Homing device for missile, which can be applied remotely

Question

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.)

Answer 1

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.)

Answer 2

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.

Answer 3

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.

Answer 4

Colors that humans cannot see.

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.

Answer 5

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.

===

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.

Answer 6

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.

Answer 7

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.

Answer 8

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.

Answer 9

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-".

Answer 10

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

Answer 11

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.