An Analysis of the Radiative Heating Environment for Aerocapture at Titan

Abstract

* Senior Research Scientist, Reacting Flow Environments Branch. Senior Member AIAA † Senior Research Scientist. Senior Member AIAA ‡ Senior Research Scientist. Associate Fellow AIAA § Senior Research Scientist. Senior Member AIAA ** Research Scientist, Aerothermodynamics Branch. Senior Member AIAA †† Research Scientist, Aerothermodynamics Branch. Fellow AIAA ‡‡ Research Scientist, Aerothermodynamics Branch. Fellow AIAA Copyright © 2003 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental purposes Abstract Details of the radiative heating analysis for the forebody of a candidate Titan aerocapture orbiter are presented. The radiative heating rates are obtained through a posteriori analysis of high-fidelity thermochemical nonequilibrium flow fields computed using modern techniques of computational fluid dynamics. Results from axisymmetric and three-dimensional analysis are presented at several points on candidate aerocapture trajectories in various model atmospheres of Titan. The radiative heating rates are found to be up to five times the peak convective heating rates, indicating that an accurate knowledge of the uncertainty of the radiative heating predictions is critical for a Titan aerocapture mission. The results also show that – (1) the radiative heating rates are dominated by the violet band system of CN, and (2) the gas mixture is optically thin. The predicted radiative heating is found to be very sensitive to the dissociation rate of molecular nitrogen – a factor of two increase in the rate, which is within the experimental uncertainty, results in a 25% decrease in the radiative heating.