Video: Inside the World's Largest Wind Tunnel

When NASA Ames runs its massive wind tunnels, the surrounding area knows it. Local aircraft are warned of potential updrafts. Electric utilities brace for sudden power draws. And nearby residents are said to hear its 300-knot airflows from miles away.

Thanks to the sponsorship of Littelfuse Inc., Design News recently had the opportunity to tour the facility, and it didn't disappoint. The National Full-Scale Aerodynamics Complex, as it's formally known, has to be experienced to be appreciated. Used primarily for aerodynamic and acoustic tests on rotorcraft and powered-lift aircraft, it's also capable of doing full-scale tests on an F/A-18 supersonic fighter jet. The facility has even been the site of one-third scale tests on the Space Shuttle.

The power it needs to perform such tests is almost mind-boggling. Air is driven by six 40-ft-diameter, 15-bladed variable-pitch fans powered by 40-pole, 6,600V synchronous motors, each rated at 18,000 HP. To spin the wooden blades, each weighing 880 lb, the facility burns up to 104 MW.

"It's equal to the energy usage of a city of 225,000 people," William Warmbrodt, chief of aeromechanics for NASA Ames Research Center, told Design News. "It's like we've introduced 225,000 people to the northern California utility grid." Up until about 20 years ago, NASA Ames had to schedule its use of the 80 ft x 120 ft tunnel with Pacific Gas and Electric Co. for fear it would use up too much of the available power on hot, sunny days. Today, NASA owns 5.5 percent of northern California's Shasta Dam, and gets its power from there, Warmbrodt told us.

All that power, however, goes to good use. By spinning the huge fans, the facility's 40 ft x 80 ft wind tunnel tops out at an airspeed of 300 knots, while the larger, 80 ft x 120 ft wind tunnel hits 100 knots. NASA engineers use those powerful winds to investigate aerodynamics and validate computational methods. They also examine aeromechanical stability boundaries of advanced rotorcraft and determine dynamic characteristics of new aircraft configurations.

"This is a very good facility for doing full aerodynamic evaluation of large-scale models," Warmbrodt said.

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