WASHINGTON — The Federal Aviation Administration has closed its investigation into the second Starship/Super Heavy launch in November, bringing SpaceX a step closer to launching its third test flight as soon as mid-March.

The FAA announced Feb. 26 that it closed the investigation into the Nov. 18 launch, designated Orbital Flight Test (OFT) 2, by accepting the root causes into the failure identified by SpaceX. That includes 7 corrective actions for the Super Heavy booster and 10 for the Starship upper stage.

On that launch, the vehicle appeared to perform as expected through stage separation. However, the Super Heavy booster broke apart shortly after separation as it was attempting to perform a controlled reentry and splashdown in the Gulf of Mexico. The Starship upper stage continued its ascent until the final minute of its burn, when it broke apart. SpaceX Chief Executive Elon Musk said in January that liquid oxygen venting triggered a fire and explosion of Starship.

The letter noted that Starship’s ascent was going normally until seven minutes and five seconds after liftoff, when the vehicle started a pre-planned dump of excess liquid oxygen. “Over the next minute, several explosions and sustained fires were observed in onboard camera aft video streams, ultimately resulting in a loss of communication between the forward and aft flight computers,” the letter stated. That led to a shutdown of all six engines and a triggering of the vehicle’s autonomous flight safety system a minute after the vent started.

SpaceX, in its own statement about the investigation, said the fires in Starship came from a leak in the aft section of the vehicle when the liquid oxygen vent started. The vehicle was carrying the excess oxidizer “to gather data representative of future payload deploy missions and needed to be disposed of prior to reentry to meet required propellant mass targets at splashdown.”

The SpaceX statement also discussed the loss of the Super Heavy booster. Thirteen of its 33 Raptor engines were firing in a “boostback” maneuver after stage separation when several engines shut down, including one that failed “energetically.” That led to the booster breaking apart at an altitude of 90 kilometers over the Gulf of Mexico.

The company said the most likely explanation for the failure is a filter blockage in a liquid oxygen line that reduced inlet pressure in engine turbopumps “that eventually resulted in one engine failing in a way that resulted in loss of the vehicle.”

The Super Heavy corrective actions, the FAA stated in its letter to SpaceX, include “redesigns of vehicle hardware to increase tank filtration and reduce slosh, updated thrust vector control system modelling, reevaluation of engine analyses based on OFT-2 data, and updated engine control algorithms.”

The Starship corrective actions, according to the FAA letter, include “hardware redesigns to increase robustness and reduce complexity, hardware changes to reduce leaks, operational changes eliminating pre-second engine cutoff propellant dumps, flammability analysis updates, installation of additional fire protection, creation of analytical guidance, performance of transient load analysis, and modeling updates.”

Neither the FAA nor the SpaceX statements offered a schedule for completing the corrective actions and launching a third test flight. Musk, in a conversation on his social media platform X Feb. 19, said he was looking to the second week of March to launch the vehicle. “Nominally it’s, like, March 8. We’re trying to get it to be sooner than March 8,” he said. “My guess is that it happens at some point in the first half of next month.” A fourth launch, he added, could take place “shortly thereafter.”

Other company officials have repeated Musk’s timeline for the mission. During a panel discussion at the FAA Commercial Space Transportation Conference Feb. 21, Nick Cummings, senior director of program development at SpaceX, said the upcoming launch will also conduct a propellant transfer test within Starship, something NASA officials previous said might be included as part of an agency “Tipping Point” award.

The company is also working to accelerate its rate of test flights. “I’m very excited about the fact that we’ve got four sets of Starships and Super Heavies basically already built at Starbase, ready to go for the next flights,” Cummings said.

The next flight, though, still requires the FAA to update SpaceX’s Starship launch license. The FAA said SpaceX must first demonstrate to the FAA that it has implemented those corrective actions. “The FAA is evaluating SpaceX’s license modification request and expects SpaceX to submit additional required information before a final determination can be made,” the agency stated.

In a briefing with reporters during the FAA conference Feb. 21, Kelvin Coleman, FAA associate administrator for commercial space transportation, since it appeared feasible to have a license ready in time for a launch by mid-March. “That’s where I’m hearing things are headed right now,” he said.

The timing of subsequent launches, he said, will depend on the outcome of the third launch. “They’re looking at a pretty aggressive launch schedule this year,” he said, with “at least nine” launches proposed for 2024. “We’ll work with them to get them back going as soon as they can.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...