HElium is very expensive / in short supply, and lacks mass, which you need for a thruster. I’m surprised they don’t use something like Argon or even Krypton, that has more mass and is similarly non-combustible.
HElium is very expensive / in short supply,
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Biden recently sold the US helium stock pile - don’t know the buyer - China?
I have a better use for that helium- let’s all take a hit and TALK LIKE DONALD DUCK!