Evaluation and Analysis of Thermal Control Materials under Ground Simulation Test for Space Environment Effects

Abstract

Thermal control materials such as white paint comprising silicone resin matrix (NASDA-1049/101-S), black paint comprising urethane resin matrix (NASDA-1049/201-U-I), aluminized polyimide adhesive tape (Sheldahl G408810) and silver-backed fluorinated ethylene propylene (silvered FEP) adhesive tape (Sheldahl G402500) were exposed to electron beam (EB), proton (H+), iron ion (Fe5+), ultraviolet (UV) and atomic oxygen (AO) radiation with ground simulation test facilities. Combined irradiation of EB → UV and another combined irradiation of EB → AO, where EB was irradiated at first and then UV or AO was irradiated, were also examined for white paint and black paint. Irradiation energies were 0.5 and 1.9 MeV for EB; 1, 3 and 10 MeV for H+; 15 MeV for Fe5+; equal to or larger than 3.1 eV for UV; and 5 eV for AO. Fluences of EB, H+ and Fe5+ were selected to simulate the environment of geostationary orbit (GEO) for 10 years. UV irradiation was equal to 300 equivalent solar days. AO fluence corresponded to the environment of low Earth orbit (LEO) for about 1 year. The solar absorptance (αS) and normal infrared emittance (εN) of the examined materials both before and after irradiation were acquired. The durability of the materials against each irradiation treatment was judged by evaluating the changes in αS and εN. White paint and black paint were strongly affected by AO, EB → UV, EB → AO and UV irradiation. White paint was also affected by EB and weakly by H+ and Fe5+. Aluminized polyimide and silvered FEP were degraded most by AO and EB. EB had a stronger effect than ions (H+,Fe5+) in all the samples, the reason for which can be explained by the larger absorbed dose with EB compared with ions. The mass loss caused by the irradiation treatment was also measured for white paint and black paint. Analytical techniques such as scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared spectroscopy (FTIR) were applied to identify morphology and composition of the materials to obtain a deeper understanding of the mechanism of space environment effects on the materials.