| RD-250 (РД-250) | |
| Country Of Origin: | USSR |
| First Date: | December 16th, 1965 |
| Designer: | OKB-456 |
| Manufacturer: | PA Yuzhmash |
| Associated: | R-36, Tsyklon-2 and Tsyklon-3 |
| Status: | Out of Production |
| Type: | liquid |
| Oxidiser: | N2O4 |
| Fuel: | UDMH |
| Mixture Ratio: | 2.6 |
| Cycle: | Gas-generator |
| Combustion Chamber: | 2 |
| Thrust(Vac): | 882kN |
| Thrust(Sl): | 788kN |
| Chamber Pressure: | 8.33MPa |
| Specific Impulse Vacuum: | 301isp |
| Specific Impulse Sea Level: | 270isp |
| Dry Weight: | 788kg (1,737lb) |
| Used In: | R-36, Tsyklon-2 and Tsyklon-3 first stage |
The RD-250 (GRAU Index 8D518) is the base version of a dual-nozzle family of liquid rocket engines, burning N2O4 and UDMH in the gas-generator open cycle.[1] 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.
The engine has seen different versions made:
Some of these engines were bundled into modules of multiple engines. The relevant modules and auxiliary engines are:
| Engine | RD-250 | RD-250P | RD-250M | RD-250PM | RD-252 | RD-262 |
|---|---|---|---|---|---|---|
| GRAU | 8D518 | 8D518P | 8D518M | 8D518PM | 8D724 | 11D26 |
| Module | 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 | 8.336MPa | 8.924MPa | ||||
| Thrust, vacuum | 881.6kN | 881.6kN | 881.6kN | 881.7kN | 940.8kN | 941.4kN |
| Thrust, sea level | 788.5kN | 788.5kN | 788.5kN | 788.7kN | N/A | N/A |
| I, vacuum | 301isp | 301isp | 301isp | 301.4isp | 317.6isp | 318isp |
| I, sea level | 270isp | 270isp | 270isp | 269.6isp | N/A | N/A |
| Length | 2600mm | 2600mm | 2600mm | N/A | 2190mm | 2190mm |
| Diameter | 1000mm | 1000mm | 1000mm | N/A | 2590mm | 2590mm |
| Dry weight | 728kg (1,605lb) | 728kg (1,605lb) | 728kg (1,605lb) | N/A | 715kg (1,576lb) | 715kg (1,576lb) |
| 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 |
Several experts think that technology from the RD-250 engine could have been transferred to North Korea from Ukraine. 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.[2] Conversely, there is analysis[3] (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.