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

Cold Gas Systems (Operate)
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Cold gas propulsion is just controlled pressurized gas source and a nozzle. It represents
the simplest form of a propulsion system.
The typical system operating with cold gas consists of a propellant tank, fill valve, filter,
pressure regulator, line pressure transducers and thrusters. The pressure regulator
provides propellant at constant pressure as the tank pressure drops.
A relief valve is incorporated downstream of the pressure regulator to prevent system
rupture in the case of a regulator failure. With regard to compressed gas systems, the cold
gas is stored at high pressures in a tank.
The vaporizing liquid system is characterized by a liquid propellant pressurized by its own
equilibrium vapor pressure and the expulsion of its vapor through a nozzle. In order to
provide completely vaporized gas, a vaporized is included in liquid cold gas systems.
Nitrogen, argon, krypton, Freon 14, ammonia and propane have been employed in
operational spacecraft, but nitrogen has been the most common cold-gas propellant.