Editing Gas-generator cycle

{{More citations needed|date=December 2021}}{{short description|Rocket engine operation method}}
[[File:Gas generator rocket cycle.svg|thumb|250px|Gas-generator rocket cycle. Some of the fuel and oxidizer is burned separately to [[Turbopump|power the pumps]] and then discarded. Most gas-generator engines use the fuel for nozzle cooling.]]

The '''gas-generator cycle''', also called '''open cycle''', is one of the most commonly used power cycles in [[Liquid-propellant rocket|bipropellant liquid]] [[Rocket engine|rocket engines.]] 

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'''. 

The gas generator cycle [[Exhaust gas|exhaust]] products pass over the turbine first. Then they are expelled overboard. They can be expelled directly from the turbine, or are sometimes expelled into the nozzle (downstream from the throat) for a small gain in efficiency.  

The main [[combustion chamber]] does not use these products. This explains the name of the open cycle. The major disadvantage is that this propellant contributes little to no thrust because they are not injected into the combustion chamber. The major advantage of the cycle is reduced engineering complexity compared to the [[Staged combustion cycle|staged combustion (closed) cycle]]. 

== Examples ==
*[[RD-107]], RD-108—Soviet engine type developed in the 1950s, used on [[R-7 (rocket family)|R-7 family]] vehicles including the active [[Soyuz-2]].<ref name="rd107">{{cite web |title=RD-107 |url=http://astronautix.com/engines/rd0107.htm |url-status=dead |archive-url=https://web.archive.org/web/20140209170032/http://www.astronautix.com/engines/rd0107.htm |archive-date=2014-02-09 |publisher=[[Encyclopedia Astronautica]]}}</ref>
*[[Rocketdyne F-1|F-1]]—[[RP-1]]/[[Liquid oxygen|LOX]] engine used on the first stage of [[Saturn V]]. Most powerful single combustion chamber liquid-fueled engine ever flown.<ref name="F1">{{cite web |title=F-1 Engine Fact Sheet |url=http://history.msfc.nasa.gov/saturn_apollo/documents/F-1_Engine.pdf |url-status=dead |archive-url=https://web.archive.org/web/20160413234758/http://history.msfc.nasa.gov/saturn_apollo/documents/F-1_Engine.pdf |archive-date=2016-04-13 |access-date=2013-04-17}}</ref>
*[[Rocketdyne J-2|J-2]]—Upper stage [[Liquid hydrogen|LH2]]/LOX engine developed in the 1960s and used on Saturn V.
*[[RS-27A]]—American RP-1/LOX engine first flown in 1990.<ref name="pump">{{cite web |author=Joe Stangeland |title=Turbopumps for Liquid Rocket Engines |url=http://www.pwrengineering.com/articles/turbopump.htm |url-status=dead |archive-url=https://web.archive.org/web/20121018020226/http://www.pwrengineering.com/articles/turbopump.htm |archive-date=2012-10-18}}</ref>
*[[Vulcain (rocket engine)|Vulcain]]—A family of European first stage engines using LH2/LOX flown on [[Ariane 5]] and [[Ariane 6]].<ref name="vulcain">{{cite web |title=Vulcain-2 Cryogenic Engine Passes First Test with New Nozzle Extension |url=http://www.esa.int/esapub/bulletin/bullet102/Coulon102.pdf |publisher=[[ESA]]}}</ref>
*[[Merlin (rocket engine family)|Merlin]]—RP-1/LOX engine developed by [[SpaceX]] for [[Falcon 9]] and [[Falcon Heavy]], used on both first and second stages.<ref>{{cite web |title=SpaceX Merlin Engine |url=http://www.spacex.com/falcon1.php#merlin_engine |url-status=dead |archive-url=https://web.archive.org/web/20110103230037/http://www.spacex.com/falcon1.php#merlin_engine |archive-date=2011-01-03 |publisher=SpaceX}}</ref>
*[[RS-68]]—LH2/LOX engine built in the 1990s by [[Aerojet Rocketdyne]]. Largest hydrogen-fueled rocket engine ever flown.<ref name="D4">{{cite web |title=Delta 4 Data Sheet |url=http://www.spacelaunchreport.com/delta4.html}}</ref>
*[[CE-20]]—Indian LH2/LOX engine developed in the 2010s for use on the [[LVM3]] launch vehicle.<ref name="ce">{{cite conference |title=Structural Analysis of Propulsion System Components of an Indigenous Cryogenic Rocket Engine
 |author=Asraff, A and Muthukumar, R and Ramnathan, T and Balan, C
 |conference=44TH AIAA/ASME/SAE/ASEE JOINT PROPULSION CONFERENCE & EXHIBIT
 |year=2008
 |url=http://arc.aiaa.org/doi/abs/10.2514/6.2008-5120 |doi=10.2514/6.2008-5120 |url-access=subscription
 }}</ref>
*[[YF-20]]—Chinese [[Dinitrogen tetroxide|N<sub>2</sub>O<sub>4</sub>]]/[[Unsymmetrical dimethylhydrazine|UDMH]] engine developed in the 1990s and used on [[Long March (rocket family)|Long March]] 2, 3, and 4.
*[[TQ-12]]—[[Methane|LCH4]]/LOX engine developed by [[LandSpace]]. First flew in 2022 on [[Zhuque-2]].

== See also ==
* [[Combustion tap-off cycle]]
* [[Expander cycle]]
* [[Pressure-fed engine]]
* [[Rocket engine]]
* [[Staged combustion cycle]]
* [[Turbopump]]

== References ==
{{Reflist}}

== External links ==
* [https://web.archive.org/web/20120414212704/http://www.aero.org/publications/crosslink/winter2004/03_sidebar3.html Rocket power cycles]
* [https://history.nasa.gov/SP-4404/ch2-6.htm Rocket-Engine Cooling] at NASA

{{Spacecraft propulsion}}
{{Thermodynamic cycles}}

[[Category:Combustion]]
[[Category:Rocket engines]]
[[Category:Rocket engines by cycle| ]]
[[Category:Spacecraft propulsion]]
[[Category:Thermodynamic cycles]]