Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Abstract

The effects of phenolic decomposition on shock-layer radiation were investigated experimentally in X2 expansion tube for a Venus entry flow. A carbon–phenolic composite aeroshell was subjected to a flow with a flight equivalent velocity of . Emission spectroscopy was used to measure boundary-layer radiation in parts of the ultraviolet (380–480 nm) and visible (620–700 nm) spectrum, and it was compared to control measurements taken with a cold steel model. With the composite model in place, the calibrated spectral radiance measured was seen to increase for the O (645.598 nm) atomic line and the (391.22 nm) band head, but it decreased for the Swan band (420–480 nm). The recorded data were then compared to numerical spectra produced by two-dimensional axisymmetric computational fluid dynamic simulations coupled to a radiation solver. Both of the applied chemistry models overpredicted CN violet band radiation, which demonstrated strong self-absorption at these conditions. Better comparisons were achieved for the Swan band radiation. At visible wavelengths, peak intensities were underestimated by the numerical simulations. Several possible reasons were hypothesized for these discrepancies.