I’m not convinced we do have a limited earth fuel budget as you say. There’s lots of options for rocket fuel and many of them are highly abundant or can be synt

I’m not convinced we do have a limited earth fuel budget as you say. There’s lots of options for rocket fuel and many of them are highly abundant or can be synthesised. For example, hydrogen and oxygen are the 1st and 3rd most abundant elements in the universe, so liquid oxygen and liquid hydrogen fuel is always going to be an option