Hypersonic speed refers to velocities above Mach 5, or five times the speed of sound, setting them apart from supersonic vehicles, which travel between Mach 1 and Mach 5.
Hypersonic flight presents major engineering challenges due to the extreme heat and pressure generated at such speeds. While supersonic vehicles break the sound barrier, hypersonic vehicles face far greater stresses, making their development more complex and costly. Supersonic aircraft encounter shock waves and moderate heat, whereas hypersonic vehicles endure intense heat flux and stronger aerodynamic forces.
Examples of hypersonic vehicles include spacecraft, intercontinental ballistic missiles (ICBMs), hypersonic cruise missiles, and experimental aircraft designed for speeds beyond Mach 5.