DIRECT SIMULATION MONTE CARLO OF VACUUM PLUMES

THE OVERALL OBJECTIVE OF THIS PROPOSED EFFORT IS THE DEVELOPMENT OF A THREE-DIMENSIONAL MONTE CARLO CODE TO MODEL THE INTERACTION OF VACUUM PLUMES WITH SPACECRAFT STRUCTURES, INCLUDING FORCES, HEATING RATES AND ROCKET EXHAUST CONTAMINANT TRANSPORT. THE SPACECRAFT GEOMETRY CAN BE SELECTED TO BE AS COMPLEX AS DESIRED. THE NUMERICAL SIMULATION RESULTS IN A MACROSCOPIC DEFINITION OF THE FLOWFIELD VARIABLES, ENCOMPASSING VELOCITY, DENSITY, TRANSLATIONAL AND ROTATIONAL TEMPERATURES, AND SPECIES CROSS DIFFUSION CAUSED BY NON-EQUILIBRIUM EFFECTS. THE FLOW AROUND THE NOZZLE LIP IS ALSO SOLVED BY MONTE CARLO. THE CONTINUUM PORTION OF THE PLUME IS OBTAINED BY THE METHOD OF CHARACTERISTICS FOR LARGE ENGINES AND FROM NUMERICAL SOLUTIONS OF THE NAVIER-STOKES EQUATIONS FOR SMALL THRUSTERS. A LINE OF MOLECULAR SOURCES IN THE CONTINUUM PLUME IS SELECTED AS AN INPUT TO THE MONTE CARLO. PHASE I ADDRESSES ONLY AXIALLY SYMMETRIC CASES. IN PHASE II THE CODE IS EXTENDED TO THREE DIMENSIONS, AND IN PHASE III THE CODE IS REPROGRAMMED FOR CHAOTIC ASYNCHRONOUS PARALLEL PROCESSING TO REDUCE THE COMPUTATIONAL TIME AND CORE REQUIREMENTS.