Hypersonic flow

Summary

Hypersonic flow is gas flow at very high Mach number, conventionally above about $5$. At such speeds the shock waves lie close to the body and the gas behind them becomes very hot. Chemical and thermal effects in the air then matter. Its theory has its own approximations, such as hypersonic similarity for slender bodies. Another is the independence of some quantities from the Mach number when it is very large. It is the regime of spacecraft re-entry and of very fast missiles. See the definition.