Miniature Ion Thruster Characterization via Discharge Plasma, Plume, and Mission Analyses

The Miniature Xenon Ion (MiXI) thruster is a 3 cm DC ion thruster developed as low-power, high effciency micro-propulsion. This work focuses on the further development of the MiXI thruster into a viable propulsion technology and investigates the capabilities of MiXI as primary propulsion on CubeSat missions. First, we set the stage for this work by investigating the viability of high dV small spacecraft missions with high effciency, high impulse propulsion, and explore the sensitivities of mission capabilities to thruster properties and performance. One important conclusion is that in the CubeSat form-factor, high impulse micropropulsion enables high dV missions of several km/s with payloads of multiple U volume and multiple kg mass, however these parameters are very sensitive to thruster parameters such as Isp, total effciency, and neutralizer cathode performance. An ion thruster model is then developed to investigate key aspects of miniature DC ion thruster discharge and thruster performance using simplifed descriptions of the plasma behavior to explore a wide range of the thruster design space. Results from this model provide clear boundaries to miniature ion thruster performance while also providing clear pathways for effectively improving thruster design for increased mission capabilities. The results from the model guide an experimental effort to experimentally investigate the 3-ring and Axial Ring-Cusp Hybrid (ARCH) discharge designs for the MiXI thruster. A small plume diagnostics suite consisting of Faraday, emissive, and ExB probes was developed and used to probe the MiXI(ARCH) plume. While no doubly charged ions were detected in the beam at the operating point measured, measurements agree with prior computational work and show a beam flatness of0.6, divergence of 5 degrees, and plume potential of 4.5 V. Later, MiXI(ARCH) was operated with a miniature discharge hollow cathode. Finally, using lessons learned from cathode integration, computational, and analytical modeling, a refned miniature hollow cathode design was developed to further improve discharge and thruster effciency. Through experimental and analytical investigation, mission studies, and further development of critical aspects of the thruster, this work shows that the MiXI thruster is an attractive propulsion option for high effciency, high specifc impulse micropropulsion