Elon Musk finally commented on the explosion of the SN10 prototype of the upcoming Starship spacecraft. According to SpaceX’s boss tweets, one of the Raptor’s engines had low thrust, so the rocket landed too hard. This damaged the legs and bottom of the machine.
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
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The low draft problem was apparently caused by a partial leakage of helium from the CH4 fuel tank.
Chris B of NASA’s Spaceflight subsequently clarified that the whole matter is quite complicated, as helium was added to the tank to avoid the complications that caused the SN8 explosion.
Musk responded to his tweet, among other things, by saying that if autogenous pressure was used, the CH4 bubbles would most likely return to a liquid state.
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
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Hopefully, all this knowledge will help ensure that the upcoming SN11 test flight runs smoothly.
Cover photo: Official SpaceX Photos, CC BY-NC 2.0
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