Spectroscopy of Chamber Plasma and Plume of a 2.4-GHz Microwave Electrothermal Thruster
Open Access
- Author:
- Feng, Vincent
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- October 31, 2022
- Committee Members:
- Amy Pritchett, Program Head/Chair
Sven G Bilén, Thesis Advisor/Co-Advisor
Robert G. Melton, Committee Member
Jesse Kane Mc Ternan, Committee Member - Keywords:
- MET
Electric Propulsion
Spectroscopy - Abstract:
- The microwave electrothermal thruster (MET) is an electric propulsion device that utilizes a cylindrical electromagnetic resonant cavity operating in a mode that maximizes the electric field near the end plates to heat a propellant gas that is exhausted through a converging–diverging nozzle. The 2.45-GHz MET developed in the 1990s at The Pennsylvania State University has been a workhorse supporting research on understanding the physical processes that occur in this type of thruster. It has been operated at different microwave power levels, propellant types, chamber pressures, and antenna heights. With an internal diameter of 10 cm and an internal height of 15.75 cm, the larger size of the 2.45 GHz MET (compared to higher frequency versions) is conducive to characterizing the plasma generated inside the chamber and in the exhaust plume The research presented in this thesis is toward a non-intrusive optical diagnostic that can measure heavy-particle temperature and electron density of the plasma in both the MET’s cavity and plume. Understanding the properties of this plasma is essential to understanding how the plasma heats the propellant, which is related to thruster efficiency, specific impulse, and thrust. A better understanding of these aspects of the MET will enable the design of flight-ready METs. This work has developed a system for using optical emission spectroscopy to characterize the heavy particle temperature and the electron density of the plasma. Due to inadequate spectrometer resolution and firing of the MET into air rather than in a vacuum, accurate heavy-particle temperature and electron density of the plasma could not be found. However, a method is described and code has been developed for finding an accurate heavy-particle temperature and electron density of the plasma with the use of a higher resolution spectrometer. In addition, simulated data has generated promising results using the methods described in this thesis.