Three Chinese astronauts who had been stranded for days in space after a suspected piece of space junk hit their spacecraft are back on Earth, the China Manned Space Engineering Office (CMSE) announced on Friday.

The agency also revealed that it had found tiny cracks in one of the windows of the crew’s Shenzou 20 return capsule—rendering it unusable.

The astronauts instead returned onboard the Shenzhou 21 spacecraft, which had originally been used by Shenzou 20’s replacement crew. China had planned to keep the Shenzhou 21 capsule docked at its Tiangong space station to return those astronauts at the end of their mission, which is currently slated for April 2026.

I’m very glad that they got home, but it is a bit disconcerting that the replacement crew apparently does not have a vehicle to come back to Earth,” says Victoria Samson, chief director of space security and stability at the Colorado-based nonprofit Secure World Foundation.

CMSE told the Chinese news agency Xinhua that a new spacecraft, Shenzhou 22, will be launched at an “appropriate time in the future,” meaning that Tiangong’s remaining three-person crew currently has no means of returning to Earth in the event of an emergency.

It’s unclear what kind of debris struck Shenzhou 20, but Samson speculated that it was likely tiny—perhaps between one and 10 centimeters in diameter—which is too small for astronomers to track.

“This again underlines the argument for not deliberately creating debris in orbit,” Samson said.