The SpaceX Polaris Dawn mission, led by fintech billionaire Jared Isaacman, launched Tuesday from the Kennedy Space Center in Florida, journeying deeper into the cosmos than any humans in half a century, since the Apollo era.

With the four-member crew's Dragon spacecraft adjusted to an orbit with a high of 434 miles (700 kilometers), pure oxygen began flowing into their suits Thursday, marking the official start of their extravehicular activity (EVA) at 1012 GMT.

A short time later, Isaacman swung open the hatch and climbed through, gripping the hand and footholds of a structure known as "Skywalker," as a breathtaking view of Earth unfolded below him.

"SpaceX, back at home we all have a lot of work to do, but from here, Earth sure looks like a perfect world," he told mission control in Hawthorne, California, where teams erupted in applause.

It was yet another major milestone for SpaceX, the company founded by Elon Musk in 2002.

Since then, SpaceX has grown into a powerhouse that in 2020 beat aerospace giant Boeing in delivering a spaceship to provide rides for NASA astronauts to the International Space Station.

"Today's success represents a giant leap forward for the commercial space industry and NASA's long-term goal to build a vibrant US space economy," NASA chief Bill Nelson wrote on X.

- Suit tests -

Prior to the hatch opening, the crew underwent a "prebreathe" procedure to remove nitrogen from their bloodstream, preventing decompression sickness. Cabin pressure was then gradually lowered to align with the vacuum of space.

Isaacman and crewmate Sarah Gillis, a SpaceX engineer, took turns outside the vehicle, spending a few minutes performing mobility tests on SpaceX's next-generation suits that boast heads-up displays, helmet cameras and enhanced joint mobility systems -- before returning inside.

Extravehicular activity officially ended after an hour and 46 minutes, following cabin re-pressurization.

While it marked a first for the commercial sector, the spacewalk fell short of the daring feats from the early space era.

Early spacewalkers, including the first, Soviet cosmonaut Alexei Leonov in 1965, floated tethered to their spacecraft, while a select few Space Shuttle astronauts used jetpacks to fly completely untethered.

Since Dragon doesn't have an airlock, the entire crew were exposed to the vacuum of space. Mission pilot Scott Poteet and SpaceX engineer Anna Menon remained strapped in throughout as they monitored vital support systems.

"The risk is greater than zero, that's for sure, and it's certainly higher than anything that has been accomplished on a commercial basis," former NASA administrator Sean O'Keefe told AFP.

- First of three Polaris missions -

The spacewalk followed an audacious first phase of the mission, during which the Dragon spacecraft reached a peak altitude of 870 miles -- three times higher than the International Space Station, in a region teeming with dangerous, high-energy particles.

All four underwent more than two years of training in preparation for the landmark mission, logging hundreds of hours on simulators as well as skydiving, scuba diving and summiting an Ecuadoran volcano.

Upcoming tasks include testing laser-based satellite communications between the spacecraft and the vast Starlink satellite constellation, and completing dozens of experiments, including tests on contact lenses with embedded microelectronics to monitor changes in eye pressure and shape in space.

Polaris Dawn is the first of three missions under the Polaris program, a collaboration between Isaacman and SpaceX.

Financial terms of the partnership remain under wraps, but Isaacman, the 41-year-old founder and CEO of Shift4Payments, reportedly poured $200 million of his fortune into leading the 2021 all-civilian SpaceX Inspiration4 orbital mission.

The final Polaris mission aims to be the first crewed flight of SpaceX's Starship, a prototype next-generation rocket that is key to founder Musk's ambitions of colonizing Mars.

Who is on SpaceX's historic private spacewalk mission?
Washington (AFP) Sept 12, 2024 - Who are the four crew members of SpaceX's Polaris Dawn mission, who made history Thursday by performing the first spacewalk by private citizens?

Billionaire Jared Isaacman, the mission's financial backer, and SpaceX employee Sarah Gillis ventured for about ten minutes outside the capsule early Thursday.

The other two passengers, SpaceX engineer Anna Menon and retired Air Force pilot Scott Poteet, remained in their seats but were exposed to the vacuum of space, as the capsule has no airlock.

Here is more information about the four history-making Americans:

- Jared Isaacman, billionaire -

The driving force behind the mission is Jared Isaacman, a billionaire who serves as mission commander.

The 41-year-old American from Pennsylvania is the CEO of the digital finance company Shift4 Payments, which he founded in his family's basement when he was only 16.

Isaacman is a seasoned pilot who is qualified to fly military aircraft and holds several world records.

He had previously gone into space in 2021 as part of another SpaceX mission he chartered, Inspiration4, which was the first orbital spacecraft to feature no professional astronauts.

His lifelong passion for space exploration aligns with SpaceX's stated goal of making humankind a "multi-planet species."

"Throughout Earth's history, there have been periods when humans, had we existed, would have been wiped out," Isaacman wrote on X in August. "If there's a technical path to ensuring humanity's survival...it seems irresponsible not to pursue it."

Isaacman is married with two daughters.

- SpaceX employees Sarah Gillis and Anna Menon -

For the first time, SpaceX has sent two of its own employees into space.

Sarah Gillis, 30, oversees astronaut training for SpaceX, and had trained Isaacman for his Inspiration4 mission.

Her husband also works for Elon Musk's company, having helped develop the propulsion system for the spacecraft used in Polaris Dawn.

Anna Menon, 38, worked for NASA before joining SpaceX, where she is a lead space operations engineer.

She wrote a children's book about space titled "Kisses from Space" that she will read an excerpt from during the mission. Proceeds from the book go to support a children's hospital.

Her husband Anil Menon was selected to be an astronaut by NASA in 2021, but unlike his spouse, he has yet to go to space.

On the first day of the Polaris Dawn mission, Gillis and Menon became the two women to have traveled the farthest from Earth, at an altitude of around 1,400 km (870 miles).

NASA did not permit women to be astronauts until years after its Apollo missions to the Moon.

- Pilot Scott Poteet -

The last Polaris Dawn participant is Scott Poteet, a US Air Force veteran who enjoys completing triathlons in his spare time.

Poteet flew combat aircraft for 20 years, including as part of the esteemed Thunderbirds air aerobatic patrol.

He serves as the mission's pilot, given his professional experience.

Poteet is also a close friend of Isaacman's, having worked for several of the billionaire's companies.

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