25 years inside the world's largest wind tunnel (pictures)

Tests conducted inside the world's largest wind tunnel at the National Full-Scale Aerodynamics Complex at NASA's Ames Research Center in Mountain View, Calif., give researchers a unique opportunity to have a controlled look at the forces affecting flight.

Originally built in 1944 at what was then the National Advisory Council for Aeronautics (NACA) Ames Aeronautical Laboratory, the wind tunnel was originally a 40-foot-by-80-foot facility, upgraded 25 years ago this week -- on December 11, 1987 -- by adding on a massive 80-foot-by-120-foot test section, and renamed the National Full-Scale Aerodynamics Complex (NFAC).

The facility has tested Vertical Take-Off and Landing (VTOL) aircraft and rotorcraft at low speeds, F-35 Lightning prototypes, a full-scale UH-60A Black Hawk rotor with Individual Blade Control, scale models of space shuttles, space parachutes, a full-scale replica of the Wright brothers' first airplane, and even tractor trailer trucks.

Here, an F/A-18 High Alpha fighter tests high angle-of-attack aerodynamics in the NFAC 80-foot-by-120-foot test section.

Testing for the Mars Science Laboratory (MSL) Curiosity rover landing parachute was also conducted at the NASA Ames 80-foot-by-120-foot test section. The parachute was the largest ever built to fly on an extraterrestrial mission. This image shows a duplicate qualification-test parachute inflated in 80-mile-per-hour wind inside the test facility. It has 80 suspension lines, is more that 165 feet long, and opens to a diameter of nearly 51 feet.

Scale model studies of some aspects of flight, including parachutes and rotorcraft, are limited because the way they interact with the air is far more complicated than fixed wing aircraft. Despite better computer simulations, there has been limited success in gathering accurate data between air and rotors and parachutes, NASA says, making full-scale testing in this wind tunnel invaluable.

A tiltrotor aircraft operating in its helicoptor-style take-off mode is seen here undergoing tests in the 40-foot-by-80-foot test section at NASA Ames.

An aerial view of the National Full-scale Aerodynamics Complex at NASA Ames Research Center in Mountain View, Calif.

A one-third scale model of the space shuttle preparing for tests in the 40-foot-by-80-foot test section.

An XSB2D-1 Navy/Douglas aircraft mounted in the 40-foot-by-80-foot test section viewed from center point in guide vanes. This was the first model tested in the tunnel following its construction in 1944.

For 40 full years before the fall of the Soviet Union, the NFAC had housed first the largest, and then the two largest, wind tunnels in the world. But no one could say for sure because until 1986 the United States did not have accurate information on the state of Soviet aerodynamics facilities.

NFAC 80-foot-by-120-foot wind tunnel drive fans. After re-powering the facility in 1980 and increasing the capacity of the wind-generating turbines, the smaller section's top wind speed was increased to 300 knots (345 mph) while the large section, which is big enough to test a Boeing 737, is capable of a top speed of 100 knots (115 mph).

The tunnel has six 40-foot diameter fans each with 15 laminated wooden blades. When operating at full power the fans turn 180 revolutions per minute, moving 60 tons of air per second, using 104 megawatts of electricity -- the equivalent of a 225,000-person city, NASA says.

In March 1999, as part of the Centennial of Flight celebration, a full-scale replica of the 1903 Wright Flyer was mounted in NASA Ames Research Center's 40-foot-by-80-foot wind tunnel for tests to build a historically accurate aerodynamic database of the flyer. For two weeks, engineers studied the replica's stability, control and handling at speeds up to 27 knots (30 mph) in the wind tunnel.

Lawrence Livermore National Labs (LLNL), Navistar, and the Department of Energy conduct a smoke test demo in the NFAC 80-foot-by-120-foot wind tunnel test section. The idea behind the project was to find a way to reduce fuel consumption at highway speeds by 10 percent, helping the commercial trucking industry and, by association, trickling down to consumer projects, cutting costs on fuel, and reducing carbon-dioxide emissions.

The continued use of the facility highlights the fact that even in the age of supercomputers and sophisticated computer modeling, wind tunnel testing is still essential to understand the realistic forces at work in aerodynamics. While the use of computers allows modeling and the introduction of a broader range of test conditions, because of their ability to produce highly accurate results in complex situations, NASA says wind tunnels like the Ames facility will continue to play an important role in the development and testing of new aircraft and a variety of other aerospace vehicles in the future.