His finalist year: 1974
His finalist project: Designing a wind tunnel that uses magnets to hold test models in place
What led to the project: As a child growing up in rural Oregon in the 1960s, Ilan Kroo was obsessed with flying. Along with friends, he built a hang glider from bamboo poles, duct tape and plastic. They took the contraption to a nearby dairy farm, ran down a hill, and would actually get a few feet off the ground before crashing. "Any landing that we could walk away from was a good landing," Kroo says.
Fortunately, he survived that learning experience and, in high school, with the help of a research program at the Oregon Museum of Science and Industry in Portland, decided to build a better wind tunnel to help him understand the aerodynamics of other flying objects. One of the big problems of wind tunnels is that the object being tested requires a support structure to stay in place as air blasts around it. But these constraints affect airflow, thereby skewing the data.
To get around this problem, Kroo built a wind tunnel lined with magnets on its top and bottom. A photo sensor monitored the test object and sent signals to change the strength of the magnets' field so they, rather than a support structure, could hold the object in a stationary position. "I learned a lot about circuits as well as wind tunnels and magnets," Kroo says. The concept also won him one of his first actual plane flights—a trip to Washington, D.C., for the final round of the 1974 Westinghouse Science Talent Search.
The effect on his career: Doing so well in a prestigious science competition encouraged Kroo to raise his sights and "made it possible for me to go to a place like Stanford," where he enrolled as a physics major. He fell in love with California, and so stayed at the university to get a PhD in aeronautics. His thesis looked at how the forces acting on hang gliders—inertia, drag, lift, the object's own elasticity—interact. At the time, in the late 1970s, hang gliding was "not a very safe thing to do," he says. He looked at the interaction between structure and aerodynamics, did wind tunnel tests, and worked with a number of hang-glider companies on implementing the findings.
After earning his PhD, Kroo took a job at NASA Ames Research Center at Moffett Field, Calif. With fuel prices skyrocketing in the early 1980s, he worked on the then-urgent idea of a more efficient airplane, although, of course, some of that interest "disappeared as fuel prices fell," he says.
What he's doing now: Though public interest in efficient planes has waxed and waned with the price of oil, Kroo has stayed on the problem. Now, as a professor at Stanford, one of his major areas of research is "sustainable aviation"—that is, "the idea of making aircraft that have a sufficiently small environmental footprint [so] that we can accommodate the growth expected in air transportation while not increasing the impact on the environment," he says.
The goal? Increase the efficiency of commercial airplanes by 50 percent. That's not a random number; Juan Alonso, a fellow professor in Stanford's aeronautics department, notes that air traffic is expected to double in the U.S. by 2025. "If you fly twice as much, you're going to have to consume half as much," he says, to avoid additional environmental damage. Typical design modifications such as lighter materials of a slightly different wing shape can produce energy savings of 2 to 5 percent. A 50 percent reduction, on the other hand, will require totally different designs, with optimization of all the different airplane components. Kroo's main contribution to the field, Alonso says, is "multidisciplinary design optimization". "He was one of the first people to realize this could be done and needed to be done."
More importantly, he actually did it. The optimization techniques he's developed (for instance, methods to help engineers minimize costs or emissions) are used all the time in industry, says Robert Liebeck, a senior fellow at Boeing and designer of the Liebeck airfoil (a wing or blade shape known for its high lift-to-drag ratio). "A lot of academics wind up answering a question nobody asked," Liebeck says. "Ilan is the opposite." His work has been quite practical, he says.
In addition to sustainable aviation and optimization, Kroo has also worked on "autonomous airplanes" (pilotless drones), making supersonic air travel a viable option, and on a vehicle known as the "foot-launched sailplane." This personal craft has some of the characteristics of a hang glider but performs like a sailplane; it can fly much longer distances much more safely.
He designed the craft with some students almost 20 years ago, and eventually licensed it commercially. These days, the aircraft that came to be known as the SWIFT is being manufactured by Belgian company Aériane. "That was really fun to see—it going from a blank sheet of paper to many of these things flying around," he says. (He has also mentored a 1987 Westinghouse finalist, Ian Patrick Sobieski.)
With three children that he'd prefer not to see crash-landing on dairy farms the way he did as a youngster, Kroo doesn't do much hang gliding anymore. However, he has flown the SWIFT. How would he describe it? "I probably can't do justice to that," he says. But, "flying at the speed of birds…totally quiet, looking down, seeing the mountains and desert floor 8,000 feet below you is unlike any other kind of flying," he says. "It's absolutely amazing."