Thrust Stand Measurements of the Conical Theta Pinch FARAD Thruster

It is found that the impulse of a pulsed inductive plasma thruster utilizing preionization is maximized for a particular ratio of the stored energy in the capacitor to the injected propellant mass. The fact that the impulse depends on the ratio of the initial stored energy to injected propellant mass agrees with previous current sheet studies, supporting the idea that a Townsend-like breakdown process strongly influences current sheet formation, and in turn, current sheet formation strongly affects the operational efficiency of the device. The optimum in half cone angle of the inductive coil can be explained in terms of a balance between the direct axial acceleration and the radial pinching contribution to thrust. From the trends in these data we conclude that operation at the correct ratio of capacitor energy to propellant mass is essential for efficient operation of pulsed inductive plasma thrusters employing a preionized propellant.