Rarefied aerodynamics of a deployable re-entry capsule

Several research activities have been already carried out in the field of low-ballistic coefficient re-entry capsules based on deployable umbrella-like aero-shield. The flexible aero-shield, made of ceramic fabrics, acts both as an aero-brake and a Thermal Protection System (TPS), making possible to perform a re-entry from orbital or suborbital conditions with relatively low values of the aero-thermo-dynamic loads. Previous studies have already analyzed Aerodynamics of similar systems, identifying self-stabilizing configurations and creating a preliminary database of force and moment coefficients in different flight regimes. This work is intended to provide a systematic overview of the aerodynamic behavior of a deployable capsule in the rarefied regime, where the differences between the re-entry trajectories from Low-Earth Orbit and suborbital flight conditions are more evident. Particular focus is given to the longitudinal stability analysis, which demonstrates that, as the continuum hypersonic regime approaches, the capsule could show a stable equilibrium condition in the unfavorable reverse attitude. This unwanted equilibrium condition could be counteracted by moving the center of gravity out of the symmetry axis. (C) 2017 Elsevier Masson SAS. All rights reserved.