I know steam turbines make props move on board ships, I’m just having trouble understanding the mechanics of rocket propulsion via nuclear reactor.
Well, there’s always Project Orion.
It’s the old action reaction concept. Instead of the reactor boiling water in the steam generator to turn a turbine, the reactor is used to heat a gas and expel it through a nozzle. The gas at a given temperature and pressure is heated by passing through or near the core which increases it temperature and pressure. When it is released through the nozzle, it creates thrust from the velocity of its molecules being released.