Improved Method for the Estimation of Spacecraft Free-Molecular Aerodynamic Properties

A numerical procedure for calculating free-molecular aerodynamic properties of spacecraft is revisited and redeveloped using improved discretization and shading techniques. New complex geometric shapes are included, allowing the user to model a high-fidelity spacecraft model divisible into elemental panels of approximately equal area to conserve resolution. The forces on exposed elements are summed across the entire geometry. New analytic methods for determining exposed panels have been developed. Combined with the use of array algebra, the improvements considerably enhance processing speeds. The fidelity of the data is tested by application to the geometry of theMars Reconnaissance Orbiter. The resulting data are comparedwith direct simulationMonte Carlo predictions. Additional case studies serve to inspect implications of geometry design versus output accuracy and processing speed.