Anode power deposition in magnetoplasmadynamic thrusters

Results of anode heat-flux and anode fall measurements from a multimegawatt self-field quasisteady magnetoplasmadynamic (MPD) thruster are presented. Measurements were obtained with argon and helium propellants for a variety of currents and mass flow rates. Anode heat flux was directly measured with thermocouplesattached to the inner surface of a hollowed section. Anode falls were determined both from floating probes and through heat flux measurements. Comparison of data acquired through either method shows excellent agreement. Anode falls varied between 4-50 V with anode power fractions reaching 70% with helium at 150 kW, and 50% with argon at 1.9 MW. The anode fall was found to correlate well with electron Hall parameters calculated from triple Langmuir and magnetic probe data collected near the anode. Two possible explanations for this result are proposed: 1) the establishment of large electric fields at the anode to maintain current conduction across the strong magnetic fields; and 2) anomalous resistivity resulting from the onset of microturbulence inthe plasma. To investigate the latter hypothesis, electric field, magnetic field, and current density profiles measured in the vicinity of the anode were incorporated into Ohm’s law to estimate the electrical conductivity. Results of this analysis show a substantial deviation of the measured conductivity from that calculated with classical formulas. These results imply that anomalous effects are present in the plasma near the anode. © 1993, American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

Duke Scholars

Author Alec Gallimore Thomas Lord Department of Mechanical Engineering and Materia ...