Elon Musk Explains Why the Starship SN10 Prototype Exploded After Landing

The third high-altitude test of a SpaceX Starship prototype ended with a successful landing on March 3 — and then, moments later, ended for a second time with an explosion.

Although the SN10, as the prototype was known, joined its two most recent predecessors in the fiery great beyond, it was still celebrated as a success for becoming the first of Elon Musk’s Mars-bound Starship prototypes to stick the landing. On Tuesday, Musk took to Twitter to elaborate on why the SN10 came in a little too hot, and clarified that a series of fixes was already in the works for the next prototype in the series, the SN11.

“SN10 engine was low on thrust due (probably) to partial helium ingestion from fuel header tank,” Musk tweeted. “Impact of 10m/s crushed legs & part of skirt.”

In subsequent tweets, Musk confirmed that the helium ingestion was likely the result of a pressurization system that had been added to the CH4 header tank to correct an error that had occurred previously with the SN8.

“If autogenous pressurization had been used, CH4 bubbles would most likely have reverted to liquid,” Musk wrote. “Helium in header was used to prevent ullage collapse from slosh, which happened in prior flight. My fault for approving. Sounded good at the time.”

Video footage of the SN10’s launch and subsequent soft landing at SpaceX’s test facility in Boca Chica, Texas, shows the rocket coming in for a speedy landing before settling in at a tilted angle, slightly aflame. Nearly a full minute after successfully completing the test flight, the rocket explodes in a massive fireball.

Musk’s tweet came as a reply to a series of photos tweeted out by a photographer that appear capture SpaceX employees testing out the landing legs of SN11 in order to ensure that they will deploy properly as it prepares for its own imminent test flight. Although SN11 is currently sitting on the launch pad in Boca Chica, SpaceX has not yet confirmed exactly when the next flight test is scheduled to occur — although some industry experts estimate it could be ready to launch as soon as next week.