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Transportation Science

What Scorpions Have To Teach Aircraft Designers 127

First time accepted submitter elloGov writes "The north African desert scorpion, Androctonus australis, is a hardy creature. Most animals that live in deserts dig burrows to protect themselves from the sand-laden wind. Not Androctonus; it usually toughs things out at the surface. Yet when the sand whips by at speeds that would strip paint away from steel, the scorpion is able to scurry off without apparent damage thanks to the unique structure of its carapace. Dr Han Zhiwu of Jilin University and colleagues have found that surface irregularities based on the scorpion's exoskeleton could substantially minimize atmospheric dust damage to aircraft."
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What Scorpions Have To Teach Aircraft Designers

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  • Scorpions (Score:5, Funny)

    by Anonymous Coward on Wednesday February 08, 2012 @11:05PM (#38976815)
    They teach aircraft designers that "Rock You Like A Hurricane" fits perfectly at air shows.
    • by Anonymous Coward
      Plus, the Scorpions are really good with the Winds of Change. Really, we should have suspected that they've got special wind issues.
  • ...if scorpions could fly.


  • What about drag (Score:1, Interesting)

    by Anonymous Coward

    A lot of work has been done lately on getting very smooth aerodynamic surfaces, because when you promote laminar flow, you can get very significant decreases in drag. Wouldn't this additional surface roughness mess that up?

    • Re:What about drag (Score:4, Interesting)

      by Narcocide ( 102829 ) on Wednesday February 08, 2012 @11:15PM (#38976911) Homepage

      I'm not sure but I think, not necessarily. They add dimples to golf balls to increase their flight distance and straighten their flight trajectories specifically to disrupt laminar flow, because over a sphere, turbulent flow actually can work better, if the dimples are just the right size and have just the right irregularity. I don't know for sure if it can be applied to aircraft though; maybe it only works on golf balls. Reference here [avkids.com].

      • Re:What about drag (Score:5, Interesting)

        by berashith ( 222128 ) on Wednesday February 08, 2012 @11:18PM (#38976937)

        Mythbusters did it to a car, and increased gas mileage. This was just using clay. If someone used decent materials, there is likely a huge gain to be had in performance. Of course, the surfaces on a plane NEED to interact with the air, so too much disturbance may not be a good thing.

        • Re:What about drag (Score:5, Informative)

          by butalearner ( 1235200 ) on Thursday February 09, 2012 @12:52AM (#38977607)

          There are a few types of drag, but for now let's just consider skin friction drag and pressure drag. For a smooth sphere the size golf ball, pressure drag (or wake drag, caused by the flow separation), is significantly higher than the skin friction because the surface area of the sphere is so small. The dimples introduce turbulence in the boundary layer (increasing skin friction) in order to delay flow separation (significantly reducing wake drag).

          For an airplane, however, this situation is reversed. The surface area is enormous, and since the shapes of the wings and the fuselage are such that they delay flow separation as long as possible, the skin friction drag is significantly higher than the wake drag. Introducing dimples will decrease wake drag like a golf ball, but it will increase the skin friction more, causing a net increase in drag.

          • Re:What about drag (Score:4, Interesting)

            by wvmarle ( 1070040 ) on Thursday February 09, 2012 @02:23AM (#38978237)

            In this scorpion-skin situation I wouldn't be surprised if the surface drag is reduced.

            Two reasons. The first is that the skin reduces erosion by the sand, which implies to me that the sand is kept away from the skin, again suggesting a thicker boundary layer, and that may decrease drag forces.

            The second reason: the shark skin effect. A while ago there were these shark skin swimsuits, purportedly increasing the performance of swimmers by reducing surface drag. The shape of a shark (and most fish) are similar to aircraft in that they are highly streamlined and have little wake, making surface drag again dominant. If that works in water, it could also work in air.

            Anyway it sounds like a straightforward experiment to test this: create two identical shapes (ball, wing, whatever), one with a polished surface and one with a dimpled/scratched surface, and put both in a wind tunnel. With or without sand.

          • by J-1000 ( 869558 )
            Mythbusters actually did an episode where they covered a car (much bigger than a golf ball, of course) in golfball-like dimples. Much to their surprise, it increased the gas mileage. Do you know how to explain that? You seem to know what you are talking about.
            • by dave420 ( 699308 )
              That's hardly scientific. Maybe the temperature changed, or the wind, or the driver's style, or whatever. One TV experiment does not good science make.
              • That's hardly scientific. Maybe the temperature changed, or the wind, or the driver's style, or whatever. One TV experiment does not good science make.

                Mythbusters is to science as pro-wrestling is to sport.

              • Re:What about drag (Score:4, Insightful)

                by realityimpaired ( 1668397 ) on Thursday February 09, 2012 @09:30AM (#38980395)

                That's hardly scientific. Maybe the temperature changed, or the wind, or the driver's style, or whatever. One TV experiment does not good science make.

                Nope, but before they did the "full scale" experiment, they did a small scale with a model car in a flow tank, with controlled temperature, and "wind" speed/direction. When they added dye to the flow, they saw that the "golf ball" car had a smaller eddy behind the car, which translates to less drag.

                I agree that the Mythbusters aren't exactly a definitive scientific resource, but sometimes they actually do their due diligence and it gets cut because it doesn't make for good TV entertainment.

                That being said, a divot is not the same as a bump, and the aerodynamics may be different. They do use a shark skin-like covering on some airplanes and boats to reduce drag, though, so there could still be some merit.

            • by mvdwege ( 243851 )

              Most obvious explanation would be a decrease of the drag coefficient (Cw). That is a known technique in automobile design to reduce fuel consumption.

              I haven't seen that particular episode, but if their experiment led to a signifcantly decreased drag coefficient, then yes, that would indeed work.


          • > causing a net increase in drag

            Forgive me, but, kindly qualify that with an "I think so, " would you please. You just don't know it's so empirically; less certitude.

            Tangentially, what this article's noted observation reminds me of is rice cooker paddles. That's right, rice ladle spoons. Some time not too long ago, a decade maybe? someone realized that if you added dimples to the plastic injection moldings so as to render a cooker ladle spoon with large protruding dimples on it---sort of like a golf ball

          • Except that this is on a microscopic level, the drag you assume is there interacting with that boundary layer of air isn't the same thing as the macro level sized dimples on a golfball. The friction you assume is there is based on a much larger texture; air is not stiff carpeting or velcro, it does not behave like a solid, it behaves more like a fluid. This suggests the reality is the opposite of your many assumptions.
          • by LWATCDR ( 28044 )

            you could add them starting at the transition point back on the airframe. Actually more than a few aircraft use vortex generators to already do this. It is usually a fix or is used where the extra lift is more important than the extra drag.

            That is the big issue here. The last place you would want to add "bumps" to an airframe is the leading edge of the wing, props, turbines, and or rotors.
            I can see the look on a gas turbine designers face now....

        • I don't see how dressing up a male plane to look female would help keep it's paint protected from the dust, unless you completely cover it up in pantyhose and make-up.
          • Very punny. As punishment for that pun, imagine, if you will, the image you will now and forever more associate with "drag strip". Not the place of the loud and fast cars, but the act of a transvestite removing all his clothes.

            Ewwwh. Virtual visual pollution, right here on slashdot.

        • by Ihmhi ( 1206036 ) <i_have_mental_health_issues@yahoo.com> on Thursday February 09, 2012 @08:08AM (#38979919)

          Hurm... I have a crazy idea...

          Anyone have a VW Golf and a ball peen hammer they're willing to part with?

          • by Anonymous Coward

            Sure! But I would need the hammer back.

      • Re:What about drag (Score:5, Informative)

        by I(rispee_I(reme ( 310391 ) on Thursday February 09, 2012 @01:17AM (#38977797) Journal

        They add dimples to golf balls to increase their flight distance and straighten their flight trajectories specifically to disrupt laminar flow, because over a sphere, turbulent flow actually can work better, if the dimples are just the right size and have just the right irregularity.

        National Geographic's "Ultimate Crocodile" has a segment where the surface of a crocodile's skin is found to have similar properties. Seems that a fish's reaction time is more than sufficient to avoid a croc's bite if the fish is alerted. A cast of a crocodile head was used in a tank to measure the way water flows around a crocodile in motion, and it was proven that the bumpy irregularities on the crocodile's skin produce lower water pressure and the crocodile's body and help it maintain stealth.

        I can't find the clip, but it's referenced here [natgeoeducationvideo.com].

      • by AB3A ( 192265 )

        Aircraft designers call these Vortex Generators [wikipedia.org]. Their purpose is to disrupt the laminar airflow. This helps the air streams to "stick" to the wing, improving control responsiveness and lowering stall speeds. The difference can be quite noticeable with some airfoil shapes, or almost unmeasurable in others, so one doesn't see them on all aircraft.

        But what the article discusses here is NOT a vortex generator or anything of that ilk. It seems to be some sort groove that can mitigate the scratching caused by

    • Re:What about drag (Score:5, Interesting)

      by Tastecicles ( 1153671 ) on Wednesday February 08, 2012 @11:23PM (#38976983)

      Doesn't seem to affect the flight characteristics of the F117A Nighthawk any... they use reinforced carbon-carbon laminate (which has a rough profile when the resin substrate sets) on its flight surfaces, not just for its physical properties (lightweight, immensely strong and very flexible), but also because that rough surface disperses RADAR and gives a fifty thousand pound strike aircraft the RADAR signature of a sparrow.

      • by Anonymous Coward

        It doesn't? The F-117 can't even fly without a computer constantly making tiny adjustments. I'm not kidding either, it would literally crash if you tried to fly it manually. It's a flying brick.

        • Re:What about drag (Score:5, Interesting)

          by Anonymous Coward on Thursday February 09, 2012 @12:33AM (#38977461)

          When I was young a friend of mine, an aviation mechanic once told me the properties of how a plane flies. He then proceeded to say the armed forces ignore that and use the philosophy "put enough power behind it, anything can fly"

        • by RobinEggs ( 1453925 ) on Thursday February 09, 2012 @12:35AM (#38977483)

          It doesn't? The F-117 can't even fly without a computer constantly making tiny adjustments. I'm not kidding either, it would literally crash if you tried to fly it manually. It's a flying brick.

          The Nighthawk was still designed as much as possible like a true airplane; it's only unstable because they couldn't build a more aerodynamic stealthy shape using only flat surfaces (they used flat surfaces because the math for radar deflection depended on computer simulations, and computers couldn't do good enough calculations for curved surfaces in the late '70s).

          Calling it a brick is really quite inaccurate. It had an amazingly narrow wingspan, but it's still a plane and it still produced sufficient lift to fly straight on a reasonable power budget. It wasn't stable without computer correction, but that doesn't mean it's a brick. It's not as if they simply strapped enough rockets onto a random shape to get it airborne.

        • Re:What about drag (Score:4, Informative)

          by Tastecicles ( 1153671 ) on Thursday February 09, 2012 @02:09AM (#38978131)

          the Nighthawk is designed, like the F-16 Falcon, to be unstable in flight. That is what gives it the important characteristic of being able to turn on a dime hence makes it ideal for close proximity combat flying as well as improved avoidance of eg missiles, cannon shells. Such instability cannot be corrected in real time by a pilot who also has the usual other shit to do in the cockpit like watch where he's going, keep a bead on the RADAR, make flight decisions... it would be far too much of a distraction and besides, if he *could* think that fast he'd be teaching Hawking. That's why instead of a copilot they have a somewhat lighter computer dedicated to maintaining trim.

        • And your point is... what, exactly?

          Most things that fly require a computer to constantly make tiny adjustments. Try throwing a dead duck, and observing its aerodynamic qualities.

          The F-117 might well be a "flying brick"-- but that is a term that describes an oversized power plant used to compensate for bad aerodynamics and has nothing to do with management of the control surfaces. There is nothing inherently bricky about fly-by-wire aircraft. Now that we have the capability to build computer controlled a

      • What surface the carbon laminate dries as is not relevant. They put special radar-absorbing paint on top of the laminate. Also, the surface anomalies of the resin are too unpredictable to work reliably to absorb radar. The rest of the low radar profile is because the chance that an large surface is actually reflecting radar beams back exactly at the radar station is minimal if you make the surfaces as flat as possible, hence the sharp edges and "flat" surfaces of stealth design. The paint is actually not th
      • Re: (Score:3, Funny)

        by naranek ( 1727936 )

        Do you mean African or European sparrow?

      • Re:What about drag (Score:4, Informative)

        by crutchy ( 1949900 ) on Thursday February 09, 2012 @03:12AM (#38978569)
        at supersonic speeds (the nighthawk's max speed is only Mach 0.92, but at that speed the local airspeed over the upper surface of the wing would be transonic), things get a bit iffy. subsonic aerodynamics don't work at transonic and supersonic speeds. you get normal and oblique shockwaves, and supersonic nozzles behave like subsonic diffusers and vice versa. sharp corners produce less drag and heat than smoothly curving surfaces
      • But this article is talking about bumps of 4mm. That would have to be done with the metal skin. And that sounds like a stress riser. Jets have already had enough trouble with the skin fatigue.... adding stress risers throughout seems like a bad idea.

        If everyone could afford the coating and it could have that big of "bumps", it might be feasible.
        • I would imagine it would be something similar to shark skin. Run your hand from head to tail on a shark, and it's practically frictionless, run it the other way and you'll strip the skin off your hand before you get six inches. Now put the shark skin on the shell of an aircraft. Trailing edges of the scales (irregularities) create areas of differential pressure that deflect particles and prevent damage to the hard surface - or in the case of a shark, actually reduces hydrostatic pressure around the mass hen

    • by plover ( 150551 ) *

      Actually, breaking up the surface is a well known technique for reducing drag. I know a company that makes a very finely etched plastic laminate for applying to the hulls of racing schooners specifically to reduce drag. It wasn't modeled on biomimetic material ( as far as I know) but it's the same idea.

      Of course their current laminates wouldn't withstand dust. They're made for water.

      • Shark Skin (Score:4, Interesting)

        by drainbramage ( 588291 ) on Thursday February 09, 2012 @12:23AM (#38977393)

        Shark Skin is not smooth, but it has low friction in a fluid, in one direction.
        I recall seeing a promo video from a company that applied such a surface to an Americas Cup boat hull.
        Possibly what you are thinking of.

        • the wetsuits used by olympic swimmers are apparently rough like shark skin
        • by Anonymous Coward

          I recall seeing a promo video from a company that applied such a surface to an Americas Cup boat hull.

          I recall that video too; it starred Peter North doing the "laminating", right? Oh, wait, a promo video.....

        • by plover ( 150551 ) *

          That sounds exactly like the stuff. It was about 10-20 years ago that they were working on it. Very cool idea.

          The thing is the forces exerted on boat hulls by the water are completely different than those on a helicopter rotor blade. A big slow moving boat in dense water is not at all like a blade spinning at near the speed of sound in thin air, being hit by sharpened grains of quartz. It would take a completely different materials technology to make it work.

          I'm imagining bonding a sheet of saran wrap o

    • by mercnet ( 691993 )

      Surface roughness can be used to transition the boundary layer from a laminar to a turbulent flow. Early separation on an airfoil causes an increase in drag. You can trip the flow with surface roughness, suction/blowing, trip wire, etc to make it turbulent and repair the separation.

      Now relating to the article I am guessing they have a turbulent boundary layer which is why sand particles are being sucked in and slammed against the blade. Having a laminar BL would prevent sand from entering it?

    • I recall reading a similar thing about the surface of a yatch hull being made to resemble "rough" shark skin. The ineventor claimed that a surface with a bit of roughness has less drag than a smooth surface and that evolution had done a very good job of optimising a sharks surface to minimze its drag.
    • rough surface increase drag, but it also energizes the airflow to make it less prone to separation at higher angles of attack

      some aircraft have devices on the wings that "trip" the boundary layer of the airflow towards the trailing edge of the wing so that the flap angle can be increased further than would otherwise be possible without stalling

      rough surfaces or boundary layer tripping devices (wires, vortex generator fins, etc) can permit huge lift/drag ratios, which are essential for large aircraft d
    • Turbulence at the surface, micro-level actually promotes macro-level laminar flow by allowing a "buffer zone" of air to form. You end up with less total volume of air in turbulence, and more in laminar flow - less drag.
  • Is it about changing winds...?
  • So there was this scorpion that wanted to cross a river...

    So there was this 747 that wanted to cross an ocean...

  • What effect do these "surface irregularities" have on drag, and therefore on fuel use?

    It would be great to cut down on dust damage, but not at the expense of making every flight more costly...

    • Golf balls have dimples...

    • by Tastecicles ( 1153671 ) on Wednesday February 08, 2012 @11:34PM (#38977075)

      My guess would be (disclaimer: I am not an aerodynamicist) that surface irregularities of a certain size proportional to the overall aerodynamic characteristic would not affect it - much unlike the golf ball. Those turbulent areas immediately aft those dimples form a static bubble of high or low pressure (depending on the vector and position of the dimple relative to the centre of mass) which cause the desired effect. In a Stealth aircraft those irregularities are designed to not affect the aerodynamic behaviour in any way: what they do, is to reduce the RADAR signature of the aircraft, hence their size is calculated for maximum RADAR dispersion. We're talking bumps, curves and ridges of less than 1/64" high. Barely enough to detect even with bare fingertips.

      On the other hand, you can make a brick fly. Look at the Rockwell Constellation series space shuttle orbiters.

      • by LWATCDR ( 28044 )

        umm no.
        stealth aircraft do not use bumps to disperse radar. The coating uses electrical properties to reduce the radar signal not physical shape. The airframes physical shape does with things like faceting and sawtooth edges. Also the Shuttle really was not a "brick" as many people like to call it. It flew very well at hypersonic speeds. At approach speed with out power it's L/D ratio was bad but probably no worse than most other high speed aircraft like fighter jets or the SR-71. It was probably a good b

    • by Anonymous Coward

      I've done academic wind tunnel research specializing in boundary layer flows. What happens is that the skin friction losses that occur as fluids (gases and liquids) flow around a body reduce the total energy that the flow has to overcome the adverse pressure gradient on the aft side.

      An intuitive physical analogy would be dropping a ball bearing on a half pipe. In ideal (energy conserving) physics modelling the ball bearing would not lose potential or kinetic energy and would reach the same height on the opp

  • UFO's have been using the "disk" design for decades, now engineers are looking at scorpions. Clearly, "black flap" technology is the logical next step.

  • by KuRa_Scvls ( 932317 ) on Wednesday February 08, 2012 @11:41PM (#38977131)

    I am Tired of these motherF**king SCORPIONS on this MotherFu**ing PLANE

    • Re:Oblig (Score:4, Funny)

      by jd2112 ( 1535857 ) on Thursday February 09, 2012 @12:23AM (#38977387)
      (stewardess) Just switch from Hard Rock to the Easy Listening channel.
      • by mjwx ( 966435 )

        (stewardess) Just switch from Hard Rock to the Easy Listening channel.

        80's hair metal is not hard rock.

        Oh never mind, the system was probably designed by someone tone deaf enough to think that dubstep is music instead of modem sounds.

  • by JoshDM ( 741866 ) on Wednesday February 08, 2012 @11:48PM (#38977161) Homepage Journal
    ...getting you over there.
  • by Anonymous Coward on Wednesday February 08, 2012 @11:57PM (#38977233)
    Planes need a poison-tipped tail to fend of pterodactyl attacks. Until they get one of those they are simply flying coffins.
  • I wish that the phrase "material science" had been around (or more discussed?) when I was younger. This kind of thing really is amazing. I'd also seen a NOVA program in which an anti-microbial surface was created with a diamond-shaped pattern of ridges based on other things in nature (someone has seen this and can give more detail).

    If I were starting much younger, I'd love to study material science. Truly amazing -- in the case of the anti-microbial surface (vs the control) they were made of the exact sa

    • The book that interested me enough to work in materials science was "Metals in the Service of Man" by Street and Alexander which I think had it's first edition in 1954. There's updated editions to at least 1989.
      It eventually was called materials science because a lot of metallurgists were working on ceramics and polymers. It's interesting stuff but just about the first sort of job against the wall when a recession comes, so I had to turn the skills I'd picked up simulating the behaviour of materials with
      • Metallurgy still exists as name, it's just part of materials science. Many people studying materials science will specialise in a family of materials such as ceramics, metallurgy or polymers.

    • This is not material science, this is aerodynamics and fluid dynamics. Material science is about the properties of the material itself: strength, flexibility, conductivity, creep, fatigue, etc, and about the processing of a material. This study is about the surface of the material; the underlying material doesn't matter much, they used metal probably simply because they are familiar with it and have the equipment to make the desired shapes out of it.

      That doesn't make this study, or material science, any les

      • The surface irregularities mentioned are in microns. At that scale it's entirely possible that the research and application would involve material science to a great degree. The basic theoretical simulation work? Maybe not as much. The applied science, very much.

        • The described experiment however was about the surface and the interaction with the air flow. How the surface irregularties were made, that was not the subject of study here. After they figure out what those dimples should look like, then the next step is indeed to talk to materials scientists on what material would be suitable and how it could be processed.

  • Nature usually does it best! Would that more of our scientists tried harder to get their cues from it, rather than trying to fight it or destroy it.
  • It seems like the features they made in the steel were far larger than those on the scorpion's outer surface. I wonder why they needed to scale it up so much.
    • My best guess: their equipment could not make it better than that.

      This sounds a bit like a professor learned something interesting about how these scorpions are not affected by the sand storms, and out of curiousity tries to find out what causes it. They went for shopping in the local pet shops, got themselves a few scorpions, took samples of the armour, and went to work with that. Put it under a microscope, add UV light (both pretty standard equipment), then made a laser scan of the surface (not so standar

  • This is semi-news.

    Similar results, even if not for abrasion, were found decades ago but for aerodynamics in general.

    Microstructures in the shape of fish scale do improve aerodynamics considerbly. That it also helps abrasion is new.

    • the term "bug smasher" has been in aircraft circles for a long time. example is the Hawker Siddeley HS 748
  • When can I paint my car with scorpion paint? I don't want it to wear a bra in public.
  • by Anonymous Coward

    How often does the scorpion molt or otherwise regenerate its exoskeleton? It's a bit tricky to do that with an aircraft.

  • Perhaps I'm wrong but scorpions, as living beings, are supposed to be able to fix possible carapace erosion, aren't they? I mean that an aircraft with an emulated scorpion surface would also be damaged in the long run. What would be really awesome is to create some sort of material with autoregenerating properties!
    • by Anonymous Coward

      Exoskeletons like that have odd growth and repair compared to what you're used to. The advantage of endoskeletons is that structural damage can be more easily repaired and the surface material (skin, muscle, fat) is very easy to repair (by comparison).

      I won't hypothesize about scorpion carapaces, but I will coment on a similar situation that I do know. Turtle shells have ridges on each 'scale' that can be used like tree rings (or fish scale ridges) to estimate the age of a turtle. Although there is growt

  • by Air-conditioned cowh ( 552882 ) on Thursday February 09, 2012 @04:11AM (#38978845)
    ...and I have to admit I've never seen him suffer from atmospheric dust damage.
  • Here's the PubMed link to the actual journal paper: http://www.ncbi.nlm.nih.gov/pubmed/22208552 [nih.gov]
  • Yes their shell is good at deflecting dust particles, but does that mean that this same shell would be good for flying...? the whole concept of airplane carapace is to make sure there is no friction from the air running across it, I would like to see how the scorpions carapace would hold up in a wind tunnel made for testing airplanes.

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