  Near-sun space-environment effects on metallic thin films solar sails as well
as hollow-body sails with inflation fill gas are considered. Analysis of
interaction of the solar radiation with the solar sail materials is presented.
This analysis evaluates worst-case solar radiation effects during
solar-radiation-pressure acceleration. The dependence of the thickness of solar
sail on temperature and on wavelength of the electromagnetic spectrum of solar
radiation is investigated. Physical processes of the interaction of photons,
electrons, protons and helium nuclei with sail material atoms and nuclei, and
inflation fill gas molecules are analyzed. Calculations utilized conservative
assumptions with the highest values for the available cross sections for
interactions of solar photons, electrons and protons with atoms, nuclei and
hydrogen molecules. It is shown that for high-energy photons, electrons and
protons the beryllium sail is mostly transparent. Sail material will be
partially ionized by solar UV and low-energy solar electrons. For a hollow-body
photon sail effects including hydrogen diffusion through the solar sail walls,
and electrostatic pressure is considered. Electrostatic pressure caused by the
electrically charged sail's electric field may require mitigation since sail
material tensile strength decreases with elevated temperature.
