Design and initial tests of a low power radio-frequency electrothermal thruster

A low power radio-frequency electrothermal thruster was designed to operate at approximately 100 watts, using inductive coupling to deliver the electrical power to a gaseous propellant injected into a 1-cm diameter quartz tube chamber. Initial cold-flow and hot-fire tests were performed on the thruster under vacuum with helium propellant to evaluate its performance from measurements of mass flow, chamber pressure, and forward and reflected power. The results suggest substantial improvements are necessary to make this a viable electrothermal thruster. Thus far, it has fallen short of the goal of reaching chamber pressures of one atmosphere by about 50%, the most apparent problem being the insufficient transfer of power to the discharge.