TECH SPACEBionic Research Points To Smart Flexible Aerospace Materials
NASA Space Science
Huntsville - March 5, 2001
The "personal aircraft" that replaces the beloved automobile in people's garages may still lie in the realm of science fiction or Saturday-morning cartoons, but researchers at NASA's Langley Research Center (LaRC) are developing exotic technologies that could bring a personal "air-car" closer to reality.
And air-cars are just the beginning.
Self-healing wings that flex and react like living organisms, versatile bombers that double as agile jet fighters, and swarms of tiny unmanned aircraft are just a few of the science-fiction-like possibilities that these next-generation technologies could make feasible in the decades ahead.
At the core of this impending quantum leap in aerospace technology are "smart" materials -- substances with uncanny properties, such as the ability to bend on command, "feel" pressure, and transform from liquid to solid when placed in a magnetic field.
"This is technology that most people aren't aware even exists," said Anna McGowan, program manager for the Morphing Project at LaRC, which develops these new technologies.
The task of the Morphing Project is to envision what cutting-edge aerospace design will be like 20 years from now and begin developing the technologies to make it happen.
For example, a personal air-car needs to be compact, yet able to fly at both very low and very high speeds.
"We know that to get a 'Jetsons' vehicle, you're probably going to need a wing that can undergo a radical configuration change," McGowan said. "The kind of wing you need at very low speed and the kind of wing you need at high speeds are completely different."
Some airplanes today can already reorient their wings, such as the Navy's F-14 Tomcat and the B-1 supersonic bomber. These planes use rigid wings mounted to large, heavy pivots in the plane's body.
In contrast, Morphing Project scientists envision a wing that will unfurl on command using "shape-memory" metal alloys or other novel "smart" materials. The material of the wing itself would bend to create the new shape.
Shape-memory alloys have the unusual property of snapping back to their original shape with great force when a certain amount of heat is applied. Any shape can be "trained" into the alloy as its original shape.
Among the exotic "smart" materials being developed by the Morphing Project, shape-memory alloys are relatively ordinary.
"What we did at NASA-Langley was basically dissect that material to answer the question, 'how does it do that?'" McGowan said. "By doing so, we can actually get down to computational modeling of these materials at the molecular level."
"Once we understand the material's behavior at that level, then we can create designer 'smart' materials," she added.
LaRC is also developing customized variations of piezoelectric materials. These substances link electric voltage to motion. If you contort a piezoelectric material a voltage is generated. Conversely, if you apply a voltage, the material will contort.
Scientists can use such properties to design piezoelectric materials that function as strain sensors or as "actuators" -- devices that create small motions in machines, like the moving of wing flaps.
Combined with micro-electronics, these materials could lead to a radical advance in airplane design.
"When we look 20 years into the future, we see airplanes that have distributed self-assessment and repair in real time," McGowan said.
"To make this technology possible, you would need to distribute these actuators and sensors throughout the wings. That's similar to how the human body operates. We have muscles and nerves all over our bodies -- so we are aware of what's happening to our bodies and we can respond to it in a number of ways."
The resemblance to biology doesn't end there. One avenue of Morphing Project research is to examine how nature does the things that it does well. Scientists hope they can learn lessons from this tutelage to improve their own designs.
"Nature does some things that we can't even get close to doing. Birds are so much more maneuverable than our airplanes are today. Birds can hover, they can fly backwards and sideways. And insects -- oh forget it! -- upside down, loop-de-loop, all sorts of things. We can't even get close to that [yet]," McGowan said.
Called "biomimetics," this practice of learning from nature has led to the development of -- among other things -- a facsimile of bone.
Bone is very light because of its porous interior, but it's also very strong. LaRC scientists can make structures similar to bone by injecting polymer microspheres into composite shells of the desired shape, then heating the spheres to make them fuse together like tiny soap bubbles.
"If you can have the strength and lightweightness of these bone-like structures that I'm talking about, then add in nerve-like sensors and these flexible actuators, what you're going to end up with is an extremely light-weight, very strong, self-sensing, self-actuating structure."
Compare that vision to the rigid, numb, heavy structures airplanes are made of today, and you'll get a sense of the dramatic difference "smart" materials could make in aerospace design.
As with all basic science, the applications of these "smart" materials will extend to technologies outside of the aerospace industry.
"We are working very closely with two different commercialization groups funded by NASA," McGowan said, "and the outlook for this technology is on the order of millions of applications."
NASA Smart Materials and Structures
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Champaign - Feb. 19, 2001
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