Fly Like A Bird

To reach the skies, the solid-state aircraft ideally would take off from the ground and ascend on its own. But that requires a lot of power and strong wings. So initially we're looking at launching prototypes from a balloon similar to those used in weather research. The aircraft would be compactly stowed in the balloon's gondola, and at the desired altitude it would be unfolded and released.

The aircraft's ability to remain aloft for long periods of time would make it ideal for imaging the Earth's surface from on high, of clear interest for both civilian and military purposes. Although not designed to carry heavy payloads, the plane could easily wield the latest generation of miniaturized cameras developed for unmanned aerial vehicles (UAVs) and micro-UAVs.

Remote sensing is another potential application. Equipped with special sensors and miniaturized mass spectrometers, the solid-state aircraft would ideally fly at an altitude of about 20 km, where Earth's atmospheric conditions are more stable and from where it would be able to monitor the troposphere, just below, where most weather activity occurs.

As a communications platform, the aircraft could carry thin-film antennas or transparent metallic antennas--both now used in automobiles--to relay signals to and from satellites and ground stations, thereby extending transmission ranges.

Perhaps most intriguing is the idea of using the aircraft to explore other planets. Take Venus. Its surface is hot and inhospitable, but at altitudes above 50 km it's actually very Earth-like, with pressure levels similar to ours, temperatures of less than 50° C, and an atmosphere containing carbon, hydrogen, oxygen, nitrogen, and other basic compounds needed for life. Given all that, plus the planet's abundant solar energy, it's one of the more likely places in our solar system to find life.

We still have much work to do to make any of that happen. The next step will be to simulate a full 3-D representation of the aircraft so that we can understand its behavior during all kinds of flight conditions. In particular, we need to understand better how to vary the airfoil's shape throughout the flapping cycle. We also plan to build a 1-kg scale model demonstrator with a 1-meter wingspan. By testing it in a wind tunnel, we'll be able to confirm the lift and drag coefficients. We'll also attach the model to a tether and fly it in a circle-which will help us further assess its aerodynamics.

Overall, the greatest challenge will be to develop a control scheme for the wings. Just getting the IPMC material to replicate the many ways that birds change their wings will be a feat in itself; controlling these intricate variations in real time will be even harder. Flight-control schemes used in conventional planes won't work; those preprogrammed systems use measurements like airspeed, altitude, and rotation to compute the plane's position and orientation, and thus the actions required to maintain stability. The solid-state aircraft will likely need to use neural networks or some other kind of artificial intelligence that will enable the aircraft to "learn" how to control itself.

To overcome these and other challenges, we'll have to recruit a multidisciplinary team of aerospace engineers, materials scientists, biologists, computer scientists, and others. It may take a lot of effort and time, but the end result will be worth it: a machine that can not only fly like a bird, but maybe even do it better.

Acknowledgments

The author wishes to thank the following for their contributions to the solid-state aircraft project: Mohsen Shahinpoor at the University of New Mexico; Phillip Jenkins, Curtis Smith, and Terri Deacey at the Ohio Aerospace Institute; Kakkattukuzhy Isaac at the University of Missouri, Rolla; Teryn DalBello at the University of Toledo, in Ohio; and David Olinger at the Worcester Polytechnic Institute, Massachusetts.