A visit to NASA Langley Research Center would be very exciting. You could meet NASA scientists and engineers working with wind tunnels. Why does NASA use wind tunnels?

Wind tunnels are basically tubes through which air - or a gas - is moved to make "wind" in the tube. This "wind" moves past objects such as airplanes or just parts from airplanes.

It is always a good idea to test a new aircraft design in a wind tunnel before you build the real aircraft. Models tested in wind tunnels will always go through design changes before engineers are satisfied with its design and test results.

There are many different types of wind tunnels around the world. NASA operates its wind tunnels at four locations in the United States. The locations are Langley Research Center in Virginia, Ames Research Center in California, Glenn Research Center in Ohio, and Marshall Space Flight Center in Alabama.

NASA Ames has the largest wind tunnel in the world. It can hold a full-sized aircraft with a wingspan up to 30 meters (100 feet). This wind tunnel is over 426 meters (1,400 feet) long and 55 meters (180 feet) high!

NASA Langley built the first wind tunnel in 1917 and began operating it in 1920. It could move air up to a speed of 145 km/hr (90 mph). At that time NASA was known as NACA - the National Advisory Committee for Aeronautics. NACA became NASA - the National Aeronautics and Space Administration - in 1958.

There are many types of wind tunnels with interesting names. They include Low-Speed (wind speeds up to 400 km/hr or 248 mph), Transonic (close to the speed of sound which is 1,223 km/hr or 760 mph at sea level), Supersonic (up to five times the Speed of Sound), and Hypersonic (between 5 and 15 times the Speed of Sound).

Wind tunnels are constructed with some very wide sections as well as some sections much smaller in size. An "open return wind tunnel" is open at both ends of the tube. It is usually largest (widest) at one end of the tube where you may even see the fan blade that creates the wind. This tube gets smaller as you move away from the fan blade. The tube begins to straighten in the next part of the wind tunnel called the Test Section. This is where you place the model (or aircraft parts) for testing. The tube widens again as you move away from the Test Section.

Another wind tunnel demonstrates the "closed return" design. This tunnel is completely contained inside a building. The tunnel moves in a "loop" inside the building. A fan is located in the tunnel on one side of the building and the test model is located in the tunnel's Test Section on the other side of the building.

Wind tunnels that move air at high speeds experience very high temperatures (up to 2,200 degrees Celsius or 4,000 degrees Fahrenheit). Air moving at such a high speed can "liquefy" where it acts more like a liquid than a gas. The air is preheated to thousands of degrees to remain as a gas.

Other gases can be used in a wind tunnel to recreate atmospheres of other planets. These gases can create very high pressure, which means the wind tunnel and its equipment may need sides several centimeters (several inches) thick.

NASA has always tested models of its manned and unmanned spacecrafts in wind tunnels before the actual craft is built. Other special objects that have been tested in wind tunnels include submarines, parachutes, and blimps (large manned balloons).

NASCAR race teams even test their race cars in wind tunnels to test and improve a car's design (shape). These teams work hard to reduce a car's drag (wind resistance). Less drag will let the car move faster and use less fuel during the race.

Recently, a team of aeronautical engineers in Virginia built a full-sized replica of the Wright brothers' glider. They tested it in a wind tunnel at Langley Research Center. This glider will be flown in Kitty Hawk, North Carolina, on December 17, 2003. This will be 100 years to the day after the Wright Brothers famous flight.

In less than 100 years, wind tunnels have allowed mankind to improve cars on the ground, aircraft in the atmosphere, and spacecrafts in space. We can only imagine what will happen with wind tunnels during the next hundred years.