RD-191

RD-191

Country of origin	Russia
Date	2001
Designer	NPO Energomash
Manufacturer	NPO Energomash /Proton-PM(in transition)
Application	Main engine
Predecessor	RD-170
Status	In use
Liquid-fuel engine
Propellant	LOX/RP-1
Mixture ratio	2.6:1
Cycle	Oxidizer-richstaged combustion
Configuration
Nozzle ratio	37:1
Performance
Thrust, vacuum	2,090 kN (470,000 lbf) at 100% throttle
Thrust, sea-level	1,920 kN (430,000 lbf) at 100% throttle
Throttle range	27–105%
Thrust-to-weight ratio	89:1
Chamberpressure	25.8 MPa (3,740 psi)
Specific impulse,vacuum	337 s (3.30 km/s)
Specific impulse,sea-level	310.7 s (3.047 km/s)
Burn time	325 seconds (Angara A5 core stage)
Gimbal range	8°
Dimensions
Length	4 m (13 ft)
Diameter	1.45 m (4 ft 9 in)
Dry mass	2,290 kg (5,050 lb)
References
References

TheRD-191(Russian:Ракетный Двигатель-191 (РД-191),lit. 'Rocket Engine 191') is a high-performance single-combustion chamberrocket engine,developed in Russia and sold byRoscosmos.It is derived from theRD-180dual-combustion chamber engine, which itself was derived in turn from the four-chamberRD-170originally used in theEnergialauncher.

The RD-191 is fueled by akerosene/LOXmixture and uses an oxygen-richstaged 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 isself-ignitingon 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. ACardan suspensionprovides for yaw and pitch controls bygimballed thrustdeflection up to 8 degrees.

A modern design, the engine incorporates sensors monitoring burn conditions. The measurements are used fortelemetryand an emergency protection system.

The engine's powerhead fulfills two additional functions, heatingheliumgas for pressurization ofpropellant tanksand generating hydraulic power forhydraulic actuatorsto 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.The primary launch vehicle utilizing this engine is theAngaracarrier rocket family, first flown in 2014.

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.In July 2014, the engine made its maiden flight, propelling theAngara 1.2pptest vehicle on a suborbital flight.In December 2014, the engine flew again, powering theAngara A5heavy carrier rocket.In the same month,Orbital Sciencesannounced it would purchase RD-181 engines, a variant of the RD-191, for use on theAntaresrocket.

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 KoreanNaro-1rocket.

RD-181

The RD-181 is based on the RD-191 and is adapted for integration on theAntaresrocket. 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 theNPO EnergomashRD-181 on the version 2 Antares launch vehicle and had contracted directly with NPO Energomash for up to 20 RD-181 engines.Two engines are used on thefirst stageof each Antares, which is currently used to carry cargo to theInternational Space Stationunder contract to NASA.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.

The two RD-181s have 440 kilonewtons (100,000 lbf) more thrust than the pairedAJ-26engines 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 20,000 kg (44,000 lb) 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 theAntares 230+upgrades, debuted with theCRS-2Cygnus NG-12mission, heat exchangers were removed from the RD-181 engine.

RD-193

Main article: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-launcherSoyuz-2.1vwhen the inventory of surplusNK-33engines is exhausted.

See also

• Comparison of orbital rocket engines

External links

• "RD-191".Energomash. Archived fromthe originalon 5 July 2014.