Online

Heffernan, Thomas Joseph

Mechanical Engineering

2020

M.S.

In the interest of mitigating high launch costs, small satellites are often chosen as secondary payloads during launch operations. Their lower mission importance dictates stringent restrictions on the propulsion systems which can be implemented as they cannot contain combustible or toxic agents; a common solution to this problem is implementation of micronozzles with cold-gas propellants in order to generate thrust. The present research explores the efficacy of leveraging microwave-assisted decomposition of a 'green' chemical blowing agent, namely Azodicarbonamide, as a propellant for use in a microthruster. The thermal evolution of a heterogeneous ferromagnetic-doped propellant is analyzed numerically using COMSOL Multiphysics in a microwave cavity. Simulation results utilizing and effective medium approximation are then compared against experimental decomposition times for various particle loading percentages using a conventional 2.45GHz multi-mode microwave and the decomposition timescale is assessed for microthruster implementation. Finally, the sensitivity of the model to material dielectric properties is considered and analyzed. Initial thermal modeling showed a promising heating timescale, though experimental results demonstrated a larger time scale than useful in existing micropropulsion concepts. The system demonstrates promising capability for green, non-combustible pre-pressurization but does not meet thruster implementation requirements; this may change due to the rapidly evolving field of microwave-heating, particularly where heterogeneous ferromagnetically-doped mixtures are concerned.