Abstract
Electric Propulsion (EP) systems can enable novel spacecraft missions requiring high total change in velocity, owing to their high specific impulse compared to chemical propulsion systems. Mature devices, such as Hall Effect Thrusters (HETs), have accumulated significant flight heritage. How- ever, established technologies do not satisfy the requirements of the rapidly growing small satellite sector, because of adverse scaling to low powers. The Halo thruster concept falls within the cat- egory of Cusped Field Thrusters (CFTs), aimed at addressing this issue. The concept concerns the use of ‘magnetic null regions’, formed through the deliberate cancellation of magnetic fields. Two such regions are produced in the thruster, a ‘null point’ at the thruster exit and an annular ‘halo’ near the anode. The work presented in this thesis has provided foundational knowledge of the performance and internal physics of the Halo thruster, using a 5 cm channel diameter, electromagnet laboratory model. Measurements of thrust, specific impulse and thrust efficiency were obtained over a wide range of operating conditions using a pendulum thrust balance in representative high vacuum, and the sensitivity of the measured performance to facility effects was assessed. Trends in plasma potential, electron temperature and plasma density internal to the discharge channel were obtained using a translating Langmuir probe, allowing the basic physics of operation of the device to be inferred. The thruster was found to exhibit comparable performance to other CFTs, with measurements shown to be robust to facility effects. Internal plasma measurements revealed behaviour similar to that of the Cylindrical Hall Thruster, with some differences due to the presence of the halo magnetic null region near the anode which might be exploited to improve performance. As a result of the research presented, design changes are suggested for future iterations. In its current embodiment, the thruster already offers advantages over heritage small satellite EP systems, and is a viable candidate for near-term industrialisation.