Opt-in Prerelease for 1.1! in Developer Articles Posted March 4, 2016 43 minutes ago, Temeter said: The first rocket engines even ran on Ethanol! At that time, people knew what was good and how to build fine rockets. Well, the first "useful" modern style rockets had engines running on ethanol. Earlier rockets used solid fuel or some pretty nasty hypergolics, including some of the bad person rocket planes. The good thing about RP-1 and Liq Hydrogen is that your engineers don't steal it for happy hour.