An experimental investigation of heaterless hollow cathode ignition
Date
2020
Authors
Ham, Ryan K., author
Williams, John D., advisor
Yalin, Azer P., committee member
Marconi, Mario C., committee member
Tomasel, Fernando G., committee member
Journal Title
Journal ISSN
Volume Title
Abstract
A hollow cathode is a specially designed plasma source that is capable of driving a large electron emission current throughout the course of a remarkably long lifetime. Given these characteristics, hollow cathodes are commonly used as electron sources in state-of-the-art plasma thrusters. Modern advancements in small-satellite technology have led to an increased demand for low-power electric propulsion systems. Given the high thrust-to-power ratio and flight-proven heritage of Hall-effect thrusters, efforts are currently being made to downsize these thrusters to a considerably small scale. By forgoing the use of a heater, heaterless hollow cathodes provide several advantages that are best realized in miniaturized Hall-effect thrusters. Unfortunately, the lack of a cathode heater gives rise to nontrivial complications in the process of igniting a plasma discharge, along with reason to believe that life-limiting cathode erosion could occur during ignition. These concerns have resulted in a lack of confidence that heaterless hollow cathode technology can endure the rigors of spaceflight qualification. In this research, heaterless hollow cathode ignition behavior was characterized. In doing so, it was found that repeatable and reliable instant start ignition behavior can be achieved when using a high propellant mass flow rate. To provide this flow condition without placing a large burden on a propellant feed system, a novel gas flow mechanism was developed and characterized. To investigate whether instant start ignition causes cathode erosion, a series of tests were performed in which heaterless hollow cathodes were subjected to a large number of ignition cycles. Microscopy revealed no indication of cathodic arc activity, and no other evidence of life-limiting erosion were observed. The instant start ignition process appears to be a viable approach to heaterless hollow cathode ignition, and we believe it provides a means for heaterless hollow cathode technology to be integrated into spaceflight propulsion systems.
Description
Rights Access
Subject
plasma propulsion
satellite technology
thruster
propulsion
electric propulsion
space technology