Numerical Analysis of a Two-Dimensional Magnetoplasmadynamic Arcjet

Abstract

The effect of electrode cone guration on thrust characteristics of a two-dimensional magnetoplasmadynamic (MPD) arcjet was numerically investigated. A simple magnetohydrodynamics (MHD) model was developed and the numerical results were compared with the experimental data for several electrode geometries. To understand the features of the e owe eld, we introduced a magnetosonic Mach number, which is dee ned as local velocity divided by a propagation speed of the MHD disturbance. Based on the magnetosonic Mach number distribution of the e owe eld, the model can explain the thrust characteristics of the MPD arcjet, especially the superiority of a short cathode under various anode cone gurations. Because the electromagnetic thrust is unaltered for the same anode cone guration, the electrothermal component of thrust makes a difference between the long and the short cathodes. With a short cathode cone guration, the large heat deposition near the cathode tip, which is inevitable to MPD arcjets, can be cone ned in the submagnetosonic region where the local e ow is accelerated to magnetosonic velocity. Then the thermal deposition into the submagnetosonic region can be efe ciently recovered through transmagnetosonic acceleration, resulting in a large thrust generation.