Concrettle Fuel: Basically made of the ground ore-gravel found in the debris of destroyed planets, mixed with a polymer of electrified plasma and a molasses/apple-cider gel. This is smoothed, dried and hardened into slabs then inserted into starships. Not viable for small appliances and its heavy and needs to be individually powered. However, is great for huge liners because it’s cheap, hardy, lasts years, easy to find and can be self installed.
Crystalline Fuel: In pure Chrystal form was used for city power but almost useless for all but the most royal vessels because its expensive and cracks easily. However, when technology and luck found a cheaper, smaller and refinable alternative, Crystalline, producing a clear, clean, cool liquid that can power anything and everything. Behold the future. However, that’s aid is only really good for inner-realm voyages as is complete factory produced and must be re-stocked.