RD-861

The RD-861 is a Soviet liquid propellant rocket engine burning UDMH and nitrogen tetroxide in a gas generator combustion cycle. It has a main combustion chamber, with four vernier nozzles fed by the gas generator output.[2] It can be reignited a single time.[4]

RD-861 (РД-861)
Country of originSoviet Union
First flightOctober 27, 1967
DesignerYuzhnoye Design Bureau
ManufacturerYuzhmash
ApplicationUpper Stage
Associated L/VTsyklon-3
PredecessorRD-854
SuccessorRD-861K
StatusOut of production
Liquid-fuel engine
PropellantN
2O
4 / UDMH
Mixture ratio2.1
CycleGas Generator
Configuration
Chamber1 + 4
Nozzle ratio112.4 (Main)
Performance
Thrust (vac.)78.71 kN (17,690 lbf)
Chamber pressure8.88 MPa (1,288 psi)
Isp (vac.)317 seconds
Burn timeup to 130s
Restarts1
Dimensions
Length1.56 m (5 ft 1 in)
Diameter1.53 m (5 ft 0 in)
Dry weight123 kg (271 lb)
Used in
Tsyklon-2 and Tsyklon-3 third stage
References
References[1][2][3][4][5]

History

When the Soviet military developed the Fractional Orbital Bombardment System, Yangel's OKB-586 proposed a new version of their R-36 ICBM, called the R-36-ORB (GRAU Index: 8K69). It incorporated an orbital warhead called OGCh (GRAU Index: 8F021), for which the RD-854 engine was developed in-house. Since the Outer Space Treaty of 1967 banned nuclear weapons in Earth orbit, but did not ban the launch systems, the Soviet Union proceeded to test their FOBS albeit without placing nuclear warheads in orbit.[6][7]

Versions

There are three versions of this engine:

  • RD-854 (GRAU Index: 8D612): First developed as the third stage engine for the R-36ORB FOBS.[1][8]
  • RD-861 (GRAU Index: 11D25): Also known as the D-25. It was the engine of the Tsyklon-3 third stage.[4]
  • RD-861K : An improved RD-861, developed for the third stage of the Tsyklon-4. The vernier nozzles were replaced with a hydraulic actuated gimbal for the whole engine. The isp was increased, the burn time tripled and the reignitions increased to three.[3][9][10]

See also

References
  1. "RD-854". Encyclopedia Astronautica. Retrieved 2016-07-06.
  2. "RD-861". Encyclopedia Astronautica. Retrieved 2016-07-06.
  3. "RD-861K". Encyclopedia Astronautica. Archived from the original on 2016-03-04. Retrieved 2016-07-06.
  4. Pillet, Nicolas. "Tsiklone - Le troisième étage" [Tsyklon - The third stage] (in French). Kosmonavtika.com. Retrieved 2016-07-06.
  5. "RD-861K". Defense Industry Of Ukraine Products And Services. Retrieved 2016-07-11.
  6. "R-36-O". Encyclopedia Astronautica. Retrieved 2016-07-06.
  7. Pillet, Nicolas. "Histoire du lanceur Tsiklone" [History of the Tsyklon launcher] (in French). Kosmonavtika.com. Retrieved 2016-07-06.
  8. Pillet, Nicolas. "Les satellites OGTch" [The OGTch satellites] (in French). Kosmonavtika.com. Retrieved 2016-07-06.
  9. "RD-861K". Yuzhnoye. Retrieved 2016-07-06.
  10. "Liquid rocket engine RD-861K". Yuzhmash. Retrieved 2015-07-06.


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