Influence of the magnetic field configuration on the performance of Helicon thrusters

The Helicon thruster (HT) is an innovative concept of electric propulsion system designed for in-space applications. The thruster relies on a Radio frequency antenna that effectively ionizes the propellant and excites helicon waves in the plasma. The antenna is thus able to heat the plasma, which then expands through a divergent magnetic field. Since no moving components or electrodes are needed to accelerate the propellant, the HT design significantly improves the thruster lifetime with respect to other electric propulsion systems. However, a low power efficiency was measured during the experimental campaigns carried out on HT prototypes. The present Thesis investigates the influence of the magnetic field configuration on the HT performance and analyses technological solutions to significantly increase the efficiency of a low-power HT. The typical thruster configuration comprises two different region: the plasma source (where the plasma is generated) and the magnetic nozzle (where the internal energy of the flow is transformed into kinetic energy). In order to reduce the power losses to the rear surface of the plasma source, in the present Thesis an axial magnetic shield is added to the standard magnetic configuration. An accurate description of the plasma behaviour is presented for each of the three region of the Helicon Thruster. The model equations, which assume that the plasma is ideal, perfectly magnetized and non-inductive, are then numerically solved. Scaling laws of an ideal Helicon Thruster are derived to analyze the effects of the magnetic field intensity. The power efficiency of the Helicon Thruster is finally evaluated as a function of the magnetic field configuration. The performed numerical investigations show that the magnetic shield improves the thruster performance, offering the possibility to reach a power efficiency higher than 50%

Lunar Propellant Factory Mission Design To Sustain Future Human Exploration

The International Space Exploration Coordination Group (ISECG) Global Exploration Roadmap (GER) is the standard document reflecting the current focus of the leading space agencies that envision space exploration missions beyond Low Earth Orbit (LEO), returning to the Moon and going to Mars in the upcoming years. The roadmap showcases the Moon as a stepping-stone for further human space exploration, by setting up a sustainable space infrastructure on its surface an orbit. Inspired from this vision, we present the result of a phase A study about a lunar propellant factory near the Shackleton south-pole crater relying on In-Situ Resources Utilization (ISRU) to produce and sell Liquid Oxygen (LOX) on the moon surface and in orbit. The overall timeline of the mission is in line with the ISECG exploration roadmap Moon phase, based on realistic technologies of advanced-enough Technology Readiness Levels (TRL). It is a second iteration on the Lunar Propellant Outpost (LUPO) mission architecture, presented during IAC 2018. We preserved and reviewed the original building blocks (Habitats, Crew Mobility Elements, ISRU Facilities, and Lunar Spaceport) of the LUPO mission architecture, and further improved the mission design, supported by trade-off analysis on different mission scenarios. An extensive analysis and optimisation have been performed on ISRU processes and surface electrical power management, the core of our infrastructure. The mission architecture also includes crew on the lunar surface, so life support systems and habitat, as well as operations concepts, have been studied in-depth, and a synthesis of all results is presented. The main aim of this iteration was to improve and refine the baseline infrastructural and technological design architecture of LUPO and reflect on missions going beyond the Moon by providing refuelling services, with sustainability and economic viability in mind