RD-856
| Country of origin | Soviet Union |
|---|---|
| First flight | December 16, 1965 |
| Last flight | January 30, 2009 |
| Designer | Yuzhnoye Design Bureau |
| Manufacturer | Yuzhmash |
| Application | Vernier |
| Associated L/V | R-36, Tsyklon-2 and Tsyklon-3 |
| Status | Out of production |
| Liquid-fuel engine | |
| Propellant | N2O4 / UDMH |
| Mixture ratio | 1.98 |
| Cycle | Gas Generator |
| Configuration | |
| Chamber | 4 |
| Performance | |
| Thrust (vac.) | 54.23 kN (12,190 lbf) |
| Chamber pressure | 7.160 MPa (1,038.5 psi) |
| Isp (vac.) | 280.5 s (2.751 km/s) |
| Burn time | up to 163s |
| Restarts | 1 |
| Gimbal range | +/- 30° |
| Dimensions | |
| Length | 0.9 m (2 ft 11 in) |
| Diameter | 3.35 m (11.0 ft) |
| Dry weight | 112.5 kg (248 lb) |
| Used in | |
| R-36, Tsyklon-2 and Tsyklon-3 second stage vernier | |
| References | |
| References | |
The RD-855 (GRAU Index 8D69M), also known as the RD-69M, is a four nozzle liquid rocket vernier engine, burning N2O4 and UDMH in a gas generator cycle. It was used on the R-36, Tsyklon-2 and Tsyklon-3 second stage as thrust vector control by gimbaling of its nozzle. The engine is distributed through a cylindrical structure that is integrated around the main engine RD-252 module. The structure includes aerodynamic protection for the nozzles. The engine was started by a pyrotechnic ignitor.
The engine was serially produced between 1965 and 1992. It was first launched on December 16, 1965 on an R-36 and its last launch was on January 30, 2009 with the last launch of the Tsyklon-3. The production capability was restarted for the Tsyklon-4 but with the apparent cancellation of the program the engine would still be out of production.
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