But Langley was a conclave of the world’s best aerodynamicists, the leading edge of the technology that was transforming not only the nature of war but civilian transportation and the economy. The distance between the NACA’s discovery of new aerodynamic concepts and their application to pressing engineering problems was so short, and the pace of their research and development so constant, that an entry-level position at the laboratory was the best engineering graduate school program in the world. Eager front-row boys from the lecture halls of MIT and Michigan and Purdue and Virginia Tech angled for a shot at getting in the door where Dorothy now sat.
With the goal of turning lady math teachers into crack junior engineers, the laboratory sponsored a crash course in engineering physics for new computers, an advanced version of the class offered at Hampton Institute. Two days a week after work, Dorothy and the other new girls filed into a makeshift classroom at the laboratory for a full immersion in the fundamental theory of aerodynamics. They also attended a weekly two-hour laboratory session for hands-on training in one of the wind tunnels, shouldering an average of four hours of homework on top of a six-day workweek. Their teachers were the laboratory’s most promising young talents, men such as Arthur Kantrowitz, who was simultaneously an NACA physicist and a Cornell PhD candidate under the supervision of atomic physicist Edward Teller.
After twelve years at the head of the classroom, the tables had turned, and for the first time since graduating from Wilberforce University, Dorothy Vaughan gave herself fully to the discipline that had most engaged her youthful mind. She had come full circle and then some, as she tried to attune her ear to the argot that flew back and forth between the inhabitants of the laboratory, all seeking to answer the fundamental question “What makes things fly?” Dorothy, like most Americans, had never flown on a plane, and in all likelihood, before landing at Langley, she had never given the question more than a passing consideration.
The first courses imparted the basics of aerodynamics. For a wing moving through the air, the slower-moving air on the bottom of the wing exerts a greater force than the faster-moving air on the top. This difference in pressure creates lift, the almost magical force that causes the wing, and the plane (or animal) attached to it, to ascend into the sky. Smooth air flowing around the wing means the plane can slip through the sky with minimum friction, the way the most efficient swimmers cut through the water. Turbulent flows, like the swirl and churn of rapids in the water, resist the plane, slowing it down and making it harder to maneuver. One of the NACA’s great contributions to aerodynamics was a series of laminar flow airfoils, wing shapes designed to maximize the flow of smooth air around the wing. Aircraft manufacturers could outfit planes with wings based on a variety of NACA specifications, like choosing kitchen appliances from a catalog for a new house. The P-51 Mustang was the first production plane to use one of the NACA’s laminar airfoils, a factor that contributed to its superior performance.
Future generations would take the advances for granted, but in the early days the mechanical birds yielded their secrets slowly, pressed by disciplined experimentation, rigorous mathematics, insight, and luck. In the heyday of the Wright brothers and the laboratory’s namesake, inventor and researcher Samuel Langley, those with a vision for a flying machine took a “cut and try” approach: make some assumptions, build a plane, try to fly it, and, if you didn’t die in the process, implement what you learned on your next attempt. Aeronautics’ evolution from a wobbly infancy to a strapping adolescence gave rise to the professions of aeronautical engineer and test pilot. Daring men—and with the exception of Ann Baumgartner Carl at Ohio’s Wright Field, they were all men—the test pilots did the “damn fool’s job” of flying an airplane directly into its weak spot. Each time the pilot pushed the aircraft to the limit, identifying how to make a good plane better and a bad plane nonexistent, he risked his own life and the loss of a very expensive piece of equipment.
A wind tunnel offered many of the research benefits of flight tests but without the danger. The basics of the tool rested on a simple concept, known even to Leonardo da Vinci: air moving at a certain speed over a stationary object was like moving the object through the air at the same speed. At its simplest, a wind tunnel was a big box attached to a big fan. Engineers blasted air over planes, sometimes full-sized vehicles or fractional-scale models, even disembodied wings or fuselages, closely observing how the air flowed around the object in order to extrapolate how the object would fly through the air.
Most of the work done at Langley was of the “compressed-air” persuasion, research conducted in one of the proliferating number of wind tunnels. The names of the tunnels alone—the Variable-Density Tunnel, the Free-Flight Tunnel, the Two-foot Smoke-Flow Tunnel, the Eleven-inch High-Speed Tunnel—challenged the uninitiated to imagine the combination of pressure, velocity, and dimension that resided therein. The Full-Scale Tunnel’s thirty-by sixty-foot test section opened wide enough to swallow a full-sized plane. Though the West Area’s Sixteen-foot High-Speed Tunnel had an exoskeleton the size of a battleship, the test section—the area where engineers, sitting at a control panel, observed the air flowing over the model—was only the size of a rowboat. But in order to accelerate the air to the necessary speed, giant wooden turbines had to accelerate the blast through the entirety of the tunnel’s circuit.
Of course, while moving the air over the object was similar to flying through the air, it wasn’t identical, so one of the first concepts Dorothy had to master was the Reynolds number, a bit of mathematical jujitsu that measured how closely the performance of a wind tunnel came to mimicking actual flight. Mastery of the Reynolds number, and using that knowledge to build wind tunnels that successfully simulated real-world conditions, was the key to the NACA’s success. Running the tunnels during the war presented yet another logistical challenge, as the local power company rationed electricity. The NACA nuts ran their giant turbines into the wee hours if necessary, engineers pressing the machines for answers to their research questions like night owls on the hunt for mice. Residents who lived near Langley complained about the sleep-disrupting roar of the tunnels. If they’d known more about the nature of the work behind the noise, and the successes being chalked up by the strange folks next door, the neighbors might have asked for a tour.