View source for Physics:Combustion tap-off cycle

{{Short description|Rocket engine power cycle}}
[[File:Combustion tap-off rocket cycle.svg|thumb|Diagram of the open-cycle combustion tap-off rocket cycle. A small portion of exhaust from the combustion chamber is tapped off to power the turbine(s).]]
The '''combustion tap-off cycle''' is a power cycle of a bipropellant rocket [[Engineering:Rocket engine|engine]]. The cycle takes a small portion of hot exhaust gas from the rocket engine's [[Engineering:Combustion chamber|combustion chamber]] and routes it through [[Engineering:Turbopump|turbopump]] turbines to pump fuel before being exhausted (similar to the [[Physics:Gas-generator cycle|gas-generator cycle]]). Since fuel is exhausted, the tap-off cycle is considered an open-cycle engine. The cycle is comparable to a gas-generator cycle engine with turbines driven by main combustion chamber exhaust rather than a separate gas generator or preburner.<ref name="gsLRPE">{{cite book|last1=Sutton|first1=George|title=History of Liquid Propellant Rocket Engines|date=November 2005|publisher=American Institute of Aeronautics & Astronautics|isbn=978-1563476495}}<!--|accessdate=3 February 2016--></ref>

The [[Engineering:Rocketdyne J-2#J-2S|J-2S]] rocket engine, a cancelled engine developed by NASA, used the combustion tap-off cycle and was first successfully tested in 1969.<ref name="j-2sTest">{{cite web|url=http://www.dtic.mil/dtic/tr/fulltext/u2/874400.pdf|archive-url=https://web.archive.org/web/20170116133040/http://www.dtic.mil/dtic/tr/fulltext/u2/874400.pdf|url-status=dead|archive-date=January 16, 2017|title=Altitude Developmental Testing of the J-2S Rocket Engine|website=Defense Technical Information Center|publisher=Defense Technical Information Center}}</ref>

By 2013, [[Company:Blue Origin|Blue Origin]], with their [[Astronomy:New Shepard|New Shepard]] launch vehicle, had successfully [[Engineering:Flight test|flight-tested]] the BE-3 engine using a tap-off cycle. According to Blue Origin, the cycle is particularly suited to human spaceflight due to its simplicity, with only one combustion chamber and a less stressful engine shutdown process. However, engine startup is more complicated, and due to the hot gas fed from the main combustion chamber into the turbopumps, the turbine must be built to withstand higher-than-normal temperatures.<ref name="awst20131209">{{cite web|last1=Norris|first1=Guy|title=Blue Origin Tests New Engine|url=http://aviationweek.com/awin/blue-origin-tests-new-engine|website=Aviation Week & Space Technology|publisher=Penton|accessdate=3 February 2016|date=9 December 2013}}</ref>  In contrast, the upper-stage variant of the BE-3, the BE-3U, uses an [[Engineering:Expander cycle|expander cycle]] to power the turbopump, and will be used on the upper stage of the [[Astronomy:New Glenn|New Glenn]] launch vehicle.<ref name=blue20180810>[https://twitter.com/blueorigin/status/1028017095643209728 BE-3 test update], Blue Origin, 10 August 2018, accessed  15 August 2018].</ref>

The Reaver 1 engine in [[Engineering:Firefly Alpha|Firefly Alpha]] uses a tap-off cycle.<ref>{{cite web|url=https://youtube.com/watch?v=ac-V8mO0lWo&t=996|title=Tour Firefly Aerospace's Factory and Test Site With Their CEO, Tom Markusic|access-date=12 October 2021}}</ref> It first flew in September 2021<ref>{{cite web |last=Neal |first=Mihir |url=https://www.nasaspaceflight.com/2021/09/firefly-maiden-flight-alpha/ |title=Firefly Aerospace's maiden flight of Alpha launch vehicle ends in failure |work=NASASpaceFlight |date=2 September 2021 |access-date=12 October 2021}}</ref> then made it to orbit on its second attempt in October 2022.<ref>{{cite web |last=Trevor |first=Sesnic |url=https://www.nasaspaceflight.com/2022/10/firefly-to-the-black/ |title= Firefly succeeds on second Alpha flight |work=NASASpaceFlight |date=1 October 2022}}</ref> 

==See also==

* Expander cycle
* Pressure-fed engine
* [[Engineering:Rocket engine|Rocket engine]]
* Staged combustion cycle
* [[Physics:Gas-generator cycle|Gas-generator cycle]]

==References==
{{reflist}}

{{spacecraft propulsion}}
{{Thermodynamic cycles}}

[[Category:Combustion]]
[[Category:Rocket engines]]
[[Category:Spacecraft propulsion]]
[[Category:Thermodynamic cycles]]

{{Sourceattribution|Combustion tap-off cycle}}