Aerodynamic influences on atmospheric in situ measurements from sounding rockets

Sounding rockets are essential tools for studies of the mesosphere and lowe r thermosphere. However, in situ measurements from rockets are potentially subject to a number of perturbations related to the gas flow around the veh icle. This paper reviews the aerodynamic principles behind these perturbati ons. With respect to both data analysis and experiment design, there is a s ubstantial need for improved understanding of aerodynamic effects. Any such analysis is complicated by the different flow regimes experienced during a rocket flight through the rarefied environment of the mesosphere and therm osphere. Numerical studies are presented using the Direct Simulation Monte Carlo (DSMC) approach, which is based on a tracing of individual molecules. Complementary experiments have been performed in a low-density wind tunnel . These experiments are crucial for the development of appropriate model pa rameterization. How ever, direct similarity between scaled wind tunnel resu lts and arbitrary atmospheric flight conditions is usually difficult to ach ieve. Density, velocity, and temperature results are presented for differen t payload geometries and flow conditions. These illustrate a wide range of aerodynamic effects representative for rocket flights in the mesosphere and lower thermosphere.