RocketMotorTwo is a hybrid rocket motor that combines the simplicity of a solid propellant rocket engine with the controllability of a liquid propellant engine. The motor consists of two main parts—a large tank which stores the liquid oxidizer (nitrous oxide), and the cartridge which stores hydroxyl-terminated polybutadiene (HTPB) solid fuel. This combination, known as the Case/Throat/Nozzle (CTN), the guts of the engine, is the portion of RocketMotorTwo donated to the museum. It is one of the only non-reusable components of SpaceShipTwo.
Why isn't the engine's Case-Throat-Nozzle reusable in Virgin Galactic's SpaceShipTwo?