USE OF PERMANENT-MAGNETS TO REDUCE ANODE LOSSES IN MDP THRUSTERS

Results from previous studies indicate that the anode fall, the princi pal source of anode heating in MPD thrusters, increases monotonically with the electron Hall parameter calculated from electron temperature, number density, and magnetic field data obtained near the anode. In a n attempt to reduce the anode fall by decreasing the local electron Ha ll parameter, a proof-of-concept test was performed in which an array of 36 permanent magnets were embedded within the anode of a high-power quasisteady MPD thruster to decrease the local azimuthal component of the induced magnetic field. The modified thruster was operated at pow er levels between 150 kW and 4 MW with argon and helium propellants. T erminal voltage, triple probe, floating probe, and magnetic probe meas urements were made to characterize the performance of the thruster wit h the new anode. Incorporation of the modified anode resulted in a red uction of the anode fall by up to 15 V with argon and 20 V with helium , which corresponded to decreased anode power fractions of 40 and 45 % with argon and helium, respectively.