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

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In nuclear electric propulsion, thermal energy from the nuclear reactor is converted into
electricity by either a static or dynamic thermal-to-electric power conversion system.
Static systems (e.g. thermoelectric generators) have the advantage of no moving parts for
high reliability, but they have low efficiencies while dynamic systems have moving parts
(e.g. turbines, generators, etc.) and they have higher efficiencies.
Power Processing System
Power processing systems are required to convert the voltage from the electric power
generator to the form required by the electric thruster.
For example, a solar electric power generator produces low-voltage DC (typically ~100 V);
this would need to be converted (via transformers, etc.) to kilovolt levels for use in an ion
thruster. The power processing system is often referred to as the power processing unit
(PPU).
Propellant Storage and Feed System
In general, liquid or gaseous propellants are stored in tanks and fed to the thruster
assembly as in chemical propulsion.
Electric Thruster Assembly to generate thrust.
Valves and piping which connect the propellant storage and feed system with the thruster
assembly.
Electric Control Unit to operate electrically valves and thrusters