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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.
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]
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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. |
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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. |
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The ideal might be, instead, to paint the front-underside of
the plane matt black. |
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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. |
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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. |
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Anything metallized on the nose cone is going to block the weather radar. |
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That's OK - it doesn't need to cover the whole nose of the aeroplane |
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//three-cornered mirror would more accurately ... than the
micro-scale retroreflective film// |
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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. |
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//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. |
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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? |
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Active countermeasures ? Baked by the military ... |
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// I may be wrong, though. // |
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Who are you, and what have you done with the real [MaxwellBuchanan] ? |
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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'." |
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//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...). |
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There are a few halfbakers who actually might benefit a lot from a little internal reflection ... |
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I prefer Total Internal Reflection, =arcsin(n2/n1). |
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// I prefer Total Internal Reflection// Isn't that just a
euphemism for navel-gazing? |
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As opposed to Naval gazing, which typically involves a smart blue uniform and a good pair of binoculars .. |
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As opposed to the naval gay scene, which is very, very
different. |
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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. |
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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 ? |
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Hilary has not yet decided what to be this Christmas, but a
subscription to Cosmopolitan is a winner either way. |
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Which reminds me. The Intercalary asked me to thank you for
the salami and wishes you a Happy St. Baxter's day. |
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//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.// |
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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? |
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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? |
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// through a camera-screen setup? // |
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Final approach by iPhoney ... THAT adds a whole new terror to commercial aviation. |
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//Anything metallized on the nose cone is going to block the weather radar. |
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Ahh, then they can refer to the pine cone outside on the windscreen, along with a bit of bladderwrack. |
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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*) |
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*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. |
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// I think you can get retroreflective film // |
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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]. |
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// The ideal might be, instead, to paint the front-underside of the plane matt black. // |
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// 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. // |
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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. |
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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. |
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// as long as each triad of mirrors is accurate, orientation is not critical. I may be wrong,
though. // |
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It wouldn't be a retroreflector if you were wrong. It would just be a mirror with extra steps. |
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// Anything metallized on the nose cone is going to block the weather radar. // |
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But a germanized nose cone is probably fine: [link] |
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... because of course Germanium is not a metal, but - like bismuth and antimony - a semi-metal or metalloid, as any fule kno. |
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//safety glasses for pilots to wear near airports
where a high proportion of the populace are
idiots// |
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Perhaps the authorities should just build airports in
different areas then. |
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Define "high proportion" - what about those places- such as france- where the proportion equals or exceeds* 100% ? |
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*not easy to achieve, but then again they've had centuries of practice. |
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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. |
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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. |
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Ah yes, the well-known "Aeroflot Approach", though that's more by accident than design... |
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I did go on an Aeroflot flight, and it didn't crash,
even a teensy bit. Spooky, no? |
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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" |
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Seppuki-no: a Japanese retail franchise specialising in end-of-
life amenities |
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In a macaroni of English and Russian, "spooky, no ..." could mean
"spooky, but [also something else]". |
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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 |
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Was that an "Alert for pedants", or an "Alert of pedantry" ? |
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