A thruster head of a water-vapor Hall thruster with a discharge channel of 15 mm in diameter and 5 mm in width was designed and developed by applying the conventional scaling law to a previously studied laboratory model. The newly designed thruster was successfully operated at discharge powers ranging from 80 to 340 W. The thrusts were estimated from the plume diagnostics, which were validated by direct measurements using a thrust stand. As a result of the performance analysis, it was revealed that the thrust exhibited a linear correlation with the discharge power, while the specific impulse and anode efficiency also varied with the discharge voltage. Unlike other internal efficiencies, higher discharge voltages did not necessarily enhance the mass utilization efficiency, especially above 250 V. This suggests that the electron temperature is less likely to increase in the high-voltage regime, possibly due to further energy losses from additional chemical processes or wall interactions.
Shirasu et al. (Thu,) studied this question.