" Typical speeds for hypersonic aircraft are greater than 3000 mph and Mach number M greater than five, M > 5. We are going to define a high hypersonic regime a

" Typical speeds for hypersonic aircraft are greater than 3000 mph and Mach number M greater than five, M > 5. We are going to define a high hypersonic regime at M > 10 to account for re-entry aerodynamics. The chief characteristic of hypersonic aerodynamics is that the temperature of the flow is so great that the chemistry of the diatomic molecules of the air must be considered. At low hypersonic speeds, the molecular bonds vibrate, which changes the magnitude of the forces generated by the air on the aircraft. At high hypersonic speeds, the molecules break apart producing an electrically charged plasma around the aircraft. Large variations in air density and pressure occur because of shock waves, and expansions. " https://www.grc.nasa.gov/www/k-12/airplane/lowhyper.html https://www.grc.nasa.gov/www/k-12/airplane/lowhyper.html