hypersonic

Hypersonic refers to speeds at least five times the speed of sound (Mach 5). In aerodynamics, hypersonic flow occurs at high Mach numbers where compressibility, viscous heating, and chemical reactions in the air become dominant. Hypersonic flight can be unmanned or manned, and occurs in the atmosphere or during reentry from space.

The regime presents unique challenges: strong shock waves, extreme heating, and complex flow phenomena such as shock–boundary-layer interaction and aerothermal loads. Materials and thermal protection systems must tolerate high temperatures; manufacturing tolerances and surface conditions are critical. Propulsion for sustained hypersonic flight often relies on air-breathing engines such as scramjets, which require high speeds before intake air is efficiently used; rocket propulsion may be used for launch or boost.

Applications include research and defense: hypersonic glide vehicles and missiles designed to travel at hypersonic speed for extended ranges; in addition, hypersonic concepts are investigated for rapid global reach and access to space. Notable programs include government and corporate research in several countries, and demonstrations such as scramjet-powered flight and hypersonic glide tests.

The field is fast-moving with ongoing technical challenges such as thermal protection, control at extreme speeds, communication in plasma, and safety and treaty considerations for weapons development.