How is a rocketlauncher steam powered?
A rocket launcher is really just a tube, with an explosive that has a propulsion device on it that shoots out the front.
I think you may mean a steampowered grenade launcher, even though with the advanced technology that is present, it'd be completely out-everythinged.
The propulsion device is substituted for an extremely condensed steam canister, with a hot-plate under it to continuously keep the water in gas form. It shoots out the pressured water vapor upon pulling the trigger, causing the rocket to blow out of the launcher. Also, due to the propulsion device's crude workings, it allows for a more random launch. The missile could swivel left or right depending on weather and other things that can slightly change the temperature and density of the steam, Styx is very fond of the idea of a unpredictable explosion coming out of nowhere onto his enemies (or companions).
