Development and Test of a Superconducting Helicon Plasma Thruster

Abstract

Helicon thrusters have emerged as a viable technology for station-keeping and deep-space exploration applications due to their high-efficiency plasma generation and amenability to propellants such as water vapor. A proposed design and performance analysis for the superconducting helicon thruster is presented. First, a zero-dimensional power flow analysis is performed, demonstrating an increase in the power efficiency for the superconducting helicon thruster versus the baseline helicon plasma thruster. This superconducting helicon thruster is composed of two subsystems: the superconducting magnet subsystem and the thermal management subsystem. The superconducting magnet subsystem shows that by using the combination of a solenoid and permanent magnet, a desirable magnetic field geometry for a helicon plasma can be supported. By adding a high-temperature (type-II) superconductor, the induced current in the superconductor that results from quenching the solenoid can sustain the same magnetic field geometry without the need to continuously power the electromagnet. The thermal management subsystem then maintains cryogenic temperatures in a closed-loop design for continuous operation of the thruster. A triple Langmuir probe was used to experimentally characterize the bulk plasma, and the downstream ion energies were measured with a retarding potential analyzer (RPA). Using the measured electron temperature and ion energies, it was shown that the baseline helicon thruster demonstrates slightly better performance metrics, however this comes at the cost of lower propulsive efficiencies. In instances where maximum thrust and maximum specific impulses are desired, the baseline helicon thruster would be more advantageous. If RF input power mitigation is of larger concern, the superconducting helicon thruster outperforms the baseline helicon thruster. Additionally, substantially larger ion beam energies were measured using the RPA compared to other independent studies. This anomalous acceleration mechanism has the potential to provide vast improvement to the performance of the helicon thruster.