Optimization of Electric Thrusters for Primary Propulsion Based on the Rocket Equation

IEPC-01-181 During the last decade, electric propulsion systems have been established for orbit maintenance of satellites. More than 150 spacecrafts are now equipped with almost 400 thrusters for this purpose. The current decade will see the use of electric propulsion for primary propulsion. The purpose of this paper is to determine optimal mission parame ters for these tasks. Depending on the mission profile, ion thrusters, Hall thrusters, thermal arcjets or MPD thrusters are preferable. All electric propulsion systems have in common that they can be operated in a wide range of the specific impulse and that the thrust efficiency and therefore also the specific power of the propulsion system depend strongly on the specific impulse. The optimal specific impulse for a particular mission depends, therefore, on the kind of thruster and the chosen propellant. This paper shows that for MPD, ion, Hall ion and thermal arcjet thrusters the optimal specific impulse for a particular mission can be determined by an optimization which is based on the rocket equation. Using, in addition, a simple cost function, the influence of the cost factors is explained. Finally, the results for a few missions for which electric propulsion systems for primary propulsion have been selected are discussed.