The RD-250 (,

GRAU index The Main Missile and Artillery Directorate of the Ministry of Defense of the Russian Federation (), commonly referred to by its transliterated acronym GRAU (), is a department of the Russian Ministry of Defense. It is subordinate to the Chief of ...

: 8D518) is the base version of a dual-nozzle family of liquid-fuel rocket engines, burning a

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...

mixture of

unsymmetrical dimethylhydrazine Unsymmetrical dimethylhydrazine (abbreviated as UDMH; also known as 1,1-dimethylhydrazine, heptyl or Geptil) is a chemical compound with the formula H2NN(CH3)2 that is primarily used as a rocket propellant. At room temperature, UDMH is a colorle ...

(UDMH) fuel with

dinitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

() oxidizer in a gas-generator open cycle. The RD-250 was developed by OKB-456 for Yangel's PA Yuzhmash

ICBM An intercontinental ballistic missile (ICBM) is a ballistic missile with a range (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...

, the R-36 (8K67). Its variations were also used on the

Tsyklon-2 The Tsyklon-2 (), also known as Tsiklon-2 and Tsyklon-M (known as SL-11 by the United States United States Department of Defense, DoD), GRAU index 11K69, was a Soviet Union, Soviet, later Ukraine, Ukrainian, orbital carrier rocket used from the ...

and

Tsyklon-3 The Tsyklon-3, also known as Tsiklon-3 and Cyclone-3 (known as SL-14 by the United States DoD), GRAU index 11K68, was a Soviet, and subsequently Ukrainian orbital carrier rocket. Overview Tsyklon-3 launching a Meteor-3 satellite at left A ...

launch vehicles. It was supposed to be used on the

Tsyklon-4 The Tsyklon-4, also known as Tsiklon-4 and Cyclone-4, was a Ukrainian carrier rocket which was being developed for commercial satellite launches. Derived from the Tsyklon-3, it had a new third stage, a larger payload fairing, and a modernised fl ...

, but since the cancellation of the project it should be considered as out of production.

Versions

The engine has seen different versions made: * RD-250 (GRAU index: 8D518): Base engine of the family. Used on the R-36. A bundle of three RD-250 form the RD-251 cluster. * RD-250P (GRAU index: 8D518P): Improved version of the RD-250. Used on the R-36P. A bundle of three RD-250P form the RD-251P cluster. * RD-250M (GRAU index: 8D518M): Improved version of the RD-250P. Used on the R-36-O. A bundle of three RD-250M form the RD-251M cluster. * RD-250PM (GRAU index: 8D518PM): Improved version of the RD-250M. Used on the

. A bundle of three RD-250PM form the RD-261 cluster. * RD-252 (GRAU index: 8D724): Vacuum optimized version of the RD-250. Used on the R-36 and

second stages. * RD-262 (GRAU index: 11D26): Improved version of the RD-252. Used on the

second stages.

Modules

Some of these engines were bundled into modules of multiple engines. The relevant modules and auxiliary engines are: * RD-251 (GRAU index: 8D723): A module comprising three RD-250. Propulsion module of the R-36 (8K67) first stage. * RD-251P (GRAU index: 8D723P): A module comprising three RD-250P. Propulsion module of the R-36P (8K68) first stage. * RD-251M (GRAU index: 8D723M): A module comprising three RD-250M. Propulsion module of the R-36-O (8K69) and

first stage. * RD-261 (GRAU index: 11D69): A module comprising three RD-250PM. Propulsion module of the

first stage.

Comparison

Possible technological transfer to North Korea

Several experts think that technology from the RD-250 engine could have been transferred to North Korea from Russia. This transfer would explain the rapid progress of North Korea in the development of two new missiles: the intermediate-range Hwasong-12 and the

intercontinental ballistic missile An intercontinental ballistic missile (ICBM) is a ballistic missile with a range (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...

(ICBM),

Hwasong-14 The Hwasong-14 () is a mobile intercontinental ballistic missile developed by North Korea. It had its maiden flight on 4 July 2017, which coincided with the United States' Independence Day. North Korea is the only known operator of this missil ...

. Due to complexity of the technology involved in this type of engine, modifications or reverse engineering seem difficult to achieve. Thus it is believable that complete hardware could have been bought on black market and directly shipped to North Korea, by Russia or Ukraine. Conversely, there is analysisNorth Korean Missile Engines: Not from Ukraine
Mariana Budjeryn & Andrew Zhalko-Tytarenko,

Atlantic Council The Atlantic Council is an American think tank in the field of international affairs, favoring Atlanticism, founded in 1961. It manages sixteen regional centers and functional programs related to international security and global economic prosp ...

, 2017-09-12 (made by two Ukrainian authors) suggesting an alternative mechanism for North Korea to receive R-36 missile engines, or an entire missile, from USSR or Russia.

References

External links