Lifetime Limitations in Hall Thrusters Operating at High Current Density

The Jet Propulsion Laboratory (JPL) has developed the conducting-wall, magnetically shielded, 10-kW class, 3,000 s specific impulse H10 Hall thruster, which has demonstrated a 2:1 power throttling ratio at 800 V (~3,000 s Isp), efficiencies greater than 50% over 6:1 power throttling, and a 50:1 power throttling ratio over 0.2–10 kW. Hall2De simulations at 800 V suggest erosion of the inner pole cover can exceed 100 μm/kh when operating at or above 20 kW and can reach 1000 μm/kh at 50 kW. Erosion rates at the outer pole cover are an order of magnitude lower than those at the inner pole cover. At 300 V, erosion rates larger than 100 μm/kh are predicted at the inner and outer front pole covers above 6 kW. Thus, at the same discharge power, lifetime can be preserved by operating at higher voltages. Even at 800-V discharge voltage, long-life (~20 kh) operation of the thruster significantly (>20 kW) above its nominal power does not seem feasible and future Hall thrusters capable of operating at more than 20 kW will likely need to maintain current density values similar to those nominal for the H10 in order to achieve long-life.