The RD-191 () is a high-performance single-

combustion chamber A combustion chamber is part of an internal combustion engine in which the air–fuel ratio, fuel/air mix is burned. For steam engines, the term has also been used for an extension of the Firebox (steam engine), firebox which is used to allow a mo ...

rocket engine A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...

, developed in Russia and sold by

Roscosmos The State Corporation for Space Activities "Roscosmos", commonly known simply as Roscosmos (), is a State corporation (Russia), state corporation of the Russian Federation responsible for space science, space flights, List of space agencies, c ...

. It is derived from the

RD-180 The RD-180 () is a rocket engine that was designed and built in Russia. It features a dual combustion chamber, dual-nozzle design and is fueled by a RP-1/ LOX mixture. The RD-180 is derived from the RD-170 line of rocket engines, which were use ...

dual-combustion chamber engine, which itself was derived in turn from the four-chamber

RD-170 The RD-170 () is the world's most powerful and heaviest liquid-fuel rocket engine. It was designed and produced in the Soviet Union by NPO Energomash for use with the Energia launch vehicle. The engine burns kerosene fuel and LOX oxidizer in fo ...

originally used in the Energia launcher. The RD-191 is fueled by a

kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...

LOX Lox is a fillet of brined salmon, which may be smoked. Lox is frequently served on a bagel with cream cheese, and often garnished with tomato, onion, cucumber, and capers. Etymology The American English word ''lox'' is a borrowing of Yiddi ...

mixture and uses an oxygen-rich

staged combustion cycle The staged combustion cycle (sometimes known as topping cycle, preburner cycle, or closed cycle) is a power cycle of a bipropellant rocket engine. In the staged combustion cycle, propellant flows through multiple combustion chambers, and is th ...

. 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 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 Cardan suspension provides for yaw and pitch controls by

gimballed thrust Gimbaled thrust is the system of thrust vectoring used in most rockets, including the Space Shuttle program, Space Shuttle, the Saturn V lunar rockets, and the Falcon 9. Operation In a gimbaled thrust system, the engine or just the exhaust nozz ...

deflection up to 8 degrees. A modern design, the engine incorporates sensors monitoring burn conditions. The measurements are used for

telemetry Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', 'far off', an ...

and an emergency protection system. The engine's powerhead fulfills two additional functions, heating

helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...

gas for pressurization of

propellant tank A propellant tank is a container which is part of a vehicle, where propellant is stored prior to use. Propellant tanks vary in construction, and may be a fuel tank in the case of many aircraft. In rocket vehicles, propellant tanks are fairly sophi ...

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 NPO Energomash "V. P. Glushko" is a major Russian rocket engine manufacturer. The company primarily develops and produces Liquid rocket engine, liquid propellant rocket engines. Energomash originates from the OKB, Soviet design bureau OKB-456, w ...

, 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 the

Angara The Angara (; ) or Angar ( мүрэн) is a major river in Siberia, which traces a course through Russia's Irkutsk Oblast and Krasnoyarsk Krai. It drains out of Lake Baikal and is the headwater tributary of the Yenisey. It is long, and has ...

carrier 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 the Angara 1.2pp test vehicle on a suborbital flight. In December 2014, the engine flew again, powering the

Angara A5 Angara A5 (Russian: Ангара-А5), is a Russian expendable heavy lift launch vehicle which consists of one URM-1 core and four URM-1 boosters, a URM-2 second stage, and an upper stage, either the Briz-M The Briz-K, Briz-KM and Briz-M ( m ...

heavy carrier rocket. In the same month,

Orbital Sciences Orbital Sciences Corporation (commonly referred to as Orbital) was an American company specializing in the design, manufacture, and launch of small- and medium- class space and launch vehicle systems for commercial, military and other governmen ...

announced it would purchase RD-181 engines, a variant of the RD-191, for use on the

Antares Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinisation of names, Latinised to Alpha Scorpii. Often referred to as "the heart of the scorpion", Antares is flanked by ...

rocket.

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 Naro-1 (), previously designated the Korea Space Launch Vehicle or KSLV (also KSLV-1), was South Korea's first carrier rocket, and the first South Korean launch vehicle to achieve low Earth orbit, Earth orbit. On January 30, 2013, the third Naro ...

rocket.

RD-181

The RD-181 is based on the RD-191 and is adapted for integration on the

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

RD-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 the

first stage First stage or First Stage may refer to: * First Stage Children's Theater, a professional American children's theater based in Milwaukee, Wisconsin * First stage (rocketry), the first stage of a multistage rocket * the first reading of a bill in t ...

of each 200-series Antares, which is currently used to carry cargo to the

International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...

under 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 more thrust than the paired

AJ-26 The NK-33 (GRAU index: 14D15) and its vacuum-optimized variant, the NK-43, were rocket engines developed in the late 1960s and early 1970s by the Kuznetsov Design Bureau for the Soviet space program's ill-fated N1 Moon rocket. The NK-33 is amon ...

engines used on the first-generation Antares.

Northrop Grumman Innovation Systems Orbital ATK Inc. was an American aerospace manufacturer and defense industry company. It was formed in February 9, 2015 from the merger of Orbital Sciences Corporation and parts of Alliant Techsystems (ATK). Orbital ATK designed, built, and deli ...

(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 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 230+ upgrades, debuted with the CRS-2

Cygnus NG-12 NG-12, previously known as OA-12, was the thirteenth flight of the Northrop Grumman robotic resupply spacecraft Cygnus (spacecraft), Cygnus and its twelfth Commercial Resupply Services flight to the International Space Station (ISS) for NASA. T ...

mission, heat exchangers were removed from the RD-181 engine. In 2022, Russia suspended engine deliveries to the United States as a result of the

Russian invasion of Ukraine On 24 February 2022, , starting the largest and deadliest war in Europe since World War II, in a major escalation of the Russo-Ukrainian War, conflict between the two countries which began in 2014. The fighting has caused hundreds of thou ...

, and Northrop Grumman cancelled the remainder of the contract in favor of moving away from the RD-181. Instead,

Antares 330 Antares (), known during early development as Taurus II, is an American expendable medium-lift launch vehicle developed and built by Orbital Sciences Corporation (later Orbital ATK and Northrop Grumman) with financial support from NASA ...

will use an engine designed by

Firefly Aerospace Firefly Aerospace, Inc. is an American private aerospace firm based in Cedar Park, Texas, that develops small- and medium-lift launch vehicles for commercial launches to orbit. The current company was formed when the assets of the former co ...

, the Miranda.

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 The NK-33 ( GRAU index: 14D15) and its vacuum-optimized variant, the NK-43, were rocket engines developed in the late 1960s and early 1970s by the Kuznetsov Design Bureau for the Soviet space program's ill-fated N1 Moon rocket. The NK-33 is am ...

engines is exhausted.

RD-191M

During the 2010s, NPO Energomash was working on the RD-191M engine, which was intended for the Angara-A5M and 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.

References

External links

* {{Russian and Soviet military designation sequences Rocket engines of Russia Rocket engines using kerosene propellant Rocket engines using the staged combustion cycle Energomash rocket engines