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Two crew members set to leave craft on tethers

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Mission is riskiest yet for Elon Musk's SpaceX

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Spacewalk will test a new line of spacesuits

(Updates with beginning of spacewalk, paragraphs 1-6; changes

story date to Sept. 12)

By Joey Roulette and Gerry Doyle

WASHINGTON, Sept 12 (Reuters) -

A crew of four aboard a SpaceX capsule embarked on the

world's first private spacewalk on Thursday, as an astronaut

eased out of the Crew Dragon spacecraft on a tether into the

vacuum of space, hundreds of miles from Earth.

Billionaire Jared Isaacman, 41, exited first about 6:52

a.m. ET (1052 GMT). After he returned a few minutes later,

SpaceX engineer Sarah Gillis, 30, was scheduled to take her turn

in space, all their maneuvers streaming live on the company's

website.

"Back at home we all have a lot of work to do, but from

here, Earth sure looks like a perfect world," Isaacman said

after emerging from the spacecraft, the planet glittering in

half shadow below him.

Before the spacewalk began, the capsule was completely

depressurized, with the whole crew relying on their slim,

SpaceX-developed spacesuits for oxygen, provided via an

umbilical connection to Crew Dragon.

The spacewalk was scheduled to last only about 30

minutes, but the procedures to prepare for it and to finish it

safely last about two hours. It was meant to test the new

spacesuit designs and procedures for the capsule, among other

things.

Isaacman, Gillis, Scott Poteet, 50, a retired U.S. Air

Force lieutenant colonel, and SpaceX engineer Anna Menon, 38,

had been orbiting Earth aboard Crew Dragon since Tuesday's

pre-dawn launch from Florida of the Polaris Dawn mission. Menon

and Poteet remained inside the spacecraft during the spacewalk.

It is the Elon Musk-led company's latest and riskiest bid to

push the boundaries of commercial spaceflight.

Isaacman, a pilot and the billionaire founder of electronic

payments company Shift4, is bankrolling the Polaris

mission, as he did his Inspiration4 flight with SpaceX in 2021.

He has declined to say how much he is paying, but the

missions are likely to cost hundreds of millions of dollars,

based on Crew Dragon's price of roughly $55 million a seat for

other flights.

FARTHEST SINCE APOLLO

Throughout Wednesday, the craft circled Earth at least six

times in an oval orbit as shallow as 190 km (118 miles) and

stretching out as far as 1,400 km (870 miles), the farthest in

space that humans have traveled since the last U.S. Apollo

mission in 1972.

The gumdrop-shaped spacecraft then began to lower its orbit

into a peak 700-km (435-mile) position and adjust cabin pressure

to ready for the spacewalk, formally called Extravehicular

Activity (EVA), the Polaris program said on social media on

Wednesday.

"The crew also spent a few hours demonstrating the suit's

pressurized mobility, verifying positions and accessibility in

microgravity along with preparing the cabin for the EVA," it

said.

Only government astronauts with several years of training

have done spacewalks in the past.

There have been roughly 270 on the International Space

Station (ISS) since it was set up in 2000, and 16 by Chinese

astronauts on Beijing's Tiangong space station.

The Polaris crew has spent 2-1/2 years training with SpaceX

mission simulations and "experiential learning" in challenging,

uncomfortable environments, said Poteet.

A record 19 astronauts are now in orbit, after Russia's

Soyuz MS-26 mission ferried two cosmonauts and a U.S. astronaut

to the International Space Station on Wednesday, taking its

headcount to 12.

Three Chinese astronauts are aboard the Tiangong space

station.

The first U.S. spacewalk in 1965, aboard a Gemini capsule,

used a similar procedure to the one planned for Polaris Dawn:

the capsule was depressurized, the hatch opened, and a

spacesuited astronaut ventured outside on a tether.

Since 2001, Crew Dragon, the only U.S. vehicle capable of

reliably putting humans in orbit and returning them to Earth,

has flown more than a dozen astronaut missions, mainly for NASA.

The agency seeded development of the capsule under a program

meant to establish commercial, privately-built U.S. vehicles

capable of ferrying astronauts with the ISS.

Also developed under that program was Boeing's Starliner

capsule, but it is farther behind.

Starliner launched its first astronauts to the ISS in June

in a troubled test mission that ended this month with the

capsule returning empty, leaving its crew on the space station

for a Crew Dragon capsule to fetch next year.