A team of engineers have built and tested a radically new kind of airplane, gathered from hundreds of small, uniform pieces. The wing can change shape to control the aircraft's aircraft and could provide a significant boost in aircraft production, aircraft and maintenance efficiency, the researchers said.
The new approach to wing design could provide greater flexibility in the design and manufacture of future aircraft. The new wing design was tested in a NASA wind tunnel and is described today in a paper in the journal Smart Materials and Structures co-author of researcher Nicholas Cramer at NASA Ames in California; MIT alumnus Kenneth Cheung SM & amp; 07 PhD & # 1
The result is a wing that is much lighter and thus much more energy efficient than those with conventional designs, whether made of metal or composites, the researchers say. Because the structure, made up of thousands of small triangles of matchstick-like struts, consists mainly of empty space, it forms a mechanical "material" that combines the structural rigidity of a rubbery polymer and the extremely light and low density of an airgel.
Jenett explains that for each of the phases of a flight – starting and landing, cruising, maneuvering, and so on – each has its own different set of optimal wing parameters, so a conventional wing is necessarily a non-optimized compromise any of these and therefore sacrifices efficiency. An ever-deformable wing could provide a much better approximation of the best configuration for each step.
Although it is possible to include motors and cables to produce the forces required to deform the blades, the team has taken this one step further and designed a system that automatically responds to changes in its aerodynamic load ratio by changing shape – a kind of self-adjusting, passive wing configuration process.
"We can achieve efficiency by matching the shape to loads at different angles of attack," says Cramer, the paper's lead author. "We can produce the exact same behavior you would do actively, but we did it passively."
This is achieved by carefully designing the relative positions of struts with varying amounts of flexibility or rigidity, designed so that the wing or parts of it flex in certain ways in response to particular forms of stress.
Cheung and others showed the basic underlying principle a few years ago and produced a one-meter-long blade that could be compared to the size of typically remotely modeled aircraft. The new version, which is about five times as long, can be compared to the size of the wing of a genuine one-person aircraft and could be easily manufactured.
While this version was handled by a team of graduate students, the repetitive process was designed to be easily accomplished by a swarm of small, simple, autonomous assembly robots. The construction and testing of the robot mounting system is the subject of a forthcoming paper, Jenett says.
The individual parts for the former wing were cut using a water jet system, and it took several minutes to make each part, Jenett says. The new system uses injection molding with polyethylene resin in a complex 3-D form and produces each part – essentially a hollow cube consisting of matchstick size struts along each edge – in just 17 seconds, he says, bringing it to a long closer at scalable production levels.
"Now we have a manufacturing method," he says. While there is a prior investment in tools once it's done, "the parts are cheap," he says. "We have boxes and boxes of them, all the same."
The resulting lattice, he says, has a density of 5.6 kg. Cubic meters. For comparison, rubber has a density of approx. 1,500 kg pr. Cubic meters. "They have the same rigidity, but ours has less than about a thousandth of the density," says Jenett.
Because the overall configuration of the wing or other structure is made up of small subunits, it really doesn't matter what the shape is "You can make any geometry you want," he says. "The fact that most aircraft are of the same shape" – essentially a pipe with wings – "is at the expense of cost. It is not always the most effective form." But massive investment in design, tools and production processes makes it easier to stay in long-lasting configurations.
Studies have shown that an integrated body and wing structure could be much more efficient for many applications, he says, and with this system, these could be easily built, tested, modified and tested.
"The research shows promise to cut costs and increase performance for large, light and rigid structures," said Daniel Campbell, a research scientist at Aurora Flight Sciences, a Boeing company not involved in this research. "Most promising near-time applications are structural applications for airships and space-based structures, such as antennas."
The new wing was designed to be as large as could be accommodated in NASA's fast wind tunnel at the Langley Research Center, where it performed slightly better than predicted, Jenett says.
The same system can also be used to make other structures, says Jenett, including the wind turbine's blade-like blade, where the ability to make on-site mounting could avoid problems of transporting longer blades. Similar compositions are being developed to build space structures and could eventually be useful for bridges and other high performance structures.
The team included researchers at Cornell University, the University of California at Berkeley in Santa Cruz, NASA Langley Research Center, Kaunas University of Technology in Lithuania and Qualified Technical Services, Inc., in Moffett Field, California. The work was supported by the NASA ARMD Convergent Aeronautics Solutions Program (MADCAT Project) and the MIT Center for Bits and Atoms.