Solar Sail Propulsion Modeling

A parametric tool for comprehensive evaluation of solar sailing thrust influences has been developed. The propulsive performance of a quadrant solar sail system has been evaluated, with consideration of specular and diffuse reflection based on the sailcraft-to-sun angles of cant and spin and local topology, together with thermal emission based on thickness and temperature. The optical properties used are based on hardware and test experience gained during the NASA In-Space Propulsion 20-m system ground demonstration program. Global topology definition, including billow and structural wrinkling, was input from FEA models of an 80-m solar sail system for 3 operating stress levels. Tabular and normalized results, and curve fit approximations to the detailed performance trends are presented, along with discussion. It was shown that the thrust behavior predicted by detailed modeling can be closely approximated by a simple sail model with an appropriately chosen effective reflectivity for each component of the total thrust vector. I. Nomenclature A = area of sail au = astronomical unit (the distance from the sail to the sun, ~ 150e6 km) a/λ = amplitude to wavelength ratio of local surface topology features α = sailcraft cant angle β = thrust bias (β = α - θ) δ = sailcraft clock angle θ = angle between thrust vector m and the sun line (X) n = sail normal vector m = thrust unit vector