Fluid modelling of magnetoplasmadynamic thrusters

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This document aims to describe the state of the art and some basic physics of self-field Magnetoplasmadynamic Thrusters (MPDT), which constitute a very interesting technology for high power (Megawatt range) space propulsion. The Thesis starts discussing the frame and expectations for electric space propulsion and the different categories of devices. Then, the operational principles and the literature background of MPDTs are briefly reviewed. The central part of the Thesis is devoted to understand and model the plasma production and acceleration processes in the MPDT chamber. A two-step progress is followed, materialized in two mathematical models. The first, the simplest one, describes the axial acceleration of a fully-ionized, hypersonic plasma beam. This allows getting familiar with main physical phenomena, dimensionless parameters, performances, parametric investigation, and mathematical methods to deal with a boundary problem of a set of algebraic-differential equations. The second model adds the neutral gas population and the multiple collisional processes taking place in the discharge, and aims to reproduce the whole plasma production stage in addition to the accelerating one. The mathematical formulation of the model is much more complex and rigorous, and the numerical integration is challenging because of the presence of singular/sonic transitions at intermediate points, the presence of terms of very different orders of magnitude, and the stiffness of boundary condition fulfilment with respect to parametric variations. A Matlab code has been totally built for this model. The comparison of the two models reveals excellent similarity and validates the two-step method followed. Further work should deal with radial dynamics and total energy balance considerations.
Astronáutica, Física del plasma, Propulsión eléctrica, Propulsores
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