Controllable nanoparticle radiative properties for high-turndown ratio heat rejection

Heat rejection systems in spacecraft are limited to rejcting heat via radiation only. This limitation to one mode of heat transfer coupled with the dynamic sink temperatures experienced during orbit result in either oversized devices or widely varying temperature conditions of the radiator. This issue results in a desire to create a radiatior capable of dynamically adjusting the amount (e.g. turndown) of heat rejection. Proposed methods for achieving high levels of turndown include mechanical louvers, electro- and thermochromic radiators, and two-loop systems. Most of these systems rely on additional control systems to ensure turndown occurs. Here we propose a novel system that passively controls heat rejection through the integration of a system with multifunctional nanoparticles with controllable radiative properties. The system is theoretically analyzed to demonstrate the performance that could be achieved by such a device.