SpaceX’s ambition to revolutionize space travel took a significant leap forward with the third flight test of Starship and Super Heavy.
This mission, conducted on March 14, 2024, from Starbase, Texas, marked a crucial milestone in developing rapidly reusable rockets, a fundamental goal for enabling humanity’s multiplanetary future, as often stressed by the company.
In an update shared on May 24th, 2024, SpaceX went a bit more in details about what happened during the third test flight, which ended with both the Super Heavy booster and the Starship upper stage being lost.
In the past weeks, the company shared very little insights about what went wrong, but now we have a more complete overview of the reasons that led to the loss of the vehicles.
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A good ascent, not so good boostback
At precisely 8:25 a.m. CT, the Starship system lifted off successfully. All 33 Raptor engines on the Super Heavy booster ignited and completed a full-duration burn during the ascent. This marked the second successful ascent for the Super Heavy booster, reinforcing its status as the world’s most powerful launch vehicle.
The critical phase of stage separation saw all six second-stage Raptor engines on Starship igniting successfully, propelling the vehicle on its intended trajectory and completing its full-duration ascent burn, unlike what happened with the loss of the Ship during the second flight.
Following stage separation, the Super Heavy booster initiated its boostback burn. The onboard flight computer commanded 13 of the booster’s 33 Raptor engines to restart and redirect the rocket toward its designated landing site. The engines performed successfully until six engines began shutting down, triggering an early, yet benign notes the company, termination of the boostback burn.
The investigation into the early boostback burn shutdown identified filter blockage in the liquid oxygen supply to the engines as the root cause. This blockage led to a loss of inlet pressure in the engine oxygen turbopumps.
SpaceX had already implemented hardware changes ahead of Flight 3 to address this issue. These modifications enabled the booster to attempt its first-ever landing burn. Future Super Heavy boosters will include additional hardware inside the oxygen tanks to enhance propellant filtration capabilities.
The Landing Attempt
Despite the early shutdown of six engines, the booster continued its descent and attempted a landing burn. This final phase commanded the same 13 engines to slow the rocket for a soft touchdown in the Gulf of Mexico. However, only seven engines were commanded to start up, with only two of them achieving mainstage ignition.
The booster experienced lower-than-expected thrust during the landing burn, resulting in loss of contact at approximately 462 meters altitude, just under seven minutes into the mission.
Data from this landing burn attempt will inform further hardware and software improvements to increase Raptor engine startup reliability under landing conditions.
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Starship’s coast phase and reentry
During the coast phase, Starship achieved several key objectives. The vehicle performed its first-ever test of the payload door in space and successfully completed a propellant transfer demonstration, moving liquid oxygen from a header tank to the main tank.
This test provided critical data for future ship-to-ship propellant transfers, essential for missions like NASA’s Artemis program, aimed at returning astronauts to the Moon.
However, several minutes into the coast phase, Starship began losing attitude control. Despite this, the vehicle continued on its nominal trajectory. The loss of attitude control led to an automatic command to skip the planned on-orbit relight of a single Raptor engine, a test that was part of the flight’s timeline.
Starship then experienced its first reentry from space, providing valuable data on heating and vehicle control during hypersonic reentry. Due to the lack of attitude control, the vehicle encountered much “higher-than-anticipated heating on both protected and unprotected areas”.
High-definition live views and extensive telemetry were transmitted in real time via Starlink terminals on Starship, SpaceX reported. The mission concluded when telemetry was lost at approximately 65 kilometers altitude, around 49 minutes into the flight.
The investigation into the unplanned roll identified clogging of the valves responsible for roll control as the “most likely” cause. SpaceX has since added additional roll control thrusters to upcoming Starships to enhance attitude control redundancy and upgraded the hardware for improved resilience to blockage.
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Post-Flight investigation and future upgrades
Following the flight test, SpaceX led the investigation with oversight from the FAA and participation from NASA and the National Transportation and Safety Board (NTSB).
Notably, neither vehicle’s automated flight safety system was triggered, and no debris impacted areas outside predefined hazard zones. Pending the FAA’s finding of no public safety impact, a license modification for the next flight can be issued without formal closure of the mishap investigation, the company said.
Launch rehearsal for Flight 4 complete pic.twitter.com/Gh8s7n4JIQ
— SpaceX (@SpaceX) May 20, 2024
The upgrades resulting from the Flight 3 test will be implemented in the next launch from Starbase, designated Flight 4, tentatively planned for June 5th, 2024. The focus is shifting from achieving orbit to demonstrating the return and reuse capabilities of Starship and Super Heavy.
The SpaceX’s team has incorporated numerous hardware and software improvements, including operational changes like the jettisoning of Super Heavy’s hot-stage adapter following boostback to reduce booster mass during the final phase of flight.
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