FAA Closes Starship Test Flight 2 Investigation
FAA Closes Starship Test Flight 2 Investigation
SpaceX Must Implement All Corrective Actions Prior to Flight Test 3
SpaceX has released a report on the anomaly that led to the self-destruction of the Starship second stage during its Super Heavy Orbital Test Flight 2 on November 18th last year.
According to a report posted to the company website, during that test, Starship successfully lifted off at 7:02 a.m. CT from Starbase in Texas. All 33 Raptor engines on the Super Heavy Booster started up successfully and, for the first time, completed a full-duration burn during ascent. Starship then executed a successful hot-stage separation, the first time this technique has been done successfully with a vehicle of this size.
Following stage separation, Super Heavy initiated its boostback burn, which sends commands to 13 of the vehicle’s 33 Raptor engines to propel the rocket toward its intended landing location. During this burn, several engines began shutting down before one engine failed energetically, quickly cascading to a rapid unscheduled disassembly (RUD) of the booster. The vehicle breakup occurred more than three and a half minutes into the flight at an altitude of ~90 km over the Gulf of Mexico.
The most likely root cause for the booster RUD was determined to be filter blockage where liquid oxygen is supplied to the engines, leading to a loss of inlet pressure in engine oxidizer turbopumps that eventually resulted in one engine failing in a way that resulted in loss of the vehicle. SpaceX has since implemented hardware changes inside future booster oxidizer tanks to improve propellant filtration capabilities and refined operations to increase reliability.
At vehicle separation, Starship’s upper stage successfully lit all six Raptor engines and flew a normal ascent until approximately seven minutes into the flight, when a planned vent of excess liquid oxygen propellant began. Additional propellant had been loaded on the spacecraft before launch in order 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.
A leak in the aft section of the spacecraft that developed when the liquid oxygen vent was initiated resulted in a combustion event and subsequent fires that led to a loss of communication between the spacecraft’s flight computers. This resulted in a commanded shut down of all six engines prior to completion of the ascent burn, followed by the Autonomous Flight Safety System detecting a mission rule violation and activating the flight termination system, leading to vehicle breakup. The flight test’s conclusion came when the spacecraft was at an altitude of ~150 km (93 miles) and a velocity of ~24,000 km/h (15,000 mph), becoming the first Starship to reach outer space.
SpaceX says it has implemented hardware changes on upcoming Starship vehicles to improve leak reduction, fire protection, and refined operations associated with the propellant vent to increase reliability. The previously planned move from a hydraulic steering system for the vehicle’s Raptor engines to an entirely electric system also removes potential sources of flammability.
The water-cooled flame deflector and other pad upgrades made after Starship’s first flight test performed as expected, requiring minimal post-launch work to be ready for vehicle tests and the next integrated flight test.
Following the flight test, SpaceX led the investigation efforts with oversight from the FAA and participation from NASA, and the National Transportation Safety Board.
Upgrades derived from the flight test will debut on the next Starship and Super Heavy vehicles to launch from Starbase on Flight 3. SpaceX is also implementing planned performance upgrades, including the debut of a new electronic Thrust Vector Control system for Starship’s upper stage Raptor engines and improving the speed of propellant loading operations prior to launch.
The company says 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.
In a statement released February 26th, the FAA said it has closed the SpaceX-led mishap investigation.
SpaceX identified, and the FAA accepts, the root causes and 17 corrective actions documented in SpaceX’s mishap report. Seven corrective actions were identified for the Super Heavy Booster including vehicle hardware redesigns, updated control system modeling, reevaluation of engine analyses based on OTF-2 flight data, and updated engine control algorithms. Ten corrective actions were identified for the Starship vehicle including vehicle hardware redesigns, operational changes, flammability analysis updates, installation of additional fire protection, and guidance and modeling updates.
The closure of the mishap investigation does not signal an immediate authorization of the next Starship launch.
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.