Numerical Study of Plasma Behavior in a Magnetoplasmadynamic Thruster Around Critical Current

A self-field magnetoplasmadynamic thruster is numerically studied for an argon mass flow rate of 0.8 g/s. We focus on the plasma behavior around the critical current, at which full propellant ionization is theoretically expected. At a discharge current higher than the critical current, the flail parameter is large at the anode surface, which leads to an obliquely skewed current profile. This skewed current profile, together with the voltage-current characteristics, show that the Hall effect plays an important role around the critical current. When operating the magnetoplasmadynamic thruster above the critical current, it is shown that the current concentration and the gas density depletion at the anode edge induce a shortage of current carriers. To circumvent the carrier shortage at high discharge currents, we employ a segmented anode. It is found that a segmented anode is effective for suppressing the current concentration and the plasma density depletion on the anode surface without degrading the performance of the thruster.