A solid rocket motor is a powerful propulsion system that burns a solid propellant—a chemical compound comprising both the fuel and the oxidizer admixed. Solid rocket motor (SRM) propulsion has many and varied applications in astronautics, such as rocket boosters to augment the lift-off capability of many space launchers, and smaller solid rocket motors can be used for in-space maneuvering or as an upper stage to place spacecraft in certain orbits. Because SRMs are designed in many sizes, with different propellant formulations, this chapter presents main formulas and motor performance characteristics, as these directly control the SRM pressure, total impulse, and thrust required. Actual data for many SRM applications are provided.