S.1 Spacecraft Propulsion Systems Chapter 1: Introduction to ...

S.6 Liquid Propellant Systems
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Monopropellant systems operate with a single (Mono) propellant to produce thrust. The
most commonly used monopropellant is anhydrous hydrazine (N2H4).
- Main performance
- Advantages
- Disadvantages
Bipropellant systems operate by the combustion of two (Bi) propellants, a fuel (e.g. MMH)
and an oxidizer (e.g. N2O4), to produce thrust.
Bipropellant systems are used e.g. for telecommunication satellites which operate in
Geostationary Orbits.
Here, propulsion systems are needed for spacecraft injection from the orbit delivered by
the launcher into circular orbit, and during station phase for orbit (north/south & east/west)
and attitude control. Therefore, these propulsion systems are also called Unified
Propulsion Systems (UPS).