Nano-Sat Scale Electric Propulsion for Attitude Control-Performance Analysis

In recent years, the complexity of CubeSat missions has been increasing steadily as the platform capabilities have drastically improved. Missions involving high-accuracy pointing and interplanetary exploration are no longer out of the reach of CubeSat-class satellites. Accordingly, the CubeSat community also has been focusing on miniaturization of propulsion systems. Thus far, these systems have been used mostly for ΔV maneuver applications and require a separate attitude control system to keep the satellite pointed in the desired direction. For fine-pointing, the currently available options are dominated by reaction-wheels and control-moment-gyros. One promising solution for this is the use of low-thrust propulsion systems for providing a combined ΔV maneuver and pointing capability. Electric propulsion systems can enable high-accuracy pointing capability while also providing orbit maneuver capability. Electric propulsion systems will not have the high slew-rate of the reaction wheels or ΔV responsiveness of conventional thrusters. However, if the main objective of the mission is in providing high-accuracy pointing, long-term stability of pointing, orbit maintenance, and long-term orbit maneuvers, multi-thruster electrical propulsion system can be substituted for the attitude control system and propulsion unit combination, resulting in volume and cost savings. This paper characterizes the performance of one such system, CubeSat attitude control system. First, the propulsion system characterization results are given. Using these performance parameters, the theoretical pointing accuracy and target dwell time are analyzed and discussed. The paper also highlights potential application of the electric propulsion system and provides comparison results of the system performance as compared to other commercially available units in terms of cost, volumetric efficiency, and resource consumption.