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The goal is to find an element which can be applied remotely to a target (like from a laser), and work as a homing device for a missile. (Or at least, to find a homing device which could be applied remotely and would be undetectable to the target.)


The setting is a slightly more technologically advanced planet earth- roughly 50 years in the future. It's of course possible to fire missiles from aircraft which will target a particular building and blow it up.

However, there's a limit to how effective that can be since the buildings are also reinforced. The more powerful the bomb the more resources it takes to create and maintain them. Thus the shift in strategy is to make existing weapons more effective.

In the story, one nation has figured out a way. They send a scout to scope out the facility ahead of time. Using various technology (not relevant for this question) they can identify the weakest point on a structure from a few hundred meters away. For example, they can find a weak seam between two pieces of reinforced concrete. If you could have the missile hit exactly on that seam, it would be more effective at breaking through the reinforcements.

The problem is, how can the scout mark that spot from 200 meters away, such that when an airplane shoots a missile the homing device can lock onto that spot?

The initial idea was for the scout to have a machine capable of shooting a laser or particle beam on that specific weak spot. The beam would carry particles of a particular element and deposit them on that precise location in a very minute layer. The missiles would somehow be able to home in on that element and thus know where exactly to hit.

There are a few problems with this idea:

  1. We couldn't find anything about a particle beam (or anything similar) which could transfer a layer of particles onto a surface. It seems like all the beams we currently have are meant to interact with the surface to create a new element, or to remove part of the surface (like an ion beam.) So we need to find the right way to transfer the particles.

  2. In order for this to be effective, the scout needs to put something down which won't be noticeable for normal inspection. That means it can't make a visible mark. So even if the scout could effectively place a regular tracking device on a small area from 200 meters away (which would be almost impossible), the device couldn't be anything regular surveillance would pick up.

  3. It needs to be something which a missile in the sky could lock on to. We were thinking at first of using a metallic element which is rare, and the missile could have a super-magnetic homing device which would only be magnetic for that specific metal. Alternatively, maybe it could be some sort of radioactive isotope which could be detected from the air.

The problem is figuring out what could create such a strong signal that an air-based device could identify it, without it being so obvious that the defense would pick it up.

So the question is:

What sort of homing mechanism can be identified by an air based missile, subtle enough that the ground defense wouldn't pick it up, and able to be precisely applied from a distance of 200 meters?


Obviously this question is based on pseudo-science; I haven't found (and don't expect to find) any actual examples of such materials. The goal is to find something which requires the least amount of bending science and sounds the most plausible- i.e. given current science, is there something which would answer the question and which readers would think could be realistic in 50 years?


edit: It was pointed out that targeting lasers do exist. The problem is it seems these only work if the laser is applied while the missile's in the air. I didn't find anything about the ability to mark a location which would be attacked at a later point.

(In the story, the scout would go around a large fortified compound and mark a dozen "weak spots" before leaving. Then, when the air assault starts, they could bomb away without needing any ground support.)

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    $\begingroup$ Have you done any research into targeting lasers? That's a commonplace real technology that would seem to fit the bill. $\endgroup$ – Catgut Jun 16 at 15:20
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    $\begingroup$ What's wrong with painting a target on the target with a paint which is invisible in the visible spectrum but is strongly reflective in infrared or in ultraviolet? Like for example, sun blocking cream. $\endgroup$ – AlexP Jun 16 at 15:40
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    $\begingroup$ @AlexP, first, the way I understood it, the scout should be able to "paint" the target from a distance, and second, if the victim knows to monitor their building with IR/UV cameras, it will still be detected. Though, as I note, that's going to be a problem with any active targeting system... $\endgroup$ – Matthew Jun 16 at 15:55
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    $\begingroup$ If you're targeting an installation then you don't need to mark them, you just need to know where they are and send the coordinates to the missile's launch platform. A targeting laser will do fine for that, it can know exactly where it is using GPS or something like it, and can tell that a target is 372.529m away from it at an angle of 74.39 degrees and declination of -12.62 degrees, it does some high school math and then communicates all that to tell the missile precisely where to impact. This can be done weeks/months/years ahead of time. $\endgroup$ – bp. Jun 17 at 5:44
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    $\begingroup$ Read Asimov's "The feeling of power". They find mathematics again after it was lost and the politician is happy, because he can teach enough math to people, and place them as pilots in the missiles instead of expensive guidance systems. $\endgroup$ – Nahshon paz Jun 17 at 13:31

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As a completely different option to my other answer... you're going about this wrong.

What you want is "passive LIDAR" (caveat: this means you missiles might only work during the day), combined with really good GPS. The scouts don't "paint" the targets in the field at all. Instead, all they do is passively collect enough visual data to build a detailed digital model of the target, and mark the weak spot in this digital model.

Then, send in a missile with similar systems (you might be able to use active sensors for the missile if the victim's response time is sufficiently long) that compares the data it gets while approaching the target to the stored digital model in order to pinpoint the weak spot. (Use GPS to get the missile pointed in the right direction and near the target, use the passive photonic acquisition/refinement systems to hit the exact spot.)

The good news is that this is totally believable; we're already working on things like self-driving cars that work on similar technology. The bad news is the onboard processing power needed by the missile is likely to be significant. (OTOH, it's not totally unbelievable that your smart phone will be able to do this sort of thing in a half century, so you might only need a few thousand dollars worth of tech to make this work. For the cost of a typical smart munition, that's not out of line.)

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    $\begingroup$ this is a great answer. It really does solve all the problems- except, as you mentioned, the need to do recon by day (which increases chances of detection). Is there any way to use night vision technology for this? $\endgroup$ – Binyomin Jun 16 at 15:59
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    $\begingroup$ I did say might. You can use FLIR or low-light cameras, but the quality might be problematic (although this is something you might hand-wave). You can also use your own light source, but your risk of detection goes WAY up if the victim has sensors to detect that. That said, since you can (theoretically) take your time scouting, whereas the missile has only seconds before impact, the image quality issue may be less of a problem for scouting. $\endgroup$ – Matthew Jun 16 at 16:03
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    $\begingroup$ There is no such thing as passive LIDAR. LIDAR is an active element that shines a Laser and detects shape by detecting reflections. I suppose you actually mean a plain old camera. $\endgroup$ – Jan Hudec Jun 17 at 8:03
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    $\begingroup$ there is the building rome in a day project where they reconstructed a 3d Colosseum from image tourists took. there is a short video there something the fancy bits $\endgroup$ – Nullman Jun 18 at 9:57
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    $\begingroup$ Given the cost of todays Anti Tank missiles or similar, I'm pretty certain that the cost of the processing power required + sensors would be well in line with other instruments of warfare / munitions. Development would be quite expensive as well, but hey, thats cutting edge military tech. 10/10 plausible technology Matthew! [I think we could IRL see that well before 50 years even, IF the tactical use for it becomes common enough] $\endgroup$ – Hobbamok Jun 18 at 10:32
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Actually, targeting lasers sound fine to me...

The scout investigates the structure, carefully aims the (visible?) targeting laser when no one is looking... then switches it off. he actual emitter is some distance from the structure, so not likely to be noticed, and the targeting dot doesn't exist once the scout leaves until the missile is about to impact. (To be clear, the emitter would be on some sort of mount, either on a stand or attached to a handy tree/pole/etc., and ideally would be camouflaged so as to be inconspicuous. The point, obviously, is that the scout can mount it and adjust it and then walk away, and when it is turned back on, it will "paint" the same spot again.)

When the missile is only a few seconds (to a minute or so) out, the lasers are sent a signal via some means that turns them on. At this point, the lasers may be noticeable, but the, er, victim has only seconds to react. You might be able to mitigate this also by using some wavelength that your missiles can 'see' but does not show up on normal surveillance systems.

You probably want to combine this with military-grade GPS so that the missile knows roughly where it needs to go without the laser. It sounds like this alone isn't sufficiently precise for your needs, but it will allow the missile to get very close before it needs the laser target, reducing the time between when the laser is active (and subject to detection) and the missile's impact.

Of course, this all assumes the victim doesn't have the ability to passively detect use of the targeting system, but that's going to be the case no matter what for any active homing system. Your best bet is going to be that it is either not cost-effective to employ such detectors, or the victim doesn't know how you're doing it. Otherwise, they can just park the same sensors as your missiles use around important structures and be warned if they are being targeted.

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  • $\begingroup$ +1 Your answer does address the problem of getting the scout out of the way. It has a downside that it requires leaving multiple laser devices set up for remote activation. This would increase the chance of detection. Also, if the laser would move (say an animal bangs into it and slightly alters the angle) it wouldn't be effective. $\endgroup$ – Binyomin Jun 16 at 15:56
  • $\begingroup$ Yes, you may need to set up in multiple spots, but it seems that problem is inherent in your premise. If multiple spots are being marked, you either mark them from the same spot — for this, that means multiple lasers set up in one location — or you have to travel to multiple locations to mark targets. If marking targets leaves anything behind (note also my other answer, which doesn't leave anything behind), that's going to increase the chance of detection no matter what it is you're leaving behind. $\endgroup$ – Matthew Jun 16 at 16:01
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    $\begingroup$ @Binyomin, the ‘laser devices’ left around are basically your average laser pointers with perhaps a little bigger laser diodes for lower dispersion. They are the size of a pencil and the scout can apply some masking after gluing them to suitable spots around the target. Yes, there is some chance security guards find some of them, but if there is several of them and are masked, chance of finding all is quite slim. $\endgroup$ – Jan Hudec Jun 17 at 8:00
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    $\begingroup$ One way to make the laser less noticeable would be to use an infra-red laser. These exist today and are in common use as aiming devices. The beam could still be seen with night-vision goggles of course, but that's just one more thing you'd need to defend yourself from them.. $\endgroup$ – Darrel Hoffman Jun 17 at 14:20
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    $\begingroup$ Presumably your scout would be equipped with IR/UV goggles anyhow (since they would ideally be working under the cover of night). And using a laser outside of the visible spectrum potentially allows you a wider time window between the beam turning on and the missile spotting it. $\endgroup$ – Darrel Hoffman Jun 17 at 14:40
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The drone is the marker.

The drone (which looks like an insect or a bird) simply lands on the weak spot. It transmits the homing signal. Okay, it's destroyed by the missile but the cost of a sacrificial drone is tiny compared with the cost of the missile itself.

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Colors that humans cannot see.

antiradar coating

https://coating.ca/anti-radar-paint/

You want your scout to have paintballs full of paint that is a color humans cannot see. Our vision is confined to the visible light, but one can detect signals from the entire EM frequency.

An easy one would be ultraviolet color. I do not mean the UV paint where you shine UV at it and it reflects in a color that you can see, although that is cool. I mean you shine UV at it and it reflects the UV. This is a legitimate color. Bees can see it. It looks black to us. If your scout had paintballs in this color, and the incoming missile could distinguish it, that could be a marker.

There is paint that can absorb radar and laser emissions as depicted above. Even better would be a paint that could better reflect radar emissions - the scouts paint mark would look like a bright spot to the radar emitted by the missile. The paint could be made to look like dirt to human eyes.

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    $\begingroup$ I thought about this, but what happens if your paintball misses, or just hits the wrong spot? $\endgroup$ – Matthew Jun 16 at 16:06
  • $\begingroup$ Paint was suggested in the comments to the OP, but I like your suggestion of paintballs as a way to mark the spot from a distance. Do paintballs splatter a lot? If the paint would spread out too much from the impact, it might be not be effective. $\endgroup$ – Binyomin Jun 16 at 16:08
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    $\begingroup$ @Matthew good point. Of course the scout would need to be a sniper, but even still nobody's perfect. There would need to be a way to remove the paint (or at least deactivate it so the missile wouldn't lock in on it.) Any suggestions? $\endgroup$ – Binyomin Jun 16 at 16:10
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    $\begingroup$ @Binyomin, paintballs don't splatter too much... an image search for "paintball wall" will give you some ideas. There is, of course, a trade-off between spot size and splatter distance; a smaller ball should splatter less, but will be harder for the missile to "see". Your biggest problem is going to be dripping. Perhaps the missile has enough computer vision smarts, though, to estimate the original impact location from the splatter. $\endgroup$ – Matthew Jun 16 at 16:48
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    $\begingroup$ @Binyomin - your scout could carry more than one type of paintball. Paintballs full of powdered sodium metal in oil will react vigorously once in the air and destroy whatever they are on. Those would be good later in the story when your scout must use them for other purposes. $\endgroup$ – Willk Jun 16 at 16:53
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The problem is, how can the scout mark that spot from 200 meters away, such that when an airplane shoots a missile the homing device can lock onto that spot?

He doesn't mark the spot.

He marks three other different spots nearby. The missile will receive and triangulate the three signals and home in the barycenter of the triangle.

Or also...

...the missile knows exactly where it is at any given time, because 50 years of GPS technology. So it only needs to know exactly where it should be. This information can be coded in three simple numbers, that can be calculated by the scout, then uploaded to the missile.

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The obvious counter for the defenders is decoys. The "weak spot" was indeed a weak spot, but it has either been internally reinforced, or the whole building has been repurposed and redesigned internally according to the knowledge of where the missile will hit. After all, if one country can scout a weak point on the enemy, so can the enemy on themselves (actually they can do it even better, since they needn't worry about being discovered).

During the Gulf War, if memory serves, Saddam Hussein employed fake tanks made of aluminum foil, cardboard and fiberglass with heaters inside, to attract enemy fire away from the real tanks (a friend of mine maintains that the deception worked because the real tanks also were made of aluminum foil, cardboard and fiberglass). You could do the same with spray-on "weak spots". When the whole building looks like a weak spot, then you no longer have obvious weak spots.

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An alternative to the "invisible paintball gun" or "particle-placing laser" that requires less skill on the part of the scout: consider bringing something closer to deliver your paint.

Drones are getting really, really small. Fifty years of advancement seems more than enough to be able to get a future scout to remote-control an inch-wide drone around the target structure and splash points on it with the sort of material your missiles can lock on to.

It seems pretty feasible to still need a scout nearby to do this; tiny drones will likely still have short aerial lifetimes and short ranges, and requiring them to be manually controlled makes enough sense for suspension of disbelief.

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    $\begingroup$ Or... they're manually controlled because a) the control system has very limited range, and b) they don't have anything like the necessary computing power to figure out the weak spots on their own, but skilled operators are really good at doing so. Just about zero disbelief needs to be suspended, there. Plus, the operator can hide in a nearby shack, which makes their lives somewhat easier, but I think it would still be good drama. $\endgroup$ – Matthew Jun 17 at 1:01
  • $\begingroup$ The marker could also be the drone itself, fly it to the point, stick it on the wall, turn on his transponder, walk away from the incomming explosion. $\endgroup$ – Ckankonmange Jun 17 at 7:32
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radioactive clear paint from an grenade fired from a M203 40 mm underbarrel grenade launcher, or the M79 Grenade launcher.

the paint would emit a signal in the form of radiation that the missile would then home into.

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  • $\begingroup$ Bombarding a building with grenades (even paint grenades) is likely to draw attention both to the scout and the fact that the building has been marked. $\endgroup$ – Beejamin Jun 18 at 2:19
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The problem

Your main issue is you want to avoid detection until it's too late. The problem is any signal your missile can use to guide itself can also be detected by the enemy.

If the missile sends a beam to scan the target, that can be picked up by something else. If the missile rides a beam to the target, that can be picked up by something else. If you paint the target with a radioisotope, that can be picked up by something else. So whatever you use, it's something you want to turn on at the last moment. That eliminates a number of candidates.

GNSS [Global Navigation Satellite System, like the American GPS] is the obvious alternative, you just need to enter the coordinates and the missile guides itself. The problem is that can be jammed. It's not a weird quirk, it's more of a feature. For some reason, most militaries don't like people knowing the exact location of their installations. So they'll jam GNSS frequencies around their bases just to spite you.

Since you are attacking a high-value target, you should assume they have the ability to detect or jam any signal. Luckily, it doesn't matter as much as you might think.

Phase 0: Intelligence

It may appear obvious, but it needs to be said. It's the first step of any good military operation. Collect, analyse, identify. You want to know all about blueprints, layout, gas pipes, fuel depots, defences, etc. That will give you the weak spots, and where they are located.

Good intelligence is never optional. You can't improvise a strike like that. You can't just send a guy with a laser pointer the day of and hope for the best. They can get intercepted, or fail to see any weak spot from their position. Then you just look silly.

For the strike, you will need precise coordinates, and you will also need a reliable weather forecast. None of this should be an obstacle for a competent military intelligence service.

Phase 1: Satellite-guidance

The good thing about GNSS is you only need a few satellites, and that, as far as I know, isn't something the enemy can detect. The bad news is it's something they can jam.

Unless you can disable such a jamming beforehand (which may give you away), you should assume you will lose GNSS at the time you need it the most, i.e. at the end for the final approach. You could use precise coordinates of the weak spots to position your missile in the right position, but you will still have to guide it the rest of the way.

You could skip precise GNSS-guidance altogether, but that means you need to skip to phase 2 earlier, giving more time to the enemy to react. I wouldn't cheap out on it.

You could also skip phase 2 altogether if your intelligence reports comes in negative on GNSS-jamming in the first place (and that's why you need good intelligence). If they aren't blocking GNSS, that makes your life easy, and they are really asking to be hit.

Phase 2: Laser-guidance

A laser beam will do the trick. It can be picked up, but so can a missile hurling a cruising speed. If your missile is already positioned in the right direction, you can turn your beam on at the last moment to finalise the approach. If you do it right, they won't have the time to react.

To paint the target, you will use a UAV. It can shine its light from beyond human visual range just as good if not better as some schmuck on the ground.

You may remember I mentioned weather. This is where it matters. Lasers are sensitive to bad weather. Don't try laser-guiding on a rainy day. That's why you need a weather forecast, to schedule the strike.

The hardware

You will need a missile that won't show up on radar, or whatever else is in use 50 years in the future. Your targeting UAV also should not get picked up by enemy radar. Those shouldn't be hard requirements.

You also need a missile launcher. I would recommend a missile cruiser in the nearest sea, mainly because missile cruisers are cool and also far away from any danger. You could also do with a jet or combat UAV.

The strike

Your missile flies to the area of the target location. This doesn't require much precision. When it is close to the target, it will use GNSS guidance to get itself in position to hit the target precisely. When it loses the GNSS signal from enemy jamming, the laser-guidance system turns on. You just need to make sure your UAV is painting the target from that moment onwards. If you do it right, the missile uses laser-guidance for its final approach. The enemy may get alerted, but at that point the missile is already tickling their nostrils.


Alternatives

Carpet bombing

It's obvious, but it you want to destroy something and one bomb doesn't do the trick, send more bombs. Eventually, it'll work. Of course, it has its drawbacks.

Beam riding

Beam riding is the cool term for guiding a missile with a beam. It means what it says, your missile "rides" the beam all the way to the target. You could replace laser-guidance with any sort of beam riding guidance. The drawback is the same (the missile can detect it, so can the enemy), and the use-case is the same (turn it on at the latest moment possible).

Particularly, if you have a particle beam technology that works in the rain, this is the time to use it. Then you don't even need to watch the weather.

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A very, very small transmitter and receiver, that's silent until the missile is close

The scout has a small dart, milimetres in diameter, or maybe even less, that contains a tiny signal receiver and emitter.

To prevent the defenders finding it, it does not emit anything by default. Both the missile, and the transmitter, have a unique identifier code. When the missile is flying towards the target, it broadcasts the unique identifier towards the target building - the transmitter see's this, then advertises its position to the missile. This could be via a GPS signal to the missile, or a visible light of a particular frequency the missile is programmed to fly towards.

This also gives the scout an option to mark multiple weak spots, that will each respond to different missiles - allowing you to fire multiple missiles to hit multiple weak spots in sequence, or all at the same time.

Or a similarly activated laser

If you think a physical object would be too easily spotted - you could employ the same mechanism to activate a laser that is pointing at the weakspot - so as the missile gets close, the standard guiding laser many missiles use today activates. The laser may be visible to the defenders, but they only have a few seconds before the missile hits - giving them just enough time to do a nice and dramatic "Oh sh-".

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  • $\begingroup$ I like your second option - don't leave anything on the target building at all. Instead, leave behind something (or several somethings) that can mark the target with the laser after the scout has left. In fact, if you had camouflaged drone robots (disguised as bits of junk, rocks, etc), you could remote pilot them into position, target the spot, and then have them go dormant until needed. $\endgroup$ – Beejamin Jun 18 at 2:22
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This would require some scanning first but... since the setting is futuristic, a mix of brainwave and body movement patterns could be used as a "fingerprint" for an individual, and a drone loaded with explosives could scan and blast the individual once the target is found. Drones like these based on face recognition even exists today: https://www.google.com/search?client=ubuntu&hs=2dS&channel=fs&ei=Q5XpXvvbJvqU5OUPt82BmA0&q=drone+explosive+face+recognition&oq=drone+explosive

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Has anyone considered the idea that massive cloud data properly beamed or routed like a goldeneye satellite or ion cannon has similar properties to using a particle beam weapon system not yet available for 20+ years... just thinking outside the box.

Might not take aircraft out but maybe it has never been tried yet? (Horrible suggestion) Why couldn't network traffic be used as the beam or path of traversal?

Is a laser beam more practical to using homing tools that shoot 100000 cloud servers pipeline directly at your target or something your targeting? Would a laser work in space or outside the atmosphere... would network data work since we know probes call home 20 years with a battery signal... make the battery into a high orbital cannon? 🥵

In science fiction, an ion cannon is a beam weapon. It shoots beams of ions (atoms or molecules with an electrical charge). Because of its power, it is usually said to be a superweapon. An ion cannon is a type of particle cannon. The particles it shoots are ionized.

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  • $\begingroup$ Yes, lasers work just fine in space. You're suggestiong modulating a maser with people's private documents and videos of amusing cats? I'm not sure I get your answer. (From review) $\endgroup$ – Tantalus' touch. Jun 18 at 17:56

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