Following the completion of slow fill for liquid hydrogen (LH2), teams encountered an issue when they started fast fill operations for LH2. After fast fill on LH2 began, a surge in pressure automatically stopped the flow of liquid hydrogen. Teams are working to troubleshoot this issue and the rocket is in a safe configuration. In the meantime, liquid oxygen flow was paused on the core stage to ensure the tanking operations for LOX and LH2 remain synchronized.
After fast fill resumes for liquid hydrogen to the core stage, teams will load minimal cryogenic propellants on the interim cryogenic propulsion stage. Because of an issue with a helium check valve found several days ago, teams will chill down the lines used to load propellant into the upper stage but not flow any actual propellant to the stage.
The clock is continuing to count down for now, and the team will work to re-synchronize the operations timeline and clock during a planned T-10-minute hold at which point the launch team will establish a new T-0.