Elon Musk reveals why the SN10 Starship exploded - Engadget

For a short while after SpaceX's SN10 Starship touched down, it seemed like the prototype made it out of its test flight unscathed. The vehicle exploded on its landing pad around a minute later, though, creating a massive inferno like its predecessors did. Now, Elon Musk has revealed what went wrong in responses sent to followers on Twitter. The SpaceX chief said the SN10 engine was low on thrust probably due to "partial helium ingestion from [the] fuel header tank" and that the impact crushed the rocket's legs and part of its skirt. SpaceX is now working on multiple fixes for the issue so that it doesn't affect SN10's successor, the SN11, anymore.

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. Multiple fixes in work for SN11.
— Elon Musk (@elonmusk) March 9, 2021

Chris Bergin of NASA Spaceflight tweeted that the issue is a "tricky one," seeing as the helium ingestion was caused by the pressurization system added to the CH4 tank to prevent what caused SN8 Starship's explosion. Musk said that's a "fair point," and he approved the change because it sounded good at the time.

Fair point. 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.
— Elon Musk (@elonmusk) March 9, 2021

SpaceX's Starship is a heavy-lift launch vehicle that's being developed to carry cargo and human passengers to Earth's orbit and beyond. SN10's explosion won't be slowing down the company's testing efforts — in fact, it recently rolled out the SN11 prototype to its Boca Chica facility to start preparing for its fourth high-altitude test launch.

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