View source for RD-191

{{short description|Russian rocket engine}}
{{Use dmy dates|date=August 2022}}
{{Infobox rocket engine
| name                       = RD-191
| image                      = RD-191 MAKS2013.JPG
| caption                    = 
| country_of_origin          = Russia
| designer                   = [[NPO Energomash]]
| manufacturer               = NPO Energomash / [[Proton-PM]] (in transition)
| date                       = 2001
| purpose                    = Main engine
| predecessor                = [[RD-170]]
| status                     = In use
| cycle                      = Oxidizer-rich [[Staged combustion cycle (rocket)|staged combustion]]
| type                       = liquid
| fuel                       = [[RP-1]]
| oxidiser                   = [[LOX]]
| mixture_ratio              = 2.6:1
| capacity                   = 
| combustion_chamber         = 
| nozzle_ratio               = 37:1
| thrust(SL)                 = {{cvt|1920|kN}} at 100% throttle
| thrust(Vac)                = {{cvt|2090|kN}} at 100% throttle
| throttle_range             = 27–105%
| specific_impulse_vacuum    = {{cvt|337|isp}}
| specific_impulse_sea_level = {{cvt|310.7|isp}}
| chamber_pressure           = {{cvt|25.8|MPa}}
| thrust_to_weight           = 89:1
| burn_time                  = 325 seconds (Angara A5 core stage)
| gimbal                     = 8°
| diameter                   = {{cvt|1.45|m}}
| length                     = {{cvt|4|m}}
| dry_weight                 = {{cvt|2290|kg}}
| references                 = <ref>{{Cite web |url=http://www.astronautix.com/engines/rd191.htm |title=RD-191 |access-date=26 December 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111111201245/http://www.astronautix.com/engines/rd191.htm |archive-date=11 November 2011 }} RD-191 Rocket Engine</ref><ref>{{Cite web |title=Angara 1.2 |url=http://www.spaceflight101.com/angara-12.html |website=Spaceflight101 |access-date=30 June 2015}}</ref>
}}

The '''RD-191''' ({{Langx|ru|Ракетный Двигатель-191|Raketnyy Dvigatel-191|Rocket Engine 191}}) is a high-performance single-[[combustion chamber]] [[rocket engine]], developed in Russia and sold by [[Roscosmos]].<ref name="wired1">{{cite news |last1=SKIBBA |first1=RAMIN |title=Turmoil Over Ukraine Could Debilitate Russia's Space Program |url=https://www.wired.com/story/turmoil-over-ukraine-could-debilitate-russias-space-program/ |agency=Wired |publisher=Condé Nast |date=4 March 2022}}</ref> It is derived from the [[RD-180]] dual-combustion chamber engine, which itself was derived in turn from the four-chamber [[RD-170 (rocket engine)|RD-170]] originally used in the [[Energia (rocket)|Energia]] launcher.

The RD-191 is fueled by a [[RP-1|kerosene]] / [[LOX]] mixture and uses an oxygen-rich [[Staged combustion cycle (rocket)|staged combustion cycle]]. In the future the engine is expected to become a workhorse in the Russian space sector, as older launch vehicles are phased out of production and service.

==Design==
Burn ignition is provided chemically, by feeding a starter fluid into the combustion chamber and gas generator, which is [[pyrophoricity|self-igniting]] on contact with liquid oxygen. The engine is capable of throttling down to 30% of nominal thrust; the design also allows for a short-duration enhanced thrust (up to 105% of nominal level) in emergency situations. A [[Gimbal|Cardan suspension]] provides for yaw and pitch controls by [[gimballed thrust]] deflection up to 8&nbsp;degrees.

A modern design, the engine incorporates sensors monitoring burn conditions. The measurements are used for [[telemetry]] and an emergency protection system.

The engine's powerhead fulfills two additional functions, heating [[helium]] gas for pressurization of [[propellant tank]]s and generating hydraulic power for [[hydraulic actuators]] to deflect the nozzle and aerodynamic rudders.

==Development==
On 5 September 2008, the creator of the engine, [[NPO Energomash]], stated that the engine had completed the full cycle of development and burn tests and is ready for manufacturing and delivery.<ref>{{Cite web |url=http://www.vz.ru/society/2008/9/5/203826.print.html |title=A new engine is ready for Angara (in Russian) |date=5 September 2008}}</ref> The primary launch vehicle utilizing this engine is the [[Angara (rocket) |Angara]] carrier rocket family, first flown in 2014.<ref>{{Cite web |url=http://www.khrunichev.ru/khrunichev_eng/live/full_news.asp?id=14884 |title=Successful Tests of Angara Stage 1 Engine |publisher=Khrunichev |date=12 December 2007 |url-status=dead |archive-url=https://web.archive.org/web/20071230141206/http://www.khrunichev.ru/khrunichev_eng/live/full_news.asp?id=14884 |archive-date=30 December 2007 }}</ref><ref>{{Cite web |last=Clark |first=Stephen |title=Russian military satellite launched on orbital debut of Angara 1.2 rocket – Spaceflight Now |url=https://spaceflightnow.com/2022/05/02/russian-military-satellite-launched-on-orbital-debut-of-angara-1-2-rocket/ |access-date=22 May 2022 |language=en-US}}</ref> 

By 2010, the engine had passed all development phases, and its nine prototypes had accumulated over 23,000 seconds in 105 firing tests, with one of them reaching the maximum running time of 3,635 seconds in 12 tests.<ref>{{Cite journal |title=Russia's liquid rocket enginges are unrivalled |last1=Chvanov |first1=Vladimir |journal=Military Parade |issue=2 |year=2010 |pages=40–41}}</ref> In July 2014, the engine made its maiden flight, propelling the [[Angara-1.2pp|Angara 1.2pp]] test vehicle on a suborbital flight.<ref>{{Cite web |last=Zak |first=Anatoly |date=29 September 2014 |title=Angara goes on its maiden voyage |url=http://www.russianspaceweb.com/angara1pp.html |access-date=22 May 2022 |website=www.russianspaceweb.com}}</ref> In December 2014, the engine flew again, powering the [[Angara (rocket family)#Angara A5|Angara A5]] heavy carrier rocket.<ref>{{Cite web |last=Graham |first=William |date=23 December 2014 |title=Russia's Angara 5 debuts with maiden launch |url=https://www.nasaspaceflight.com/2014/12/russias-angara-5-maiden-voyage/ |access-date=22 May 2022 |website=NASASpaceFlight.com |language=en-US}}</ref> In the same month, [[Orbital Sciences Corporation|Orbital Sciences]] announced it would purchase RD-181 engines, a variant of the RD-191, for use on the [[Antares (rocket)|Antares]] rocket.<ref>{{Cite web |last=Smith |first=Marcia |date=17 December 2014 |title=Orbital Sciences to Use Russian RD-181 for Antares |url=https://spacepolicyonline.com/news/orbital-sciences-to-use-russian-rd-181-for-antares/ |access-date=22 May 2022 |website=SpacePolicyOnline |language=en-US}}</ref>  

==Variants==

===RD-151===
A version of the RD-191 with thrust reduced to 170 tonnes, called RD-151, was fire-tested on 30 July 2009. The first flight test of this engine was conducted on 25 August 2009 as part of the first launch of South Korean [[Naro-1]] rocket.<ref name="ENERGOMASH_NARO_LAUNCH_1">{{Cite web |url=http://www.npoenergomash.ru/eng/about/news/news_94.html |title=First launch of KSLV-1 is conducted |date=25 August 2009}}</ref><ref>{{Cite web |url=http://english.yonhapnews.co.kr/techscience/2009/08/11/6/0601000000AEN20090811006200320F.HTML |title=S. Korea to launch first space rocket on Aug. 19 |date=25 August 2009}}</ref>

===RD-181===

The RD-181 is based on the RD-191 and is adapted for integration on the [[Antares (rocket)|Antares]] rocket. While the RD-193 was designed as a close replacement for the NK-33, on 17 December 2014, Orbital Sciences announced that it would use the [[NPO Energomash]] RD-181 on the version 2 Antares launch vehicle and had contracted directly with NPO Energomash for up to 20 RD-181 engines.<ref>{{Cite web |title=ГОДОВОЙ ОТЧЕТ ОАО «НПО «Энергомаш» за 2014 год. page 20 |url=http://www.npoenergomash.ru/netcat_files/File/byh_otchet/god_otchet_2014.doc |date=2015 |publisher=«НПО «Энергомаш» |archive-url=https://web.archive.org/web/20161031101234/http://www.npoenergomash.ru/netcat_files/File/byh_otchet/god_otchet_2014.doc |archive-date=31 October 2016 |url-status=dead }}</ref> Two engines are used on the [[first stage (rocketry)|first stage]] of each 200-series Antares, which is currently used to carry cargo to the [[International Space Station]] under contract to NASA.<ref name=aw20141216>{{Cite news |last1=Morring |first1=Frank Jr. |title=Antares Upgrade Will Use RD-181s In Direct Buy From Energomash |url=http://aviationweek.com/space/antares-upgrade-will-use-rd-181s-direct-buy-energomash |access-date=28 December 2014 |work=Aviation Week |date=16 December 2014 }}</ref> While Russian press had stated that the contract was valued at US$ 1 billion with options, Orbital stated on 26 January 2015 that even when exercising all the options the contract was less than that amount, and that the initial contractual commitment was significantly less than that. On 19 February 2015, Orbital ATK said that its revamped Antares rocket featuring a new main engine would make its first launch in March 2016. On 29 May 2015, Orbital stated that the new engines had successfully conducted seven certification firings and all went as expected. It also stated that the first two flight models were doing final tests and would be delivered to Orbital in early July.<ref name=rsw-rd181>{{Cite web |url=http://www.russianspaceweb.com/rd181.html |title=RD-181 |first1=Anatoly |last1=Zak |publisher=russianspaceweb.com |access-date=4 June 2015}}</ref><ref name=sn-20141217>{{Cite web |url=http://spacenews.com/orbital-sciences-orders-rd-181-engines-for-antares-rocket/ |title=Orbital Sciences Orders RD-181 Engines for Antares Rocket |first1=Peter B. |last1=Selding |publisher=SpaceNews |access-date=4 June 2015}}</ref><ref name=sn-20150126>{{Cite web |url=http://spacenews.com/orbital-sciences-expects-rd-181-delivery/ |title=Orbital Sciences: Russian Press Overstate RD-181 Contract Value |first1=Peter B. |last1=Selding |publisher=SpaceNews |access-date=4 June 2015}}</ref><ref name=sn-20150219>{{Cite web |url=http://spacenews.com/re-engined-antares-to-carry-space-station-cargo-in-2016-debut/ |title=Re-engined Antares To Carry Space Station Cargo in 2016 Debut |first1=Peter B. |last1=Selding |publisher=SpaceNews |access-date=4 June 2015}}</ref><ref name=sn-20150529>{{Cite web |url=http://spacenews.com/orbital-atk-sees-commercial-satellites-as-top-growth-area/ |title=Orbital ATK Sees Commercial Satellites as Top Growth Area |first1=Peter B. |last1=Selding |publisher=SpaceNews |access-date=4 June 2015}}</ref><ref>{{Cite journal |journal=[[:ru:Новости космонавтики |News of Cosmonautics]] |volume=8 |year=2012 |issue=22 |title="Энергомаш" в новом тысячелетии |author=Афанасьев И. |url=http://www.npoenergomash.ru/netcat_files/File/Solncev.pdf}}</ref>

The two RD-181s have {{Convert|100000|lbf|kN|order=flip}} more thrust than the paired [[AJ-26]] engines used on the first-generation Antares. [[Northrop Grumman Innovation Systems]] (formerly Orbital) modified the core stage to accommodate the increased performance, and then to finish up its CRS-1 cargo contract commitment to NASA for delivering a total of {{Convert|20000|kg|abbr=on}} of cargo in only four additional flights, rather than the five more that would have been required with the AJ-26/Antares combination. The AJ-26 engines were just rebranded NK-33 rocket engines used for the ill-fated Soviet N1 and upgraded N1F rocket, which was planned to be the rocket to take cosmonauts to the surface of the Moon.

For the [[Antares_(rocket)#Antares 200 series|Antares 230+]] upgrades, debuted with the [[Commercial_Resupply_Services#Commercial Resupply Services phase 2 - Awards and flights flown|CRS-2]] [[Cygnus NG-12]] mission, heat exchangers were removed from the RD-181 engine.<ref>{{Cite web |url=https://spaceflightnow.com/2019/11/02/space-station-resupply-mission-successfully-launches-from-virginia/ |title=Space station resupply mission successfully launches from Virginia |first1=Stephen |last1=Clark |publisher=Spaceflight Now |access-date=2 November 2019 }}</ref><ref>{{Cite web |url=https://www.northropgrumman.com/Capabilities/Antares/Documents/Antares_UsersGuide.pdf |title=Antares Users Guide, Release 3.0 |publisher=Northrop Grumman |date=August 2018 |access-date=3 November 2019 |archive-date=6 September 2018 |archive-url=https://web.archive.org/web/20180906052537/https://www.northropgrumman.com/Capabilities/Antares/Documents/Antares_UsersGuide.pdf |url-status=dead }}</ref> 

In 2022, Russia suspended engine deliveries to the United States as a result of the [[Russian invasion of Ukraine]], and Northrop Grumman cancelled the remainder of the contract in favor of moving away from the RD-181.<ref>{{Cite web |title=Russia Suspends RD-181 Rocket Engine Deliveries To U.S. {{!}} Aviation Week Network |url=https://aviationweek.com/space/russia-suspends-rd-181-rocket-engine-deliveries-us |access-date=2025-02-07 |website=aviationweek.com}}</ref><ref>{{Cite web |last=Kuhr |first=Jack |date=2023-08-03 |title=Northrop Grumman Says Goodbye to Russian Engines |url=https://payloadspace.com/northrop-grumman-says-goodbye-to-russian-engines/ |access-date=2025-02-07 |website=Payload |language=en-US}}</ref> Instead, [[Antares 330]] will use an engine designed by [[Firefly Aerospace]], the [[Miranda (engine)|Miranda]].<ref>{{Cite web |last=Foust |first=Jeff |date=2023-11-29 |title=Firefly conducts first Miranda engine test |url=https://spacenews.com/firefly-conducts-first-miranda-engine-test/#:~:text=Seven%20Miranda%20engines%20will%20power%20the%20first%20stage,stage%20previously%20used%20on%20Antares%20with%20Russian%20engines. |access-date=2025-02-07 |website=SpaceNews |language=en-US}}</ref> 

===RD-193===
{{main|RD-193}}

In April 2013, it was announced that a further derivation, the RD-193, had completed testing. This version is lighter and shorter, designed for use on the light-launcher [[Soyuz-2.1v]] when the inventory of surplus [[NK-33]] engines is exhausted.<ref>{{Cite web |title=New engine for light rocket "Soyuz" prepare for mass production at the end of the year |url=http://www.novosti-kosmonavtiki.ru/news/7229/ |publisher=Новости космонавтики |access-date=8 April 2013 |language=ru}}</ref>

===RD-191M===
During the 2010s, NPO Energomash was working on the RD-191M engine, which was intended for the [[Angara A5|Angara-A5M]] and [[Angara A5|Angara-A5V]] rockets. The engine was test-fired in 2016, reaching 110 percent above the thrust of the original variant, the company's officials said. In May 2024, Roskosmos said that a full cycle of autonomous tests of components for the RD-191M engine had been completed at NPO Energomash by the end of 2023 and on July 8, 2024, NPO Energomash announced that it had completed tune-up tests of RD-191M. According to the company, the first RD-191M engine for tune-up tests had been manufactured at the end of 2023.<ref>{{cite web |url=https://www.russianspaceweb.com/rd191.html |title= RD-191 engine |work=RussianSpaceWeb |access-date=16 September 2024}}</ref>

== See also ==
* [[Comparison of orbital rocket engines]]

== References ==
{{Reflist}}

==External links==
{{commonscat|RD-191}}
* {{Cite web |title=RD-191 |publisher=Energomash  |url=http://www.npoenergomash.ru/eng/engines/rd191/ |archive-url = https://web.archive.org/web/20140705154556/http://www.npoenergomash.ru/eng/engines/rd191/ |archive-date = 5 July 2014}}

{{Rocket engines}}
{{RD-170 rocket engine family}}
{{Russian and Soviet military designation sequences}}

[[Category:Rocket engines of Russia]]
[[Category:Rocket engines using kerosene propellant]]
[[Category:Rocket engines using the staged combustion cycle]]
[[Category:Energomash rocket engines]]