Supersonic wind tunnels have existed since the 1920s and Mach 3+ versions were built in Germany during World War 2 for the V2 project. See https://en.wikipedia.

Supersonic wind tunnels have existed since the 1920s and Mach 3+ versions were built in Germany during World War 2 for the V2 project. See https://en.wikipedia.org/wiki/Supersonic_wind_tunnel https://en.wikipedia.org/wiki/Supersonic_wind_tunnel