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SpaceX Starship Flight 9

On May 27, 2025, Starship’s ninth flight test successfully lifted off at 6:36 p.m. CT from Starbase, Texas. The flight test began with the first Super Heavy booster to be reflown starting up successfully and completing a full-duration ascent burn with all 33 of its Raptor engines before separating from Starship’s upper stage in a hot-staging maneuver. During separation, Super Heavy performed the first ever deterministic flip followed by its boostback burn.

After completing the boostback burn, Super Heavy flew at a significantly higher angle of attack than previous flights during its descent back to Earth, reaching a peak angle of approximately 17 degrees. This trajectory was a flight experiment to gather data on the limits of the booster’s performance. Once it reached the planned splashdown area, the booster relit 12 of the planned 13 engines for its landing burn. Shortly after the burn started, an energetic event was observed near the aft end of the vehicle followed by loss of telemetry. Final data was received from the booster approximately 382 seconds into flight and at approximately 1 kilometer in altitude over the designated clear zone.

The most probable cause for the failure at landing burn was higher than predicted forces on the booster structure, specifically on the booster’s fuel transfer tube, due to the increased angle of attack experiment. Post-flight analysis showed that vehicle loads exceeded the capabilities of the transfer tube which is believed to have experienced a structural failure, resulting in a mixing of methane and liquid oxygen and subsequent ignition. For the remaining flight tests using this version of the Super Heavy booster, the angle of attack for booster descent will be lowered to decrease aerodynamic forces and minimize the likelihood of structural failure.

SpaceX works with an experienced global response provider to retrieve any debris that may wash up in South Texas and/or Mexico as a result of Starship flight test operations. During the survey of the expected debris field from the booster, there was no evidence of any floating or deceased marine life that would signal booster debris impact harmed animals in the vicinity.

Following a successful stage separation, the Starship upper stage lit all six of its Raptor engines and flew along its expected trajectory. Approximately three minutes into the burn, sensors in the nosecone detected a steady increase in methane levels. This continued until approximately five minutes into the burn when pressure began to rapidly decrease in the main fuel tank while pressure simultaneously increased in the nosecone. Starship’s systems were able to compensate for the drop in main tank pressure and completed the ascent burn, achieving the planned velocity and Second Stage Engine Cutoff (SECO).

After engine shutdown, the elevated nosecone pressure combined with planned nosecone venting led to a large amount of attitude error, which continued to build up until the vehicle’s automatic fault systems disabled nosecone venting. The attitude error resulted in the ship automatically skipping the payload deploy objective, which was also unable to be completed as the higher nosecone pressure resulted in adverse loads on the mechanism responsible for opening the payload door.

The vehicle was able to gradually decrease its attitude error using reaction control thrusters until nosecone venting was reenabled as planned. Roughly 40 seconds after nosecone vents were reenabled, onboard cameras showed liquid methane entering the nosecone and temperatures on multiple sensors and controllers started dropping. This eventually triggered automatic passivation commands on the vehicle, resulting in Starship skipping the in-space burn and venting all remaining propellant into space.

Starship reentered Earth’s atmosphere in an off-nominal attitude and communication was lost during entry. Final telemetry from Starship was received approximately 46 minutes into the flight test, while the vehicle was approximately 59 kilometers in altitude and inside the designated entry area over the Indian Ocean. There were no autonomous flight safety system mission rule violations or initiation of the flight termination system.

SpaceX led the investigation efforts with oversight from the FAA and participation from NASA, the National Transportation Safety Board, and the United States Space Force.

The most probable root cause for the loss of the Starship upper stage was traced to a failure on the main fuel tank pressurization system diffuser. Cameras inside the vehicle showed a visible failure on the fuel diffuser canister, which is located inside the nosecone volume on the forward dome of the main fuel tank. While pre-flight analysis did not show a predicted failure, SpaceX engineers were able to recreate the failure using flight conditions when testing at the facility in McGregor, Texas.

To address the issue on upcoming flights, the fuel diffuser has been redesigned to better direct pressurized gas into the main fuel tank and substantially decrease the strain on the diffuser structure. The new design underwent a more rigorous qualification campaign, subjecting it to flight-like stresses and running for more than ten times the expected service life with no damage.