Staged combustion cycle (rocket)
Staged_combustion_rocket_cycle.png
The staged combustion cycle is a power cycle of a bipropellant rocket rocket engine. Some of the propellant is burned in a pre-burner and the resulting hot gas is used to power the engine's pumps. The gas is then injected into the main combustion chamber, along with the rest of the propellant and combustion is completed.
The advantage of the staged combustion cycle is an abundance of power, creating very high chamber pressures and high engine efficiency at low altitude. The disadvantages are harsh turbine conditions, high temperature plumbing required to carry hot gases and a very complicated feedback and control design.
Staged combustion engines are the most difficult types of rocket engines to design. A simplified version is called the Gas-generator cycle.
The Space shuttle main engine is an example of a staged combustion engine.
Staged combusion was invented by Soviet engineers under V.P. Gluskho. Also referred to as "closed cycle", the first staged-combustion engine was the 11D33, a LOX/Kerosene engine used on the 4th stage of the 8K78 "Molniia" rocket in 1960. N2O4/UDMH engines using staged combustion were developed by 1963 and installed on the Proton rocket in 1965. The Russian RD-180 engine, purchased by NASA for the Atlas III and V rockets, also employs this technique.
In the West, the first laboratory staged-combustion test engine was built in Germany in 1963, by Ludwig Boelkow.