Uncertainty Quantification and Sensitivity Analysis of Ice Giant Aerocapture Aerothermodynamics

A sensitivity analysis and uncertainty quantification of the aerothermodynamic environments of an entry vehicle along an ice giant aerocapture trajectory are presented. Sources of uncertainty include chemical reaction-rate coefficients, transport properties, vibrational-relaxation rates, and the freestream methane concentration. The convective heating is most sensitive to transport properties and the hydrogen electron-impact ionization rate coefficient. The stagnation region is dominated by dissociation/ionization phenomena, while the shoulder region is dominated by recombination. Uncertainty in the convective-heating distributions ranges from 4.10 to 11.7%. Radiative-heating uncertainty is higher, with upper bounds exceeding 160% of the nominal predictions. A minor sensitivity of the radiative heating to the freestream methane concentration is observed at lower altitudes, but most of the uncertainty at the stagnation point and along the frustum is attributed to the dissociation of [Formula: see text] with partner H. At lower altitudes, the shoulder radiative heating is highly sensitive to the reverse direction of hydrogen ionization reactions, both via heavy-particle and electron impact. Aerodynamic coefficients are relatively insensitive to the CFD input parameters, with uncertainties of a few percent at most. Finally, the effects of including [Formula: see text] on the aerothermodynamic uncertainty are studied. Inclusion of [Formula: see text] is found to decrease both the nominal radiative heating and corresponding uncertainty intervals, in some cases by up to 40%. Furthermore, a decrease in the sensitivity of radiative heating to hydrogen dissociation uncertainty is observed, and a corresponding increase in sensitivity to hydrogen ionization and the freestream methane concentration is produced.