Two were cut late last week from the six-month expedition, which is due to blast off in late September. Boeing has to free up the parking place for SpaceX's arrival.
Boeing encountered serious flaws with Starliner long before its June 5 liftoff on the long-delayed astronaut demo.
Starliner's first test flight went so poorly in 2019—the capsule never reached the space station because of software errors—that the mission was repeated three years later. More problems surfaced, resulting in even more delays and more than $1 billion in repairs.
The capsule had suffered multiple thruster failures and propulsion-system helium leaks by the time it pulled up at the space station after launch. Boeing conducted extensive thruster tests in space and on the ground, and contended the capsule could safely bring the astronauts back. But NASA disagreed, setting the complex ride swap in motion.
Starliner will make a faster, simpler getaway than planned, using springs to push away from the space station and then short thruster firings to gradually increase the distance. The original plan called for an hour of dallying near the station, mostly for picture-taking; that was cut to 20 or so minutes to reduce the stress on the capsule's thrusters and keep the station safe.
Additional test firings of Starliner's 28 thrusters are planned before the all-important descent from orbit. Engineers want to learn as much as they can since the thrusters won't return to Earth; the section containing them will be ditched before the capsule reenters.
The stuck astronauts—retired Navy captains—have lived on the space station before and settled in just fine, according to NASA officials. Even though their mission focus has changed, "they're just as dedicated for the success of human spaceflight going forward," flight director Anthony Vareha said.
Their blue Boeing spacesuits will return with the capsule, along with some old station equipment.
NASA hired Boeing and SpaceX a decade ago to ferry its astronauts to and from the space station after its shuttles retired. SpaceX accomplished the feat in 2020 and has since launched nine crews for NASA and four for private customers.
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