NASA and SpaceX on Wednesday called off the launch of a four-member replacement crew to the International Space Station, to bring back NASA astronauts Butch Wilmore and Sunita Williams, who went on a 8-day mission and now stuck in space for nine months.

NASA delayed the launch of SpaceX’s Falcon flight with a four-member crew onboard after it detected an error in its hydraulic system. “NASA and SpaceX have scrubbed Wednesday’s launch attempt of the agency’s Crew-10 mission to the International Space Station due to a hydraulic system issue with a ground support clamp arm for the Falcon 9 rocket at Launch Complex 39A at NASA’s Kennedy Space Center in Florida,” the space agency said in a statement. 

Concerns over a critical hydraulic system arose less than four hours before the launch of Falcon’s planned evening lift-off from NASA’s Kennedy Space Center. The four crew members–NASA astronauts Anne McClain and Nichole Ayers, JAXA (Japan Aerospace Exploration Agency) astronaut Takuya Onishi, and Roscosmos cosmonaut Kirill Peskov exited the spacecraft after NASA decided to delay the launch. The launch had to be pushed to Friday (local time) owing to unfavourable weather on Thursday (local time). 

“NASA’s SpaceX Crew-10 now is targeting no earlier than 7:03 p.m. EDT Friday, March 14, to launch four crew members to the International Space Station. Mission managers met this evening and decided to wave off a launch attempt on Thursday, March 13, due to high winds and precipitation forecasted in the flight path of Dragon,” it said. 

The crew will replace Wilmore and Williams, who have been up there since June. The two test pilots had to move into the ISS for an extended stay after Boeing’s new Starliner capsule encountered major breakdowns in transit.