Grubisic, Angelo and Gabriel, S.B.
Hollow cathode thrust mechanisms
In Proceedings of the 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibition.
American Institute of Aeronautics and Astronautics. 24 pp.
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This paper investigates propellant acceleration mechanisms within hollow cathode thrusters based on the results of previous experimental testing. Experiments were conducted on a T5, T6 and ¼ inch cathode. An indirect pendulum micro-thrust-balance was built for the measurement of thrust production in the T5, T6 cathodes while a hemispherical energy analyzer was used for ion energy measurements in the ¼ inch hollow cathode. The data suggest that the thrust mechanism of hollow cathodes is composed primarily of gas dynamic mechanisms, particularly as a result of an intense electron pressure at the cathode exit, and magneto-hydro-dynamic (MHD) forces at high currents and very low flow rates arising from the self-induced azimuthal magnetic field within the orifice. While this initial characterization can only loosely attribute the relative magnitude each mechanism plays it does show evidence for each. Smaller cathodes, such as the T5, operate at lower currents in a more arcjet like mode and show the necessary performance and efficiency to compete with conventional propulsion systems at a mission level.
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