Abstract: Miniature ion thrusters, capable of efficiently producing 1-2 mN of continuous thrust, are a mission enabling technology that offer an attractive option as a primary propulsion system for small spacecraft and as part of an attitude control system for larger spacecraft. Ion thruster discharges already exhibit impressive performance at conventional scales (~30 cm in diameter); however, scaling to smaller sizes (~3 cm) presents considerable challenges. The higher surface area-to-volume ratio increases the plasma loss to the walls, especially the high-energy “primary” electrons which are the source of the discharge energy. This research effort addresses the miniaturization of direct current (DC) discharges via a series of careful investigations (i.e., near-field cusp-confinement, discharge experiments, computational efforts, and theoretical analyses). These investigations provided insight into the plasma behavior and loss mechanisms within small-scale DC discharges. This insight was then used to develop and demonstrate a highly efficient miniature-scale direct current ion source called the Axial Ring-Cusp Hybrid (ARCH) discharge. Implemented as a 3 cm ion thruster, it can potentially achieve a discharge loss of 160 eV/ion and mass utilization efficiencies of 0.89 — performance values that have previously only been attainable by conventional-scale ion thrusters. Performance data and discharge maps show that this approach provides “perfect” confinement of the primary electrons, high plasma electron density, and high plasma uniformity along the extraction plane. The improve performance will greatly expand the mission capabilities of many future spacecraft missions be providing the high efficiency of ion thrusters at small powers and scales.

Bio: Ben Dankongkakul is a Ph.D. candidate in Aerospace Engineering with a minor in Plasma Physics at the University of California, Los Angeles, under the advisement of Dr. Richard Wirz. He also earned both his B.S. in 2009 and M.S. in 2012 in Aerospace Engineering at the same institution. He was a recipient of the California Space Grant Consortium Fellowship and the UCLA Dissertation Year Fellowship. His experimental research focuses on magnetic cusp confinement and the behavior of miniature-scale plasmas which aims to improve the performance of DC gridded ion thrusters.