Electric propulsion devices are rapidly replacing traditional chemical rockets on government and commercial spacecraft. Electric propulsion devices possess a combination of high specific impulse and high thrust efficiency that drastically reduce the mass of propellant required to perform a specific mission. Satellite operators leverage these characteristics to reduce the mass and related size of a spacecraft while maintaining its payload capability. Thus, the same on-orbit capability is achieved at a signicantly lower launch cost. Concurrently, NASA uses electric propulsion to execute missions that are not possible with chemical rockets. The drawback of electric propulsion is that the thrust level is limited by the electrical power available on the spacecraft. Thus, the required operational life of contemporary electric propulsion devices is thousands of hours.
The Hall effect thruster (HET) is a type of electric propulsion that has a high thrust density. HETs are routinely flown on geosynchronous spacecraft. Currently, HET development requires expensive, high-risk, ground-based qualification tests that exceed 7,000 hours to demonstrate the necessary on-orbit lifetime. To date, modeling efforts have been unable to predict the dominant failure mechanism observed in HET qualification tests. In particular, how quickly is the ceramic HET discharge channel eroded by the accelerated plasma?
In response to this issue, the Air Force Office of Scientific Research (AFOSR) has initiated a research program to study plasma-wall interactions. This presentation discusses an AFOSR-sponsored effort to develop a fundamental understanding of how the HET discharge plasma erodes the boron-nitride discharge channel. This knowledge will facilitate our ability to predict HET lifetime and will influence the design of future high-power HETs.
