RD-864

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]}

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	[1][2][3][4][5][6][7][8][9]

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	[1][5][6][10]

History

When the Soviet military developed an improved version of the R-36M ICBM, Yangel's OKB-586 developed a new engine for the third stage, the RD-864. Developed between 1976 and 1978 it flew for the first time on October 31, 1977. With the START I and START II the some 150 R-36M and R-36M UTTKh were retired and to be destroyed by 2007.^[1][4] So, a civilian application was looked for and during the 1990s, Yuzhnoe Design Bureau (the R-36M designer) successfully developed the Dnepr launch vehicle.^[3] It flew for the first time on April 21, 1999, and as of June 2016 it is still operational.^[12] So, while the production of the RD-864 has long since been finished, the engine is still to this day operational.^[12][13]

The RD-869 was an improved version for the most powerful Soviet ICBM ever, the R-36M2 (15A18M). It had improved efficiency, restart capability and burn life over the RD-864.^[1][10] As of January 2016 there are still 46 operational R-36M2 (RS-20V, SS-18) and thus the RD-869 is still in service, if out of production.^[13]

Versions

There are two versions of this engine:

• RD-864 (GRAU Index: 15D177): First developed as the third stage engine for the R-36M UTTKh (15A18) ICBM and, by extension, on the Dnepr launch vehicle.^[1][5]
• RD-869 (GRAU Index: 15D300): An improved version of the RD-864. It has improved efficiency, restart capability and burn life. It is used on the R-36M2 (15A18M).^[1][6]

See also

• RD-843 - A single chamber version of the RD-864
• R-36M UTTKh - The most powerful ever Soviet ICBM for which the RD-864/869 engines were created.
• Dnepr - A Ukrainian small rocket project that uses the RD-864.
• Yuzhnoe Design Bureau - The RD-864/869 designer.
• Yuzhmash - A multi-product machine-building company that's closely related to Yuzhnoe and manufactures the RD-864/869.