Winds of Change

In September 1938, winds traveling at more than 100 miles per hour ripped through an MIT lab but left no destruction in their path. For decades after, the winds continued to howl, sweeping past scores of World War II airplanes and through the skyscraper-lined streets of Boston, Chicago, and New York City. Model airplanes and model skyscrapers, that is. The wind, generated by a 2,000-horsepower motor, is merely a tool in one of the Institute’s most dynamic labs: the Wright Brothers Memorial Wind Tunnel.

Even before the Wright brothers’ famous first flight in 1903, engineers used wind tunnels to test potential flying machines. MIT built its first wind tunnel in 1896–a meter-wide wooden contraption whose gentle 15-mile-per-hour winds would be of little value in the approaching age of manned flight. Over the next 40 years, MIT built six more tunnels in a continual effort to keep pace with rapidly improving airplane technology.

The Wright Brothers Tunnel, which was first tested in 1938, had an impressive top speed of 400 miles per hour. It, too, was quickly outpaced by faster tunnels, but it didn’t fade into oblivion as its predecessors had. Wind speed isn’t everything when it comes to airflow: there’s also pressure. With its airtight chamber (thanks to a shell made of steel instead of the traditional wood), the Wright Brothers Tunnel could be pressurized, allowing researchers to experiment with scaled-down models and still get results that correlated with those of life-size tests. At the time of its construction, the tunnel was one of only two in the U.S.–the other owned by the National Advisory Committee for Aeronautics (NACA), the federal agency that eventually became NASA–that could vary its internal pressure, so it was immediately in demand. During World War II, the wind tunnel ran day and night. “None of the aircraft companies prior to World War II had their own wind tunnels,” says Frank Durgin, associate director of the Wright Brothers Tunnel from 1969 to 1991. But when the war ended, most aircraft companies built wind tunnels of their own–and interest in supersonic airflow was growing. The Wright Brothers Tunnel’s wind speeds fell well short of those required to test supersonic designs, and demand for the tunnel declined dramatically as a result. The Wright Brothers Tunnel was “really quite idle” in the 1950s and early 1960s, Durgin says.

Durgin revitalized the tunnel by enlisting it in more architectural testing, such as measuring the effects of strong winds on tall buildings. Most notably, Durgin provided data on the effects of wind on Boston’s John Hancock Tower when, in the early 1970s, several of the building’s glass panels inexplicably fell out and shattered.

These days, wind tunnels are highly specialized. Automobile companies have their own tunnels, which would never be used to test aircraft, and vice versa. The Wright Brothers Tunnel is still available for some commercial testing, but it is primarily used as a teaching tool for students in Course XVI. Durgin, who still stops by on occasion to help set up experiments, says the tunnel could be improved by renovations to reduce turbulence. “It’s kind of a crude device at this point, but it’s still a viable tunnel,” he says. “It was remarkable what they did, and the fact that it’s still going is amazing.”