The Crew-10 mission will send four astronauts to the space station to take over for Butch Wilmore and Suni Williams’ crew, finally allowing their return home.

NASA and SpaceX on Wednesday night scrubbed the Falcon 9 launch of a flight intended to retrieve from the International Space Station astronauts Suni Williams and Butch Wilmore, who have spent nine months in orbit.

The new crew needs to get to the International Space Station before Butch Wilmore and Suni Williams can head home after nine months in orbit.