Gas-generator cycle (rocket)
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The gas generator cycle is a power cycle of a bipropellant rocket rocket engine. Some of the propellant is burned in a gas-generator and the resulting hot gas is used to power the engine's pumps. The gas is then exhausted.
The advantage of the gas-generator cycle is an abundance of power, creating very high chamber pressures and high engine efficiency at low altitude. It is also a simpler design than the (similar) staged combustion cycle. The main disadvantage is lost efficiency due to discarded propellant.
As in most cryogenic rocket engines, some of the propellant in a gas-generator cycle is used to cool the nozzle and combustion chamber, increasing efficiency and allowing higher engine temperature and efficiency.
The merlin rocket engine is a recent example of a gas-generator engine.