Indian-origin NASA astronaut Sunita Williams dances as she arrives at ISS

NASA test pilots Indian-origin astronaut Sunita Williams and Butch Wilmore arrived at the International Space Station (ISS) in the Boeing Starliner on Thursday (June 6).

Boeing's new capsule was delayed by last-minute thruster trouble that almost derailed the docking for this first test flight with astronauts. The 420-km-high link-up over the Indian Ocean culminated more than a day of continuing drama for Boeing's astronaut flight debut carrying Butch Wilmore and Sunita Williams.

Sunita entered the space station first, dancing on the way in to music. Wilmore followed, snapping his fingers. They embraced the seven space station residents. Both of them were welcomed by the ringing of a bell, an ISS tradition.

'A little dance party - that's the way to get things going'

“It was such a great welcome, a little dance party,” said Williams. “That's the way to get things going.”

The 59-year-old Sunita is the first woman to pilot and test a new crewed spacecraft on its first mission. This is her third trip to the ISS.

Boeing plans to keep Starliner at the space station for at least eight days before guiding it to a landing in the western US.

“Nice to be attached to the big city in the sky,” Wilmore said once the hooks between the two spacecraft were tight.

Helium leaks

The Starliner capsule already had one small helium leak when it rocketed into orbit with the two NASA astronauts on Wednesday (June 5). Boeing and NASA managers were confident they could manage the propulsion system despite the problem and that more leaks were unlikely. But just hours into the flight, two more leaks cropped up and another was discovered after docking.

Circled the world for an extra hour

Later, five of the capsule's 28 thrusters went down. The astronauts managed to restart four of them, providing enough safety margin to proceed. By then, Starliner had passed up the first docking opportunity and circled the world for an extra hour alongside the station before moving in.

The thrusters’ problems were unrelated to the helium leaks, NASA's commercial crew program manager Steve Stich said after the docking.

Going forward in the flight, “we have some tools in our tool kit to manage this,” Stich said.

Earlier in the day, before the thrusters malfunctioned, officials stressed that the helium leaks posed no safety issues for the astronauts or the mission.

Helium is used to pressurise the fuel lines of Starliner's thrusters, which are essential for manoeuvring. Before liftoff, engineers devised a plan to work around any additional leaks in the system. A faulty rubber seal, no bigger than a shirt button, is believed to be responsible for the original leak.

‘Enough helium for the trip home’

Boeing program manager Mark Nappi said there should be plenty of helium in reserve for the trip home.

After the space shuttles retired, NASA hired Boeing and SpaceX to ferry astronauts to and from the space station. SpaceX's taxi service began in 2020. Boeing was supposed to start around the same time, but was held up for years by safety concerns and other troubles.

Stich said none of the problems so far would require a repeat of an astronaut test flight before certifying the capsule for regular use.

(With agency inputs)