| Country of origin | Soviet Union |
|---|---|
| First flight | December 16, 1965 |
| Last flight | January 30, 2009 |
| Designer | Yuzhnoye Design Bureau |
| Manufacturer | Yuzhmash |
| Application | Vernier |
| Associated LV | R-36, Tsyklon-2 and Tsyklon-3 |
| Status | Out of production |
| Liquid-fuel engine | |
| Propellant | N2O4 / UDMH |
| Mixture ratio | 1.97 |
| Cycle | Gas generator |
| Configuration | |
| Chamber | 4 |
| Performance | |
| Thrust, vacuum | 328 kN (74,000 lbf) |
| Thrust, sea-level | 285.4 kN (64,200 lbf) |
| Chamber pressure | 6.570 MPa (952.9 psi) |
| Specific impulse, vacuum | 292 s (2.86 km/s) |
| Specific impulse, sea-level | 254 s (2.49 km/s) |
| Burn time | Up to 127 s |
| Restarts | 1 |
| Gimbal range | ±41° |
| Dimensions | |
| Length | 1.74 m (5 ft 9 in) |
| Diameter | 3.81 m (12.5 ft) |
| Dry mass | 320 kg (710 lb) |
| Used in | |
| R-36, Tsyklon-2 and Tsyklon-3 first stage vernier | |
| References | |
| References | |
The RD-855 (Russian: Ракетный Двигатель-855, romanized: Raketnyy Dvigatel-855, lit. 'Rocket Engine 855', GRAU index: 8D68M), also known as the RD-68M, is a liquid-fueled rocket engine with four nozzles. As a vernier engine, it provides fine steering adjustments for rockets. It is powered by a hypergolic mixture of unsymmetrical dimethylhydrazine (UDMH) fuel with dinitrogen tetroxide (N2O4) oxidizer. This combination is hypergolic, meaning the two substances ignite on contact, eliminating the need for an external ignition source.
The RD-855 can orient its chambers within a range of ±42° using hydraulic cylinders. Each chamber on the Tsyklon rockets is protected by an aerodynamic cover, and these covers are equipped with small retro-rockets allowing for separation from the second stage.
The RD-855 utilizes the gas generator cycle, in which a portion of the propellant is burned in a pre-burner to produce hot gases that drive the engine's turbopumps, and then the gases are discarded without passing through the main combustion chamber.
It played a key role in rockets such as the R-36, Tsyklon-2, and Tsyklon-3, steering these rockets by adjusting its nozzles. The engine is housed in a cylindrical structure that surrounds the primary RD-251 engine. This arrangement provides protection for the nozzles and ensures the successful detachment of the rocket's first stage. The RD-855 is activated two seconds before the main RD-251 engine.
Manufactured from 1965 to 1992, the RD-855's inaugural flight was on December 16, 1965, aboard the R-36 missile. Its most recent known flight was on January 30, 2009, with the Tsyklon-3. Although there were plans to restart its production for the Tsyklon-4, the engine remains out of production following the potential discontinuation of the program.
See also
- R-36 – The Soviet ICBM for which the RD-855 was created.
- Tsyklon-2 – A Soviet small rocket that uses the RD-855.
- Tsyklon-3 – A Soviet small rocket that uses the RD-855.
- Tsyklon-4 – A Ukrainian small rocket project that would have used the RD-855.
- Yuzhnoe Design Bureau – The RD-855 designer bureau.
References
- "RD-855". Encyclopedia Astronautica. Archived from the original on April 30, 2002. Retrieved 2016-07-06.
- ^ Pillet, Nicolas. "Tsiklone - Le premier étage" [Tsyklon - The first stage] (in French). Kosmonavtika.com. Retrieved 2016-07-06.
- ^ "RD-855". Yuzhnoye. Archived from the original on 29 May 2015.
- Krebs, Gunter Dirk (2016-04-24). "Tsiklon". Gunter's Space Page. Retrieved 2016-07-05.
External links
- Yuzhnoye Design Bureau English-language home page Archived 2021-06-29 at the Wayback Machine
- Yuzhmash Home Page
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