Four astronauts were set to launch aboard a SpaceX Falcon 9 rocket on Wednesday evening. Due to the problem while preparing to take off, there will be no other launch on Wednesday, but NASA said there will be opportunities on Thursday and Friday.
"There was an issue with the hydraulic system on the ground side out at launch complex 39A," NASA commentator Derrol Nail said. "This was an issue that involved one of the clamp arms on the transport erector. This is a ground issue, everything was fine with the rocket and spacecraft itself."
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"This is an issue that SpaceX first made the crew aware of at T-minus four hours. They were working it, gathering data, but continuing with the countdown in hopes that they would have enough data to resolve the issue," he said.
The crew was in the process of exiting the spacecraft after the launch was scrubbed. Astronauts Butch Wilmore and Sunita Williams will have to wait at least one more day to return to Earth.