Space Environmental Testing of Novel Candidate Materials for Multilayer Insulation

Abstract

Multilayer insulation forms the outer barrier of a satellite towards space. Polymer foils used in multilayer insulation have to withstand the space environment for mission durations often lasting well above 10 years. This paper outlines the space environmental test campaign performed to qualify novel and advanced polymer foils to reduce blanket mass and replace export-controlled materials. Complete multilayer insulation layups were irradiated; these were composed of thicker outermost layers of the reference material Kapton®, a white polyimide and an alternative, conductive black polyimide and up to seven thin internal, aluminized or polyethylene terephthalate and polyethylene naphthalate layers separated by nonwoven spacers. One sample set consisted of polyether-ether-ketone foil and internal vacuum-deposited-aluminum-coated polyether-ether-ketone layers. Materials were exposed to ultraviolet, electrons and protons simulating a 15-year geostationary orbit mission. Absorptance was measured at various stages in situ during the exposures, and emittance was measured ex situ at the beginning and end of the test. With tensile testing, exposure influence on foil mechanical properties was determined and compared with pristine and reference materials. Although the white polyimide was sensitive to ultraviolet and showed strong degradation after ultraviolet and proton exposure, degradation of all other materials was within expected limits and compatible to state-of-the-art foils.