Numerical Investigation on Charring Ablator Geometric Effects: Study of Stardust Sample Return Capsule Heat Shield

摘要

Sample geometry is very influential in small charring ablative articles where 1D assumption might not be accurate. In heat shield design, 1D is often assumed since the nose radius is much larger than the thickness of charring. Whether the 1D assumption is valid for the heat shield is unknown. Therefore, the geometric effects of Stardust sample return capsule heat shield are numerically studied using a material response program. The developed computer program models material charring, conductive heat transfer, surface energy balance, pyrolysis gas transport and orthotropic material properties in 3D Cartesian coordinates. Simulation results show that the centerline temperatures predicted by 3D model are quite close to 1D model at the surface, but not the case inside the material. The pyrolysis surface gas blowing behaviors are quite similar but differences are observed at later time. Orthotropic model predicted a very different heat shield response to both the isotropic model and the 1D model.