GAINESVILLE, Fla. --- A University of Florida aerospace engineering team is a step closer to reaching the ambitious goals of a military research program aimed at developing tiny, affordable airplanes for use in battlefield surveillance and other military situations.
Two UF aerospace engineering professors and their graduate students have built and successfully flight tested a 6-inch airplane, the Defense Advanced Research Projects Agency's target size in a major initiative to develop so-called "micro air vehicles."
"The military wants a plane the size of a small bird," said Peter Ifju, an assistant professor of aerospace engineering. "We came up with design modifications that gave us control over our plane at very high angles of attack, which allowed us to shrink it to the target size without compromising maneuverability or stability."
UF, one of several universities and private companies at work on micro-air vehicles nationwide, is not the first to build and fly such a small plane. But it is so far the only team do so using a latex- and carbon-fiber flexible wing design and one of just a few teams that have achieved such a small plane using cheap, off-the-shelf components.
"We've taken kind of a low-end approach to the problem because these planes will be most useful if they are inexpensive and easy to build in large quantities," said Dave Jenkins, an associate professor of engineering. "Our goal has been to get the basic aerodynamics down and go from there."
Ifju, Jenkins and graduate students Scott Ettinger and Luis Martinez began building the bat-like planes earlier this year to reduce weight and make the planes less vulnerable to turbulence. Steady refinements to the design have resulted a rapid reduction in the size of the planes from a minimum size of 12 inches less than a year ago.
The latest reduction was made possible by reshaping the torpedo-like tail of the airplane and placing it directly in the path of the "prop wash," or the wind generated by the propeller, Ifju said. While previous designs lost stability at certain angles of flight, the tail's position now guarantees a steady flow of air over the ailerons, elevators and rudder that control the plane's movement, Ifju said.
"The control surfaces are always in the sweet spot," he said.
The military's goal is a plane that can fly quietly for at least 20 minutes with a tiny video camera attached. The idea is to give soldiers the ability to scope out nearby enemy terrain without placing themselves or other friendly troops in danger.
While Ifju said the UF plane doesn't yet meet all those goals -- it has yet to be tested with a video camera aboard, though a camera equipped 8-inch version flew well -- the flexible wing design offers great potential, he said. That's because the design lends stability without so-called "active" control components on board, such as gyroscopes that sense the plane's movement and make adjustments to ensure it stays aloft, he said.
Contrasting other planes, which require expensive and hard-to-find materials, the planes are also cheap to build. Ifju estimated the cost of the 6-inch plane at no more than $300.
Now that the UF researchers have reached the target size, they plan to turn their attention to other areas, such as building an independent navigation system that would not require a remote control operator.
"We'd like to make one chip that would integrate all the electronics: the image from the camera, a digital processing system and navigation controls," said Ettinger, the graduate student. "That would make the plane capable of truly autonomous flight."
The UF team's research is funded by a $20,000 seed grant from the National Science Foundation. Ifju said the team is currently applying for further grants from NSF and NASA.
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