RF PLASMA THRUSTERS FOR SMALLSAT APPLICATIONS

The following is the first of a series of tests, dedicated to determining the feasibility of using the RF glow discharge phenomenon for a low power propulsion system. The main goals of this preliminary study are to explore electrode wear and characteristic operating parameters such as frequency, RF power, mass flow rate and gap distance. The RF thruster concept is characterized by a low-power RF glow discharge established between co-axial electrodes, analogous in design to an arcjet thruster. RF power sustains the plasma and ‘suspends’ charged particles within the electrode gap. The time duration of a half cycle does not allow the statistical majority of ions and electrons in the electrode gap to transverse the gap distance before the polarity reverses and causes the charged particles to be attracted in the opposite direction. The glow discharge is powered by an RF power supply encompassing a frequency range between 10 and 175 MHz. The power delivered to the glow discharge is in the range of 20 to 110 W and depends on the particular settings of the fundamental operating parameters. This paper explored the issue of electrode damage that may be caused by a glow discharge and compared it to DC glow discharge with equivalent operating conditions. In addition, it discusses the approach to a sensitivity study exploring the relations between the fundamental operating parameters (frequency, power, mass flow rate, and gap distance) and temperature.