Solid propellants are a type of fuel used in rockets and missiles. They are made by mixing a fuel with an oxidizer, which allows the propellant to burn and produce thrust. Unlike liquid propellants, solid propellants are easier to handle and store, making them popular for many applications, including space launches and military operations. When ignited, solid propellants burn from the inside out, creating hot gases that expand and exit through a nozzle. This process generates the necessary force to propel the rocket or missile forward. Examples of solid propellants include hydroxyl-terminated polybutadiene (HTPB) and ammonium perchlorate.