In Situ Utilization of Water as a Propellant for a Next-Generation Plasma Propulsion System

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A. Schwertheim et al. (2019), JBIS72, pp.7-11

Refcode: 2019.72.7

Abstract:
We propose that a Hall Effect styled electric propulsion system could be optimized to operate on the oxygen and hydrogen generated by the electrolysis of water in space. Water is an ideal propellant to benefit from In Situ Resource Utilization, due to it being found abundantly throughout the solar system. In comparison to other electric propellants water is easily storable at high densities, non-toxic and inexpensive. By operating the neutralizing cathode of the electric propulsion system on the hydrogen, and operating the anode on the oxygen generated from electrolysis, the poisoning effect of the oxygen plasma is mitigated. The fitness of oxygen as an electric propellant using plasma simulation tools is assessed. A zero-dimensional plasma kinetic Boltzmann solver called ZDPlasKin is employed to simulate the plasma chemistry interactions of oxygen under the plasma conditions within a typical Hall Effect Thruster (HET). We find that the main source of energy loss in the ionization of O2 is due to the dissociation and subsequent electrical excitation of the particles. A plasma is simulated with a particle density of 1014 m-3 O2 molecules, and a seed electron population with a temperature in a Maxwellian distribution cantered at 10 eV. Once steady state is reached, 32% of the particles are ionized to either O2+ or O+. We present PlasmaSim, a novel particle-in cell-plasma simulation tool which we validate against ZDPlasKin for a xenon plasma. When modelling a SPT-100 HET operating on 5.5mgs-1 of xenon, our current version of the code predicts an Isp of 1550s, a thrust of 83.6mN, and breathing mode oscillations at 18.2kHz, which are all in agreement with experimental results found in the literature.