NASA is testing lightweight planes with folding wings

Polycount

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The fixed-wing plane may be a thing of the past if NASA's latest venture is successful. The space agency as part of the "Spanwise Adaptive Wing" (SAW) project recently began testing planes with the ability to fold their wings during flight in the interest of improving maneuverability and speed.

This concept is nothing new (aircraft as old as the XB-70 Valkyrie had folding wings) but NASA's method of implementing it is. Previously, planes had to use heavy hydraulic systems to fold their wings, a technique NASA believes is too "cumbersome" to be practical nowadays.

Instead, the agency is taking advantage of a new wing material dubbed "shape memory alloy" that can react to high temperatures to change its shape - in NASA's case, this temperature activation will work by using "thermal memory in a tube" that can function and move as an actuator.

"We wanted to see: can we move wings in flight, can we control them to any position we want to get aerodynamic benefits out of them, and could we do it with this new technology," said Othmane Benafan, SAW Co-Principal Investigator. "Folding wings has been done in the past, but we wanted to prove the feasibility of doing this using shape memory alloy technology, which is compact, lightweight, and can be positioned in convenient places on the aircraft."

Thanks to this technology, NASA has been able to reduce the overall weight of their test planes by as much as 80 percent compared to older implementations of the system. This drastic weight reduction could help NASA achieve more efficient supersonic flight, allowing their aircraft to more safely and efficiently fly faster than the speed of sound.

"There’s a lot of benefit in folding the wing tips downward to sort of ‘ride the wave’ in supersonic flight, including reduced drag," said SAW Principal Investigator Matt Moholt. "This may result in more efficient supersonic flight."

The SAW project team intends to continue developing and improving upon this technology over time to usher in the "next generation" of supersonic flight. Moholt hopes the team will be able to "not only reduce drag but also increase performance" as an aircraft transitions between subsonic and supersonic speeds in the future.

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jobeard

Posts: 13,957   +1,774
This is crazy. What's wrong with using a second wing? There is no need in making the wing span so wide.
There are high aspect ratio designs in several aircraft; gliders and the Lockheed U2 to cite two. Such wings give higher lift and less drag and thus provide a higher altitude performance.



the U2:
 

jobeard

Posts: 13,957   +1,774
This is not the first time drooping wingtips have been used - - aka the XB 70[SIZE=6] Valkyrie[/SIZE]

 

Polycount

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This is not the first time drooping wingtips have been used - - aka the XB 70[SIZE=6] Valkyrie[/SIZE]
Correct, as I noted in the article. The major difference here is the way they accomplish it - the Valkyrie required heavy hydraulics which affected the maneuverability of the aircraft and weighed it down quite a bit. NASA's new approach eliminates that, from what I can tell.
 
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Capaill

Posts: 1,200   +737
This may have benefits for the military where they regularly cruise at supersonic speed but developments like this seem pointless for commercial aviation unless they can find a way to remove or absorb the sonic boom.
 
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jobeard

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The SST Concorde avoided this problem by cruising at high altitude and reducing speed as it was approaching the destination airport. Unfortunately the design was not economically viable as the passenger load was too small.

 
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Uncle Al

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An additional question. Since most of these light weight materials are based on carbon-fiber, I am curious how much testing has been or is being done on material fatigue? In early commercial flight nobody suspected aluminum skinned aircraft would experience such issues, While CF is lighter and stronger, it will have a critical time when it is subject to failure. Having it bend in flight would seem to cause greater stresses and possibly shorten it's lifespan as well ....
 
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jobeard

Posts: 13,957   +1,774
In early commercial flight nobody suspected aluminum skinned aircraft would experience such issues,
Good point - - and it frequently gets ignored.
The de Havilland DH 106 Comet was the world's first commercial jet in service, 1969 and it experienced a fatal incident on this issue. More recently, Aloha Airlines Flight 243 (AQ 243, AAH 243) was a scheduled Aloha Airlines flight between Hilo and Honolulu in Hawaii. On April 28, 1988, a Boeing 737-297 serving the flight suffered extensive damage after an explosive decompression in flight where the skin ruptured but the plane was able to land.
 
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jobeard

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You know as well as I do those planes can stay in the air at low speeds. For some reason you are not even considering my idea, when you know it would work.
But the drooping wingtip is a HIGH SPEED design element, like the ground effects designs in Nascar -- quite useless at normal street speed limits.
 
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cliffordcooley

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But the drooping wingtip is a HIGH SPEED design element, like the ground effects designs in Nascar -- quite useless at normal street speed limits.
I'm sitting here reading this over and over trying to figure out what it has to do with my original comment.
 

tipstir

Posts: 2,854   +199
Wings or no Wings to gain more speed, yet unman drones, X-Rockets all flying around. Do we need do or say more. Supersonic planes yet we still pay more for flying to and from. Let NASA spend the billions on this project and see what the end results will be more speed or just the same.
 
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jobeard

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I'm sitting here reading this over and over trying to figure out what it has to do with my original comment.
Basically because all aviation has been diverting away from biplanes since 1909:
The Blackburn First Monoplane (also known as Monoplane No 1) was a British experimental aircraft constructed by Robert Blackburn in 1909.
The closest thing to a biwing is the FA-18 with the stubby winglets along the nose of the fuselage

upload_2018-1-25_15-4-41.jpeg
 
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cliffordcooley

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Basically because all aviation has been diverting away from biplanes since 1909:
I think I found an answer that I understand. You may have stated as much above talking about lift, I just didn't see it.

https://en.wikipedia.org/wiki/Biplane
In a biplane aircraft, two wings are placed one above the other. Each provides part of the lift, although they are not able to produce twice as much lift as a single wing of similar size and shape because the upper and the lower are working on nearly the same portion of the atmosphere and thus interfere with each other's behaviour. For example, in a wing of aspect ratio 6, and a wing separation distance of one chord length, the biplane configuration will only produce about 20 percent more lift than a single wing of the same planform.
 
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jobeard

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Well done :)

The interesting con on this is the Stagger Wing Beachcraft, developed from an observation that a biplane was more stable inverted that right-side-up. The leading edge of the lower wing is more forward than the upper wing, changing the center of lift.

circa 1931

upload_2018-1-25_15-31-15.jpeg
 
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mbrowne5061

Posts: 1,599   +905
The SST Concorde avoided this problem by cruising at high altitude and reducing speed as it was approaching the destination airport. Unfortunately the design was not economically viable as the passenger load was too small.

Yes, and the passenger load was small because Boeing's own attempt at developing a supersonic commercial aircraft failed - so they lobbied congress to block commercial supersonic air travel over the continental United States. This effectively 'locked' the Concord into just a couple routes (NYC-London, NYC-Paris), given its range. Had they been able to make trans-American flights, it might have broke even at the high end of the market, and that would have allowed more efficient second generation supersonic commercial aircraft to start showing up at more segments of the market.
 
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mbrowne5061

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An additional question. Since most of these light weight materials are based on carbon-fiber, I am curious how much testing has been or is being done on material fatigue? In early commercial flight nobody suspected aluminum skinned aircraft would experience such issues, While CF is lighter and stronger, it will have a critical time when it is subject to failure. Having it bend in flight would seem to cause greater stresses and possibly shorten it's lifespan as well ....
The CF isn't bending. That is still a 'traditional' mechanical bearing for rotation. What is different is how that force is generated inside of the bearing. Instead of an electric motor or hydraulics, its a "shape memory alloy", which is a fancy way of saying that the metal bends back between one or more positions based on how much energy (thermal or electric, traditionally) is applied to it.

Yeah, CF doesn't really bend at all. Its essentially fancy fiberglass. If it was a solid piece you bent as far as displayed in the video, it would snap.
 
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jobeard

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Sorry, your into the politics, the small passenger capacity was a design issue for supersonic airframe design.
 

jobeard

Posts: 13,957   +1,774
...which is a fancy way of saying that the metal bends back between one or more positions based on how much energy (thermal or electric, traditionally) is applied to it.
A metallurgist would laugh at that.

Gold is easily folded over upon itself and unfolded without tearing AND with little force. The property has nothing to do with proportional thermal, electric or other forces being applied.

As CF is much like fiberglass, being built-up by succeeding layers, its ability to be deformed is inversely proportional to its thickness.

see http://www.physics.uwo.ca/~lgonchar/courses/p2800/Chapter6_Mechanical_Handouts.pdf
 
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mbrowne5061

Posts: 1,599   +905
A metallurgist would laugh at that.

Gold is easily folded over upon itself and unfolded without tearing AND with little force. The property has nothing to do with proportional thermal, electric or other forces being applied.

As CF is much like fiberglass, being built-up by succeeding layers, its ability to be deformed is inversely proportional to its thickness.

see http://www.physics.uwo.ca/~lgonchar/courses/p2800/Chapter6_Mechanical_Handouts.pdf
I have dual degrees in mechanical and electrical engineering - sometimes you need to remember you're on a non-professional forum and 'dumb' things down. Shape Memory Alloys and Carbon Fiber are two completely different materials with completely different internal structures.
https://en.wikipedia.org/wiki/Shape-memory_alloy
 

tipstir

Posts: 2,854   +199
In the Movie "The Final Countdown" The Jets used in that movie could position the wings all the way back and thus have full throttle and high speed flight. Yet those would be considered folding wings..