NASA rolled its Artemis II moon rocket off its seaside launch pad Wednesday to return it to the Vehicle Assembly Building for repairs after a helium pressurization issue delayed the mission.

The 23.6-million-pound rocket and launch platform traveled four miles over 10–12 hours using an Apollo-era crawler-transporter.

Engineers will access the rocket’s upper stage, the Interim Cryogenic Propulsion Stage (ICPS), to fix the helium system, which is critical for propellant pressurization, tank purging, and fire prevention.

The rollback also allows replacement of batteries in the SLS self-destruct system and ICPS, while previous hydrogen leaks at the base of the rocket have already been addressed, CBS News has reported.

Artemis II’s launch of four astronauts, originally planned for February, is now postponed to no earlier than April 1 due to these technical issues and limited monthly launch opportunities.