The key piece of equipment at the San Diego Wind Tunnel is a 20-foot fan, powered by a 2,250 horsepower motor, that accelerates air up to 270 miles per hour. (Technically, that makes them a “low-speed” wind tunnel.) The air travels in a loop from the fan, through the test section—which is narrower, to help the air speed up, like water going through a canyon—and then eventually returns to the fan, saving energy. The facility, which dates back to 1947, has its roots in the aerospace industry. “We’ve tested virtually every airplane that Boeing flies here,” says Martin Dine, the tunnel’s general manager. Because the testing space is just 8 by 12 feet by 15 feet long, aircraft makers use scale models of their craft.