A Study of Ablation-Flowfield Coupling Relevant to Orion Heatshield

The coupled interaction between an ablating surface and the surrounding aerothermal environment is studied. An equilibrium ablation model is coupled to the LAURA flowfield solver, which allows the char ablation rate (ṁc) to be computed as part of the flowfield solution. The wall temperature (Tw) and pyrolysis ablation rate (ṁg) may be specified by the user, obtained from the steady-state ablation approximation, or computed from a a material response code. A 32 species thermochemical nonequilibrium flowfield model is applied, which permits the treatment of C, H, O, N, and Si containing species. Coupled ablation cases relevant to the Orion heatshield are studied. These consist of diffusionlimited oxidation cases with Avcoat as the ablation material. The ṁc values predicted from the developed coupled ablation analysis were compared with those obtained from a typical uncoupled ablation analysis. The coupled results were found to be as much as 50% greater than the uncoupled values. This is shown to be a result of the cumulative effect of the two fundamental approximations inherent in the uncoupled analysis.

[1]  P. Rini,et al.  Elemental Demixing in Air and Carbon Dioxide Stagnation Line Flows , 2004 .

[2]  P. Roth,et al.  Shock Tube Study of Silicon Atom Oxidation by CO and CO2 , 1994 .

[3]  Harry Partridge,et al.  Chemical-kinetic parameters of hyperbolic Earth entry , 2000 .

[4]  Diffusion model comparisons for direct reentry applications , 2003 .

[5]  Tahir Gokcen,et al.  N2-CH4-Ar Chemical Kinetic Model for Simulations of Atmospheric Entry to Titan , 2004 .

[6]  M. Wright,et al.  Recommended Collision Integrals for Transport Property Computations Part 2: Mars and Venus Entries , 2007 .

[7]  R. Gupta,et al.  Aerothermodynamic Analysis of Stardust Sample Return Capsule With Coupled Radiation and Ablation , 1999 .

[8]  R. A. Thompson,et al.  The addition of algebraic turbulence modeling to program LAURA , 1993 .

[9]  Ethiraj Venkatapathy,et al.  Computational Aerothermodynamic Design Issues for Hypersonic Vehicles , 1997 .

[10]  D. Bianchi,et al.  A numerical approach for high-temperatures flows over ablating surfaces , 2007 .

[11]  Richard A. Thompson,et al.  Implementation of a Blowing Boundary Condition in the LAURA Code , 2008 .

[12]  Dave Olynick.  Aerothermodynamics of the Stardust sample return capsule , 1998 .

[13]  Kam-Pui Lee,et al.  Hypersonic viscous shock-layer solutions over long slender bodies. I - High Reynolds number flows , 1990 .

[14]  D. Hash,et al.  Validation Process for Blowing and Transpiration-Cooling in DPLR , 2007 .

[15]  M. Wright,et al.  Recommended Collision Integrals for Transport Property Computations Part 1: Air Species , 2005 .

[16]  E. P. Bartlett,et al.  An analysis of the coupled chemically reacting boundary layer and charring ablator. Part 3 - Nonsimilar solution of the multicomponent laminar boundary layer by an integral matrix method , 1968 .

[17]  P. Roth,et al.  High‐Temperature Kinetics of Si Atom Oxidation by NO Based on Si, N, and O Atom Measurements. , 1993 .

[18]  Kazuhisa Fujita,et al.  Impact of Ablation Gas Kinetics on Hyperbolic Entry Radiative Heating , 2006 .

[19]  Donald M. Curry,et al.  An Evaluation of Ablation Mechanisms for the Apollo Heat Shield Material , 1971 .

[20]  Peter A. Gnoffo,et al.  Implementation of Radiation, Ablation, and Free Energy Minimization Modules for Coupled Simulations of Hypersonic Flow , 2009 .

[21]  D. Bushnell,et al.  Calculation of nonequilibrium hypersonic turbulent boundary layers and comparisons with experimental data , 1970 .

[22]  M. Werle,et al.  Nonsimilar Solution for Laminar and Turbulent Boundary-Layer Flows over Ablating Surfaces , 1972 .

[23]  R. Svehla,et al.  Estimated Viscosities and Thermal Conductivities of Gases at High Temperatures , 1962 .

[24]  Graham V. Candler,et al.  Review of Chemical-Kinetic Problems of Future NASA Missions, II: Mars Entries , 1993 .

[25]  P. Gnoffo,et al.  Multi-Component Diffusion With Application to Computational Aerothermodynamics , 1998 .

[26]  Variation of the Van Driest damping parameter with mass transfer. , 1973 .