Editing RL10 (section)

{{short description|Liquid fuel cryogenic rocket engine, typically used on rocket upper stages}}
{{Use mdy dates|date=April 2017}}
{{update|reason=Info in the improvements section is dated|date=June 2020}}
{{Infobox rocket engine
| name                       = RL10
| image                      = RL-10 rocket engine (30432256313).jpg
| image_size                 = 250
| caption                    = An RL10A-4 engine in London's [[Science Museum, London|Science Museum]]
| country_of_origin          = [[United States]]
| first_date                 = {{Start date|1962}} (RL10A-1)
| manufacturer               = [[Aerojet Rocketdyne]]
| purpose                    = [[Upper stage]] engine
| associated                 = [[Atlas (rocket family)|Atlas]]{{, }}[[Delta III]]{{, }}[[Delta IV]]{{, }}[[Saturn I]]{{, }}[[Space Launch System|SLS]]{{, }}[[Titan IIIE]]{{, }}[[Titan IV]]{{, }}[[Vulcan Centaur]]<br>'''Canceled''': [[McDonnell Douglas DC-X|DC-X]]{{, }}[[OmegA]]{{, }}[[Centaur (rocket stage)#Shuttle-Centaur (Centaur G and G-Prime)|Space Shuttle]]
| status                     = In production
| type                       = liquid
| oxidiser                   = [[LOX]]
| fuel                       = {{chem2|LH2|link=LH2}}
| mixture_ratio              = 5.88:1
| cycle                      = [[Expander cycle]]
| nozzle_ratio               = 84:1 or 280:1
| thrust(Vac)                = {{convert|110.1|kN|abbr=on}}
| specific_impulse_vacuum    = {{cvt|465.5|isp}}
| length                     = {{convert|4.15|m|abbr=on}} w/ nozzle extended
| diameter                   = {{cvt|2.15|m}}
| dry_weight                 = {{cvt|301|kg}}
| used_in                    = [[Centaur (rocket stage)|Centaur]], [[Delta Cryogenic Second Stage|DCSS]], [[S-IV]]
| references                 = <ref name="EA10B2" />
| notes                      = Performance values and dimensions are for RL10B-2.
}}

The '''RL10''' is a [[liquid-fuel rocket|liquid-fuel]] [[cryogenic rocket engine]] built in the [[United States]] by [[Aerojet Rocketdyne]] that burns [[Cryogenic fuel|cryogenic]] [[liquid hydrogen]] and [[liquid oxygen]] propellants. Modern versions produce up to {{convert|110|kN|sigfig=5|abbr=on}} of [[thrust]] per engine in vacuum. RL10 versions were produced for the [[Centaur (rocket stage)|Centaur]] [[upper stage]] of the [[Atlas V]] and the [[Delta Cryogenic Second Stage|DCSS]] of the [[Delta IV]]. More versions are in development or in use for the [[Exploration Upper Stage]] of the [[Space Launch System]] and the Centaur V of the [[Vulcan (rocket)|Vulcan]] rocket.<ref name="Aerojet Rocketdyne 2" />

The [[expander cycle]] that the engine uses drives the [[turbopump]] with waste heat absorbed by the engine combustion chamber, throat, and nozzle. This, combined with the hydrogen fuel, leads to very high [[specific impulse]]s (''I''<sub>sp</sub>) in the range of {{convert|373|to(-)|470|isp|abbr=on}} in a vacuum. Mass ranges from {{convert|131|to(-)|317|kg|abbr=on}} depending on the version of the engine.<ref>{{Cite web |title=RL-10C |url=http://www.astronautix.com/r/rl-10c.html |url-status=dead |archive-url=https://web.archive.org/web/20161228011427/http://astronautix.com/r/rl-10c.html |archive-date=December 28, 2016 |access-date=2020-04-06 |website=www.astronautix.com}}</ref><ref>{{Cite web |title=RL-10A-1 |url=http://www.astronautix.com/r/rl-10a-1.html |url-status=dead |archive-url=https://web.archive.org/web/20161228075543/http://astronautix.com/r/rl-10a-1.html |archive-date=December 28, 2016 |access-date=2020-04-06 |website=www.astronautix.com}}</ref>