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Evaluating Variable-Emissivity Surfaces for Radiative Thermal Control

2022; American Institute of Aeronautics and Astronautics; Volume: 36; Issue: 4 Linguagem: Inglês

10.2514/1.t6555

1533-6808

Michael T. Barako, Austin Howes, Luke A. Sweatlock, Vladan Janković, Philip W. C. Hon, Jesse Tice, Michelle L. Povinelli, Mark W. Knight,

Spacecraft Design and Technology

Variable-emissivity materials enable "adaptive radiators" to control heat flow and regulate the temperature of spacecraft. Although most variable-emissivity engineering efforts focus on achieving the maximum emissivity contrast (a design variable), the radiator performance is ultimately determined by the resulting temperature profile of the system (the objective function). Here, these temperatures are used to define, evaluate, and optimize the variable-emissivity design space for adaptive radiators that produce desired temperature profiles under prescribed dynamic heat loads. Rather than iterating toward the asymptotic emissivity targets of zero and unity, many quasi-steady and transient systems can achieve optimized thermal control under more relaxed emissivity targets that simplify the radiator design. Examples of thermochromic radiators in dynamic operational environments are considered, where the temperature dependence of the total, hemispherical emissivity is derived from both spectrally engineered metasurfaces and phase-change materials. This reimagination of adaptive radiators shifts the design and optimization of variable-emissivity materials away from simple emissivity extrema and toward system-tailored thermal performance.