RD-855

The RD-855 (GRAU Index 8D68M), also known as the RD-68M, is a four nozzle liquid rocket vernier engine, burning N2O4 and UDMH in a gas generator cycle.[3] It was used on the R-36, Tsyklon-2 and Tsyklon-3 first 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-251 module. The structure includes aerodynamic protection for the nozzles and small retro engines to assure the separation of the first stage.[2] The engine was ignited two second before the RD-251 main engine.[2]

RD-855 (РД-855)
Country of originSoviet Union
First flightDecember 16, 1965
Last flightJanuary 30, 2009
DesignerYuzhnoye Design Bureau
ManufacturerYuzhmash
ApplicationVernier
Associated L/VR-36, Tsyklon-2 and Tsyklon-3
StatusOut of production
Liquid-fuel engine
PropellantN
2O
4 / UDMH
Mixture ratio1.97
CycleGas Generator
Configuration
Chamber4
Performance
Thrust (vac.)328 kN (74,000 lbf)
Thrust (SL)285.4 kN (64,200 lbf)
Chamber pressure6.570 MPa (952.9 psi)
Isp (vac.)292 s (2.86 km/s)
Isp (SL)254 s (2.49 km/s)
Burn timeup to 127s
Restarts1
Gimbal range+/- 41°
Dimensions
Length1.74 m (5 ft 9 in)
Diameter3.81 m (12.5 ft)
Dry weight320 kg (710 lb)
Used in
R-36, Tsyklon-2 and Tsyklon-3 first stage vernier
References
References[1][2][3]

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

References
  1. "RD-855". Encyclopedia Astronautica. Retrieved 2016-07-06.
  2. Pillet, Nicolas. "Tsiklone - Le premier étage" [Tsyklon - The first stage] (in French). Kosmonavtika.com. Retrieved 2016-07-06.
  3. "RD-855". Yuzhnoye. Retrieved 2016-07-06.
  4. Krebs, Gunter Dirk (2016-04-24). "Tsiklon". Gunter's Space Page. Retrieved 2016-07-05.


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