A SpaceX Falcon 9 was waiting prepared at neighboring Space Launch Complex 40 (SLC-40) and waiting to launch a US military GPS satellite.
On Wednesday, November 3, from Space Launch Complex 41 (SLC-41) at Cape Canaveral Air Force Base, a United Launch Alliance (ULA) Atlas V 531 rocket was scheduled to launch the NROL-101 flight, a classified payload for the United States government’s National Reconnaissance Office (NRO).
Ultimately, the Atlas V NROL-101 mission’s ULA launch attempt was scrubbed Wednesday night due to an anomaly with launchpad ground support equipment.
Admittedly, with ground winds remaining a worry during the countdown window, the weather did not look promising either.
The launch teams confirmed that an anomaly had been discovered with “a ground valve issue with the liquid oxygen system for the first stage of Atlas V.” With an hour and forty-seven minutes to go, just five seconds after a scheduled fifteen-minute hold had been released.
The discovery initiated an immediate stop to the countdown and launch teams entered an unplanned hold that would postpone the targeting.
ULA performed remote troubleshooting at first, but the anomaly was not resolved and it would be necessary for a return-to-pad team to join the protected launchpad to physically investigate.
To investigate the valve that was limiting the flow of liquid oxygen (LOx) to the first stage of the Atlas V rocket, an anomaly team was deployed.
The hold lasted for over an hour, causing the propellant lines to warm up to a temperature that would have to be re-cooled until the countdown resumed.
A scrubbed ULA mission for the NRO usually means that a neighboring SpaceX mission must wait until the issue is resolved and ULA gets its rocket off the nearby launchpad. With Wednesday’s scrub, however, that was not the case.
ULA stood down to try to launch the Atlas V 531 again on Friday, November 6, instead of a standard 24-hour recycle, for a 48-hour recycle.
This paved the way for SpaceX to retain its planned Thursday, November 5 launch date within a launch window that runs from 6:24 to 6:39 p.m. for approximately fifteen minutes. From SLC-40. EST (2324-2339 UTC)