Computational and experimental characterisation of water-fuelled hall effect Thrusters

In this thesis, the use of water as a propellant for Hall Effect Thrusters (HETs) as an alternative to conventional xenon-fuelled HETs is explored. This is motivated by water’s cost-effectiveness, multifunctionality, environmental benefits, and potential for In-Situ Resource Utilisation. Two propulsion methods are investigated: 1) water electrolysis propulsion, where oxygen and hydrogen are generated by a water electrolyser on board a spacecraft, and 2) a direct water vapour feed. A Particle-In-Cell computational model is developed to simulate water-based HET operation, incorporating all key propellant reactions and most-recent techniques to improve fidelity. The experimental tests progressed from oxygen-fuelled HETs with krypton cathodes to the first end-to-end water electrolysis system directly fuelled by a water electrolyser (i.e., an oxygen-fuelled HET in combination with a hydrogen-fuelled cathode). The first and second generation of water electrolysis HETs, referred to as WET-HET and AQUAHET, are tested and optimised to achieve the best possible performance; with AQUAHET showing a Δηtr = 20% higher thrust efficiency for the same operating power. In the best-performing case, the AQUAHET produced a thrust of T = 51.0 ± 0.3 mN, anode specific impulse of Isp = 3119 ± 27 s, and anode thrust efficiency of ηtr = 24.4 ± 0.3 % at a discharge power of Pd = 3200 ± 1 W, whereas for the WET-HET it was obtained a thrust of T = 21.5±0.4 mN, Isp = 3617±69 s, and ηtr = 17.1±0.7 % at Pd = 2232±1 W. Tests using hydrogen as a cathode propellant yielded a Δηtr = 10% efficiency drop compared to krypton. Water-vapour propulsion is also assessed, with water electrolysis showing a Δηtr = 20% efficiency advantage. Additionally, radiofrequency excitation is investigated as a mechanism to improve the efficiency of these systems. This work presents the most up-to-date comprehensive assessment of water-fuelled HET propulsion...