Boundary layer stability analysis of Mars Science Laboratory aeroshell

The NASA Mars Science Laboratory (MSL) is scheduled to enter the Mars atmosphere in 2010. Compared to previous Mars entry vehicles, it is larger and heavier and will enter the atmosphere at an angle of attack to generate lift. As a result, the convective heat fluxes will be relatively large, and there is the possibility of transition to turbulence which would significantly increase the heating levels. In particular, the boundary layer grows rapidly on the leeward side, potentially resulting in an unstable boundary layer and early transition, as demonstrated in recent shock tunnel tests. The shock tunnel data also indicate the possibility of windside transition (near the stagnation point) for some cases. In this work, we will study the stability of the boundary layer on the MSL vehicle using a newly-developed parabolized stability equation (PSE) solver. This code uses high-quality mean flow fields provided by computational fluid dynamics simulations to predict the growth rate of boundary layer disturbances, including the effects of finite-rate chemical reactions and internal energy relaxation. The results of this analysis can be used to predict the location of transition to turbulence and to assess the sensitivity of transition to flow conditions and geometry. The methods of analysis and the results in this paper, although presently directed towards the MSL geometry, will be equally applicable to blunt body aerocapture at small body targets such as Mars, Venus, and Titan.