Facing the Heat Barrier - National Aeronautics and Space Admin. - Bog

Hypersonics is the study of flight at speeds where aerodynamic heating dominates the physics of the problem. Typically this is Mach 5 and higher.
Hypersonics is an engineering science with close links to supersonics and engine design.
Within this field, many of the most important results have been experimental. The principal facilities have been wind tunnels and related devices, which have produced flows with speeds up to orbital velocity.