Anode power deposition in applied field magnetoplasmadynamic thruster

Abstract

Applied field magnetoplasmadynamic thrusters (AF-MPDTs) are one of the potential thrusters for high power space propulsion. However, the high anode power deposition limits the improvement in the thruster’s efficiency. According to previous research studies, the anode voltage drop is supposed to be the main factor of the anode power deposition in AF-MPDTs without considering the effect of the centrifugal force. Actually, the centrifugal force cannot be neglected when the magnetic field is high, where the anode voltage drop is not the only dominant factor of the anode power deposition. Due to the significant centrifugal force, there might be no obvious shortage of charge carriers near the anode surface in AF-MPDTs with propellant injection between the cathode and anode. The electrons will be compressed to the anode surface instead of the cathode. In order to investigate the reason for the anode power deposition in AF-MPDTs, a model considering the effect of the centrifugal force is established. The calculated anode power deposition shows good agreement with the corresponding experimental data. In addition, when the magnetic field is high, the viscous heating cannot be neglected, which is as significant as the anode sheath heating and Joule heating. Finally, in order to reduce the anode power deposition, a magnetic field distribution with a high value near the cathode and a low value near the anode is proposed. According to the evaluation by the model, the anode power deposition can be reduced by 30% via the new magnetic field when the magnetic field exceeds 0.1 T.