaceX say in an update on X.
He has now returned to inside of the spacecraft.
Image source, SpaceX
Pallab Ghosh
Science correspondent
We saw Jared Isaacman step outside and then saw the view from his helmet. His first words were "beautiful world".
"Back at home we all have a lot of work to do, but from here Earth sure looks like a perfect world," he says as he steps out into space.
It goes down like "one small step" - a moment of history that will be remembered.
Georgina Rannard
Science reporter
This is the moment we’ve been waiting for - Jared Isaacman has just stepped out of the Resilience spacecraft to start his spacewalk. We’re expecting engineer Sarah Gillis to follow afterwards.
Behind them are the two other crew, also wearing the innovative spacesuits in the craft that is now at the same pressure as the space vacuum outside.
These few twists and turns in space are a huge step forward for private space travel - signalling it is capable of matching or even beating publicly-funded exploration.
For decades only government space agencies have pulled this off. Now Isaacman’s risky venture has seemingly paid off.
Isaacman paid for this - using his own money to buy the mission from company SpaceX. The billionaire Elon Musk behind SpaceX will be hoping to make a lot more money from this business in the future.
But exciting though these moments are, we are still a long way from ordinary people having the cash for their own personal spacewalk 435 miles above Earth.
It's the moment we've been waiting for.
Billionaire Jared Isaacman steps out into space on the first ever private spacewalk.
Once he gets back to his seat, it will be mission specialist Sarah Gillis's turn to go.
Image source, SpaceXA cheer erupts from SpaceX HQ as the spacecraft hatch fully opens.
Image source, SpaceXPallab Ghosh
Science correspondent
We are about to witness a moment of history. Jared Isaacman is about to enter the vacuum of space, when he gets the final go-ahead.
Image source, SpaceXIsaacman is opening the hatch to the spacecraft.
He's preparing to step out onto the first private spacewalk in just a few moments.
There is the option to pause cabin venting (meaning the pressure goes down), SpaceX says, if the astronauts need a moment to adjust.
But everything is going very well so far, with no pauses necessary.
Pallab Ghosh
Science correspondent
The pressure inside Dragon starting to go down, SpaceX says.
It's taking slightly longer than planned. In space, things don't always go to plan.
Mission commander Jared Isaacman has his hands on the hatch and is ready to go...
Image source, SpaceXAnd remember - watch it all on this page, by pressing play above or below.
SpaceX are sharing the location of the spacecraft as it orbits the Earth.
Founder Elon Musk says that "Dragon is now more than three times further from Earth than the Space Station".
Image source, SpaceXThe final "pre-breathe" is under way, which purges all remaining nitrogen from the crews' bodies, SpaceX says on X.
Pallab Ghosh
Science correspondent
The EVA (extravehicular) process has started. Here's Jared Isaacman eagerly awaiting to open the hatch - and make history.
Image source, SpaceXSpaceX confirms the astronauts are safe to exit the spacecraft - the official start to today's spacewalk.
The astronauts are looking impressively calm.
Image source, SpaceXAs we've just seen, the crew are suited up. But what are they wearing?
The Polaris Dawn crew are in extravehicular activity (EVA) spacesuits.
"The EVA suit provides greater mobility, external, a state-of-the-art helmet heads-up display and camera, new thermal management textiles, and materials borrowed from Falcon’s interstage and Dragon’s trunk," according to the Polaris programme.
The spacesuit features spiral zippers at the waist and zippers on the forearms.
The polycarbonate visor provides "thermal insulation" and has been "externally coated with copper and indium tin oxide", with an "anti-fog treatment" on the inside.
The programme adds that the suit has "dual capability", external - used for both intravehicular and extravehicular activities.
We're now seeing first images of the crew inside the cabin, suited up and ready for their spacewalk.
Image source, SpaceXPallab Ghosh
Science correspondent
The spacewalk is less than half an hour away. We will see the astronauts depressurising their cabin and then take their first steps outside of the aircraft.
It is the first time a spacewalk has been attempted without an airlock for decades, and that carries its own risks. They will be wearing special suits - and all four of the crew will be suiting up.
They are a rookie crew - only the billionaire Jared Isaacman has been in space. The other three are first-timers.
There's a lot of jeopardy riding on it. They have been practising for several years, they have gone through training - but it is always a nerve-jangling experience when it first starts.
Image source, ReutersClassical violinist turned mission specialist Sarah Gillis, 30, will exit the spacecraft once the mission's commander Jared Isaacman returns to his seat.
Gillis changed paths when her high-school mentor and former NASA astronaut Joe Tanner encouraged her to study aerospace engineering.
In 2015 she completed an internship at SpaceX, where she is now a Lead Space Operations Engineer.
She oversees Space X's astronaut training programme and trained the first all-civilian crew to go to orbit in 2021, known as Inspiration4.
SpaceX say the crew has been in a "pre-breathe" period, which prepares them for the environment inside the EVA suits by gradually lowering Dragon's cabin pressure and increasing the oxygen concentration.
During the spacewalk, all four crew members will be exposed to the vacuum of space once the Dragon's hatch is open.
Commander Jared Isaacman and Mission Specialist Sarah Gillis will exit the craft or around 12 minutes each and perform a series of suit mobility tests.
Isaacman - the mission commander - is first up in around 45 minutes.