Hydrogen is always my go-to for thrusters. works everywhere, powerful and only needs ice. even once i've progressed in my save most of the time i don't switch to ion. would rather use that power for JumpDrives than for running my thusters, such as ion or atmospheric.

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EDIT: oops, thought this was the space engineers subreddit. my bad. but it's still good advice. so i'm gonna leave it.