Radiation Modeling for Reentry of Hayabusa Sample Return Capsule

Abstract

Predicted shock-layer emission signatures during the reentry of the Japanese Hayabusa capsule are presented and compared with flight measurements conducted during an airborne observation mission in NASA’s DC-8 Airborne Laboratory. For selected altitudes at 11 points along the flight trajectory of the capsule, lines of sight were extracted from flowfield solutions computed using the high-fidelity computational fluid dynamics code Dplr. These lines of sight were used as inputs for the line-by-line radiation code Neqair, and emission spectra of the air plasma were computed in the wavelength range from 300 to 1600 nm, a range that covers all of the different experiments onboard the DC-8. In addition, the computed flowfield solutions were postprocessed with the material thermal response code Fiat, and the resulting surface temperatures of the heat shield were used to generate thermal emission spectra based on Planck radiation. Both spectra were summed and integrated over the flowfield. The resulting emission at each trajectory point was propagated to the DC-8 position and transformed into incident irradiance to be finally compared with experimental data.