RD-864 (РД-864)| Country of origin | Soviet Union |
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| First flight | 31 October 1977 |
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| Designer | Yuzhnoye Design Bureau |
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| Manufacturer | Yuzhmash |
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| Application | Upper stage |
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| Associated LV | R-36M UTTKh and Dnepr |
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| Successor | RD-869 |
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| Propellant | N2O4 / UDMH |
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| Mixture ratio | 1.8 |
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| Cycle | Gas-generator |
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| Chamber | 4 |
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| Thrust | - High thrust mode: 20.2 kN (4,500 lbf)
- Low thrust mode: 8.45 kN (1,900 lbf)
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| Chamber pressure | - High thrust mode: 4.1 MPa (590 psi)
- Low thrust mode: 1.7 MPa (250 psi)
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| Specific impulse | - High thrust mode: 309 s (3.03 km/s)
- Low thrust mode: 298 s (2.92 km/s)
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| Burn time | Up to 600 seconds |
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| Restarts | Up to 25 |
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| Gimbal range | ±55° |
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| Length | 4,020 mm (13 ft 2 in) |
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| Diameter | 1,420 mm (4 ft 8 in) |
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| Dry mass | 199 kg (439 lb) |
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| R-36M UTTKh and Dnepr third stage |
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| References | |
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RD-869 (РД-869)| Country of origin | Soviet Union |
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| First flight | March 1986 |
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| Designer | Yuzhnoye Design Bureau |
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| Manufacturer | Yuzhmash |
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| Application | Upper Stage |
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| Associated LV | R-36M2 |
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| Predecessor | RD-864 |
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| Propellant | N2O4 / UDMH |
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| Mixture ratio | 1.8 |
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| Cycle | Gas-generator |
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| Chamber | 4 |
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| Thrust | - High thrust mode: 20.47 kN (4,600 lbf)
- Low thrust mode: 8.58 kN (1,930 lbf)
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| Chamber pressure | - High thrust mode: 4.1 MPa (590 psi)
- Low thrust mode: 1.7 MPa (250 psi)
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| Specific impulse | - High thrust mode: 313 s (3.07 km/s)
- Low thrust mode: 302.3 s (2.965 km/s)
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| Burn time | Up to 700 seconds |
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| Restarts | Up to 50 |
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| Gimbal range | ±55° |
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| Length | 4,020 mm (13 ft 2 in) |
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| Diameter | 1,420 mm (4 ft 8 in) |
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| Dry mass | 196 kg (432 lb) |
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| R-36M2 third stage |
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| References | |
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The RD-864 (Russian: Ракетный Двигатель-864, romanized: Raketnyy Dvigatel-864, lit. 'Rocket Engine 864', GRAU index: 15D177) is a Soviet liquid-fuel 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 four combustion chambers that provide thrust vector control by gimbaling each nozzle in a single axis ±55°. It is used on the third stage of the R-36M UTTKh (GRAU index: 15A18) and Dnepr. For the R-36M2 (GRAU index: 15A18M), an improved version, the RD-869 (GRAU index: 15D300) was developed.