Study of thermal protection system defects using a one-domain porous media model

The interactions between the aerothermal environment and the material result in highly coupled, multi-physics problems that are critical challenges in optimizing design margins and mission risk. These complex issues involve coupled multiple physical phenomena, such as heat transfer, material degradation, structural integrity, etc. posing critical challenges in optimizing design margins and mission risk. A significant challenge remains in understanding the material response in off-design scenarios when the TPS is subjected to unpredicted conditions not captured by ground experiments. These off-design scenarios include the possibility of TPS cavities on the shield that are generated by micrometeoroids and orbital debris (MMOD) impact— an alarming issue due to the significant increase in space debris— or internal cracks propagation due to internal pressure build-up .



Enabling design by analysis requires the development of high-fidelity tools that couple flow and material behavior. A main challenge lies in developing suitable and robust numerical techniques that accurately track the material interface and in defining proper boundary conditions that capture material degradation . The material response in the presence of defects introduces added complexities, such as augmented heating, pyrolysis gas flow driven by pressure gradients, alterations to heat conduction due to material anisotropy, etc. A main concern with MMOD impact while in transit include gas flow through porous cavity walls and potential mechanical material failure.



In this work, we study TPS defects using a one-domain porous media model based on the volume-averaged Navier-Stokes (VANS) equations . We generalize the governing equations to solve the flow field and the material in a unified approach The strong coupling between each phase mitigates modeling assumptions in conjugate heat-transfer coupling. This allows for a natural progression of the material interface due to heterogeneous reactions and the blowing of pyrolysis gases from the porous material without the need for complex boundary conditions.

During the lecture, we will show a series of TPS defect test cases under extreme spacecraft entry conditions utilizing the one-domain porous media model.