Encyclopedia Astronautica

Isayev N2O4/UDMH rocket engine. 19.6 kN. Phobos propulsion module, later adapted as Fregat upper stage. In production. Isp=327s. Gas generator cycle. Nominal and low-thrust thrust levels.

Low thrust version with 1400 kgf, chamber diameter of 0.68 m, chamber pressure of 67 bar, specific impulse 316 seconds. Chamber pressure 97 / 67. Specific impulse 327 / 316 sec.

Application: Phobos propulsion module.


Throttled thrust(vac): 13.700 kN (3,080 lbf). Engine: 75 kg (165 lb). Chamber Pressure: 97.00 bar. Area Ratio: 153.8. Thrust to Weight Ratio: 26.66. Oxidizer to Fuel Ratio: 2.

Status: In production.
Unfuelled mass: 75 kg (165 lb).
Height: 1.03 m (3.37 ft).
Diameter: 0.84 m (2.75 ft).
Thrust: 19.60 kN (4,406 lbf).
Specific impulse: 327 s.
Burn time: 2,000 s.
First Launch: 1966-1987.

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Associated Countries
See also
Associated Launch Vehicles
  • Soyuz 11A511U / Fregat Russian orbital launch vehicle. Standard Soyuz universal booster with the Fregat upper stage, derived from the propulsion system for Lavochkin interplanetary probes. More...
  • Soyuz ST / Fregat ST Uprated Soyuz booster designed for commercial customers. Upgraded engines, modern avionics, reduced non-Russian content. Uses Fregat upper stage. More...

Associated Manufacturers and Agencies
Associated Propellants
  • N2O4/UDMH Nitrogen tetroxide became the storable liquid propellant of choice from the late 1950's. Unsymmetrical Dimethylhydrazine ((CH3)2NNH2) became the storable liquid fuel of choice by the mid-1950's. Development of UDMH in the Soviet Union began in 1949. It is used in virtually all storable liquid rocket engines except for some orbital manoeuvring engines in the United States, where MMH has been preferred due to a slightly higher density and performance. More...

  • Haeseler, Dietrich, "Personal communication", 1998 December..

Associated Stages
  • Fregat N2O4/UDMH propellant rocket stage. Loaded/empty mass 6,535/1,100 kg. Thrust 19.60 kN. Vacuum specific impulse 327 seconds. Upper stage developed from propulsion bus for Lavochkin lunar and planetary probes (Luna Ye-8, Mars M1, Fobos 1F). 20 restarts. More...

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