One of the major technological challenges associated with the access to planetary surfaces is the entry of the space vehicle in the planetary atmospheres at superorbital speeds. The problem is the very large heat released to the vehicle surface by the surrounding gas either as convective heating or as radiation. Optimization of the thermal shield design can have a profound impact on the overall mission mass, volume (and therefore energy and cost) budgets. However, a poor knowledge of the physics of hypersonic entry is the limiting factor. Uncertainties increase with the entry speed, in particular as radiation becomes a considerable contribution to the overall heat load. Significant advance can only be achieved when the uncertainties in the physical modelling have been considerably reduced. The main goal of this study is, therefore, a thorough analysis of the physics behind space vehicle entry into planetary atmospheres and an improvement of crucial elements of the modelling that allows reliable predictions of flight conditions. This study is therefore concerned with the development of advanced chemico-physical and plasma models of hypersonic entry flows. Advanced models mean the description of the nonequilibrium chemical kinetics of the high temperature medium on the basis of a state-to-state approach. This approach, in turn, calls for a microscopic description of the elementary processes that play a role in the high temperature reactive gas mixtures surrounding the space vehicles during the entry phase. The predictive capabilities of the theoretical models will be assessed against well defined experimental measurements and their impact on the overall heat flux to the surface will be estimated by Computational Fluid Dynamics simulations of realistic ground and flight tests.