Reshaping Aircraft

Flight engineers have always looked to nature for inspiration. Now they’re taking an even closer look. Using materials and computer systems that automatically sense and respond to their environments, scientists at a NASA-funded Texas research consortium are building components for dramatically experimental aircraft. The new planes and spacecraft will be stronger and lighter; they also will be able to “heal” damage to their systems, make themselves more aerodynamic under shifting conditions, and even morph their wing shapes during flight.

About 30 researchers at six universities are being funded through the new Texas Institute for Intelligent Bio-Nano Materials and Structures for Aerospace Vehicles, headquartered at Texas A&M University in College Station. “The challenge is really can we mimic nature,” says Satish Nagarajaiah, a Rice University civil engineer involved in the project. To create aircraft that perform more like insects and birds, the researchers will develop composite materials that incorporate organic and biological molecules for use in structural materials, sensors, and actuators. Such control surfaces as flaps, which have been used for decades, could be replaced by wings that continuously morph to maximize aerodynamics and consume less fuel.

The institute’s functionalized-nanomaterials group, for instance, is modifying carbon nanotubes-pipelike carbon molecules with unusual structural and electronic properties-to create a “skin” for advanced aircraft, says group leader Enrique Barrera, a Rice University mechanical engineer. The outer layer will be sensitive to changes in airflow and mechanical stress; and it will use the carbon nanotubes as tiny actuators to help the machines modify their shapes in response to changing aerodynamic conditions.

In addition to developing the materials, the institute’s researchers will have to create entirely new methods for controlling the vehicles. Today’s pilots adjust the positions of such surfaces as flaps and rudders, but the new planes will change their shapes completely and may have 100 times as many sensors and actuators, predicts David Zimmerman, a University of Houston mechanical engineer who heads the institute’s intelligent-systems group. “The theory for handling that just doesn’t exist today,” he says. So his group is developing new control algorithms that will allow a plane to “decide” what shape to assume on the basis of input from its sensors.

Although it may take 15 years to build an aircraft with the ability to reshape itself in response to its environment, structural and sensing components created by the consortium may make their way into spacecraft and the International Space Station in just two to three years, Barrera says. “NASA certainly has put a lot of effort into this,” says Rick Claus, an electrical engineer at Virginia Polytechnic Institute and a former NASA engineer. But coming up with improved materials with the characteristics needed to achieve the institute’s goals, he cautions, “is going to be a difficult thing.”