# How do you figure out fuel specific impulse non-experimentally?

Simple question, probably very complicated answer:

Without building a test engine/rocket and finding out experimentally, that is to say, based on chemical characteristics alone, how can one compute the expected specific impulse of a given fuel?

• Fuels produce energy, you can estimate how much for given mixtures from known reactions (or study those regions independently). Then you have to know how your engine transforms that into motion (or whatever else it's supposed to do). I would assume this to be an more or less everyday problem for engine engineers... I think there is another stack exchange for that... – Martin - マーチン Oct 14 '18 at 10:39