Rarefaction effects on hypersonic boundary-layer stability over a blunt cone at varying degrees of wall cooling and nose bluntness in near-continuum regime

Near-space hypersonic vehicles at 40--60 km altitude encounter local rarefaction effects that influence the boundary-layer stability and the laminar--turbulent transition. By incorporating slip boundary conditions and nonlinear constitutive relations into the Navier--Stokes equations and linear stability theory, we systematically investigate hypersonic boundary-layer stability over a blunt cone under near-continuum conditions. The results show that rarefaction thins the boundary layer and stabilizes second-mode instabilities, particularly at high wall temperatures or with small bluntness. These results offer new insights into hypersonic stability and transition in the near-continuum regime.