Numerical and Experimental Investigation of Magnetohydrodynamic Effects on Radiative Heating During Superorbital Earth Reentry

Numerical predictions of radiative heat flux were performed on a representative Mars return (Earth reentry upon return from Mars) condition with a flight equivalent velocity of 15.1 km & sdot;s-1, produced by the University of Queensland's X2 expansion tube. The primary goal was to numerically evaluate the effect of an externally applied magnetic field on radiative heat flux to a scaled test model based on NASA's Stardust vehicle. Numerical simulations used the Eilmer4 computational fluid dynamics (CFD) code coupled with NASA's NEQAIR code for radiation calculations. A two-dimensional, axisymmetric magnetohydrodynamic (MHD) model was implemented in order to model MHD effects. The numerical results predicted a significant increase of 54% to stagnation point radiative heat flux when the magnet was used, and a smaller increase of 8% to afterbody radiative heat flux. An attempt was made to compare the numerical predictions to experimental measurements. A spherical permanent magnet fitted into the test model provided a stagnation point magnetic flux density of 0.68 T. A radiation gauge was developed consisting of a thin-film heat flux gauge placed behind an optical window, enabling isolation of the radiative heat flux component. Several challenges were encountered, including the absorbance calibration of the radiation gauges, chemical contamination of the test flow, and noisy measurements when the magnet was on. These prevented firm conclusions to be made and warrant further experiments to validate the CFD results.