WASHINGTON — The failure of SpaceX’s Starship on its most recent test flight had a different root cause than the previous failure, despite happening at about the same time.
SpaceX released details May 23 about the cause of the Flight 8 mishap that took place March 6, when several Raptor engines on the Starship upper stage shut down and the vehicle started to tumble. The vehicle reentered, breaking up over the Caribbean.
The timing of the Flight 8 failure was similar to Flight 7 in January, which also featured several engine shutdowns and a loss of communications about eight and a half minutes after liftoff. However, SpaceX says the two failures had different causes.
“While the failure manifested at a similar point in the flight timeline as Starship’s seventh flight test, it is worth noting that the failures are distinctly different,” the company stated.
In the case of Flight 8, SpaceX said one of the center Raptor engines in Starship suffered a hardware failure, details of which the company did not disclose. That failure enabled “inadvertent propellant mixing and ignition” that caused the loss of the Raptor. Immediately thereafter, the other two center Raptor engines shut down, along with one of the three outer vacuum-optimized engines with larger nozzles. The vehicle then lost control authority.
The company said it made changes to the Raptors in the Starship upper stage, with “additional preload” on key joints and a new nitrogen purge system as well as improvements to the propellant drain system. A future version of Raptor in development will also have reliability improvements to address the problem seen on Flight 8.
On Flight 7 in January, SpaceX, said the vehicle suffered a harmonic response several times stronger than expected, creating additional stress on the vehicle’s propulsion system. That caused leaks that triggered a fire in the engine bay.
“The mitigations put in place after Starship’s seventh flight test to address harmonic response and flammability of the ship’s attic section worked as designed prior to the failure on Flight 8,” SpaceX said.
The SpaceX statement about Flight 8 came a day after the Federal Aviation Administration provided its final approval for the next Starship test flight, Flight 9, which SpaceX confirmed is scheduled for no earlier than May 27 at 7:30 p.m. Eastern.
A major change for Flight 9 involves the Super Heavy booster. Flight 9 will involve the first reflight of that booster, using a booster that originally launched on Flight 7. Some components of the booster were replaced after Flight 7, but SpaceX said a “large majority” of the booster will be hardware that previously flew, including 29 of its 33 Raptor engines.
Unlike the previous four test flights, SpaceX will not attempt to recover the Super Heavy booster with a “catch” by the launch tower at Starbase. The booster will instead test new flight profiles after separation, including controlling how it flips to orient itself for a boostback burn and use a higher angle of attack on its descent, both intended to reduce the propellant needed to recover the booster. SpaceX will also test alternative engine landing profiles.
“To maximize the safety of launch infrastructure at Starbase, the Super Heavy booster will attempt these experiments while on a trajectory to an offshore landing point,” SpaceX said, with a “hard splashdown” planned off the coast from Starbase.
The Starship upper stage will attempt many of the same demonstrations planned for previous flights but which could not be carried out because of the failures. That includes a Raptor engine relight while in space, deployment of eight mass simulators of next-generation Starlink satellites and tests of reentry technologies.