Most wind tunnels test models. For most of the 20th century, American aeronautical engineers had two tunnels big enough to swallow the real thing: a propeller-driven hangar at Langley, Virginia, and an even larger one at Moffett Field in California. Fighters, flying saucers, lifting bodies and spacecraft all went inside, bolted to struts, while fans the size of houses blew a gale over them.

This is the story of those two machines, and of some of the strangest things ever put in front of them.

Langley’s Full-Scale Tunnel

The National Advisory Committee for Aeronautics, NASA’s predecessor, ran its first wind tunnel at Langley in 1920. Within a decade its engineers wanted something far more ambitious: a tunnel big enough to test a complete aeroplane rather than a scale model, so that the awkward corrections between model and full size simply disappeared.

Construction began in the spring of 1930 under NACA engineer Smith J. DeFrance. The tunnel was dedicated on 27 May 1931, the largest wind tunnel in the world. Its open test section measured 30 by 60 feet, and two propellers, each 35 feet 5 inches across and driven by a 4,000-horsepower electric motor, pulled air through it at between 25 and 118 mph. The building alone was 434 feet long.

The first aircraft in, on dedication day, was a Vought O3U-1 Corsair II biplane. The tunnel made its reputation in 1938, when a Brewster F2A-2 Buffalo went in for a “drag clean-up”: engineers found and removed so many small sources of drag that the fighter gained 31 mph. Within 18 months, 18 more aircraft had been through the same process. Before and during the Second World War, almost every major American high-performance fighter passed through it, along with oddities such as the Vought V-173 “Flying Pancake”.

In March 1943 it hosted perhaps its most secret visitor, a captured Japanese Mitsubishi Zero, rolled straight off Langley Field and into the tunnel on its way to further testing at Wright Field.

Later work ranged from Mercury capsules to the British P.1127, forerunner of the Harrier, and an investigation into a 1968 accident involving the Lunar Landing Training Vehicle. NASA closed the tunnel in 1995, but Old Dominion University took it over the following year and ran it for industry and students, including car and truck testing. The last test, on 4 September 2009, was of the Boeing X-48 blended-wing-body demonstrator. The building was demolished in 2010 and 2011. One of its two giant fans is now displayed in the Boeing Milestones of Flight Hall at the National Air and Space Museum in Washington.

Ames: Six Fans and a Wall of Wind

By the late 1930s the NACA wanted a second full-scale facility on the West Coast, and a bigger one. At its new Ames laboratory at Moffett Field, California, it built a tunnel with a 40- by 80-foot test section, powered by six 40-foot fans. It began operating in June 1944. With steel rationed for the war effort, the builders used cement-based transite siding for the structure and laminated spruce for the fan blades.

Each fan was driven by a 6,000-horsepower electric motor. NASA’s own caption for the 1944 photograph notes that the airflow, at up to 230 mph, was still a tornado-force wind. Over the following decades the tunnel took in the A-26 Invader, the F-84 Thunderjet, the F-86 Sabre and later the F-14 Tomcat, the AV-8B Harrier II, the V-22 Osprey and a scale model of the Space Shuttle, as well as parachutes for the Apollo programme.

Some of the most photographed tests were of machines that looked as if they should never fly. In January 1961 the Avro Canada VZ-9 Avrocar, a US Army and Air Force-funded flying saucer, sat on struts in the 40 by 80 while engineers studied the stability and control problems that kept it from ever flying much higher than a few feet.

The Flying Bathtub

In 1963 the tunnel took in the M2-F1, a wingless lifting body built at NASA’s Flight Research Center at Edwards with a plywood shell over a tubular steel frame. Its shape earned it the nickname “the flying bathtub”. The idea was to test whether a returning spacecraft could fly and land using lift from its body alone.

After the first ground-tow attempts behind a souped-up Pontiac convertible on Rogers Dry Lake in March 1963, the M2-F1 was taken to Ames for full-scale tunnel runs, with research pilot Milt Thompson and engineers working its control surfaces during the tests. The programme went on to make more than 400 car tows and 77 aircraft-towed flights, and paved the way for the heavier lifting bodies, including the M2-F2, and ultimately for the Space Shuttle.

The World’s Largest Wind Tunnel

In the 1980s NASA rebuilt the Ames tunnel. The six fans were given new 22,500-horsepower motors, pushing the 40 by 80 section to 345 mph, and a second, even larger test section was added: 80 by 120 feet, fed through an intake NASA compares to a football field standing on its edge. The combined facility was dedicated as the National Full-Scale Aerodynamics Complex on 11 December 1987. Its 80- by 120-foot section, capable of 115 mph, is the largest wind tunnel test section in the world and big enough for a full-size Boeing 737.

NASA closed the complex in 2003. The US Air Force stepped in, its Arnold Engineering Development Complex took over management in 2006, and the tunnels were back in operation in 2007. They have since tested everything from rotorcraft to the parachute for NASA’s Mars Science Laboratory, a canopy more than 165 feet long. In 2024 the 40 by 80 turned 80.

The People in the Tunnels

The tunnels were built and run by thousands of engineers, technicians and “computers”, many of them women. At Langley, Mary Jackson worked in the 4- by 4-foot Supersonic Pressure Tunnel and in 1958 became NASA’s first Black female engineer. Her story, told in the book and film Hidden Figures, is one reason these tunnels are remembered as much for the people inside them as for the machines.

Computational fluid dynamics has taken over much of the work since, and several historic tunnels are gone. But as our explainer on what happens inside a wind tunnel sets out, nothing has yet fully replaced putting the real thing in front of a real wind.

Sources: NASA History Office, “30 x 60-Foot Full Scale Tunnel (Building 643)”; National Air and Space Museum, “The NACA/NASA Full-Scale Wind Tunnel” (John Anderson, 2015); NASA Ames, “Testing on the Ground Before You Fly”; Arnold Air Force Base, “NFAC marks 80th anniversary of 40- by 80-foot tunnel”; NASA, “Where Are They Now: M2-F1 Lifting Body”; NASA image archives and Historic American Engineering Record via Wikimedia Commons.