The US Federal Aviation Administration (FAA) has closed its investigation into the case of another exploding SpaceX rocket with a list of corrective actions to be implemented before Starship can fly again.

SpaceX led the investigation into the incident, which was overseen by the FAA. NASA and the National Transportation Safety Board were also granted official observer status.

As a reminder, SpaceX had another go at launching a Starship Super-Heavy rocket on November 18, 2023. Following stage separation, the Super-Heavy booster exploded during its boostback burn then the second stage suffered its own "Rapid Unscheduled Disassembly" after a planned venting of liquid oxygen resulted in fires and the inflight termination system was activated.

It was an improvement over the first launch of Starship, which exploded before staging occurred and tore up much of the launchpad, but not an unqualified success.

In January, SpaceX boss Elon Musk pinned the blame for the failure of the second stage on the venting of the liquid oxygen.

He said: "If it had had a payload, it would have made it to orbit. Because the reason it didn't quite make it to orbit was we vented the liquid oxygen, and the liquid oxygen ultimately led to fire and an explosion ... we normally wouldn't have had that liquid oxygen if we'd had a payload so, ironically, if it had had a payload it would have reached orbit."

According to SpaceX, it transpired that a leak in the aft section of the spacecraft had developed during the venting. Combustion then led to the six Raptor engines shutting down at the end of the ascent burn and the activation of the Autonomous Flight Safety System. Starship was approximately 150 km up and traveling at around 24,000 kph at the time.

As far as the booster is concerned, the most likely candidate for the failure was a fuel filter blockage, which resulted in a loss of engine pressure. The boostback burn uses 13 of the stage's 33 Raptor engines, but several began shutting down prematurely before one failed "energetically," resulting in the Gulf of Mexico being showered with Super-Heavy fragments.

For the booster, seven corrective actions were identified, including redesigns of vehicle hardware to increase tank filtration and reduce slosh, and updated engine control algorithms. Ten corrective actions were identified for Starship, including hardware redesigns to increase robustness and reduce complexity, hardware changes to reduce leaks, and additional fire protection.

On the plus side, SpaceX noted that the water-cooled flame deflector and other upgrades to the launch pad functioned as expected, meaning there is little work needed for the ground systems ahead of the next test launch, which will feature a new electronic thrust vector control system for the upper stage Raptor engines.

The closure of the mishap investigation does not mean SpaceX is immediately authorized to launch another Starship. A spokesperson for the FAA said: "Prior to the next launch, SpaceX must implement all corrective actions and receive a license modification from the FAA that addresses all safety, environmental and other applicable regulatory requirements.

"The FAA is evaluating SpaceX's license modification request and expects SpaceX to submit additional required information before a final determination can be made."

And SpaceX? It posted: "More Starships are ready to fly, putting flight hardware in a flight environment to learn as quickly as possible.

"Recursive improvement is essential as we work to build a fully reusable launch system capable of carrying satellites, payloads, crew, and cargo to a variety of orbits and Earth, lunar, or Martian landing sites." ®

https://www.theregister.com//2024/02/27/faa_closes_spacex_mishap_investigation/