ELI5: Explain Like I'm 5

Steam rocket

A steam rocket is a type of spaceship that uses steam as its power source. Steam is a type of water vapor that forms when water is heated. The steam rocket gets hot water from its fuel (often a form of liquid hydrogen) and turns it into steam. This steam then passes through a turbine, which spins around very quickly, to create a lot of energy. This energy pushes the hot steam through a nozzle at the back of the rocket and out of the engine. As the steam leaves the back of the rocket it pushes the rocket forward and up, like a jet engine. So, a steam rocket is like a jet engine that uses hot steam instead of hot air to make it go!