SpaceX Starship SN10 Explosion: Elon Musk Explains What Went Wrong

Elon Musk has detailed just what went wrong with the SpaceX SN10 Starship, after the latest prototype landed only to promptly explode earlier this month. At first, all seemed to be going unexpectedly well for the test rocket, which had completed a mesmerizing controlled descent back to the landing pad.

When it touched down, apparently safely, it seemed like SpaceX had nailed one of the most complex parts of the process for making a reusable, more cost-effective rocket. About sixty seconds later, though, flames and wreckage were dominating the pad, after the Starship exploded.

SpaceX dispatched a Boston Dynamics robot dog to explore the remains of the SN10 rocket, trying to figure out just what went wrong in the process. Elon Musk has now shared some insight in that, along with taking responsibility for one of the key decisions which it seems led to the explosion.

The "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. Multiple fixes in work for SN11."

The presence of helium, however, was an intentional one, not an accident. After it was pointed out that the helium pressurization was added to the Starship prototype's CH4 header tank to avoid the same issue that a previous prototype, SN8, encountered, Musk agreed that it contributed to SN10's explosion.

Back in November 2020, the rocket encountered an issue with pneumatic pressure, with the liquid oxygen header tank pressure increasing.

"If autogenous pressurization had been used, CH4 bubbles would most likely have reverted to liquid," Musk agreed. "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."

Of course, prototypes like SN10 are designed to help work through these sort of challenges, and SpaceX clearly is still in the midst of development. That includes identifying when intended fixes actually could be presenting more of an issue than helping with it. Asked about whether baffles would be used to prevent the slosh issue in future rockets, Musk said that they were actually present on SN10, and could've been part of the problem.

"There were baffles, but one may have acted like a straw to suck bubbles in from above liquid/gas level," he explained. "Something similar happened on an early Falcon 1 flight, resulting in unexpectedly high liquid oxygen residuals at main engine cutoff."

The Starship SN11 prototype has already been constructed, and SpaceX is currently in preparation to launch another high-altitude test.