Technical Report Soulas, George C. Glenn Research Center NASA/TM-2011-216970, E-17598 WBS 284848.02.01.03.04 PARTICLE FLUX DENSITY; CYLINDRICAL BODIES; APERTURES; FLOW EQUATIONS; FREE MOLECULAR FLOW; MAXWELL-BOLTZMANN DENSITY FUNCTION; GAS DENSITY; THICKNESS RATIO; WALL TEMPERATURE; REFLECTION