Hall-Effect Thrusters for Deep-Space Missions: A Review

For several decades, Hall-effect thrusters (HETs) are being used in several applications, such as orbiting satellites, deep space missions, etc. This article studies the effect of several parameters, namely, thruster geometry, magnetic field, wall material, and different propellants that significantly influence thruster performance. It was reported that annular thrusters are preferred for deep space missions, whereas, cylindrical thrusters are widely used in low power applications, such as station keeping of satellites. The lifespan of HET is a crucial parameter that is decided by the erosion of the thruster wall. Magnetically shielded thrusters are preferred not only to reduce the erosion but also the secondary emission of electrons. The overall effect of magnetic shielding is the improvement in thruster performance and its lifespan. Boron nitride and mixture of boron nitride and silica (borosil) were found to be the most appropriate thruster wall materials due to their lowest electron emission and reduced ion-wall interaction. Over the years, Xenon has been the best choice among several propellants for the HET operation. Other potential propellants include Krypton, Bismuth, Iodine, etc.