Big, unmanned spy planes, like the Predators flying over Iraq, have plenty of problems. For starters, they are expensive to build and operate. More important, some can be relatively easy to spot. Shrinking such planes so that they weigh less than two ounces would result in the perfect vehicle to get a bird’s-eye view of the terrain.
Of course, flying a craft as small as 4^1/2 inches wide comes with its own difficulties—the smaller the flyer, the more unstable and less energy efficient it becomes. To smooth the flight of such small planes, Peter Ifju, a professor of mechanical and aerospace engineering at the University of Florida, created a flexible wing (built onto the prototype plane at right) that can keep a steady course in the face of gusty winds. Inspired by the wings of bats, Ifju built a carbon fiber skeleton covered with a latex membrane that pacifies gusts ...
