|Ph.D Student||Binyamin Rubin|
|Subject||Analysis and Numerical Experimentation of Onboard Diagnostic|
Systems for Hall Thrusters
|Department||Department of Aerospace Engineering||Supervisor||Professor Emeritus Guelman Mauricio|
|Full Thesis text|
During the last years there has been an increased interest in the use of electric propulsion on different spacecraft. High specific impulse of electric propulsion enables to increase the payload mass or life span of the spacecraft.
The Hall thruster, one of the types of electric propulsion, has become the most widely used type of electric propulsion. One of the important directions in Hall thruster research is the investigation of thruster operation in flight. The satellite environment in flight is different from the environment which exists in the laboratory. As a result there are differences in the thruster operation during flight or ground tests. In order to measure these differences it is necessary to equip Hall thrusters operating in space with different diagnostic systems. The purpose of these systems is to provide onboard real time information on the thruster operation. Moreover, diagnostic systems capable of providing information of processes inside the thruster enable identification of the reasons of possible thruster malfunctions during flight.
In the present work two methods, which enable obtaining information on the processes inside the Hall thruster during flight and are suitable for application in Hall thruster onboard diagnostic system are proposed and developed.
The first method enables measurement of the Hall current distribution in the Hall thruster acceleration channel. The determination of Hall current distribution enables to improve the understanding of the processes in the Hall thruster and to determine the approximate thrust value in real time. The method is based on non-contact measurements of the steady-state magnetic field induced by the Hall current outside the acceleration channel. The approach to Hall current structure determination is based on the inverse magnetostatic problem solution using a two-dimensional constrained regularization. Optimal number and positions of magnetic sensors are determined and the solutions using simulated measurements with and without simulated noise are obtained.
The second method of active non-contact diagnostics uses artificially excited large-scale electron gradient waves (EGW). This method enables to obtain information on the plasma parameters distribution inside the thruster acceleration channel. The waves may be excited using a small magnetic coil placed outside the acceleration channel. Using two or more sensor coils it is possible to measure the resonant frequencies of the EGW in the acceleration channel, which themselves depend on the plasma parameters distribution.
An example of malfunction identification using the proposed methods is also presented.