It is necessary to use a special heat protecting system if an unprotected structure will inevitably be destroyed upon being subjected to energy flux action (convective, radiant, or some other). The most heat resistant metals without heat protection can be used (upper limit), if the heat fluxes are of 0.25 MW/m~2 (surface equilibrium temperature is about of 1500 K). This threshold is determined conditionally since in the majority of cases the heat impact can be worsened by oxidation processes. Recently, thin coatings deposited onto ceramics by means of evaporation and withstanding up to 2000℃ over a hundred hours were developed. They were patented after the Shuttle and Buran flights. It is evident that these achievements in the field of material science should be taken into account when we choose flight conditions for hypersonic vehicles [1].
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