RD-864

RD-869 (РД-869)
Country of origin	Soviet Union
First flight	March 1986
Designer	Yuzhnoye Design Bureau
Manufacturer	Yuzhmash
Application	Upper Stage
Associated LV	R-36M2
Predecessor	RD-864
Liquid-fuel engine
Propellant	N2O4 / UDMH
Mixture ratio	1.8
Cycle	Gas-generator
Configuration
Chamber	4
Performance
Thrust	High thrust mode: 20.47 kN (4,600 lbf); Low thrust mode: 8.58 kN (1,930 lbf);
Chamber pressure	High thrust mode: 4.1 MPa (590 psi); Low thrust mode: 1.7 MPa (250 psi);
Specific impulse	High thrust mode: 313 s (3.07 km/s); Low thrust mode: 302.3 s (2.965 km/s);
Burn time	Up to 700 seconds
Restarts	Up to 50
Gimbal range	±55°
Dimensions
Length	4,020 mm (13 ft 2 in)
Diameter	1,420 mm (4 ft 8 in)
Dry mass	196 kg (432 lb)
Used in
	R-36M2 third stage
References
References

RD-864 (РД-864)
Country of origin	Soviet Union
First flight	31 October 1977
Designer	Yuzhnoye Design Bureau
Manufacturer	Yuzhmash
Application	Upper stage
Associated LV	R-36M UTTKh and Dnepr
Successor	RD-869
Liquid-fuel engine
Propellant	N2O4 / UDMH
Mixture ratio	1.8
Cycle	Gas-generator
Configuration
Chamber	4
Performance
Thrust	High thrust mode: 20.2 kN (4,500 lbf); Low thrust mode: 8.45 kN (1,900 lbf);
Chamber pressure	High thrust mode: 4.1 MPa (590 psi); Low thrust mode: 1.7 MPa (250 psi);
Specific impulse	High thrust mode: 309 s (3.03 km/s); Low thrust mode: 298 s (2.92 km/s);
Burn time	Up to 600 seconds
Restarts	Up to 25
Gimbal range	±55°
Dimensions
Length	4,020 mm (13 ft 2 in)
Diameter	1,420 mm (4 ft 8 in)
Dry mass	199 kg (439 lb)
Used in
	R-36M UTTKh and Dnepr third stage
References
References

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.^[1] 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.^[5] For the R-36M2 (GRAU index: 15A18M), an improved version, the RD-869 (GRAU index: 15D300) was developed.^[1]^[6]^[10]^[11]

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