This report documents an investigation of the performance of quasisteady MPD thrusters at high power levels. An axisymmetric configuration is used for the MPD thruster, with various cathode and anode sizes, over a wide range of experimental conditions. Thrust is determined from impulse measurements with well known current waveforms, while instantaneous measurements are made for all other variables: mass flow rate, current and voltage. It is demonstrated that, under well defined conditions, the thrust produced has a predominantly self magnetic origin, and the experimental results are in good agreement with analytical predictions. It is found that the self magnetic thrust is directly proportional to the square of the current, the proportionality constant depending only on the ratio of anode and cathode radii. As a check on the validity of the thrust performance measurements, exhaust jet velocities are measured using doppler shift techniques, and calorimetric determinations of the power lost to the electrodes are made. These measurements also aid in the understanding of MPD thruster performance under conditions where aerodynamic contributions to the thrust, or electrode erosion are important. The complete set of impulse measurement data is presented in the Appendix, so as to be useful for extracting additional information, and comparison with other studies.