Aerodynamic Analysis of an Entry Capsule at Titan in Transition Regime

Abstract

The interest of the scientific community in Titan, Saturn’s largest moon, is still strong. In fact, after the successful Cassini–Huygens mission, which landed the Huygens capsule on Titan, other missions are planned in the coming years. The aims of this work are to provide the extent of global aerodynamic force, to provide thermal and aerodynamic loads on a capsule entering Titan atmosphere, and to evaluate the effects of chemistry on 1) flowfield parameters, 2) surface catalyticity, 3) temperature and pressure distributions on a heat shield, and 4) global aerodynamic force. To develop this study, the authors used the Huygens capsule and related entry trajectory. The study was carried out in the altitude interval of 295–470 km by means of the direct simulation Monte Carlo codes: DS2V for the solution of two-dimensional/axisymmetric flowfields, and DS3V for the solution of three-dimensional flowfields. The Titan atmosphere is a mixture of nitrogen, methane, and argon. The chemical model is made of 221 reactions, making gas around the capsule a mixture of 18 species. Chemistry strongly influences local aerodynamic quantities, both in the flowfield and on the capsule surface; whereas the chemical effects on the global aerodynamic force are negligible. Our computations also verified the lack of ionization.