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Comment by Cieplak | Hacker News Reader

Wonder how many watts that thing is putting out, and at what frequencies. In theory it could kill a person if it pulsed the correct harmonics. Will be interesting to see drones with Faraday cages. Some teenager on YouTube did something similar:

https://m.youtube.com/watch?v=DoOT2_Z-GIE

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Looking ahead to the next 20-30 years of warfare, I've often thought that despite the fun we're currently having with aerial drones, a lot of the real drone future is going to be with autonomous ground drones, because of their ability to carry more armor, shielding, etc., without having to literally carry it into the air. Our current conception of a "drone" is really hard to bring up to military spec once this sort of countermeasure becomes militarily common.

I don't mean that air-based drones will be useless, I just think they're going to see more constrained missions than we might currently be imagining. And I do mean just the common conception of drones... things arguably properly described as "autonomous planes" will continue to be important and will probably continue to grow both in importance and in physical size.

I think you're right. Once you factor in high efficiency solar panels (like the germanium ones in satellites) land based drones can infiltrate enemy territory and sleep for months or years until they're needed.

Sleeper photovoltaic cells?

For someone who has been out for a hike and been startled by a rattlesnake a step away, I can imagine a terrifying world of small, ground-based area denial robots that spring to action faster than our reaction time can avoid them.

Like a mine with a brain.

As scary as that sounds, I feel it is better than the mindless landmines laying around from past wars. In theory, when the war is done you could hit the disarm or recall button unlike conventional mines.

Unless the drone mine gets hacked. It might even have a protocol to shield itself from a fuel-air bomb, which is a common form of mass-mine detonation.

I've never heard of a fuel-air bomb used for demining... APOBS is used a lot, and no matter how clever the mine is - it can't ignore a chain of explosives going off on top of it.

It's not objectively the best Sci-Fi I've seen, but I have a soft spot for Crichton's film "Runaway" which has some of that in it.

Imagine - a mobile drone factory, digging itself in in the hinterlands, harvesting solar energy and water, producing mobile hydrogen-IEDs - the minefields of the future will be hard to undo.

This is pretty much the premise of Philip Dick's Second Variety, made into the movie Screamers.

Thanks for the tip. I didn't know that one had any kind of movie adaptation.

Screamers is surprisingly underrated. It's one of the best pop-sci-fi movies from nineties imho.

The ending to that story was particularly delightful.

Does that sound like a paperclip optimizer? Because it certainly looks like a paperclip optimizer. Think of it: eventually humanity goes extinct because the whole world is land mines...

arms race has it all taken care of - in response to autonomous IED making drones there will be autonomous drones clearing up the minefields and hunting down those IED making and installing drones. Of course to deal with the hunter drones the IED making/installing drones will have special protector drones ... Humans just need to relax in the deep soft chair and enjoy the popcorn.

Well if it's solar powered, we can easily take it out with an inexpensive sticky black paint bomb. Second, while you won't run out of water, you will run out of other stuff for your hydrogen IED drones.

Now a much better thing to do instead of making IED drones would be to melt sand or rock into appropriately formed projectiles so that one has an autonomous artillery piece that does not require reloading.

There are much better explosives to use than hydrogen. One could use the haber process to make ammonia and use some biological carbon sources to make pretty much any explosive worth using.

Landmines are probably cheaper though.

The Russians are focusing on ground based combat drones almost exclusively. Their air drones seem to be geared toward surveillance.

Because Russia's war will be next door and on the ground.

The US relies on air power tho if you look at BDA imagery released not a small percentage of the so called drone strikes are more likely than not to have been conducted by mannned strike fighters as drones can't carry things that would leave that big of a crater.

> Our current conception of a "drone" is really hard to bring up to military spec once this sort of countermeasure becomes militarily common.

This isn't really for drones. It's for frying ground-based electronics like cell phones. Drones are the smoke screen to hide that fact.

As for drones, motors and batteries are quite hardy against quick microwave pulses. A bit of aluminum foil makes a good, light Faraday cage. Optocouplers can isolate radio and GPS modules from the actual motor control systems.

I would expect you can fry an RC drone, but an autonomous one operating inertially or capable of switching so when radio/GPS goes away is probably pretty easy to shield.

In addition, this kind of system is always going to have a range vs width tradeoff. Can the drones get inside this thing's range where they can still be effective even if they are "ballistic"?

Dumb old bombs are really effective if you just give them a little bit of GPS to improve their accuracy. You don't have to get very close for the GPS adjustment to be devastatingly effective.

> This isn't really for drones. It's for frying ground-based electronics like cell phones. Drones are the smoke screen to hide that fact.

Or imagine a smaller system integrated on a humvee that can destroy electronics in anything along the path a few dozen meters in front and in a smaller side/side area. That'd end the IED threat from anything other than a purely mechanical IED (not sure if many of those are around anymore, as everything assumes electronics will work nowadays).

Nope, insurgents found a way around that a long time ago when convoys started including jammers. Hybrid detonation systems: radio arm the device outside of jamming range, mechanical switch detonated the IED once the vehicle triggers it.

Or they simply use long wire buried in sand.

I only saw that a couple of times, in one case we caught the guy - he still had the 9v in his pocket (why he'd keep it I don't know). If you watch their videos you see that they prefer to be much further back than what is practical with a wire commanded detonation. There were rumors of laser commanded detonators, but I doubt it happened enough to warrant any sort of countermeasures.

When my brother was doing Op-For at camp Irwin he used one of the sensors from a garage door for simulated IEDs. Pressure plates, lasers, motion sensors, you name it and it'll make something go boom.

This is why IEDs are so effective in asymmetric warfare. They are cheap and anyone can get parts =(

I assume you're talking about the safety beams that prevent the door from closing on obstacles. Have you ever had the door go down on command and then halt, without any obstacle in the way? They're very noisy sensors - lots of false positives, not the sort of thing you want to wire up a massive bomb. They also actively emit light, so not very stealthy.

The first time I saw the results of an IED blast was a day after I arrived in Iraq. I had to shake a tree in order to retrieve the trousers of the guy who blew himself up planting the thing. That happened a lot. Making IEDs isn't very hard, but making a lot of them without eventually blowing yourself up is.

For the next 20-30 years, drones will be built to fly above the range of such weapons and remain extremely effective.

No they won't there is an upper limit to flight and if by some means these drones would be closer to space than to the ground you put those weapons in space or on high altitude tethered platforms.

>>I've often thought that despite the fun we're currently having with aerial drones, a lot of the real drone future is going to be with autonomous ground drones, because of their ability to carry more armor, shielding, etc., without having to literally carry it into the air.

While I agree with the idea that there will be more fun ahead with ground-based drones, wouldn't an air-dominance doctrine still hold in drone-drone warfare as it exists today in conventional wars?

I imagine both ground and air drone warfare evolving at similarly terrifying rates over our lifetimes.

> In theory it could kill a person if it pulsed the correct harmonics

If you're thinking about RF, then frequency doesn't matter that much. It's just that absorption and penetration slowly change with frequency, that's all. There are no "deadly frequencies" there.

If you're thinking about modulating the RF with some signal matching the heart rate or some brain waves, that's... interesting, but I'm not sure if it has ever been proved to work.

Frequencies considered especially dangerous occur where the human body can become resonant, at 35 MHz, 70 MHz, 80-100 MHz, 400 MHz, and 1 GHz.

https://en.wikipedia.org/wiki/Radiation_burn

At frequencies near the body's natural resonant frequency, RF energy is absorbed more efficiently, and maximum heating occurs

http://www.arrl.org/rf-radiation-and-electromagnetic-field-s...

I stand corrected, I forgot about resonance.

Thanks for those.

Having trouble trying to understand how what I read fits in, but the guy who designs those massive mega wattage sound systems for festivals - Funktion1 - commented in an interview about how there are, essentially, lethal sound waves of sorts.

>There was this French bloke at the turn of the 20th century who built a giant whistle that produced sub-bass frequencies of around 7.1 or 7.2 Hz. The first time that he got it to work, he liquidized himself. It just turned his insides to mush—poor bugger.

http://djtechtools.com/2014/04/10/funktion-ones-tony-andrews...

With a drone encased in a full faraday cage, how would the operator control it? Therein lies the problem unless it was preprogrammed and fully autonomous. That might work.

Line of sight lasers are one possibility, but those are vulnerable to dazzlers.

Good luck with getting GPS then.

With a good enough AI and a detailed aerial map onboard, you may not need it.

Place the receptor outside of the cage, put a resistor and a biggish capacitor, a varistor and a fuse on the communication line, and it's good enough for any disposable machine.

Faraday cages don't block DC, so use that to provide power.

Then run a simple optical fiber cable for communication to an antenna that lies outside the cage.

If you are really good you have multiple antennas that are kept off (with the circuit physically disconnected from the antenna). If you get hit with a pulse activate the next antenna.

It's possible to make simple electronics that can survive such a pulse, with auto-reset fusible links, and you use those for activating the antenna.

Or even a small door and "push" the antenna out of the Faraday cage when needed.

> Faraday cages don't block DC, so use that to provide power.

Drones carry their own power source - usually a LiPo battery.

What you're proposing would not work if the phaser could just keep firing (which seems likely). Onboard AI seems the solution (assuming the Faraday cage is effective enough, which remains to be seen).

> Drones carry their own power source - usually a LiPo battery.

You misunderstood me. Use that to provide power to the antenna which is outside the Faraday cage, and the battery is inside.

> What you're proposing would not work if the phaser could just keep firing

The phaser has a range though. So program the drone to fly up and away if it gets hit (no need for AI to do that). Then reactivate communication and stay away from the phaser area.

I think this is an expensive solution, which would increase radar cross signature almost certainly. Also, it would protect against a weapon that isn't fielded while doing nothing for any conventional weapons.

Source: I flew UAVs "drones" for the US Army for 482 combat flight hours in Iraq. Lookup the wikipedia for "Ground Control Station" for an old pic of an 18 year old me @ the UAV training center "black tower" in Ft Huachuca, AZ.

https://en.wikipedia.org/wiki/Ground_control_station

Yeah. The solution is likely more along the lines of making the drones cheap and disposable, and fighting these systems with traditional air defense suppression.

Very much agreed. I see this "phaser" system as a neat tool that could work along side conventional anti-air such as Patriot batteries to make it pretty difficult to gain air superiority.

One thing about the Faraday cage is that is has a maximum frequency - when the wavelength becomes comparable to the cell size in the wire frame. Any higher frequency will just go through.

This is a problem as microwaves are in the centimeter range. The mesh then would have to be dense. That would raise aerodynamic issues.

I'm not saying it's not doable. I'm just raising the obvious concerns about basic challenges from the laws of physics.

You could put your propellers outside and away from the cage, with their motors inside the cage. This would also greatly reduce the size and weight of the cage.

That might work. The "cage" would be more like a sleeve in the region of the arm - just creeping out on the arm like a mesh tube (or even continuous foil tube) to protect the wires, electronics, and motors. A small hole would allow the motor hub to stick out of the cage, and the prop would be on top of that, outside the cage.

Heck, all the wires, electronics, and motors could be inside the "arm". Then coat that with some EM shield material (like a metal foil).

I like it.

Of course, from "like it" to "it's actually effective" there's still the nagging little field test to perform. It's the old shell-vs-armor game, since EM radiation has a penetration depth - Faraday cages are not magically 100% effective, make a thin enough one, and a powerful EMP would still do some damage inside. So now you need to carry thicker, heavier EMP armor.

I think they are magically 100% effective. Unless the cage is breached, nothing will get through. However, an EMP pulse could melt holes in the foil.

However it also means the drone has no GPS; no wireless signaling; no sensors outside the foil at all. It becomes a dumbfire dead-reckoning device.

> I think they are magically 100% effective.

No, they are not. Even a continuous, zero-hole metallic bubble will leak some radiation inside, depending on frequency, nature of material, wall thickness, etc.

Start here:

https://en.wikipedia.org/wiki/Penetration_depth

then continue reading about absorbance, skin effect, etc.

I see. Only for zero-resistance metal would skin depth be zero.

At microwave frequencies, skin depth is essentially zero (microns anyway) for most metals. So until the bag is melted, nothing will get through.

Wouldn't a large amount of targeted RF incident upon an ungrounded faraday cage induce a large enough charge accumulation to also pose a threat to the drone (and anything around it)?

It's not ionizing radiation. Even if it did that, with a metallic shield on the outside, any amount of static charge on its surface generates zero field inside - this is a perk of metallic shielding.

Two real issues with massive RF energy density:

1. Penetration depth. Even if you have a continuous metallic bubble with no holes, some RF radiation still leaks inside, depending on material nature, thickness, frequency, etc. The amount is small, but it's not zero.

2. If energy density in the RF beam is huge enough, the shield / cage starts heating up. You could conceivably melt it if you take this game far enough, or poke holes in it.

There is a net zero electric field inside, true, but isn't that because a charge accumulates on the inside surface of the cage that is equal and opposite to that induced on the outside surface?

With regard to #1, I agree, but the degree of RF leakage is not universally small - it depends on the frequencies you encounter and the properties of your cage (material, mesh thickness and "pore" size, etc). As frequency increases (and wavelength decreases), your pore size must decrease to effectively block it, eventually becoming a solid shell (through which propellers will, of course, generate no thrust). I agree with #2.

> There is a net zero electric field inside, true, but isn't that because a charge accumulates on the inside surface of the cage that is equal and opposite to that induced on the outside surface?

No. In a conductor, all free charges migrate to the outside surface.

You don't need a full cage. As the beam can only originate from the ground you can just shield the vulnerable bottom half. Don't see how this weapon can work against sophisticated adversaries.

Ground based targets is part of the scope for the weapon - just mount it on a plane (maybe a large drone!)

I always thought a Faraday cage had to be grounded but after a bit of reading I think that is not actually the case.

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