SpaceX has released the results of its investigation into the failure of the Starship Flight 8 test mission, pinpointing a hardware issue in the upper stage’s propulsion system as the root cause. The March 6 flight ended with the Starship vehicle tumbling and breaking up during reentry over the Caribbean Sea. The company emphasized that the failure was unrelated to the one that occurred during Flight 7 in January, despite both incidents unfolding approximately eight and a half minutes after liftoff.
Credit: SpaceX
According to SpaceX, the failure on Flight 8 originated from a center Raptor engine on the upper stage suffering a non-specified hardware malfunction. This failure caused unintended mixing and subsequent ignition of liquid methane and liquid oxygen propellants within the engine. The event led to an energetic overpressure that destroyed the engine. Seconds later, the other two sea-level Raptor engines at the vehicle’s centerline automatically shut down, along with one of the three vacuum-optimized Raptors. With only two functioning vacuum Raptors remaining and an unbalanced thrust profile, the vehicle lost control authority and began to tumble.
Telemetry data indicated that the issue occurred approximately five and a half minutes into the ascent burn. SpaceX reported a bright flash in the aft section near the failed Raptor engine, followed by a cascade of shutdowns. Communication with the spacecraft ceased about two minutes later, at roughly T+9:30, prior to the activation of any destruct protocols. The Autonomous Flight Safety System, which remained operational, likely triggered upon loss of signal, initiating a controlled breakup of the vehicle.
Post-flight analysis identified torch ignition issues caused by excessive local thermal conditions near the igniters as a contributing factor in several engines' failure to relight during descent phases. The company successfully replicated these ignition issues in ground testing, confirming thermal stress near the igniters as the source.
In response, SpaceX is implementing several technical modifications:
- Engine Joint Reinforcement: Additional preload is being applied to key engine joints to mitigate mechanical vulnerabilities under high dynamic loads.
- New Nitrogen Purge System: Designed to prevent the accumulation of fuel-rich mixtures in confined spaces within the engine bay by purging volatile vapors.
- Improved Propellant Drainage: Updates to the upper stage’s propellant management system aim to reduce the risk of residual liquid oxygen and methane pooling in critical areas.
Enhanced Insulation for Igniters: Added thermal protection around torch igniters to maintain functionality during relight phases, especially during boostback and landing burns.
Additionally, the company has accelerated development of the Raptor 3 engine, which will incorporate further reliability upgrades targeting the failure mechanisms seen in both Flights 7 and 8.
Flight 7, by comparison, suffered from a structural response to unanticipated harmonic vibrations. These vibrations—several times stronger than expected—produced high-frequency stress in the vehicle’s aft "attic" section, leading to system-wide leaks and a subsequent fire. Mitigations implemented after Flight 7, including damping of harmonic oscillations and flammability reduction measures, were validated as successful in Flight 8.
SpaceX has received final approval from the FAA to proceed with its next test, Flight 9, targeted for no earlier than May 27 at 7:30 p.m. Eastern. This mission introduces the first reuse of a Super Heavy booster, specifically Booster 10, which previously flew during Flight 7. Of the 33 Raptor engines onboard, 29 are reused, with four being replaced following post-flight inspections.
Flight 9 also marks a departure from previous recovery strategies. SpaceX will not attempt a mechanical "catch" using the launch tower’s arms. Instead, the booster will test:
- Aerodynamic Flip Maneuvering: Adjusting attitude using grid fins and thrust vectoring to orient for a boostback burn.
- High Angle of Attack Reentry: A more aggressive trajectory to reduce required propellant for deceleration.
- Alternative Engine Landing Profiles: New sequencing and throttling techniques for booster relighting and descent control.
The booster will perform these tests along a trajectory terminating in a hard splashdown in the Gulf of Mexico, minimizing risk to the Starbase launch site.
The Starship upper stage, meanwhile, is expected to complete a suite of objectives previously interrupted, including:
- Raptor Vacuum Engine Relight in Space: Demonstrating restart capabilities critical for orbital missions.
- Payload Deployment Simulation: Releasing eight mass simulators of second-generation Starlink satellites.
- Reentry Heatshield Evaluation: Testing thermal protection tiles and flight dynamics for high-speed atmospheric return.
All debris from the Flight 8 failure fell within a pre-designated Debris Response Area, and coordination with the Bahamian government ensured cleanup and environmental monitoring. No hazardous materials were found, and no significant marine or ecological impact was detected.
“Starship is built to redefine space access through full and rapid reusability,” SpaceX said in a statement. “Although progress will include setbacks, testing hardware in flight is essential to developing a safe, reliable system for the future of space exploration.”
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