Encyclopedia Astronautica

N2O4/UDMH propellant rocket stage. Loaded/empty mass 650/150 kg. Thrust 2.45 kN. Vacuum specific impulse 315.2 seconds. The AVUM propulsion module was composed of a UDMH/NTO bipropellant main engine with a re-ignition capability and a cold gas attitude control system, based on two clusters of three thrusters, each having a 50 N thrust.

The AVUM upper stage performed the following functions:

  • roll control during second, third and fourth stage flights
  • attitude control during coasting phase
  • correction of axial velocity error due to solid rocket motor
  • performance scatter
  • generation of the required velocity change for orbit circularisation
  • satellite pointing
  • payload(s) release manoeuvres

The AVUM avionics module provided the following services:

  • flight control and mission management
  • telemetry
  • localisation and neutralisation
  • power supply and distribution

Status: In production.
Gross mass: 650 kg (1,430 lb).
Unfuelled mass: 150 kg (330 lb).
Height: 1.74 m (5.70 ft).
Diameter: 1.90 m (6.20 ft).
Span: 1.90 m (6.20 ft).
Thrust: 2.45 kN (551 lbf).
Specific impulse: 315 s.
Burn time: 317 s.

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Associated Countries
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...

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