Engine Model: MR-508. Other Designations: Low Power Hydrazine Arcjet. Designer: Rocket Research. Application: Communications satellite N-S stationkeeping, MMAS 7000. Propellants: Hydrazine. Thrust(vac): 0.23 N (0.05 lbf). Isp: 502 sec. Burn time: 234,000 sec. Mass Engine: 1.34 kg (2.95 lb). Diameter: 0.0927 m (0.3041 ft). Length: 0.24 m (0.80 ft). Chambers: 1. Chamber Pressure: 4.80 bar. Area Ratio: 100.00. Thrust to Weight Ratio: 0.0100. Country: USA. Status: In Production. First Flight: 1993. Last Flight: 1995. First Flight: Telstar 4 (December 1993). qualified autumn 1991. Flown: 6 (28 produced) planned to end-1995. Dry Mass: 1338 gm. Length: 24.4 cm. Max Diameter: 9.27 cm. Mounting Method: bolted four places. Propellant: hydrazine at 0.068-0.077 gm/sec over Shell 405 catalyst and 1.8 kW. electric arc. Feed Method: GN2 or Ghe at 14.9-20.4 atm through Wright Components 9 W dual seat. solenoid valve. Thrust: 0.20-0.23 N. Isp: 502 sec vacuum. Time to Full Thrust: N/A. Expansion Ratio: 100:1. Nozzle Length: 0.879 cm. Nozzle Cooling Method: radiative. Combustion Chamber Pressure: 4.1-4.7 atm. Combustion Chamber Temperature: 800 Celsius. Combustion Chamber Cooling Method: radiative. Duty Cycle: 5 minutes minimum to 65 hr maximum. Itotal: 654 kNs.