Global model of an iodine gridded plasma thruster

Abstract

International audienceMost 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, expensive to produce, and used in a number of competing industrial applications. Alternatives to xenon are currently being investigated, and iodine has emerged as a potential candidate. Its lower cost and larger availability, its solid state at standard temperature and pressure, its low vapour pressure and its low ionization potential make it an attractive option. In this work, we compare the performances of a gridded ion thruster operating separately with iodine and xenon, under otherwise identical conditions using a global model. The thruster discharge properties such as neutral, ion, and electron densities and electron temperature are calculated, as well as the thruster performance parameters such as thrust, specific impulse, and system efficiencies. For similar operating conditions, representative of realistic thrusters, the model predicts similar thrust levels and performances for both iodine and xenon. The thruster efficiency is however slightly higher for iodine compared with xenon, due to its lower ionization potential. This demonstrates that iodine could be a viable alternative propellant for gridded plasma thrusters

Concepts, Capabilities, and Limitations of Global Models: A Review

“…For investigations of general properties, a simple planar or cylindrical geometry is usually sufficient . However, if a particular device is to be modeled for the purposes of comparison with experiment, then more complicated geometries are often required, as well as considerations of gas flow and mechanical pumping systems …”

“…Results from a global model of a gridded thruster, showing a comparison of overall thruster efficiencies using iodine or xenon as a propellant as a function of mass flow rate. Reprinted with the permission of AIP Publishing.…”

“…[7][8][9] However, if a particular device is to be modeled for the purposes of comparison with experiment, then more complicated geometries are often required, as well as considerations of gas flow and mechanical pumping systems. [10][11][12][13] Alongside geometrical considerations, the method by which power is deposited in the plasma must also be determined. It is important to know if the plasma is powered through a DC or AC drive, and if this is radio frequency (RF), or another waveform, and whether this is capacitively or inductively coupled, [14][15][16] or both.…”

“…In order to provide a first analysis of such a system, and to estimate important parameters such as efficiencies, global models have been used. [12,13] The first example considered a xenon plasma driven as a cylindrical ICP capped at one end by a grid. The global model developed by Chabert et al [12] has similarities with that developed in Section 2.1.…”

“…This model was extended by Grondein et al [13] to include iodine as a feed gas, in order to evaluate its properties as a novel propellant. This extension resulted in the consideration of six species, including negative ions, atomic iodine neutrals, and molecular positive ions, and considerations were made for the effect of the grid on the effective area seen by each species.…”