Propulsion mechanisms in a helicon plasma thruster

Abstract

Electric thrusters offer an attractive option for various in-space propulsion tasks due to their high thrust efficiencies. The performance characteristics of a compact electric thruster utilizing a helicon plasma source is investigated with the goal of identifying potential thrust mechanisms. Performance characteristics such as thrust, specific impulse, ion cost and thrust efficiency are discussed and related to plasma parameters. The design and fabrication of a prototype compact helicon thruster is presented, including design of a radio-frequency power delivery system, electromagnets and a propellant flow system. The design of plasma diagnostics and associated measurement techniques are discussed including a retarding potential analyzer, mach probes and langmuir probes. These diagnostics are used to measure plasma properties such as electron temperature, plasma density, and ion flow velocities. Thruster performance characteristics are then derived from these measurement results. Significant ion acceleration is demonstrated in both Argon and Nitrogen plasmas and potential mechanisms for this are discussed.