[1][2] Other trisonic wind tunnels currently in operation are those located at NASA's Marshall Space Flight Center,[3][4] National Researach Council Canada's 1.5 m Trisonic Wind Tunnel Research Facility and the French-German Research Institute of Saint-Louis,[5] ISRO's Vikram Sarabhai Space Centre (VSSC) in Thiruvananthapuram, and 1.2m Trisonic Wind Tunnel Facility at National Aerospace Laboratories.
Because a blow-down tunnel can build up pressure over a long period time, it can release air at faster speeds.
During the hot summer season, NATWT ran on a night schedule to balance its load with public air conditioning.
When the valve was opened, the compressed air passed through the settling chamber, nozzle, and the test section, where instrumented aerodynamic models were mounted.
The diffuser area included a colander-like sieve made of 1-inch-thick (25 mm) steel to catch debris in the event of a catastrophic model failure.
The speed of the air was determined by the pressure of the spheres and the cross sectional area of the wind tunnel nozzle and diffuser.
The NATWT could change the shape of the nozzle by operating a series of hydraulic pistons that would bend one-inch thick steel plates into the desired contour.