A Practical Solid-Propellant Micro-Thruster

Abstract

Miniaturization of solid-propellant thrusters is an area of active research that has been motivated by the reduction in size of aerospace systems and the advancement of micromachining techniques. Though this micro-propulsion problem seems simplistic compared to the macro-scale counterpart, an efficient and reliable device has yet to be produced. A millimeter-scale novel composite solid-propellant thruster design that builds on pervious work [1] and increases efficiency is here presented. Current designs made primarily out of silicon suffer from high thermal losses and, in extreme cases, flame quenching due to the augmented surface area to volume ratio associated with miniaturization. Moreover, the reduced device dimensions drive the combustion reaction to complete outside of the thruster, misemploying the majority of the chemical energy. This occurs because the propellant mixing and chemical time do not scale with size, while the residence time does decrease as the size of the thruster decreases [2]. A novel thruster design that increases the propellant residence time is being characterized using ammonium perchlorate/binder composite propellant. The thruster geometry recycles thermal energy to the unburned propellant grain increasing its temperature and, therefore, burning rate and combustion efficiency. In addition, propellant formulation has been optimized for the thruster minimization.