Hollow Cathodes for 100-kW MPD Thrusters

Multiple-channel hollow cathodes are of crucial importance for MPD thrusters. While single-channel cathodes are still suitable for 10-kW class discharges, at higher powers the multiple-channel configuration seems at present the only option for limiting the electrode erosion and the power losses in the cathode region. Unfortunately multiple-channel cathodes are difficult and costly to manufacture and as for single-channel ones the investigation of the internal plasma is very difficult. Hence, the availability of a numerical model as reliable design tool, allowing to limit the number of required tests would be very important. Whereas for single-channel cathodes some sophisticated models already exist in literature, reliable and numerically affordable multi-channel cathodes modeling is difficult to achieve. After a brief review of main efforts and results at Alta and RIAME-MAI on hollow cathodes development during the past years, a new multiple-channel hollow cathode model is presented and the results in terms of plasma parameters, voltage drop and cathode temperature are shown for a 100-kW, argon-fed MPD thruster.