X3 nested-channel Hall thruster

X3 is a 100-kW-class laboratory Hall thruster with three concentric discharge channels sharing a central cathode. Developed through University of Michigan and NASA collaboration, it explores how nested channels can increase power while limiting the footprint of a high-power thruster. In the published 2017 xenon test campaign at NASA Glenn, all seven channel combinations operated stably across a 5–102 kW total-power test matrix. Maximum measured thrust was 5.4 ± 0.1 N at 99 kW and 400 V; specific impulse ranged from 1,800 to 2,650 s with approximately ±60 s uncertainty. The maximum-thrust point and maximum-power point were separate measurements. First fired in 2013, X3 is documented as research hardware rather than a flown propulsion installation.