Can't reply to your other post unfortunately, but that's not true about rocket propulsion not working in a vacuum. You just have to mix the fuel with an oxidize

Can't reply to your other post unfortunately, but that's not true about rocket propulsion not working in a vacuum. You just have to mix the fuel with an oxidizer if oxygen isn't available. (EDIT: Or just use a method of propulsion other than combustion, but they are usually not as effective)