‘Propellers To Scramjets’

16-Foot Tunnel Leaves Powerful Legacy

By MARNY SKORA
Langley Research Center

Langley Research Center’s 16-Foot Transonic Tunnel will retire at the end of the month, one month shy of 63 years of service.

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.

Much of the staff has already disbursed — other tunnels on Center are clamoring for experienced workers. The employees who remain are completing the final test. They will then begin an orderly closeout of the historic tunnel, inventorying hardware and removing equipment that can be used elsewhere.

The last test — a NASA-Air Force-Boeing cooperative study of a single-engine test demonstrator launch configuration — underscores the tunnel’s legacy: aerospace research across the entire flight range.

The 16-Foot tunnel began operation in November 1941. Since that time, it has supported Agency initiatives, all major aircraft companies and most major military programs in their development stages and in ongoing propulsion integration research.

Its heritage reads like a “Who’s Who” of famous aircraft and spacecraft: Corsair, Bell X-1, Buffalo, Thunderbolt, Hustler, Aardvark, Eagle, Hornet, Harrier, Galaxy, X-15, Apollo, RLV, Shuttle, Tomcat, B-1, B-2, X-43, to name just a few. In addition, many fundamental aviation advances were made at the tunnel that applied generally to a broad range of subsonic transports and military concepts.

The road to greatness

Wind tunnel testing played a major role in the resounding success of American aircraft during the World War I. With few exceptions, most U.S. fighters and bombers in the air and in development in the 1940s depended on air-cooled engines. Entering service as the 16-Foot High-Speed Tunnel, the Langley facility was perfect for solving the cooling problems being encountered with air-cooled engines.

The tunnel could duplicate subsonic, high-speed flight quickly and cheaply. Full-size engines were mounted in its test section and operated at various power levels while hundreds of thermocouples measured temperatures at crucial spots. When hot spots were discovered, the cowling and internal baffling could be modified on the spot. New tests could be run immediately, in contrast to lengthy and expensive flight tests. In addition, researchers improved the aerodynamic performance of high-speed propellers by using an electric dynamometer.

After a decade, Langley was in the process of repowering the huge high-speed wind tunnel to boost airspeeds into the low-supersonic range. Since all supersonic aircraft would have to fly through the transonic range — at least briefly — knowing what happened in this transition zone was critical to fighters and bombers being planned in the post-war era. The opportunity to convert it into a transonic tunnel was seized immediately and the 16-Foot Transonic Tunnel was born. This major modification in 1950 increased tunnel capability to Mach 1.1 and added an octagonal slotted test section with a 60,000-hp drive system.

Yet another modification in 1961 added a compressor driven by a 36,000-hp motor and increased the Mach number to about 1.3. In 1990, new fan blades were installed and a new control room was added.

With each upgrade, the tunnel helped change the face of aviation and push the boundaries of space exploration. Breakthrough nozzle and thrust vectoring technologies were developed. In fact, the 16-Foot tunnel tested everything from high-speed propellers to the shapes of the first atomic weapons to today’s scramjet-powered vehicles.

A noted historian and author once wrote that the wind tunnel dominated aeronautical research just as the microscope dominated biology, the telescope astronomy, and the particle accelerator nuclear physics. The legacy of the 16-Foot Transonic Tunnel upholds that concept.

Marny Skora is head of Langley’s Public Affairs Office.

Langley Research Center employee Linda Bangert examines a Boeing Super Cruiser Fighter model in the test section of the 16- Foot Transonic Tunnel in 1990. Bangert is currently assigned to the Quiet Aircraft Technology Project.

NASA file photo