The Wind Tunnel’s Future

Is the wind tunnel obsolete? In a word, no. But the value and merit of the tunnel in the early 21st century must be evaluated in the light of manifold other techniques that researchers can now employ. The range of these new techniques, particularly CFD, coupled with the seeming maturity of the airplane, has led some observers to conclude that there is little need for extensive investment in research, development, and infrastructure.[630] That facile assumption has been carried over into the question of whether there is a continued need for wind tunnels. It brings into question the role of the wind tunnel in contemporary aero­space research and development.

A 1988 New York Times article titled "In the Space Age, the Old Wind Tunnel Is Being Left Behind” proclaimed "aerospace engineers have hit

a dead end in conventional efforts to test designs for the next generation of spaceships, planetary probes and other futuristic flying machines.” The technology for the anticipated next generation in spacecraft technol­ogy that would appear in the 21st century included speeds in the escape velocity range and the ability to maneuver in and out of planetary atmo­spheres rather than the now-familiar single direction and uncontrolled descents of today. At the core of the problem was getting realistic flight data from a "nineteenth century invention used by the Wright brothers,” the wind tunnel. William I. Scallion of NASA Langley asserted, "We’ve pushed beyond the capacity of most of our ground facilities.” NASA, the Air Force, and various national universities began work on meth­ods to simulate the speeds, temperatures, stress, forces, and vibration challenging the success of these new craft. The proposed solutions were improved wind tunnels capable of higher speeds, the firing of small-scale models atop rockets into the atmosphere, and the dropping of small test vehicles from the Space Shuttle while in orbit.[631]

The need for new testing methods and facilities reflected the chang­ing nature of aerospace craft missions and design. Several programs per­ceived to be pathways to the future in the 1980s exemplified the need for new testing facilities. Proponents of the X-30 aerospace plane believed it would be able to take off and fly directly into space by reaching Mach 25, or 17,000 mph, while being powered by air-breathing engines. In 1988, wind tunnels could only simulate speeds up to Mach 12.5. NASA intended the Aeromanuevering Orbit Transfer Vehicle to be a low-cost "space tug” that could move payloads between high – and low-Earth orbits beginning in the late 1990s. The vehicle slowed itself in orbit by graz­ing the Earth’s outer atmosphere with an aerobrake, or a lightweight shield, rather than relying upon heavy retrorockets, a technique that was impossible to replicate in a wind tunnel. NASA planned to launch small models from the Space Shuttle for evaluation. The final program con­cerned new interplanetary probes destined for Mars; Jupiter; Saturn’s moon, Titan; and their atmospheres, which were much unlike Earth’s. They no longer just dropped back into Earth’s or another planet’s atmo­sphere from space. The craft required maneuverability and flexibility as incorporated into the Space Shuttle for better economy.[632]

NASA allocated funds for the demolition of unused facilities for the first time in the long history of the Agency in 2003. The process required that each of the Research Centers submit listings of target facilities.[633] NASA’s Assistant Inspector General for Auditing conducted a survey of the utilization of NASA’s wind tunnels at three Centers in 2003 and reported the findings to the directors of Langley, Ames, and Lewis and to the Associate Administrator for Aerospace Technology. Private indus­try and the Department of Defense spent approximately 28,000 hours in NASA tunnels in 2002. The number dwindled to 10,000 hours in 2003, dipping to about 2,500 hours in 2008. NASA managers acknowledged there was a direct correlation between a higher user fee schedule intro­duced in 2002 and the decline in usage. The audit also included the first complete list of tunnel closures for the Agency. Of the 19 closed facili­ties, NASA classified 5 as having been "mothballed,” with the remain­ing 14 being "abandoned.”[634]

Budget pressures also forced NASA to close running facilities. Unfortunately, NASA’s operation of the NFAC was short-lived when the Agency closed the facility in 2003. Recognizing the need for full-scale testing of rotorcraft and powered-lift V/STOL aircraft, the Air Force leased the facility in 2006 for use by the AEDC. The NFAC became operational again in 2008. Besides aircraft, the schedule at the NFAC accommodated nontraditional test subjects, including wind turbines, parachutes, and trucks.[635]

In 2005, NASA announced its plan to reduce its aeronautics budget by 20 percent over the following 5 years. The budget cuts included the closing of wind tunnels and other research facilities and the elimination of hundreds of jobs. NASA had spread thin what was left of the aero­nautics budget (down $54 million to $852 million) over too many pro­grams. NASA did receive a small increase in its overall budget to cover the costs of the new Moon-Mars initiative, which meant cuts in aviation – related research. In a hearing before the House Science Subcommittee

on Space and Aeronautics to discuss the budget cuts, aerospace industry experts and politicians commented on the future of fundamental aeronautics research in the United States. Dr. John M. Klineberg, a former NASA official and industry executive, asserted that the NASA aeronautics program was "on its way to becoming irrelevant to the future of aeronautics in this country and in the world.” Representative Dennis Kucinich, whose district included Cleveland, the home of NASA Glenn, warned that the United States was "going to take the ‘A’ out” of NASA and that the new Agency was "just going to be the National Space Administration.”[636]

Philip S. Anton, Director of the RAND Corporation’s Acquisition and Technology Policy Center, spoke before the Committee. RAND concluded a 3-year investigation that revealed that only 2 of NASA’s 31 wind tun­nels warranted closure.[637] As to the lingering question of the supremacy of CFD, Anton asserted that NASA should pursue wind tunnel facility, CFD, and flight-testing to meet national testing needs. RAND recom­mended a veritable laundry list of suggested improvements that ranged from the practical—the establishment of a minimum set of facilities that could serve national needs and the financial support to keep them run­ning—to the visionary—continued investment in CFD and focus on the challenge of hypersonic air-breathing research.

RAND analysts had concluded in 2004 that NASA’s wind tunnel facilities continued to be important to continued American competitiveness in the military, commercial, and space sectors of the world aerospace industry while "management issues” were "creating real risks.” NASA needed a clear aeronautics test technology vision based on the idea of a national test facility plan that identified and maintained a minimum set of facilities.

For RAND, the bottom line was the establishment of shared financial support that kept NASA’s underutilized but essential facilities from crumbling into ruin.[638] Anton found the alterna­tive—the use of foreign tunnels, a practice many of the leading

aerospace manufacturers embraced—problematic because of the myriad of security, access, and availability challenges.[639]

NASA’s wind tunnel heritage and the Agency’s viability in the inter­national aerospace community came to a head in 2009. Those issues centered on the planned demolition of the most famous, recognizable, and oldest operating research facility at Langley, the 30- by 60-Foot Tunnel, in 2009 or 2010. Better known by its NACA name, the Full-Scale Tunnel was, according to many, "old, inefficient and not designed for the computer age” in 2009.[640] The Deputy of NASA’s Aeronautics Test Program, Tim Marshall, explained that the Agency decided "to focus its abilities on things that are strategically more important to the nation.” NASA’s focus was supersonic and hypersonic research that required smaller, faster tunnels for experiments on new technologies such as scramjets, not subsonic testing. In the case of the last operator of the FST, Old Dominion University, it had an important mission, refining the aerodynamics of motor trucks at a time of high fuel prices. It was told that economics, NASA’s strategic mission, and the desire of the Agency’s landlord, the U. S. Air Force, to regain the land, even if only for a park­ing lot in a flood zone, overrode its desire to continue using the FST for landlocked aerodynamic research.[641]

In conclusion, wind tunnels have been a central element in the success of NACA and NASA research throughout the century of flight. They are the physical representation of the rich and dynamic legacy of the organization. Their evolution, shaped by the innovative minds at Langley, Ames, and Glenn, paralleled the continual development of aircraft and spacecraft as national, economic, and technological missions shaped both. As newer, smaller, and cheaper digital technologies emerged in the late 20th century, wind tunnels and the testing methodologies pioneered in them still retained a place in the aerospace engineer’s toolbox, no matter how low-tech they appeared. What resulted was a richer fabric of opportunities and modes of research that continued to contribute to the future of flight.