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retroreflective aeroplane coating

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There is a sort of laser target which NASA have put on the moon, which is a three-sided mirror, in the shape of three sides of a cube. If you fire a laser into this it bounces off all three surfaces (usually) and then back to the sender on a path parallel to the output path and offset by only a tiny amount. By timing the round-trip time of laser pulses sent to the moon, NASA measure how far away the moon is and how this changes over time.

This idea is to coat the nose of aeroplanes with a surface made up of these mirrors, with each mirror being 2-3cm square. You could then cover the whole thing in a curved sheet of Perspex or something for aerodynamics. The effect of this is that when idiots on the ground fire laser pointers at aeroplanes to dazzle the pilots (which happens every day, endangering many commercial flights), unless they were very lucky and managed to fire the laser right into the cockpit on their first attempt, they'd get a few dazzling flashes of light back from the aeroplane, reducing their ability to continue to accurately aim at the aeroplane.

hippo, Dec 17 2019

Wikipedia: Retroreflective sheeting https://en.wikipedi...reflective_sheeting
Mentioned in my anno, and thought to be available by [Max] [notexactly, Dec 21 2019]

Wikipedia: Retroreflector § On roads https://en.wikipedi...oreflector#On_roads
Mentioned in my anno. Mentions retroreflective paint. The article also has a diagram comparing rays between a corner cube and a glass sphere. [notexactly, Dec 21 2019]

Wikipedia: Matt Black https://en.wikipedia.org/wiki/Matt_Black
Mentioned in my anno. Looks like Wikipedia only knows what two of the three Matt Blacks look like, though. [notexactly, Dec 21 2019]

Space Exploration Stack Exchange: Why is Sentinel 3B's dish antenna overwrapped with metallized film? https://space.stack...ith-metallized-film
Mentioned in my anno. [notexactly, Dec 21 2019]

[link]






       I think you can get retroreflective film which is essentially the same think, but on a micro scale and therefore flexible enough to stick on to curved surfaces.   

       Whether it would deter, however, is another issue. As it stands, the idiot on the ground will find it very difficult to know if they've hit the plane (let alone the cockpit). With this material, they'll get a bright (but probably not blinding) reflection to tell them they're at least hitting the plane.   

       The ideal might be, instead, to paint the front-underside of the plane matt black.   

       Another option would be to coat the cockpit windows in a tailored film that selectively absorbed the handful of tight laser bands in common use, to protect the pilots without blocking most other light sources much.
MaxwellBuchanan, Dec 17 2019
  

       I thought the three-cornered mirror would more accurately direct the laser back to the source than the micro-scale retroreflective film, so that the idiot would be nearly-blinded rather than just see a bright reflection. It's also true that this would allow the idiot to know they were on target but as long as they ended up sufficiently blind this shouldn't matter. The film is a good idea - in principle it could just be incorporated into safety glasses for pilots to wear near airports where a high proportion of the populace are idiots.
hippo, Dec 17 2019
  

       Anything metallized on the nose cone is going to block the weather radar.
8th of 7, Dec 17 2019
  

       That's OK - it doesn't need to cover the whole nose of the aeroplane
hippo, Dec 17 2019
  

       //three-cornered mirror would more accurately ... than the micro-scale retroreflective film//   

       I'm not sure. I think the film still uses 3-cornered mirrors, but on a micro-scale and with similar precision. The great thing about the 3c-m idea is that as long as each triad of mirrors is accurate, orientation is not critical. I may be wrong, though.   

       //as long as they ended up sufficiently blind this shouldn't matter// The idiot could just wear dark glasses to allow them to see a "hit" without being dazzled.   

       Given how lasers work, should it not be possible to develop a sort of active protection - an array of lasers mounted on the plane that, when triggered by an incoming beam of a few mW, would release a 100W beam in the reverse direction?
MaxwellBuchanan, Dec 17 2019
  

       Active countermeasures ? Baked by the military ...   

       // I may be wrong, though. //   

       Who are you, and what have you done with the real [MaxwellBuchanan] ?
8th of 7, Dec 17 2019
  

       No no no - you misunderhend. When I said "I may be wrong", I meant "I may be wrong when I said 'I'm not sure'."
MaxwellBuchanan, Dec 17 2019
  

       //orientation is not critical//
Of course it's not critical; that's the point! As long as the beam of light is incident within the "cone" that the cube- corner defines, it will be reflected back at the source; maximum offset is determined by the size of the cube (minimum is effectively zero regardless of size...).
neutrinos_shadow, Dec 17 2019
  

       There are a few halfbakers who actually might benefit a lot from a little internal reflection ...
8th of 7, Dec 17 2019
  

       I prefer Total Internal Reflection, =arcsin(n2/n1).
neutrinos_shadow, Dec 17 2019
  

       // I prefer Total Internal Reflection// Isn't that just a euphemism for navel-gazing?
MaxwellBuchanan, Dec 17 2019
  

       As opposed to Naval gazing, which typically involves a smart blue uniform and a good pair of binoculars ..
8th of 7, Dec 17 2019
  

       As opposed to the naval gay scene, which is very, very different.
MaxwellBuchanan, Dec 17 2019
  

       Yes, it's a puzzle as to why they don't put the strapline "Rum, sodomy and the lash" on the recruiting posters - probably because they don't want the likes of your cousin Hilary Leslie re-enlisting.   

       Is (s)he coming to the Christmas party by the way ? A bit of a steer on a suitable gift would help ... are we talking candles and scented bath oil this year, or a slab if Carlsberg Special Brew and a set of adjustable spanners ?
8th of 7, Dec 17 2019
  

       Hilary has not yet decided what to be this Christmas, but a subscription to Cosmopolitan is a winner either way.   

       Which reminds me. The Intercalary asked me to thank you for the salami and wishes you a Happy St. Baxter's day.
MaxwellBuchanan, Dec 17 2019
  

       //tailored film that selectively absorbed the handful of tight laser bands in common use, to protect the pilots without blocking most other light sources much.//   

       At the moment, the common lines are 405, 450, 475, 532, then lots above 600nm. Given the difficulty of making a multi band pass filter for the gaps between those AND future lines combined with the notoriously conservative aviation certificaiton and the length of service life.... I think having some glasses on hand would be cheaper. Perhaps a proceedure change where the pilot monitoring is observing the descent through a camera-screen setup?
bs0u0155, Dec 18 2019
  

       hmmm, could instrumentation on the aircraft detect and use the direction of the reflected beam to send GPS coordinates of the idiots location to ground based authorities?   

       // through a camera-screen setup? //   

       Final approach by iPhoney ... THAT adds a whole new terror to commercial aviation.
8th of 7, Dec 18 2019
  

       //Anything metallized on the nose cone is going to block the weather radar.   

       Ahh, then they can refer to the pine cone outside on the windscreen, along with a bit of bladderwrack.
not_morrison_rm, Dec 19 2019
  

       Those are a bit sophisticated for most pilots, so they then to keep them hanging just outside the window of the control tower (the pine cone and seaweed, not the pilots*)   

       *Pilots do sometimes get hung out to dry just outside the control tower window, but not for weather forecasting purposes - more as an object lesson to the others.
8th of 7, Dec 19 2019
  

       // I think you can get retroreflective film //   

       Yes: [link]. You can also get retroreflective paint, which is what we use for road markings over here. Instead of tiny corner-cubes, it has tiny glass spheres that do approximately the same thing: [link].   

       // The ideal might be, instead, to paint the front-underside of the plane matt black. //   

       Which one?: [link]   

       // I thought the three-cornered mirror would more accurately direct the laser back to the source than the micro-scale retroreflective film, so that the idiot would be nearly-blinded rather than just see a bright reflection. //   

       You can get retroreflective materials with various reflection angles. You'd have to use a very narrow-angle retroreflector to return sufficient light at long ranges, but that (if there even are retroreflective coatings available that reflect so narrowly) might result in less light getting to the laserer's eyes when the plane is low to the ground, if the laserer isn't holding the laser pointer near their head.   

       I don't think being dazzled or nearly blinded will hinder aircraft-lasering (though it might deter it). On the contrary, it might well make it easier. Just shine your laser pointer around in the direction of the plane until you get a strong flash of light in your eyes, and use conical scanning to track the plane from there.   

       // as long as each triad of mirrors is accurate, orientation is not critical. I may be wrong, though. //   

       It wouldn't be a retroreflector if you were wrong. It would just be a mirror with extra steps.   

       // Anything metallized on the nose cone is going to block the weather radar. //   

       But a germanized nose cone is probably fine: [link]
notexactly, Dec 21 2019
  

       ... because of course Germanium is not a metal, but - like bismuth and antimony - a semi-metal or metalloid, as any fule kno.
8th of 7, Dec 21 2019
  

       //safety glasses for pilots to wear near airports where a high proportion of the populace are idiots//   

       Perhaps the authorities should just build airports in different areas then.
AusCan531, Dec 21 2019
  

       Define "high proportion" - what about those places- such as france- where the proportion equals or exceeds* 100% ?   

       *not easy to achieve, but then again they've had centuries of practice.
8th of 7, Dec 21 2019
  

       One problem with that idea is that, once you build an airport, even an idiot with a laser pointer knows that's where the planes will be.   

       What's needed is to train pilots in rough-terrain landings, so that nobody can be sure which field a plane is likely to land in or take off from.
MaxwellBuchanan, Dec 22 2019
  

       Ah yes, the well-known "Aeroflot Approach", though that's more by accident than design...
8th of 7, Dec 22 2019
  

       I did go on an Aeroflot flight, and it didn't crash, even a teensy bit. Spooky, no?
not_morrison_rm, Dec 24 2019
  

       Count Spucchino: a minor character in "Three Gentlemen of Verona, and Two Nice Ladies from Treviso, and Then This Other Man About Whom, Frankly, We Have Doubts"   

       Seppuki-no: a Japanese retail franchise specialising in end-of- life amenities   

       In a macaroni of English and Russian, "spooky, no ..." could mean "spooky, but [also something else]".
pertinax, Dec 30 2019
  

       Ahem, my version of hb (gone but not forgotten) did at least have a pedant alert, with flashing bits and a warship whoop, whoop etc
not_morrison_rm, Dec 30 2019
  

       Was that an "Alert for pedants", or an "Alert of pedantry" ?   

       Just asking ...
8th of 7, Dec 30 2019
  
      
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