WASHINGTON — SpaceX’s Falcon 9 successfully launched a set of Starlink satellites on July 27, the vehicle’s first flight since an upper stage anomaly 15 days earlier.
The Falcon 9 rocket lifted off from Kennedy Space Center Launch Complex 39A at 1:45 a.m. EST. The company confirmed the successful deployment of its payload of 23 Starlink satellites just over an hour later.
This is the first launch of the Falcon 9 rocket since July 11, which also carried Starlink satellites. A liquid oxygen leak in the rocket’s upper stage prevented the stage’s Merlin engine from performing a second burn to circularize its orbit, stranding the 20 Starlink satellites in orbits too low for their survival.
SpaceX announced on July 25 that it had identified the leak as a crack in a pressure sensor sensing line in the upper stage. The crack was caused by fatigue from engine vibration as well as an ineffective clamp to constrain the line. SpaceX said it would remove the line in the near term because the sensor data is not needed.
The leak caused what SpaceX called “excessive cooling” of engine components. That included the ignition fluid, called TEA/TEB, needed to restart the Merlin engine. “It moved through its line because it was too cold, too slowly,” Sarah Walker, SpaceX’s director of Dragon mission management, said during a July 26 NASA briefing on the upcoming Crew-9 mission to the International Space Station. “Without that ignition fluid present when the fuel and oxygen started to mix, it caused damage to a number of engine components.”
The “hard start,” as the engine anomaly is called, did not cause significant damage to the stage, she said, allowing it to deploy the satellites and passivate. “But there were a few components of the engine that were damaged, which did not allow it to complete that second burn.”
SpaceX plans to launch two more Falcon 9s on July 28, one from Cape Canaveral Space Force Station and one from Vandenberg Space Force Base, each carrying Starlink satellites. The first non-Starlink Falcon 9 customer since the anomaly could be NASA and Northrop Grumman, with a Cygnus cargo ship on a Falcon 9 scheduled to launch from Cape Canaveral as early as August 3.
NASA has been closely monitoring SpaceX’s investigation into the upper stage anomaly. “SpaceX has been very transparent,” Steve Stich, NASA’s commercial crew program manager, said at the July 26 briefing, with NASA teams embedded in the investigation.
He said the agency agrees with the investigation results and the planned repair. The sensor line that cracked, he said, “was potentially a little under-engineered, I would say, for that environment.” The sensor line’s removal will go through a “rigorous certification” that will include reviews of changes to the vehicle’s software that will no longer use data from that sensor before Crew-9 launches, currently scheduled for no earlier than Aug. 18.
He said the incident showed that even small things on a vehicle can have major consequences. “SpaceX made a small change to another transducer” that provides pressure measurements on the same sensing line, without knowing how sensitive that line was to vibration, and also removed a clamp. “It was a small change that you would think was harmless,” he said. “It’s a good lesson learned for all of us in human spaceflight, and spaceflight in general, that small changes matter.”
SpaceX’s statement on the failure investigation and Walker’s comments at the NASA briefing described the sensor line removal as a short-term fix. Asked what a long-term solution might entail, Walker pointed to a forthcoming report on the upper stage anomaly investigation. “There are a number of actions that we have coming up in the coming weeks,” she said, but did not specify what those actions might be.
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