Application of iodine plasma for electric propulsion

Abstract

Most state-of-the-art electric space propulsion systems, such as gridded and Hall effect thrusters, use xenon as the propellant gas. However, xenon is very rare and expensive to produce, and it is used in a number of competing industrial applications. Iodine is emerging as an attractive alternative to xenon in several electric propulsion technologies. Its lower cost and larger availability, solid state at standard temperature and pressure, its low vapor pressure and its low ionization potential make it an attractive option. Attempts to implement an alternative to xenon propellants (Iodine, O2 , N2 , H2 , CO2 etc) in conventional propulsion systems have been met with measured success. However, the use of chemically reactive species, such as O2, H2, or iodine, requires the chosen propulsion platform to be chemically compatible with the propellant. Significant reductions in the operational lifetime of the thruster because of chemical incompatibility negates any potential increase in thruster performance or propellant availability. Thus, careful material selection for the electric propulsion system itself and for the components employed on the satellite is required in the light of a typical space mission duration of several years. Due to the more complex reaction processes and energy loss channels in iodine plasma´s however, as well as the historical lack of reliable collision cross-section data, the development of accurate theoretical and numerical models has been hindered. The development of techniques that can be applied to chemically dissimilar propellants, focusing on electromagnetic behaviour, would represent a significant improvement in the state of discharge characterization and thruster analysis. In this work, we conducted a comparative analysis of the existing modeling results for various types of electric propulsion using iodine as a propellant gas, as well as the results of experiments with iodine plasma with an emphasis on the thrust-to-power ratio.

Keywords

• electric propulsion
• plasma thrusters
• alternative propellants
• iodine