Not stranded but staying longer: NASA on astronauts

Two NASA astronauts will stay longer at the International Space Station as engineers troubleshoot problems on Boeing's new space capsule that emerged on the trip there.

NASA on Friday did not set a return date but said the astronauts were safe.

"We're not in any rush to come home," said NASA's commercial crew program manager Steve Stich.

Veteran NASA test pilots Butch Wilmore and Suni Williams blasted off aboard Boeing's Starliner capsule for the orbiting laboratory on June 5. It was the first astronaut launch for Boeing after years of delays and setbacks.

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The test flight was expected to last a week or so, enough time for Wilmore and Williams to check out the capsule while docked at the station. But problems with the capsule's propulsion system, used to manoeuvre the spacecraft, prompted NASA and Boeing to delay the flight home several times while they analysed the trouble.

As Starliner closed in on the space station a day after launch, last-minute thruster failures almost derailed the docking. Five of the capsule's 28 thrusters went down during docking; all but one thruster was restarted.

Starliner already had one small helium leak when it rocketed into orbit and several more leaks cropped up during the flight. Helium is used to pressurise fuel for the thrusters. Boeing said this week that the two problems aren't a concern for the return trip.

In delaying the astronauts' return, NASA and Boeing said they needed more time to collect information about the thruster trouble and leaks while the capsule was docked. Both are in the service module, a unit attached to the capsule that burns up during reentry.

NASA initially said the Starliner could stay docked at the space station for up to 45 days due to battery limits. But in-flight tests have shown that limit can be extended, Stich said.

Officials said they won't set a return date while they do ground tests of capsule thrusters in the New Mexico desert, which were expected to last a couple of weeks. They want to try to replicate the situation that occurred during docking.

"I want to make it very clear that Butch and Suni are not stranded in space," said Stich, adding that Starliner is designed for a mission of up to 210 days.

After the space shuttle fleet retired, NASA turned over astronaut rides to private companies. Elon Musk's SpaceX has made nine taxi flights for NASA since 2020. NASA plans to alternate between SpaceX and Boeing in ferrying crews to and from the space station.