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On Wednesday, November 3, a United Launch Alliance (ULA) Atlas V 531 rocket was set to launch mission NROL-101 – a payload classified for the US government’s National Reconnaissance Office (NRO) – from Space Launch Complex 41 (SLC-41) at Cape Canaveral Air Force Station. At nearby Space Launch Complex 40 (SLC-40) a SpaceX Falcon 9 was ready and waiting to launch a US military GPS satellite just the next day.
Eventually, due to an anomaly with the launch pad’s ground support equipment, the ULA launch attempt of the Atlas V NROL-101 mission was canceled Wednesday evening. Sure, the weather didn’t look promising even with the offshore winds remaining a concern throughout the countdown window.
With an hour and forty-seven minutes left – just five seconds after a planned fifteen-minute suspension was released – the launch teams announced that an anomaly had been discovered with “a ground valve problem with the system. liquid oxygen for the Atlas V first stage. ” The discovery initiated an immediate countdown stop, and the launch teams entered an unplanned suspension that would have delayed the expected launch time.
At first, ULA conducted remote troubleshooting, but the anomaly was not resolved and a return-to-platform team would have been required to enter the secure launch pad to physically investigate.
An anomaly team was deployed to investigate the valve that restricted the flow of liquid oxygen (LOx) to the first stage of the Atlas V rocket. The hold remained for over an hour allowing the propellant lines to heat up to a temperature that would be needed to be cooled down again before resuming the countdown.
Eventually, the team returning to the pitch were able to evacuate the platform and secure it for launch once again. Cooling procedures to return the propellant lines to an operating temperature began but were stopped almost immediately. The anomaly had not been fully rectified and there was not enough time left in the launch window to redirect it and cool the propellant lines. This led to the launch attempt canceled.
Typically, a clean-up ULA mission for the NRO means that a nearby SpaceX mission has to wait until the problem is resolved and ULA lifts its rocket off the nearby launch pad. However, this was not the case with the scrub on Wednesday. ULA has given up on 48-hour recycling, rather than a typical 24-hour recycling, to attempt to re-launch the Atlas V 531 on Friday 6 November.
This paved the way for SpaceX to maintain its planned launch date of Thursday, November 5 during a launch window that spans approximately fifteen minutes from 6:24 pm to 6:39 pm EST (2324-2339 UTC) from SLC-40. .
After a successful static fire test on all nine Merlin 1D engines, SpaceX will attempt to launch GPSIII-SV04 satellite for the US Army for the second time on Thursday, November 5.
The previous launch attempt on Friday 2 October was thwarted at T-2 seconds due to abnormal behavior when starting the engine. The unexplained early start of two Merlin 1D engines was ultimately determined to be caused by “an unexpected increase in pressure in the turbomachinery gas generator,” as explained by SpaceX CEO Elon Musk.
The engine anomaly required a thorough investigation of all Merlin 1D engines on the launch vehicle, as well as a thorough investigation of the engines on two Falcon 9 launch vehicles designated for future NASA missions – the Commercial’s first operational rotation mission. Crew Program, Crew-1, and the launch of NASA’s and European Space Agency’s Earth observation satellite, the Michael Freilich Sentinel-6. The engines were eventually replaced on all three Falcon 9 launch vehicles.
A live hosted webcast of Thursday’s launch attempt will be provided on the company’s website and is expected to be available for viewing approximately fifteen minutes before takeoff.
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