WASHINGTON — SpaceX’s Falcon 9 successfully launched an array of Starlink satellites early July 27 in the vehicle’s first flight since an upper stage anomaly 15 days earlier.
Falcon 9 lifted off from Launch Complex 39A at the Kennedy Space Center at 1:45 a.m. ET. The company confirmed the successful deployment of its payload of 23 Starlink satellites just over an hour later.
The launch was the first for the Falcon 9 since the late July 11 launch that 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 make a circular orbit, stranding the 20 Starlink satellites in orbits too low to survive.
SpaceX announced on July 25 that it had traced the leak to a crack in a sensing line for an upper stage pressure sensor. The crack was caused by engine vibration fatigue as well as a clamp that was ineffective in restraining the rope. SpaceX said it will remove the line as a short-term solution because the data from the sensor is not needed.
The leak caused what SpaceX called “overcooling” of engine components. This includes the ignition fluid called TEA/TEB which is required to restart the Merlin engine. “It moved through its line because it was too cold, too slow,” 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 widespread damage to the stage, she said, allowing it to deploy the satellites and passivate. “But there were several engine components that were damaged that prevented it from completing this second burn.”
SpaceX is scheduled to perform two more Falcon 9 launches on July 28, one from Cape Canaveral Space Force Station and the other from Vandenberg Space Force Base, each carrying Starlink satellites. The first non-Starlink customer for the Falcon 9 since the anomaly could be NASA and Northrop Grumman, with the launch of the Falcon 9’s Cygnus cargo spacecraft from Cape Canaveral scheduled for August 3.
NASA closely followed 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 involved in the investigation.
He said the agency agreed with the outcome of the investigation and the planned correction. The sense line that cracked, he said, “was potentially a little bit under-engineered, I would say, for this environment.” Removing the sense line will go through “rigorous certification,” which includes reviews of vehicle software changes that already they will not use data from this sensor until the launch of Crew-9, which is currently scheduled for no earlier than August 18.
He said this incident highlights that even small items on a vehicle can have big consequences. “SpaceX made a small change to a different transducer” that provides pressure measurements on the same sensor line without knowing how sensitive that line is to vibration, along with removing a clamp. “It was a small change that you would think was harmless,” he concluded. “It’s a good lesson for all of us in human spaceflight and spaceflight in general that small changes matter.”
Both SpaceX’s statement on the failure investigation and Walker’s comments at the NASA briefing described removing the sensor line as a short-term solution. Asked what might lead to a long-term correction, Walker referred to a report coming out soon on the investigation into the upstream anomaly. “There are a number of actions that will be coming our way in the coming weeks,” she said, but did not specify what those actions might be.
