Ultraviolet and Vacuum-Ultraviolet Radiation Effects on Spacecraft Thermal Control Materials

Abstract

Ultraviolet (UV) and vacuum ultraviolet (VUV) light has been found to contribute significantly to materials degradation in earth orbiting spacecraft. UV/VUV radiation is ubiquitous, occurring at all orbital altitudes and, while the effects of degradation sources such as atomic oxygen may be more pronounced at certain altitudes (e.g. low earth orbit), damage due to UV/VUV radiation will be present in all orbiting vehicles. Of the materials used in spacecraft construction thermal control materials (e.g. blankets and paints) show the most significant degradation due to UV/VUV exposure. This degradation manifests itself as surface erosion in polymers and as an increase in absorptivity (darkening) in both polymers and thermal paints. It is this change in absorbance that compromises the thermal control properties of the materials. The temperature of the spacecraft is proportional to the ratio of its solar absorptivity (αsolar) to its emissivity (∊).