RD-250

The RD-250 (, GRAU index: 8D518) is the base version of a dual-nozzle family of liquid-fuel rocket engines, burning a hypergolic mixture of unsymmetrical dimethylhydrazine (UDMH) fuel with dinitrogen tetroxide () oxidizer in a gas-generator open cycle. The RD-250 was developed by OKB-456 for Yangel's PA Yuzhmash ICBM, the R-36 (8K67). Its variations were also used on the Tsyklon-2 and Tsyklon-3 launch vehicles. It was supposed to be used on the Tsyklon-4, but since the cancellation of the project it should be considered as out of production. Three engines from this family bundled together make the corresponding RD-251 propulsion module.

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 Tsyklon-3. 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 Tsyklon-2 second stages. RD-262 (GRAU index: 11D26): Improved version of the RD-252. Used on the Tsyklon-3 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 Tsyklon-2 first stage. RD-261 (GRAU index: 11D69): A module comprising three RD-250PM. Propulsion module of the Tsyklon-3 first stage.

Comparison

+ RD-250 Family of Engines Engine RD-250 RD-250P RD-250M RD-250PM RD-252 RD-262 GRAU 8D518 8D518P 8D518M 8D518PM 8D724 11D26Module RD-251 RD-251P RD-251M RD-261 N/A N/A Module GRAU 8D723 8D723P 8D723M 11D69 N/A N/A Development 1962-1966 1967-1968 1966-1968 1968-1970 1962-1966 1968-1970 Propellant N2O4/UDMH Combustion chamber pressure Thrust, vacuum Thrust, sea level N/A N/A I, vacuum I, sea level N/A N/A Length N/A Diameter N/A Dry weight N/A Use R-36 (8K67) 1st stage R-36P (8K67P) 1st stage R-36-O (8K67-O)and Tsyklon-2 1st stage Tsyklon-3 1st stage R-36, R36P, R-36-O,Tsyklon-2 2nd stage Tsyklon-3 2nd stage

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 (ICBM), Hwasong-14. 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, 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.

RD-250

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