Sunday update: Elon Musk, SpaceX's founder and CEO, posted Sunday on his social media platform X that the company has completed 57 corrective actions required before the second integrated test flight of the Starship rocket. Six more corrective actions will be implemented before future missions. This story has been updated to add Musk's statement.
The Federal Aviation Administration said Friday it has closed an investigation into the problems SpaceX encountered on its first full-scale Starship test launch in April, but federal regulators won't yet give a green light for the next Starship flight.
"The closure of the mishap investigation does not signal an immediate resumption of Starship launches at Boca Chica," the FAA said in a statement, referring to the location of SpaceX's Starship launch facility at Boca Chica Beach in South Texas.
The nearly 400-foot-tall Starship rocket, the largest ever built, is standing on its launch pad in Texas for the upcoming test flight, which could happen before the end of this month, pending FAA approval.
If all goes according to plan, the rocket's Super Heavy booster, powered by 33 methane-fueled Raptor engines, will burn for nearly three minutes, then the Starship upper stage will light its own Raptor engines to accelerate to near-orbital velocity, fast enough to send the vehicle on a flight three-quarters of the way around the world. The booster will attempt to descend to a controlled splashdown in the Gulf of Mexico, testing maneuvers for future flights to recover and reuse the rocket.
But the first test flight of Starship didn't get that far. SpaceX recently submitted to the FAA the results of its investigation into the Starship test launch, which ended about four minutes after liftoff on April 20.
Multiple Raptor engines on the rocket's Super Heavy booster failed, and the vehicle lost its steering, causing it to twist out of control in the upper atmosphere. An autonomous self-destruct system issued a command to blow up the rocket, but it took longer than expected for Starship to break apart. The rocket finally disintegrated in a ball of flame.
The FAA's statement Friday confirms that federal regulators have completed their review of SpaceX's mishap investigation report, which cites multiple root causes that led to the April 20 test flight ending a few minutes after liftoff. SpaceX deemed the test flight a success because it allowed engineers to gather data on the rocket's performance. The mishap investigation report itself contains SpaceX proprietary data and information governed by US export control laws and is not available for public release, according to the FAA.
"The FAA has been provided with sufficient information and accepts the root causes and corrective actions described in the mishap report," wrote Marcus Ward, manager of the FAA's safety assurance division, in a letter to SpaceX. "Consequently, the FAA considers the mishap investigation that SpaceX was required to complete to be concluded."
Now SpaceX must convince the FAA it has checked off a list of corrective actions to prevent the same failures from occurring on the next Starship test flight. SpaceX said in a statement Friday that lessons learned from the April 20 launch are "directly contributing to several upgrades being made to both the vehicle and ground infrastructure to improve the probability of success on future Starship flights."
Starship fixes
The FAA said Friday that SpaceX needs to complete 63 corrective actions identified after the Starship launch in April, but said SpaceX only must implement those actions that impact public safety ahead of the next Starship flight. Then SpaceX must apply for and receive a modification to its launch license "that addresses all safety, environmental and other applicable regulatory requirements" prior to the upcoming launch, the FAA said.
Elon Musk, SpaceX's founder and CEO, posted a list on Sunday of the 63 corrective actions on his social media platform X, formerly known as Twitter. "Congrats to SpaceX for completing & documented the 57 items required by the FAA for Flight 2 of Starship!" Musk wrote. The remaining six corrective actions coordinated between SpaceX and the FAA are only needed for later Starship flights, he said.
The FAA is responsible for ensuring commercial launch operations do not endanger the public or property, and the agency is also charged with overseeing the effect of launches on the environment.
"Corrective actions include redesigns of vehicle hardware to prevent leaks and fires, redesign of the launch pad to increase its robustness, incorporation of additional reviews in the design process, additional analysis and testing of safety critical systems and components including the Autonomous Flight Safety System, and the application of additional change control practices," the FAA said.
FAA officials have previously said they have a regular dialogue with SpaceX managers during the launch licensing process. NASA and the National Transportation Safety Board participated in the investigation as observers. NASA is eager for SpaceX to move forward with more Starship test flights because the space agency will rely on the vehicle as a human-rated lander for astronauts traveling to the Moon.
The letter from the FAA to SpaceX, dated Thursday, indicated SpaceX has not yet applied for its license modification request, which must provide evidence the company has implemented the corrective actions adopted in response to the April 20 launch. Then the FAA will need to review the application before giving the go-ahead for the next Starship test flight.
Before Musk's statement Sunday, it was apparent that SpaceX has already addressed many, if not all, of the specific corrective actions identified by the FAA in its final report. SpaceX has completed the launch pad redesign, and the company said it has fixed the problems on the rocket itself—which is now installed on its launch pad for the next Starship flight—that led to the propellant leaks and fires in the aft end of the Super Heavy booster during the April 20 launch.
The fires eventually severed connection with the rocket's primary flight computer, SpaceX officials wrote in an update posted Friday on the company's website.
"This led to a loss of communications to the majority of booster engines and, ultimately, control of the vehicle," SpaceX said. "SpaceX has since implemented leak mitigations and improved testing on both engine and booster hardware. As an additional corrective action, SpaceX has significantly expanded Super Heavy’s pre-existing fire suppression system in order to mitigate against future engine bay fires."
Musk said in June that engineers planned to modify leak-prone fuel manifolds on the Raptor engines. The previous design was susceptible to leaks, where hot gas could seep through bolt holes used to attach the manifold to the engine. New Raptor engines will have an improved manifold design, but the list of corrective actions shared by Musk suggested this change will be implemented in the future. For the second Starship flight, technicians planned to add more torque to bolts to address the concern about leakage of super-heated gas.
One of the more prominent issues on the FAA's list of corrective actions involves the Autonomous Flight Safety System (AFSS), which uses pyrotechnic charges to split open the rocket's propellant tanks. Normally, this should almost instantly lead to the break-up of the vehicle. SpaceX said all of the detonators fired as expected after the rocket flew off course during the April test flight, but there was an "unexpected delay" following the system's activation before the rocket broke apart.
"SpaceX has enhanced and requalified the AFSS to improve system reliability," the company said, without providing any additional details. This is a vital system for public safety because it is designed to prevent an errant rocket from threatening people. SpaceX and FAA officials did not respond to questions submitted by Ars on Friday regarding the flight safety system issue on the last Starship launch.
As Ars has previously reported, the next Starship test flight will also debut a hot-staging separation system, in which the Starship's second-stage engines will ignite to push the ship away from the Super Heavy booster. Had the rocket stayed on track through stage separation on the April 20 test flight, the separation system would have released the Super Heavy booster from the Starship vehicle before ignition of the second-stage engines. The rocket assigned to the upcoming test flight will have a structural ring on top of the booster to vent the upper-stage engine exhaust during the ignition sequence.
Concrete underneath the launch mount buckled from the blast from the Super Heavy booster's Raptor engines during the April launch, which vaulted chunks of debris thousands of feet from the pad. Sand and dust from the launch pad rained down on communities miles away. SpaceX added a water-cooled steel flame deflector under the launch mount to prevent the problem from happening again. The new flame deflector withstood a pair of engine test-firings of the Super Heavy booster last month.
In comments earlier this year, Musk outlined several other upgrades to debut on the next Starship test flight. Those include electric thrust vector controls to replace the hydraulic steering system used on the April 20 launch, reducing the potential points of failure in that area, according to SpaceX. Musk said engineers were adding stronger shielding around each of the booster’s 33 Raptor engines to protect them from explosions of nearby engines, a measure intended to reduce the chance of cascading failures.
"Testing development flight hardware in a flight environment is what enables our teams to quickly learn and execute design changes and hardware upgrades to improve the probability of success in the future," SpaceX said. "We learned a tremendous amount about the vehicle and ground systems during Starship’s first flight test. 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."
