Plasma Detachment Mechanisms in Propulsive Magnetic Nozzles
Final rept. 7 Mar 2012-6 Mar 2013
UNIVERSIDAD POLITECNICA DE MADRID (SPAIN)
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A 2D fluid model of the helicon source has been derived and matched to a similar model of the magnetic nozzle. Attention has been given to the 2D neutral depletion and the plasma confinement from rear and lateral walls of the source. Source performances are given in terms of the propellant utilization and production efficiency. Ranges of design and operational parameters for optimal performances are identified. Analytic solutions compare well with numerical solutions within appropriate parametric ranges. The matching of the source model with a divergent MN model has allowed the first complete characterization of the plasma discharge in a helicon plasma thruster. Additionally, it has allowed to solve a previous inconsistency in relating the plasma temperature with the absorbed power, which turns out to involve the plasma expansion in the MN. The different contributions to the thrust and the energy balance have been analyzed. Encouraging values of the thrust efficiency are obtained. Further work should try to couple this plasma flow model with a 2D model of the plasma-wave interaction, in order to ascertain the validity of the assumptions made in the flow model here or how they should be modified. For instance, a non-Maxwellian distribution function of electrons could modify the results. Also, a downstream plasma detachment model would allow us to avoid the downstream plate included here.
- Electric and Ion Propulsion