1985: Adding lasers makes even a supersonic wind tunnel more awesome.
In the 1980s, NASA engineers at the Lewis Research Center in Cleveland, Ohio (now the John H. Glenn Research Center at Lewis Field) developed all sorts of propeller prototypes. In this particular test run, they bounced lasers off the blades to measure deflection while abusing them them in the supersonic wind tunnel.
The 8-by-6-foot (2.4 by 1.8 meter) Supersonic Wind Tunnel (8x6 SWT) is NASA’s only transonic propulsion wind tunnel. The perforated stainless steel walls provide a boundary layer when the airflow is at transonic speeds. Airflow can reach a maximum of Mach 2.0.
Image credits: NASA