La NASA y el MIT MUESTRAN REVOLUCIONARIO PROTOTIPO DE AVIÓN


 AERONÁUTICA

Reproducimos aquí un artículo publicado por la sección Ciencia del diario ABC de Madrid. Esto es para mantener a nuestros lectores informados sobre las últimas novedades en Aeronáutica.

El prototipo ha sido ensamblado a partir de pequeñas piezas idénticas y podría permitir diseños más ligeros y eficientes





 
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Ingenieros de la NASA y del Instituto Tecnológico de Massachusetts (MIT) han construido y probado un nuevo tipo de ala que no tiene que ver con ninguna diseñada hasta la fecha. Hecha a partir de cientos de diminutas piezas idénticas, como si de un tejido se tratara, es capaz de deformarse para controlar el vuelo del avión. Y no solo eso: su producción sería relativamente barata y ahorraría grandes costes tanto en el mantenimiento como en el vuelo, ya que se trata de un ala 1.000 veces más ligera que las fabricadas con caucho.
Así lo aseguran Nicholas Cramer y Kenneth Cheung, de la NASA, junto con Benjamin Jenett, un estudiante graduado del MIT, cuyas pruebas en un túnel de viento de la agencia espacial estadounidense acaban de publicarse en la revista «Smart Materials and Structures».
«En lugar de requerir superficies móviles separadas para controlar el giro y la inclinación del avión, como hacen los alerones en las alas convencionales, el nuevo sistema de ensamblaje permite deformar toda la ala, o partes de ella, incorporando una mezcla rígida y flexible», afirma el MIT en un comunicado. Para que la estructura del ala no quede a la vista, los ingenieros proponen una cubierta delgada de polímero, similar al utilizado en las celosías que componen el material.

El resultado es un ala mucho más ligera y, por lo tanto, mucho más eficiente en el uso de la energía que los diseños convencionales. En la actualidad, las alas necesitan configuraciones distintas de los alerones dependiendo de cada una de las fases del vuelo, por lo que el ala en sí sacrifica eficiencia. «Un ala que es constantemente deformable podría proporcionar una mejor aproximación de la mejor configuración para cada etapa», señalan desde el MIT.
Así, debido a que la estructura, compuesta por miles de pequeños triángulos de resina de polietileno -aunque parecen construidos a base de cerillas-, se encuentra compuesta principalmente de espacio vacío, forma un «metamaterial» mecánico -a la vista, los triángulos forman un poliedro- que combina la rigidez estructural de un polímero similar a la goma y la extrema ligereza y baja densidad de un aerogel. Y además, aunque podría hacerse, no es necesario incluir motores o cables para deformar las alas cuando quiera el piloto, sino que éstas se acoplan a la forma ideal del momento porque responden automáticamente al responder a las diferentes tensiones que se ejercen sobre ellas en un vuelo. «Somos capaces de producir exactamente el mismo comportamiento que activarías con un botón, pero de forma pasiva», afirma Cramer.

Construido por un enjambre de nanorrobots autónomos

El equipo ensambló a mano el ala de un metro de largo, a semejanza de la de un avión de aeromodelismo. El siguiente paso es fabricar una de cinco metros como la de un monoplaza real. Aunque en este caso ya no será producida manualmente, sino por un enjambre de nanorrobots autónomos. Y no es ciencia ficción, puesto que los investigadores aseguran haber diseñado la estructura pensando en esta forma de fabricación y que en un próximo artículo darán más claves al respecto para empezar a construirla en serie.
Esta ala fue ensamblada a mano, pero las versiones futuras podrían ser ensambladas por robots en miniatura especializados
Esta ala fue ensamblada a mano, pero las versiones futuras podrían ser ensambladas por robots en miniatura especializados - Kenny Cheung, Centro de Investigación Ames de la NASA
«Si bien hay una inversión inicial en herramientas, las piezas son baratas en sí», señala Jennet, quien señala que la celosía resultante tiene una densidad de 5,6 kilogramos por metro cúbico. A modo de comparación, el caucho tiene una densidad de alrededor 1.500 kilogramos por metro cúbico: «Nuestro material tiene la misma rigidez, pero con una densidad que es la milésima parte que la del caucho», afirman. 


Y todo esto no serviría solo para aviones. Se están desarrollando ensamblajes similares para construir estructuras espaciales, y eventualmente podrían ser útiles para puentes y otras estructuras de alto rendimiento.

MIT and NASA engineers demonstrate a new kind of airplane wing


AERONAUTICS
We reproduce here an article published on MIT News. This is to keep informed our readers of the latest news in Aeronautics.

Assembled from tiny identical pieces, the wing could enable lighter, more energy-efficient aircraft designs.



A team of engineers has built and tested a radically new kind of airplane wing, assembled from hundreds of tiny identical pieces. The wing can change shape to control the plane’s flight, and could provide a significant boost in aircraft production, flight, and maintenance efficiency, the researchers say.
The new approach to wing construction could afford greater flexibility in the design and manufacturing 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-authored by research engineer Nicholas Cramer at NASA Ames in California; MIT alumnus Kenneth Cheung SM ’07 PhD ’12, now at NASA Ames; Benjamin Jenett, a graduate student in MIT’s Center for Bits and Atoms; and eight others.
Instead of requiring separate movable surfaces such as ailerons to control the roll and pitch of the plane, as conventional wings do, the new assembly system makes it possible to deform the whole wing, or parts of it, by incorporating a mix of stiff and flexible components in its structure. The tiny subassemblies, which are bolted together to form an open, lightweight lattice framework, are then covered with a thin layer of similar polymer material as the framework.


The result is a wing that is much lighter, and thus much more energy efficient, than those with conventional designs, whether made from metal or composites, the researchers say. Because the structure, comprising thousands of tiny triangles of matchstick-like struts, is composed mostly of empty space, it forms a mechanical “metamaterial” that combines the structural stiffness of a rubber-like polymer and the extreme lightness and low density of an aerogel.
Jenett explains that for each of the phases of a flight — takeoff and landing, cruising, maneuvering and so on — each has its own, different set of optimal wing parameters, so a conventional wing is necessarily a compromise that is not optimized for any of these, and therefore sacrifices efficiency. A wing that is constantly deformable could provide a much better approximation of the best configuration for each stage.
While it would be possible to include motors and cables to produce the forces needed to deform the wings, the team has taken this a step further and designed a system that automatically responds to changes in its aerodynamic loading conditions by shifting its shape — a sort of self-adjusting, passive wing-reconfiguration process.
“We’re able to gain efficiency by matching the shape to the loads at different angles of attack,” says Cramer, the paper’s lead author. “We’re able to produce the exact same behavior you would do actively, but we did it passively.”
This is all accomplished by the careful design of the relative positions of struts with different amounts of flexibility or stiffness, designed so that the wing, or sections of it, bend in specific ways in response to particular kinds of stresses.
Cheung and others demonstrated the basic underlying principle a few years ago, producing a wing about a meter long, comparable to the size of typical remote-controlled model aircraft. The new version, about five times as long, is comparable in size to the wing of a real single-seater plane and could be easy to manufacture.
While this version was hand-assembled by a team of graduate students, the repetitive process is designed to be easily accomplished by a swarm of small, simple autonomous assembly robots. The design and testing of the robotic assembly system is the subject of an upcoming paper, Jenett says.
The individual parts for the previous wing were cut using a waterjet 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 mold, and produces each part — essentially a hollow cube made up of matchstick-size struts along each edge — in just 17 seconds, he says, which brings it a long way closer to scalable production levels.
“Now we have a manufacturing method,” he says. While there’s an upfront investment in tooling, once that’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 kilograms per cubic meter. By way of comparison, rubber has a density of about 1,500 kilograms per cubic meter. “They have the same stiffness, but ours has less than roughly one-thousandth of the density,” Jenett says.
Because the overall configuration of the wing or other structure is built up from tiny 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 the same shape” — essentially a tube with wings — “is because of expense. It’s not always the most efficient shape.” But massive investments in design, tooling, and production processes make it easier to stay with long-established configurations.
Studies have shown that an integrated body and wing structure could be far more efficient for many applications, he says, and with this system those could be easily built, tested, modified, and retested.
"The research shows promise for reducing cost and increasing the performance for large, light weight, stiff structures," says Daniel Campbell, a structures researcher at Aurora Flight Sciences, a Boeing company, who was not involved in this research. "Most promising near-term 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 high-speed wind tunnel at Langley Research Center, where it performed even a bit better than predicted, Jenett says.
The same system could be used to make other structures as well, Jenett says, including the wing-like blades of wind turbines, where the ability to do on-site assembly could avoid the problems of transporting ever-longer blades. Similar assemblies 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, the University of California at 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 NASA ARMD Convergent Aeronautics Solutions Program (MADCAT Project), and the MIT Center for Bits and Atoms.