This paper's focus is on the aerodynamic and aerothermal loads that a reusable launch vehicle (RLV) during descent. The analysis is performed on a working design of the THEMIS demonstrator developed at Ariane Group SAS under an ESA contract. The paper describes the effects of parameters of the configuration of the nozzles. Impacts of these changes in shape on the aerothermal loads and the aerodynamic behaviour of the vehicle are addressed through the analysis of global aerodynamic coefficients and the static stability of the vehicles. Furthermore, the phenomena occurring in the flow field and its impacts on the heat flux distribution are investigated: