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Accession Number N14-0004052
Title Study of Aerothermodynamic Modeling Issues Relevant to High-Speed Sample Return Vehicles.
Publication Date Apr 2014
Media Count 38p
Personal Author C. O. Johnston
Abstract This paper examines the application of state-of-the-art coupled ablation and radiation simulations to highspeed sample return vehicles, such as those returning from Mars or an asteroid. A defining characteristic of these entries is that the surface recession rates and temperatures are driven by nonequilibrium convective and radiative heating through a boundary layer with significant surface blowing and ablation products. Measurements relevant to validating the simulation of these phenomena are reviewed and the Stardust entry is identified as providing the best relevant measurements. A coupled ablation and radiation flowfield analysis is presented that implements a finite-rate surface chemistry model. Comparisons between this finite-rate model and a equilibrium ablation model show that, while good agreement is seen for diffusion-limited oxidation cases, the finite-rate model predicts up to 50% lower char rates than the equilibrium model at sublimation conditions. Both the equilibrium and finite rate models predict significant negative mass flux at the surface due to sublimation of atomic carbon. A sensitivity analysis to flowfield and surface chemistry rates show that, for a sample return capsule at 10, 12, and 14 km/s, the sublimation rates for C and C3 provide the largest changes to the convective flux, radiative flux, and char rate. A parametric uncertainty analysis of the radiative heating due to radiation modeling parameters indicates uncertainties ranging from 27% at 10 km/s to 36% at 14 km/s.
Keywords Ablation
Convective heat transfer
Flow distribution
High speed
Mars sample return missions
Surface reactions
Surface temperature

Source Agency National Aeronautics and Space Administration
NTIS Subject Category 46B - Fluid Mechanics
51A - Aerodynamics
84 - Space Technology
Corporate Author National Aeronautics and Space Administration, Hampton, VA. Langley Research Center.
Document Type Conference proceedings
Title Note N/A
NTIS Issue Number 1421
Contract Number N/A

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