I've just finished reading Rimward, and the one thing that struck me strange was how the Titanians are using the hydrocarbon lakes as energy sources. From what I've read, there is no free oxygen on Titan, so there's no cost effective way to burn them. The rulebook on p343 even states that Titanian jets carry their own oxygen. (Though it does not state the same for Venus with its CO2 atmosphere). ( I also interpret this as an indication that nuclear batteries do not have the power/weight output for flight, and fusion reactors are not practical for aircraft. ) I have found this article: http://science.nasa.gov/science-news/science-at-nasa/2007/04may_methaneb... about methane rockets, and the fuel part would apply equally to jets, but the article seems to assume that oxygen is brought from earth. Come to think of it, the economy actually works in terms of rocket/jet fuel: Split water into hydrogen and oxygen, use the oxygen as oxydizer for methane, and compress the hydrogen as MH for spaceships. Still, using fusion energy to split water, then burning the oxygen with methane sounds like a net energy loss compared to just using plain fusion for terrestrial power (electricity) generation. Did I miss something, or is this simply a (minor and inconsequential) mistaken piece of flavor in the book ? Any chemists around ?