Anode power deposition in quasisteady magnetoplasmadynamic thrusters

Spatially resolved anode heat flux measurements of a pulsed quasisteady magnetoplasmadynamic (MPD) thruster have been made by embedding thermocouples to the inner surface of a hollowed anode. Results obtained using argon propellant at mass flow rates of 4 and 16 g/s with the thruster operating at currents between 824 kA, are presented. These operating conditions correspond to thruster power levels of between 340 kW and 6 MW. In addition, floating probe measurements serve as a second means of estimating the magnitude of anode power deposition. Electron temperature and anode current densities were measured which, with heat flux measurements, permit an estimate of the anode fall to be made. The results of this work show that for moderate values of J2/m (<100 kA2-s/g), the anode fall voltage increases linearly with thruster current and its independent of propellant mass flow rate. The fraction of thruster power deposited into the anode is 42% at 1 MW and less than 20% at 6 MW. At any given operating condition, an inverse relationship is observed between the local anode fall and the local anode current density.