In aerodynamics, a hypersonic speed is one that is highly supersonic (even though the origin of the words is the same: "super" is just the Latin version of the Greek "hyper"). Since the 1970s, the term has generally been assumed to refer to speeds of Mach 5 and above.

The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since individual physical changes in the airflow (like molecular dissociation and ionization) occur at different speeds; these effects collectively become important around Mach 5. The hypersonic regime is often alternatively defined as speeds where ramjets do not produce net thrust.

Read more about HypersonicCharacteristics of Flow, Classification of Mach Regimes, Similarity Parameters, Regimes

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