National Transonic Facility
|Center:||Langley Research Center|
|Historic Eligibility:||National Register Eligible|
|Important Tests:||Boeing 777, Space Shuttle, Boeing 767, B-2 Bomber, A-6 Intruder, F-18 Hornet|
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The site of the National Transonic Facility (NTF) was originally the site of Langley’s first large supersonic wind tunnel. The 4 x 4-Foot Supersonic Pressure Tunnel was a hurried necessity and designing began February 1945 with completion scheduled by the end of 1945. NACA launched the project of building a Mach 2 tunnel within 10 months. Contractors were hired for the mechanical design and actual fabrication of the tunnel. Near the end of 1945, the objective was near completion but a 2-year strike halted production of the compressor and operation didn’t begin until 1948.
Many important military and space vehicle tests were conducted in the 4 X 4-Foot Supersonic Pressure Tunnel. Century Series fighters like the F-102 and F-105, the B-58 supersonic bomber, and the X-2 research aircraft were all tested here. It was such an asset to NACA that it underwent modifications in 1950 for new drive motors which increased the horsepower from 6,000 to 45,000 (continuous) and 60,000 (intermittent). During the early 1970's, operation of the 4 X 4 Supersonic Pressure Tunnel was transferred to the 16-Foot Transonic Tunnel staff. During this period the facility was used for performance tests on military aircraft such as the F-14 and F-15 (See It's yours. No, it's yours.) and for general research on nozzle performance and propulsion airframe integration. The last research run in the facility was conducted on a Single-Engine High-Pressure Air Nacelle Model on September 2, 1976 and the"official" tunnel retirement date was September 3, 1976. The tunnel was decommissioned in 1977, as plans for NTF were conceived. Parts of the 4 X 4 were integrated into NTF’s design like drive motors, cooling towers, and surrounding support facilities.
The need for the large transonic tunnel was accepted nationally during the 1960s. The acceptance came after breakthroughs were made with the 0.3 meter transonic cryogenic tunnel at Langley. Many plans and alternatives were made but all of them were terminated due to extremely high costs. NASA’s recent successes with cryogenics backed a proposal for a 2.5 meter cryogenic transonic tunnel. The U.S. Air Force wanted an intermittent high-pressure Ludweig-tube tunnel for transonic test requirements. Both of these facilities would have been expensive to build so it prompted the federal government to combine the projects and build one National Transonic Facility. The approximate cost was $85 million but it would serve to fulfill all U.S. commercial, military, and scientific requirements. Completion date was set for 1982 and the first ton of cryogenic nitrogen flowed through NTF in 1983.
NTF is high-pressure, cryogenic, and closed circuit. Super-cold nitrogen gas is used in the test section at high pressure to simulate true flight aerodynamics. The facility has a drive power of 135,000 hp and reaches Mach 1.2 speeds. What makes NTF unique is it can test models from one-fifteenth scale to full because it can adjust the airflow according to the model size unlike traditional wind tunnels. NTF has provided the highest quality of flight Reynolds number aeronautical data to the research, industry, and Department of Defense communities. Noteworthy tests in NTF include the Boeing 777, the Space Shuttle and Booster, the Boeing 767, the B-2 Bomber, the A-6 Intruder, and the F-18 Hornet.
Today, NTF at Langley is used for tests in cruise performance, configuration aerodynamics validation, support of stability and control, and stall buffet onset. What also makes NTF unique is that it has a 150 cubic foot space vacuum used for testing. The vacuum was completed in 1965. NTF also has its own liquid nitrogen plant to supply the facility with the nitrogen gas needed for testing. Groundbreaking for the plant was in October of 2007 and the plant is fully operational today.
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See 4X4 Tunnel Models for tests conducted prior to change to NTF in 1977.