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978-3-8439-1548-9, Reihe Physik
Feasibility of a down-scaled HEMP Thruster
115 Seiten, Dissertation Justus-Liebig-Universität Gießen (2013), Softcover, B5
Many on-going and planned ESA science and Earth Observation missions are based on precision attitude control and formation flying. All these missions impose strong requirements on propulsion system which should provide low thrust, low noise, and high precision thrust vectors in up to 16 directions. Also as the most of these missions have a platform with limited solar cell arrays, the power consumption of the propulsion system should be as low as possible.
The idea of using a small High Efficiency Multistage Plasma (HEMP) thruster system for such missions is very attractive due to the relatively low complexity and low system mass. So the ability of down-scaling a HEMP-T to the μN range is investigated experimentally in the current document.
Using optical spectroscopy, the electron temperature of the plume is derived. The influence of housing material on the operation space and beam profile is characterised. The positive effect of a ferromagnetic housing on the beam profile is observed due to the shielding of the magnetic field. Nevertheless, a strong limitation on the operation space was noticed which impedes a wide dynamic thrust range.
A measurement campaign studying systematically the influence of the geometrical dimensions of the essential thruster parameters on operation, beam profile and ion acceleration is presented. Additionally, the anode material was varied and showed relevance to ion acceleration distribution. A possible approach to increase the dynamic thrust range by applying an additional potential was studied (post-acceleration) which shows promising advantages.
A basic model to calculate the electron trapping in the magnetic field was developed and applied to a common μHEMP thruster with and without magnetic shielding. So the most relevant areas for thruster operation are identified and the major difference between the two housing materials is shown. The work closes with a discussion about the feasibility of a μHEMP thruster which uses the results of the measurements. In the outlook further studies are proposed to gain a deeper understanding of the thruster operation.
Interesting options to reduce thrust and retain the high efficiency of a HEMP thruster are found, but since complex processes are involved, further studies are necessary.