SpaceX is preparing for the return to flight of its Falcon 9 on Monday evening following week without flying its workhorse rocket after a booster caught fire and exploded after landing. Two missions are on tap if the weather cooperates: one in California and the other in Florida.
The most recent Falcon 9 launch was more than a week ago on March 2 when SpaceX sent a batch of 21 Starlink satellites into low Earth orbit. During a pair of news briefings on Friday connected to upcoming NASA missions, SpaceX leaders added some key context to what caused the loss of that booster after only five flights.
Speaking at a news conference following a flight readiness review for the Crew-10 mission to the International Space Station, Bill Gerstenmaier, vice president of Build and Flight Reliability at SpaceX, said about 85 seconds into the launch of the Starlink 12-20 mission, there was a fuel leak in the first stage booster, tail number B1086, and kerosene sprayed onto a hot component of the engine. He said that caused it to vaporize and become flammable.
Because there wasn’t enough oxygen to interact with the leaked fuel, it didn’t catch fire during the ascent, he said. But about 45 seconds after B1086 landed on their droneship, ‘Just Read the Instructions,’ there was enough oxygen available to get into the engine compartment and a fire broke out.
“It subsequently blew out the barrel panel on the side of the rocket, just like it was designed to. The fire was all contained in the engine compartment,” Gerstenmaier said. “Even if we would’ve had a problem during ascent, this shows that the fire and the damage would be contained in just a single engine out, which still allows us to accomplish the entire mission.”
During Friday’s briefing Gerstenmaier said they were still trying to figure out what caused the fuel leak, stating that “It’s pretty difficult to determine what was cause and what was effect from the fire.” He said once the droneship returned to Port Canaveral, they were able to remove the engine section and more thoroughly examine it.
In a separate briefing on Friday, about the launch of NASA’s SPHEREx and PUNCH missions, Julianna Scheiman, the director of NASA Science Missions for SpaceX, said that both SpaceX and NASA’s Launch Services Program (LSP) “reviewed the data from that launch to make sure there’s no concern or risk to ascent, especially for these important science missions.”
Denton Gibson, the launch director for LSP, said his team also did an independent assessment of the Starlink 12-20 launch mishap.
“As part of NASA Launch Services Program, one of our major roles is that we have a mission assurance role. So a lot of these evaluations, we do independent of SpaceX to give it a fresh set of eyes, a different set of eyes, to ensure that we are not incurring any risk to our mission,” Gibson said.
The mishap was also assessed by the Federal Aviation Administration (FAA), which temporarily grounded the Falcon 9 fleet. They accepted the findings of the SpaceX-led mishap investigation and approved the Falcon 9 to return to operational flights on March 4.
Because NASA oversees the launches of both Crew-10 and SPHEREx/PUNCH, it has final say on whether those Falcon 9 missions are ready for launch.
Other issues with integrating the SPHEREx and PUNCH payloads drove more than a week of launch delays for that rideshare mission. Meanwhile, a late swap of Dragon spacecraft for the Crew-10 mission has largely driven that schedule and as of Friday, teams were working to resolve some outstanding concerns, like coating degradation seen on some of the vehicle’s thrusters.
Additional issues
Beyond describing the anomaly with B1086 on March 2, Gerstenmaier also went into some detail regarding an upper stage issue during the Starlink 11-4 mission launch on Feb. 1.
He said a “small oxygen leak” caused a thrust vector control line to freeze, which caused a loss of attitude control on the Falcon 9’s second stage.
“The control was still good enough that the Starlink satellites were deployed properly, but when the deorbit burn came around, the rocket couldn’t get in the right configuration for the deorbit burn,” Gerstenmaier said. “So as the software assessed, it skipped the deorbit burn, it passivated the stage and this stage ultimately reentered, I think, last week over Poland.”
He went on to say that launches supporting a Crew Dragon spacecraft are “too short for this freezing to occur, so it’s really not a concern for us.” Gerstenmaier said as a precaution though, they added some additional checks and “tightened our abort limits, such that if we have any kind of oxygen leak on the second stage, we’ll detect that prior to pre-launch.”
Gerstenmaier said they would also be able to check their fixes during a static fire test of the Falcon 9 rocket being used for the Crew-10 mission. That test fire happened Sunday, March 9, at 10:48 p.m. EDT (0248 UTC) and will be evaluated as part of NASA and SpaceX’s launch readiness review.
The FAA didn’t ground the Falcon 9 fleet during the Starlink 11-4 incident, but some debris from the Falcon 9 upper stage did crash to Earth in Poland. No injuries were reported.
While not identical, SpaceX did have an issue with its upper stage following the deployment of the Dragon spacecraft supporting the Crew-9 mission in September 2024. That prevented a deorbit burn from being performed and in that case, did result in a temporary grounding of the Falcon 9 fleet.