ETD

• air-breathing
• cubesat
• electric propulsion
• multi-cusped magnetic field
• plasma thruster
• very low earth orbit

The utilization of Very Low Earth Orbits (VLEOs) offers extensive advantages for satellites payload performance and mission cost, but requires propulsion systems capable of constantly operating to counteract the atmospheric drag. While traditional electric thrusters are ultimately limited by their onboard propellant capacity, Air-Breathing Electric Propulsion (ABEP) systems propose to continuously collect the encountered atmospheric gases and use them for propulsion.
This thesis presents the design of a CubeSat scale Multi-Cusped Field Thruster (MCFT) specifically optimized to operate in air-breathing conditions, facing the challenges of a low mass flow rate and a propellant both corrosive and difficult to ionize. The MCFT concept represents a potentially convenient selection for small scale ABEP thanks to its high plasma confinement and versatile operations, while maintaining an overall simple architecture.
A basic scaling methodology is proposed and employed to define the discharge channel dimensions solely from the thruster requirements and a suitable reference. Channel diameter and propellant flow rate scaling laws, based mainly on the thruster power level, are verified with experimental data from literature.
An optimized design for the Periodic Permanent Magnet (PPM) system is obtained by targeting magnetic field characteristics related to better thruster performance, such as high magnetic mirror ratios and a flat exit separatrix, through magnetostatic simulations on FEMM software.
A modular mechanical design is achieved to enable the experimental characterization of different thruster configurations, allowing for a change in the number of magnetic stages and their length with a limited amount of total components. An high transparency annular anode and an upstream opened channel geometry are also employed, making possible to test the thruster in both pipe-fed and air-breathing mode with the same ceramic channel and unchanged anode geometry. A thermal verification of the thruster design is accomplished through numerical simulations on COMSOL Multiphysics, ensuring operating temperatures compatible with the magnets and the other materials.