Is hydrogen peroxide used as rocket fuel?

Answer 1

In outer space there's no oxygen, so no combustion can take place unless you bring along your own. Hydrogen peroxide is a convenient way to do that: it's a strong oxidizing agent and it's considerably more dense than oxygen gas. You could liquify oxygen to make it more dense, of course, but then you need either stronger, thicker walls to withstand the pressure in the tank or heavy refrigeration equipment, both of which increase the weight of the rocket. Hydrogen peroxide doesn't need to be compressed or refrigerated, since it's already liquid.

Answer 2

Yes, hydrogen peroxide can be used as a rocket propellant in liquid-fueled rockets. It can be either used as a monopropellant or as an oxidizer in bipropellant rockets to generate thrust by decomposing into water and oxygen in the presence of a catalyst.