Definition
A speed greater than five times the speed of sound (above Mach 5). At these speeds, airflow behavior changes dramatically and intense aerodynamic heating becomes a dominant design factor.
Plain English
Going faster than five times the speed of sound. At this kind of speed, the air itself heats up enormously as the aircraft pushes through it.
Context Anchor
Seen in high-speed aerodynamics, reentry vehicle, missile, spacecraft, and airframe heating discussions; it is not a normal operating range for training aircraft.
Derivation
From the Greek 'hyper' meaning 'over' or 'beyond,' combined with 'sonic' from the Latin 'sonus' meaning 'sound.' Literally 'beyond sound' — and in practice, well beyond it.
Why Pilots Care
Hypersonic flight is mostly the realm of military, experimental, and spaceflight vehicles. For maintenance technicians, it matters because hypersonic structures face heating and material stresses that are very different from those on conventional aircraft.
Grounding Statement
At hypersonic speed, the air ahead of the vehicle is compressed and heated so strongly that the aircraft or vehicle must be designed to survive that environment.
Intuition Check
Hypersonic does not just mean “very fast.” In aviation, it refers to a specific speed range: about Mach 5 or faster.
Example Sentence 1
The X-15 research aircraft reached hypersonic speed during several of its flights, exceeding Mach 6.
Example Sentence 2
Special materials protect the airframe when operating at hypersonic speed.