Tunnels Will Blow You Away

Langley Open House Features Wind Tunnels

October 11, 1992|By KIRK SAVILLE Daily Press

HAMPTON — Taller than three-story buildings, the twin fans resemble giant ship propellers yanked out of water.

Sixty years after they were installed in what looks like a metal warehouse, the wooden blades can still kick up hurricane-force winds.

And researchers still wait for years to test models of the world's most sophisticated airplanes in the wind tunnel - aircraft that would have been hard to imagine when the facility was designed in the late 1920s.

NASA Langley Research Center's full-scale tunnel, declared a Historic Landmark in 1985, is NASA's oldest operating wind tunnel. It is one of 40 tunnels at Langley, and one of five that will be open to the public during the center's open house on Saturday.

Winds in Langley's tunnels can blow at 250 degrees below zero and at 10 times the speed of sound. NASA's Ames Research Center in California has some of the world's largest wind tunnels, but Langley may have one of the broadest collections of wind tunnels in the world.

``We probably have the greatest spectrum from small to large and through the speed ranges than anywhere else,'' said Donald Baals, a former Langley researcher and co-author of the book ``Wind Tunnels of NASA.''

Model planes, a few feet long, used in the tunnels can cost more than $1 million. Billions of dollars and the futures of entire aerospace companies can ride on tests done in Langley's tunnels.

Many military and commercials planes now in use were tested in Langley tunnels at some stage of their development, and all planes make use of technological advances made in the center's tunnels.

Tests have not been limited to airplanes. The Mercury space capsule, the space shuttle, helicopters and submarines have all been placed in the tunnels.

Researchers are now using wind tunnels to test concepts for a supersonic airliner and a plane that can fly into space.

Whatever the uses, the basic principle of a wind tunnel is the same almost a century after the Wright brothers used their wind tunnel to figure out the mechanics of flight.

``The wind tunnel concept has basically stayed put,'' Baals said.

Fans usually suck air over a scale model of a plane mounted in what's called the test section of the tunnel. Instruments in the model provide information on how the wind affects the plane.

Engineers are particularly interested in measuring properties called lift, how the wings are acting to pull the plane up, and drag, the aircraft's resistance to air flowing smoothly over its surface.

Tiny holes on the body of the model are connected to tubes to provide readings of air pressure on the model's surface.

The full-scale tunnel was finished in 1931 at a cost of $950,000. Its winds travel about 100 mph. ``That was flight speed back then,'' said Dana Dunham, head of Langley's flight dynamics branch. ``Now most planes land faster than that.''

Even though planes now routinely fly faster than the speed of sound, there is still a three-year wait to use the tunnel, Dunham said. Much of the work done in the tunnel concerns how to control planes.

For example, models might be outfitted with dual tail fins for some tests and single tails for others to examine how to best control the plane, Dunham said. In other tests, the flaps used to steer planes can be adjusted to check their performance.

The tunnel was designed to test full-sized planes - the area of the tunnel that holds the models is big enough to fit a small house. Every type of American fighter plane used in World War II was tested in the tunnel.

Planes in the tunnel are attached to scales. As air flows over the wings, forcing the plane up and down, the scale's reading changes.

In the past, researchers would stand at the scales, recording the changes. Now electronics record the information, giving engineers instantaneous readouts.

In the early years, calculations were worked by ``computers,'' women working with slide rules. Now high-speed electronic gear give engineers instantaneous data readouts, and computer models help researchers know what to look for.

One of the planes recently tested in the tunnel is a 30-foot-long model of an airliner that would fly faster than the speed of sound. After sixty years of testing, there's no end in sight for uses of the full-scale tunnel. ``We have no plans to stop operating,'' Dunham said. ``With a three-year wait, it's hard to see how we'd stop operating.''

A few miles away from the full-scale tunnel, near Langley's border with Armistead Avenue, a dense plume of white fog pours out of a stack whenever the center's newest major tunnel is operating. The National Transonic Facility, which is unlike any wind tunnel in the world, was completed in 1982.

The fog comes from liquid nitrogen used to cool the tunnel to 250 degrees below zero. After the nitrogen is used in the tunnel, it is vented outside. Because about 80 percent of the Earth's atmosphere is nitrogen, the release is harmless.

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