Solar Sail Propulsion Limitations Due to Hydrogen Blistering

Metallized thin films are commonly considered for solar sail membranes operating in the interplanetary space. A key characteristic of this environment is the solar wind, with its charged low energy <10 keV particles. Aluminum subjected to low energy protons undergoes recombination processes between protons and metal electrons, resulting in the formation of blisters on the surface. Blistering results in degradation of the reflective properties of the solar sail membrane. Specimens were tested at environmental conditions derived from a conceptual sub-L1 mission. They were exposed to 2.5 keV protons at temperatures between -176 degrees C and 113 degrees C. The exposed samples exhibited visible color changes; from shiny metallic to dim light gray. Reflectivity measurements revealed reductions in specular reflectance, which results in changes to the propulsion characteristics of a sailcraft subjected to similar environmental conditions. (C) 2020 COSPAR. Published by Elsevier Ltd.