text: A Trisonic Wind Tunnel (TWT) is a wind tunnel so named because it is capable of testing in three speed regimes – subsonic, transonic, and supersonic. The earliest known trisonic wind tunnel was dated to 1950 and was located in El Segundo, California before it closed in 2007. Other trisonic wind tunnels currently in operation are those located at NASAs Marshall Space Flight Center, National Researach Council Canadas 1.5 m Trisonic Wind Tunnel Research Facility and the French-German Research Institute of Saint-Louis, ISRO's Vikram Sarabhai Space Centre(VSSC) in Thiruvananthapuram, India.