The staged combustion cycle is a power cycle of a bipropellant rocket engine. In the staged combustion cycle, propellant flows through multiple combustion chambers, and is thus combusted in stages. The main advantage relative to other rocket engine power cycles is high fuel efficiency, measured through specific impulse, while its main disadvantage is engineering complexity.
Oxidizer-rich turbine exhaust from a SpaceX Raptor preburner shown during a 2015 sub-system test on a test stand at Stennis Space Center. In the full-flow rocket engine, the preburner exhaust is fed into a turbine and then into the main combustion chamber.
A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordance with Newton's third law. Most rocket engines use the combustion of reactive chemicals to supply the necessary energy, but non-combusting forms such as cold gas thrusters and nuclear thermal rockets also exist. Vehicles propelled by rocket engines are commonly used by ballistic missiles and rockets. Rocket vehicles carry their own oxidiser, unlike most combustion engines, so rocket engines can be used in a vacuum to propel spacecraft and ballistic missiles.
RS-68 being tested at NASA's Stennis Space Center
Viking 5C rocket engine used on Ariane 1 through Ariane 4
Armadillo Aerospace's quad vehicle showing visible banding (shock diamonds) in the exhaust jet