In the framework of atmospheric re-entry, the scope of this thesis is to investigate a subsonic-hypersonic aerothermodynamic similarity for probe designing and high-enthalpy testing. After a review of the foundations of aerothermodynamics, Local Heat Transfer Simulations and high-order reactive boundary layer theory are used to build a mapping from flight conditions to ground facilities . A two-dimensional computational approach is then performed on an axi-symmetric probe with different shapes and physical conditions with the software ARGO. A comparisons with hypersonic simulations are used at last to validate the method with a real test case.