Interactions within a Cluster of Low Power Hall Thrusters

This work examines a long duration Hall thruster start transient caused by the vacuum chamber environment. During operation of a cluster of four Hall thrusters, large anode discharge fluctuations, visible as increased anode current and a more diffuse plume structure, occur in an apparently random manner. For single thrusters, the transient appears as a smoothly decaying elevated anode current with a diffuse plume which persists for less than 500 seconds. The start transient is characterized by severe 18 kHz oscillations which dominate the anode discharge. This contrasts with typical steady state behavior of a strong DC component overlaid with a low amplitude 25 kHz component. The main discharge chamber has been previously determined to be the source of this behavior. The work shows that transient appears to be a result of the release of water previously hydrated on to on the surface layer of the boron nitride acceleration channel insulator. This material is a declared work of the U.S. Government and is not subject to copyright protection in the United States . 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 20-23 July 2003, Huntsville, Alabama AIAA 2003-5006 This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. 2 thrust and impulse from an initial short duration firing. For this reason, understanding the characteristics of this anode current start transient may also be important for missions with short duration initial firings.