Scaling of Efficiency with Applied Magnetic Field in Magnetoplasmadynamic Thrusters

was then calculated using the voltage data along with a semi-empirical thrust formula derived and veried previously for the same thruster. The non-useful voltage component (the voltage associated with the thruster’s power losses) was found to scale linearly with current and applied magnetic eld and inversely with mass ow rate. This behavior was attributed to electrode sheath eects and decreased conductivity with increasing applied magnetic eld. The eciency was found to increase with applied magnetic eld for all current and mass ow rate values and the enhancement of the eciency by the applied magnetic eld was found to be greater when the mass ow rate is reduced. The observed minimum in the eciency vs current curve was related to interplay between the components of the thrust and was shown experimentally and analytically to increase with increasing applied eld and decreasing mass ow rate.