Cryogenic Deep Space Thermal Control Coating

Abstract

This paper describes a thermal control coating that should allow non–heat-generating objects, such as cryogenic tanks and superconductors, to reach and maintain cryogenic temperatures in deep space locations far from the infrared (IR) emission of a planet and at least 1 astronomical unit from the Sun. This new coating is designed to reflect nearly all of the Sun’s irradiance, while still permitting far-IR emission, allowing steady-state temperatures as low as 50 K to be achieved. A brief background on currently available thermal control coatings is given, followed by a discussion on how this new coating circumvents the limitations of the state-of-the-art approaches. The theory behind these new coatings is reviewed, followed by models yielding predicted emissivities over broad spectral ranges. From this, the predicted steady-state temperatures for different coating thicknesses, materials, geometries, and environments are obtained. Experimental data are provided on two versions of this coating in a low-fidelity deep space environment, substantiating the predicted performance. The final section presents a straw-man model showing how these coatings could be used to facilitate the transport of liquid oxygen to Mars.