NASA has said it has still not decided how to bring home two astronauts from the International Space Station (ISS) after their spacecraft developed faults on their outward voyage.
In a news conference on Wednesday, the space agency said Butch Wilmore and Suni Williams, who arrived at the ISS in June expecting to be there for eight days, may yet have to stay until February.
The astronauts arrived there on a Boeing Starliner – the first crew to use the craft.
But the vessel suffered thruster failures and helium leaks en route, raising doubts about whether it could carry them back to Earth safely – leaving the pair in space limbo.
The thrusters are crucial for holding the capsule in the right position when it comes time to descend from orbit.
If NASA decides not to use the Starliner, which Boeing has said is able to return them safely, they would catch a ride on SpaceX’s next flight, which would mean staying at the space station until next Februar.
But by that point, they will have been in space for eight months.
NASA’s space operations mission chief Ken Bowersox told reporters they are analysing more data before making a decision – either by the end of next week or the beginning of the next.
He said: “We’ve got time available before we bring Starliner home and we want to use that time wisely.”
Switching to SpaceX would also involve standing down two of the four astronauts due to be on board the SpaceX flight, currently scheduled for late September.
Wilmore and Williams would take the empty seats in SpaceX’s Dragon capsule once that half-year mission ends.
NASA’s safety chief Russ DeLoach added: “We don’t have enough insight and data to make some sort of simple, black-and-white calculation.”
Mr DeLoach said the space agency wants to make room for all opinions, unlike what happened on NASA’s two shuttle tragedies, Challenger and Columbia, when dissenting views were ignored.
“That may mean, at times, we don’t move very fast because we’re getting everything out, and I think you can kind of see that at play here,” he said.
One complication is that the space suits they used to travel to the ISS on Starliner would not be suitable on the SpaceX craft, if it’s used to take them home, meaning they may have to return to Earth suitless.
The BBC, quoting Joel Montalbano, NASA’s deputy associate administrator, said: “They would come unsuited in the [SpaceX] Crew Dragon.”
Another problem is that the space station has just two parking places for US craft, so Boeing’s capsule would have to leave before the SpaceX Dragon arrived in order to free up a spot.
Wilmore and Williams are retired navy captains who spent months aboard the space station years ago, been helping with experiments and repairs since they arrived.
NASA chief astronaut Joe Acaba said: “They will do what we ask them to do. That’s their job as astronauts.
“This mission is a test flight and as Butch and Suni expressed ahead of their launch, they knew this mission might not be perfect.”