Three men (look closely) stand inside Arnold Engineering Development Complex's 16-foot supersonic wind tunnel facility. The tunnel, seen here in 1960, is housed at Arnold Air Force Base, Tennessee, but is now inactive.
The wind tunnel was capable of Mach numbers between 1.60 and 4.75 through a test section 4.8 meters wide and 20.2 meters long. It served as a large-scale testing facility for aircraft and propulsion systems. Like many large-scale and high-speed wind tunnel facilities in the United States, it is no longer active. In recent years, many unique wind tunnel facilities at NASA, military bases, and universities have been closed down, depriving researchers and engineers of the ability to include large-scale testing in their design and development of new technologies.