Editing Expander cycle (section)

== Expander bleed cycle ==
[[Image:Expander bleed cycle (coolant tap-off).svg|thumb|right|250px|Expander bleed cycle. Expander open cycle (Also named coolant tap-off).]]
This operational cycle is a modification of the traditional expander cycle. In the bleed (or open) cycle, instead of routing all of the heated propellant through the turbine and sending it back to be combusted, only a small portion of the heated propellant is used to drive the turbine and is then bled off, being vented overboard without going through the combustion chamber. The other portion is injected into the combustion chamber. Bleeding off the turbine exhaust allows for a higher turbopump efficiency by decreasing [[backpressure]] and maximizing the pressure drop through the turbine. Compared with a standard expander cycle, this allows higher engine thrust at the cost of efficiency by dumping the turbine exhaust.<ref name=aiaa-paper2003-4597 /><ref name=mhitr-vol48n4p36t43 />

The [[LE-5A|Mitsubishi LE-5A]] was the world's first expander bleed cycle engine to be put into operational service.<ref name="tsj1993">{{cite web|url=https://www.jstage.jst.go.jp/article/tsj1973/21/3/21_3_138/_pdf|archive-url=https://web.archive.org/web/20210528150902/https://www.jstage.jst.go.jp/article/tsj1973/21/3/21_3_138/_pdf|script-title=ja:わが国の液体ロケットエンジンの現状と今後の展望|page=10|language=ja|author=Akira Konno|publisher=Turbomachinery Society of Japan/[[J-STAGE]]|date=October 1993|archive-date=May 28, 2021|access-date=January 24, 2022}}</ref> The [[LE-9|Mitsubishi LE-9]] is the world's first first stage expander bleed cycle engine.<ref name="nikkei20210202">{{cite web|url=https://xtech.nikkei.com/atcl/nxt/column/18/01540/00008/|archive-url=https://web.archive.org/web/20220124045358/https://xtech.nikkei.com/atcl/nxt/column/18/01540/00008/ |script-title=ja:H3ロケットの主エンジン「LE-9」熱効率向上で世界初に挑戦|language=ja|author=Shinya Matsuura|publisher=Nikkei Business|date=February 2, 2021|archive-date=January 24, 2022|access-date=January 23, 2022}}</ref>

[[Blue Origin]] chose the expander bleed cycle for the [[BE-3#BE-3U |BE-3U]] engine used on the upper stage of its [[New Glenn]] launch vehicle.<ref>{{cite web |url=https://www.blueorigin.com/news/new-glenn-completes-second-stage-hotfire |title=New Glenn Completes Second Stage Hotfire |publisher=Blue Origin |date=September 23, 2024}}</ref>