Extended Lifetime Low Power Hall Thrusters

The Air Force has identified low power Hall thrusters as critical for mass and power limited satellites. Propulsion requirements include, maneuvering, precise formation flying, stationkeeping and extensive drag make-up. Busek's 200 W Hall thruster hasthe demonstrated performance characteristics of pulse operation and high thrust efficiency and specific impulse to provide all microsatellite propulsion needs. However, system lifetimes greater than 3000 hours are envisioned to meet mission needs forinspection, servicing and sparse aperture formation flying. At present, Busek's 200 W Hall thruster has not demonstrated this mission requirement.A Hall thruster's operating lifetime is dictated by sputter erosion of surfaces in contact with the high-energy ion beam. The highest erosion rates typically occur on the insulator surfaces near the exit plane of the thruster.In the proposed Phase I program, we will improve the lifetime of our 200 W Hall thruster through a combination of magnetic field shaping, neutral flow distribution, improved sputter resistant materials and design changes to the discharge region of thethruster. Busek will also develop and validate a method for numerically predicting the lifetime of the thruster using advanced plasma simulations that track particles impacting the walls and account for erosion induced geometry changes to the dischargechannel over time.In Phase II, an upgraded design will be prepared and a 3000 hour lifetest performed. Busek's low power Hall thruster can fulfill all the propulsion needs on low mass and power limited microsatellites. Developing a long life thruster will open additional mission opportunities where long mission duration and/or continuous thrusting arerequisites. Also science and earth observation micro satellites that need extensive drag make-up (high DV) can be met with a long life thruster. The thruster could also be used for deorbiting of both small and large satellites at EOL as is now mandatedby recent regulations.