RD-861
| Country of origin | Soviet Union |
|---|---|
| First flight | October 27, 1967 |
| Designer | Yuzhnoye Design Bureau |
| Manufacturer | Yuzhmash |
| Application | Upper stage |
| Associated LV | Tsyklon-3 |
| Predecessor | RD-854 |
| Successor | RD-861K |
| Status | Out of production |
| Liquid-fuel engine | |
| Propellant | N2O4 / UDMH |
| Mixture ratio | 2.1 |
| Cycle | Gas generator |
| Configuration | |
| Chamber | 1 + 4 |
| Nozzle ratio | 112.4 (main) |
| Performance | |
| Thrust, vacuum | 78.71 kN (17,690 lbf) |
| Chamber pressure | 8.88 MPa (1,288 psi) |
| Specific impulse, vacuum | 317 seconds |
| Burn time | Up to 130s |
| Restarts | 1 |
| Dimensions | |
| Length | 1.56 m (5 ft 1 in) |
| Diameter | 1.53 m (5 ft 0 in) |
| Dry mass | 123 kg (271 lb) |
| Used in | |
| Tsyklon-2 and Tsyklon-3 third stage | |
| References | |
| References | |
The RD-861 (Russian: Ракетный Двигатель-861, romanized: Raketnyy Dvigatel-861, lit. 'Rocket Engine 861') is a Soviet liquid propellant rocket engine burning a hypergolic mixture of unsymmetrical dimethylhydrazine (UDMH) fuel with dinitrogen tetroxide (N2O4) oxidizer in a gas generator combustion cycle. It has a main combustion chamber, with four vernier nozzles fed by the gas generator output. It can be reignited a single time.