With the proposed research project, the influence of thermal and chemical non-equilibrium on the flow around and downstream of an obstacle in the size of the local boundary-layer thickness in a hypersonic flow as it is characteristic for a re-entry scenario of a space-traveling vehicle at the Mach number M=25 and the alti-tude of H_100km shall be investigated with numerical simulation. As NASA is plan-ning to return to the moon in order to go to mars in the intermediate future, the de-sign of the space capsule as was practiced for the Apollo project has been revived.
Central questions associated with the re-entry flow are still unanswered. The flow around the stagnation point can be simulated with quasi-steady methods rather ac-curately as post-flight investigations on return capsules have shown. In contrast, the flow along the heat shield, especially in the presence of surface imperfections and non-equilibrium is poorly understood.
In the present case, the National Aeronautics and Space Administration (NASA) is interested in the flow around cubic objects, which attach the capsule to the launch vehicle, protruding the boundary-layer. The horse-shoe vortex around the object leads to the transfer of high-temperature gases towards the surface leading to increased ablation in front of the object and in the center part of the wake. The turbulent behaviour of the wake can lead to a strong increase in heat transfer downstream of the protruding object subject to thermal and chemical nonequilibrium.
The interaction with the surface material can lead to catastrophic failure of the heat shield and the underlying material whereas the deterioration of the protruding object is of no importance as it is replaced after flight. The proposed investigations shall give insight into the role of chemical and thermal non-equilibrium with changing in-flow conditions (atmospheric height and Mach number) and varying dimensions of the object in question and a backward-facing step to mini-mize the local heat transfer increasing overall safety of the mission. Design safety factors in the respec-tive areas on the heat shield can then be reduced.