Engine Model: RD-855. Manufacturer Name: RD-855. Other Designations: D-68M. Designer: Yuzhnoye. Developed in: 1962-67. Application: Tsyklon stage 1 attitude control engine. Propellants: N2O4/UDMH. Thrust(vac): 328.000 kN (73,737 lbf). Thrust(sl): 285.400 kN (64,160 lbf). Isp: 292 sec. Isp (sea level): 254 sec. Burn time: 127 sec. Mass Engine: 320 kg (700 lb). Diameter: 3.81 m (12.49 ft). Length: 1.74 m (5.71 ft). Chambers: 4. Chamber Pressure: 65.70 bar. Oxidizer to Fuel Ratio: 1.97. Thrust to Weight Ratio: 90.94. Country: Ukraine. Status: Out of Production. The autonomous four-chamber pump-fed single-run engine burned hypergolic propellants in a gas generator scheme (without afterburning of the generator gas). Most valves were activated by pyrotechnics. The engine flow scheme tapped off both propellants to the feed the oxidizer tank pressurization gas generator, as well generator gas for the fuel tank pressurization mixer. Thrust controlled to within ±10% of nominal value, propellant mixture ratio within ± 5.6%. Engine thrust controlled by gimballing each of the four chambers in one plane, ± 41 deg.
Bibliography:- Shnyakin, V N, Shidkostnye Raketye Dvigateli - Opisanie i Osnovnye Tekhnicheskie Dannye, GKB Yuzhnoe "Yangel", Dnepropetrovsk 1996 via Dietrich Haeseler.
