The gas-generator cycle is a power cycle of a pumped liquid bipropellant rocket engine. Part of the unburned propellant is burned in a gas generator (or preburner) and the resulting hot gas is used to power the propellant pumps before being exhausted overboard, and lost. Because of this loss, this type of engine is termed open cycle. Usage Gas-generator combustion engines include the following: Vulcain, HM7B Merlin RS-68 RS-27A J-2X F-1 RD-107 CE-20 Rocket launch systems that use gas-generator combustion engines: Ariane 5 Falcon 9, Falcon Heavy Delta IV Saturn V Soyuz Geosynchronous Satellite Launch Vehicle III Long March 3B, Long March 2F Rocket Lab Neutron Miura 5 See also Combustion tap-off cycle Expander cycle Pressure-fed engine Rocket engine Staged combustion cycle References External links Rocket power cycles Rocket-Engine Cooling at NASA Combustion Rocket engines Spacecraft propulsion Thermodynamic cycles