Thermal analysis of space station windows in low Earth orbit. Intermaterial comparison of fused silica and acrylic glass

Calculating the temperatures of windows of space stations in Low Earth Orbit (LEO) is crucial for ensuring their structural integrity. We present a comprehensive thermal analysis that considers direct solar radiation, Earth’s albedo effect, infrared radiation from the Earth and convective heat exchange with the internal environment. The thermal balance equation incorporates the time variation of these contributions due to orbital motion for windows with different orientations, to determine the temperature of the materials, factoring in key parameters such as absorptivity, transmissivity, reflectivity, and their dependence on the radiation wavelength spectrum. Referring to the conditions of the Cupola of the International Space Station as a paradigmatic example, we compare the thermal performance of two common window materials: fused silica and acrylic glass. Our results indicate that the higher transmissivity of fused silica makes it insensitive to solar and albedo radiation, reducing temperature values and their dependence on plate thickness and exposure variability due to orbital motion. In contrast, the higher absorptivity of acrylic glass results in much higher temperatures, proportional to the thickness, with a cyclical dependence on the orbital period. This analysis provides insights for the design and selection of window materials in space station construction, ensuring their durability and functionality in the conditions of LEO.