Parallel, steady/unsteady DSMC simulations of the aerodynamics of sounding rockets

Over the past several decades, atomic oxygen (AO) measurements taken from sounding rocket sensor payloads in the Mesosphere and lower Thermosphere (MALT) have shown marked variability. AO data retrieved from the second Coupling of Dynamics and Aurora experiment (CODA II) have shown that the data is highly dependent upon rocket orientation. Many sounding rocket payloads including CODA II, contain AO sensors that are located in close proximity to the payload surface and are thus significantly influenced by compressible, aerodynamic effects. These effects serve to inhibit the AO sensors' ability to accurately determine undisturbed atmospheric conditions. The present research numerically models the influence caused by these aerodynamic effects using a newly developed parallel, steady/unsteady, three-dimensional, DSMC solver entitled foam DSMC. The solver's parallel capabilities as well as it's unsteady functionality demonstrates significant improvements over previous research conducted by the present authors'. The solver is used to simulate the steady flow regime at two kilometer intervals along both the up-leg and down-leg trajectories. Unsteady results are also presented and simulated near apogee. The results are used to create correction functions based on the ratio of undisturbed to disturbed flowfield concentrations. The numerical simulations verify the experimental results showing the strong influence of rocket orientation on concentration. The correction functions, when applied to unconnected CODA II data sets, show a significant improvement in terms of minimizing the effects of compressible flow aerodynamics.