I’m not sure I’d call it “rocket fuel” in the traditional sense, hydrazine is used (these days) as a thruster monopropellant when already out in space. It’s pretty fascinating actually - a monopropellant doesn’t combust with another fuel like you’d think, it gets passed through a solid lattice that creates a reaction within the monopropellant alone and expands, causing thrust. Since it’s only used in space it dissipates and doesn’t get in contact with anything it can be toxic to. However, this is usually why they tell you to stay away from crashed satellite bits if you happen to find them randomly, there’s a chance they’re contaminated with hydrazine.
