Low-current hollow cathode evaluation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76856/1/AIAA-1999-2575-648.pd

Parametric investigation of orifice aspect-ratio on low current hollow cathode power consumption

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76725/1/AIAA-1998-3345-942.pd

Thermal Characterization of a Hall Effect Thruster

The thermal characteristics of a Hall thruster directly influence thruster and spacecraft design. High temperatures affect the magnetic coil capabilities and cause higher insulator erosion rates, influencing both thruster performance and lifetime. The Hall thruster transfers heat through both radiation and conduction, and the spacecraft must handle this additional thermal energy. An infrared camera provides a non-intrusive method to analyze the thermal characteristics of an operational Hall thruster. This thesis contains the thermal analysis of a Busek Co. Inc. 200 W Hall thruster, using a FLIR ThermaCAM SC640 infrared camera. The Space Propulsion Analysis and System Simulator Laboratory at the Air Force Institute of Technology on Wright-Patterson Air Force Base provided the location for thruster set up and operation. The infrared camera furnishes the surface temperatures for the entire thruster, and approximates the transient heating behavior during start up, steady state, and shut down. Thermocouples verify and correct the camera data. Experimentally determined emissivities characterize the materials of the thruster. In addition, a view factor analysis between the camera pixels and the alumina sprayed portion of the cathode determines the exchange of radiation between the pixels and cathode surface. This process develops a technique to map surface temperatures of complex geometries with confidence in the actual values. Accurately mapping the surface temperatures of a Hall Effect thruster will improve both thruster efficiency and lifetime, and predict the thruster\u27s thermal load on a satellite

Evaluation of low -current orificed hollow cathodes.

The research presented in this dissertation aims to scale orificed hollow cathodes for low-current electric propulsion applications. To realize the same effectiveness as 1-kW class electric propulsion systems, sub-300-W class thrusters require cathode power consumption of a few Watts at most. A number of 3.2-mm outer diameter cathodes were fabricated from designs based on scaling existing 6.4-mm diameter cathodes to low-current. A parametric experimental investigation examined the role of cathode geometry and materials in determining the power consumption. A thermographic investigation concluded that conduction was the primary heat loss mechanism from the cathode tip. Both the internal and external plasma environments were mapped, and the results were used both to study the electron emission processes and to validate the predictions of a hollow cathode model. In order to quickly evaluate the merits of a particular design, a hollow cathode model was developed based on previous works. The model predicted the plasma properties in the insert and orifice regions of the hollow cathode. From these properties, power consumption was estimated, and the factors limiting the cathode efficiency were examined. The results of the experimental and theoretical investigations were used to design a second-generation cathode which consumed twenty percent less power than its predecessors. The second-generation cathode operated in spot-mode consuming as little as 8-W or requiring a flow rate of only 0.6-sccm.Ph.D.Aerospace engineeringApplied SciencesPlasma physicsPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132119/2/9959746.pd