Ablation and Aero-thermodynamic Studies on Thermal Protection Systems of Sharp-Nosed Re-entry Vehicles

A quasi-one-dimensional ablation analysis for a sharp-nosed, reusable, re-entry vehicle that could possibly be used in an unmanned space program, has been carried out by using an in-house code. The code is based on the boundary immobilization technique and the solution has been obtained using the tri-diagonal matrix algorithm (TDMA). The heat fluxes on the spherical nose cap that are used to determine the ablation rate of a thermal coating applied over the surface of the vehicle are obtained by performing a steady state aero-thermodynamic analysis. The aero-thermodynamic analysis for the viscous, compressible flow under consideration is carried out by using FLUENT 6.2. The computational fluid dynamics (CFD) simulations are performed at three locations on the trajectory that the vehicle follows, on re-entry. These simulations yield the temperature and heat flux distributions along the surface of the vehicle and the latter are given as input to the ablation code. The shell material of the vehicle is assumed to be zirconium boride $(ZrB2)$⁠. The code is validated with benchmark cases and the flow and heat transfer characteristics are also discussed. In brief, the present work presents a methodology for coupling an ablation code with CFD simulations from a commercial code, to study the effect of change of the nose region on the ablation process.