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Thermal control is a challenge for spacecraft as they must maintain internal components within operating limits despite significant fluctuations in external and internal thermal loads. Satellites often rely on dynamic thermal control to manage internal temperatures depending on the thermal environment. However, many of these systems are actively managed, relying on the satellite’s internal electronics to control the radiator’s behavior. The problem of thermal control is compounded for small satellites, such as CubeSats, which have high power dissipation per unit surface area, stringent size/weight restrictions, and reduced thermal mass. Passive thermal control is particularly attractive for such small systems, potentially offering increased reliability and simplicity. Attempts at passive, dynamic thermal control of spacecraft radiators have been demonstrated in the literature using louvers actuated by bimetallic coils and radiators deployed by shape memory alloys. In this work, we propose a dynamic thermal control method for CubeSats by using bimetallic coils to passively deploy an array of four triangular radiator fins that, when folded, comprise the external face of a CubeSat. This approach differs from previous approaches as it uses mass efficient, triangular radiative fins as well as bimetallic coils to passively actuate the panels, as opposed to shape memory alloys. The advantages of this design include reduced complexity, cost, volume, and weight when compared to traditional deployable radiators in addition to increased redundancy by using an array of panels. An experimental demonstration of the proposed design is presented indicating the ability to passively deploy a single radiator fin using custom bimetallic coils at a rate of approximately 3.9° of angular rotation per 1 °C with minimal hysteresis. A preliminary model of our design indicates the possibility to achieve a turndown ratio of greater than 7:1. Experimental and numerical prediction results are presented as a motivation for exploration of the proposed design in ongoing work. 

The ability to control radiative behavior through the angular positioning of structured surfaces (e.g. the cavity effect) offers the ability to provide thermal management in dynamic radiative environments. Structures comprised of origami tessellations offer a means to achieve angular cavities that approach black-like behavior during collapse by exploiting use of the cavity effect. Expanded origami surfaces exhibit intrinsic radiative properties while collapsed surfaces exhibit increasingly black-like behavior as the cavity aspect ratio increases. Actuation of such surfaces provides the means to achieve any apparent radiative behavior between these two extremes. This work explores the use of three origami structures (finite V-groove, hinged V-groove and Miura-ori) and their respective apparent radiative properties as a function of cavity geometry using Monte Carlo ray tracing. Results are presented as a function of tessellation geometry and degree of actuation (i.e. collapse). Ray tracing models are benchmarked with V-groove geometries for which analytical models exist in the literature. Convergence for ray independence was determined to be satisfactory when the standard error of the mean for every test case was less than 0.005. Deviation in the apparent absorptivity for finite V-groove relative to the infinite V-groove is quantified. The apparent absorptivity of the Miura-ori fold exhibits sensitivity to the fold geometry when the angle of the unit cell is varied, but is relatively insensitive to the length ratio of the panel. The variable nature of the net radiative heat transfer, achievable through actuation, affords a method for thermal management of components with variable heat dissipation and/or variable radiative environments.