Article · Wikipedia archive · Last revised Aug 6, 2026

RD-856

The RD-856, also known as the RD-69M, is a four-nozzle liquid-fuel rocket vernier engine, burning a hypergolic mixture of unsymmetrical dimethylhydrazine (UDMH) fuel with dinitrogen tetroxide oxidizer in a gas generator cycle. It was used on the R-36, Tsyklon-2 and Tsyklon-3 second stage as thrust vector control by gimbaling of its nozzle. The engine is distributed through a cylindrical structure that is integrated around the main engine RD-252 module. The structure includes aerodynamic protection for the nozzles. The engine was started by a pyrotechnic ignitor.

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RD-856 (РД-856)
Country of originSoviet Union
First flightDecember 16, 1965
Last flightJanuary 30, 2009
DesignerYuzhnoye Design Bureau
ManufacturerYuzhmash
ApplicationVernier
Associated LVR-36, Tsyklon-2 and Tsyklon-3
StatusOut of production
Liquid-fuel engine
PropellantN2O4 / UDMH
Mixture ratio1.98
CycleGas generator
Configuration
Chamber4
Performance
Thrust, vacuum54.23 kN (12,190 lbf)
Chamber pressure7.160 MPa (1,038.5 psi)
Specific impulse, vacuum280.5 s (2.751 km/s)
Burn timeUp to 163 s
Restarts1
Gimbal range±30°
Dimensions
Length0.9 m (2 ft 11 in)
Diameter3.35 m (11.0 ft)
Dry mass112.5 kg (248 lb)
Used in
R-36, Tsyklon-2 and Tsyklon-3 second stage vernier
References
References123

The RD-856 (Russian: Ракетный Двигатель-856, romanized: Raketnyy Dvigatel-856, lit. 'Rocket Engine 856', GRAU index: 8D69M), also known as the RD-69M, is a four-nozzle liquid-fuel rocket vernier engine, burning a hypergolic mixture of unsymmetrical dimethylhydrazine (UDMH) fuel with dinitrogen tetroxide (N2O4) oxidizer in a gas generator cycle.3 It was used on the R-36, Tsyklon-2 and Tsyklon-3 second stage as thrust vector control by gimbaling of its nozzle.3 The engine is distributed through a cylindrical structure that is integrated around the main engine RD-252 module. The structure includes aerodynamic protection for the nozzles.2 The engine was started by a pyrotechnic ignitor.2

The engine was serially produced between 1965 and 1992. It was first launched on December 16, 1965 on an R-36 and its last launch was on January 30, 2009 with the last launch of the Tsyklon-3. The production capability was restarted for the Tsyklon-4 but with the apparent cancellation of the program the engine would still be out of production.4

See also

See also

References

References

  1. "RD-856". Encyclopedia Astronautica. Archived from the original on June 27, 2002. Retrieved 2016-07-06.
  2. Pillet, Nicolas. "Tsiklone - Le deuxième étage" [Tsyklon - The second stage] (in French). Kosmonavtika.com. Retrieved 2016-07-06.
  3. "RD-856". Yuzhnoye. Archived from the original on 29 May 2015.
  4. Krebs, Gunter Dirk (2016-04-24). "Tsiklon". Gunter's Space Page. Retrieved 2016-07-05.
External links