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NASA's 16-Foot Transonic Tunnel Leaves Powerful Legacy

When the massive fan blades stop turning for the last time on September 30, 2004, the steel walls of the 16-Foot Transonic Tunnel will continue to reverberate with an incredible history of aeronautical research spanning over six decades.

Aerial view of the 16-foot transonic wind tunnel

Image to right: Aerial view of the NASA Langley Research Center 16-Foot Transonic Wind Tunnel. Image credit: NASA

The stone "NACA" plate over the building's main entrance at NASA's Langley Research Center only hints at the historical significance of the facility. The sheer size of the tunnel is awe-inspiring. Footsteps and voices echo in an unworldly fashion. Lights project ominous shadows, creating deceptive scale and optical illusions. The tunnel's characteristic roar can be heard all over the Center. Standing in the test section, one gets an eerie feeling of the power and forces this huge machine can generate.

Originally known as the 16-Foot High-Speed Tunnel, the new facility, opened in 1941, was perfect for solving the cooling problems encountered in air-cooled aircraft engines. Instead of lengthy and expensive flight tests, full-size engines and nacelles could be mounted in the tunnel and run at varying power levels. The benefits of tunnel testing also allowed for the collection of data from hundreds of temperature sensors that could not be monitored in free flight.

As we learned more and technology advanced, the tunnel was reconfigured with slotted walls and a 60,000 horsepower drive system. Tunnel speeds increased to Mach 1.1. Later in the '50s, a hydrogen peroxide system was added as researchers continued to push the envelope. The revolutionary idea of a VTOL jet was tested.

Space Shuttle model in the 16-foot Transonic Tunnel

Image to left: A model of the Space Shuttle in the 16-Foot Transonic Wind Tunnel. Image credit: NASA

In the '60s, '70s and '80s, the 16-Foot was the premier research facility for propulsion system and airframe integration. In the control room, researchers began to use new terms like, "thrust vectoring" and "square intakes and nozzles". In 1961, an additional compressor driven by a 36,000 hp motor was added that increased the tunnel's Mach number to 1.3. A parade of unfamiliar yet exciting shapes were mounted on the tunnel's massive sting and evaluated, changed, and tested again. A model of the Saturn rocket and escape tower was bolted to the tunnel floor to study the effects of wind and atmospheric turbulence. In 1990, the tunnel received new fan blades, and a new control room.

The tunnel was 50-years old in 1991. Engineers who had worked in its cathedral-like structure came from all over the country to revisit, reminisce and revel in its longevity and unparalleled record of operation and accomplishment.

Over the past sixty plus years, a "Who's Who" of famous and infamous aircraft and spacecraft names and numbers found themselves in the 16-Foot's air stream: Corsair, Bell X-1, Buffalo, Thunderbolt, Hustler, Aardvark, Eagle, Hornet, Harrier, Galaxy, X-15, Apollo, RLV, Shuttle, and Tomcat, B-1 , B-2, X-43, to name just a few. It is even rumored that the Fat Man and Little Boy atomic weapons designs had 16-Foot Tunnel time.

Researchers and technicians monitor a test in the tunnel control room

Image to right: Researchers and technicians monitor a test in the Control Room of the 16-Foot Transonic Wind Tunnel. Image credit: NASA

All major aircraft companies and the military have come to the tunnel to solve problems and explore new ideas. They conducted research in the 16-Foot Tunnel because it was well maintained, continually upgraded, and they liked its capabilities and trusted its data.

Retiring the tunnel is part of a national initiative to optimize government-owned wind tunnels. A NASA/Department of Defense alliance studying investment planning in wind tunnel assets recommended the shutdown in 2002. Since that time, the tunnel and its staff of scientists, engineers and technicians have worked to complete research commitments.

The last test - a NASA/Air Force/Boeing cooperative study of a single-engine test demonstrator launch configuration - underscores the tunnel's contributions and its legacy: aerospace research from propellers to scramjets.

Bill Uher
NASA Langley Research Center