SpaceX has released a report detailing the cause of the Starship vehicle’s destruction during its seventh test flight on January 16th. The company attributes the loss to an unexpectedly strong harmonic response. This unexpected response created propellant leaks in the vehicle's “attic” section, near one of its six Raptor engines. Two flashes were observed, followed by sustained fires and a subsequent loss of communication with the Starship approximately 8 minutes and 20 seconds after liftoff.
“These eventually caused all but one of Starship’s engines to execute controlled shut down sequences and ultimately led to a loss of communication with the ship,” SpaceX stated. The company's investigation revealed that the harmonic response was "several times stronger in flight than had been seen during testing," leading to increased stress on the propulsion system's hardware. The propellant leaks resulting from this stress could not be fully vented, leading to the fires which caused the engine shutdowns.
To address these issues, SpaceX conducted a 60-second static fire test of the Starship built for Flight 8 on February 12th. “The 60-second firing was used to test multiple engine thrust levels and three separate hardware configurations in the Raptor vacuum engine feedlines to recreate and address the harmonic response seen during Flight 7,” the company explained. This testing informed hardware modifications to the fuel feedlines, adjustments to propellant temperatures, and a new operating thrust target.
Further improvements include the addition of vents and a gaseous nitrogen purge system to minimize the flammability within the attic section. SpaceX plans to launch Flight 8 as early as February 28th, pending FAA approval of their investigation into Flight 7. This launch will include several objectives from Flight 7, such as deploying four mass simulators for next-generation Starlink satellites and testing new reentry protection technologies.
“Starship’s seventh flight test was a reminder that developmental progress is not always linear, and putting flight hardware in a flight environment is the fastest way to demonstrate how thousands of distinct parts come together to reach space,” SpaceX concluded. "Upcoming flights will continue to target ambitious goals in the pursuit of full and rapid reusability.”