BGR SCIENCE

We now know why Starship SN10 detonated after landing

By Mike Wehner @MikeWehner
March 10th, 2021

SpaceX’s Starship program is a very, very big deal for the company. It’s still in its infancy, with test flights not yet reaching Earth orbit, but in the future, we might see Starships taking humans to Mars or even further. With all that in mind, you can understand why every launch of a Starship prototype is important for both SpaceX and, potentially, humanity, but with a trio of explosions marring the past three launches, it’s been a trying time for the company.

Now, with the image of Starship SN10 exploding on the landing pad still fresh in everyone’s mind, SpaceX boss Elon Musk has finally offered up some details that could explain why the mighty rocket was a one-launch wonder.

According to Musk, some issues that were already being workeout for the next prototype likely contributed to SN10’s landing issues. To be clear, the spacecraft did “land,” but it did so without a bit too rough for its landing legs to handle. The prototype apparently crushed its own legs when it landed, and Musk thinks he knows why.

“SN10 engine was low on thrust due (probably) to partial helium ingestion from fuel header tank. Impact of 10m/s crushed legs & part of skirt,” Musk explained in an exchange on Twitter. He then went on to explain why the helium ingestion was an issue to begin with: “If autogenous pressurization had been used, CH4 bubbles would most likely have reverted to liquid. 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.”

The prior flight Musk is referencing here was SN8, which also ended in an explosion. In attempting to solve one problem, SpaceX may have inadvertently created another. But that’s all in the past now, and SpaceX is looking forward to proving that it can land its Starship without an explosion following in the minutes that follow.

Musk did note in follow-up tweets that SpaceX isn’t totally set on using legs for Starship in the future. It’s possible, Musk said, that the company will opt for a “catch” technique rather than a controlled landing. It wouldn’t be pretty, but as Musk admits, it would probably be a more reliable option.

“Might just catch the ship with the launch tower, same as booster,” Musk explained. “Could just have it land on a big net or bouncy castle. Lacks dignity, but would work. But, optimized landing propellant is only ~5% of dry mass, so it’s not a gamechanger.”