Assessment of Electrical Conductivity in Rarefied Flow about Mars Entry Vehicles

During atmospheric entry at Mars, the generation of ions and free electrons across the bow shock generates a locally conducting flow. The electrical conductivity, in concert with a magnetic field, may be utilized to generate a Lorentz force to augment aerodynamic forces on the vehicle. Direct simulation Monte-Carlo is used to determine flowfield properties around an entry vehicle at Mars with high Knudsen numbers where continuity equations are not valid. Vibration temperature and electron number density are used to compute the electrical conductivity around the vehicle for three different vehicle sizes at several altitudes and velocities. Results are compared against previous electrical conductivity models. The electrical conductivity calculation in this study agrees well with the low ionization approximation and Otsu method, but the magnitude is significantly lower than that predicted by Kim’s method. Analytic expressions for the shock width, average conductivity in the shock, and velocity in the shock are developed. Resultant model fit errors are less than 10% of the direct simulation Monte-Carlo results.