PRELIMINARY DESIGN OF A MICRO-SCALE SOLAR THERMAL PROPULSION SYSTEM

*The authors have previously demonstrated how a micro-scale solar thermal engine, using storable propellants and simplified subsystems, can provide small spacecraft (20-400 kg) with significant orbital transfer capabilities, sufficient for geosynchronous orbit insertion, lunar, and interplanetary missions. Such missions have long been considered to be beyond the reach of small satellites; the vast majority of applications have focused on activities in Low Earth Orbit. This paper notes several mission applications of interest and their likely requirements, outlines key trades and decision points in the micro-scale engine design process, and provides a rationale for selected engine configurations. Propellant and propellant storage system selection, solar concentrator materials and structural configuration, solar receiver materials and heat transfer characteristics, and the ramifications of the design for the host satellite’s testing and on-orbit operations discussed in detail. The performance of the baseline solar thermal engine is compared to several competing concepts, including chemical monopropellant and bipropellant schemes.