EMP attack on the US...how bad could it be?

Factual Questions
1

I’m reading a series of books atm that have as the central plot point a sneak EMP attack on the US from North Korea. In the story, the EMP attack hits the US completely unobserved (:dubious:) and at an optimal distance for maximum damage (that is, it hits CONUS, presumably since it’s set on the East Coast of the US). This strike basically takes out all infrastructure…cars, cell phones, power grids, all electronics, basically everything. I won’t get into the details of what happens after, but one thing that strikes me is there doesn’t seem to be any effort (6 months later) to rebuild basic electricity. All of the places in the books are dark, with no electric lights or generators. All cars made before 1980 are completely dead, but there doesn’t even seem to be a concerted effort (despite the seeming abundance of fuel all over the place) to get most vehicles back in order.

So, my GQ questions are…how bad could it be? What are we talking about here. I THINK I know the answer, as I’ve wargamed this scenario in various emergency operations exercises, but mainly they talk about things being down for weeks or maybe a month or two, and not everything being down. I don’t see why, say, a generator that doesn’t use electronics would be knocked out, for instance. It seems to me that, while this would be very bad, there would be things you could do.

Also, in the books, the US military is seemingly completely out of the picture (and, of course, there is zero government support from FEMA and the like). While I find this part of the book pretty much complete bullshit, it brings up the question…would it take out the entire military? Aren’t some of their vehicles and other support systems hardened for EMP?

Anyway, don’t want to get into picking the books apart (I’m doing that already in my own head, with plenty of :rolleyes:), but wanted to get the GQ 'dope on EMP, as I’m finding a lot of conflicting stuff on the internet (as usual) and not getting a very clear and consise answer.

2

First of all, with current technology, the only way to get a decent sized EMP is with a nuke. I know sometimes folks can be a bit unobservant about some things, but I think that North Korea setting off a nuke is something that at least a few people would notice.

Anything less than a nuke is going to have a very small area of effect and wouldn’t be worth worrying about.

A lot of things could be affected by a large enough EMP, but some things will survive. Metal boxes shield things from EMPs as the electric fields tend to go around over the surface the box and leave anything inside unharmed. There’s also a magnetic component to an EMP (electro-MAGNETIC pulse, after all), and that magnetic wave will induce currents in things. The magnetic wave will induce currents in the box too though, which will weaken the magnetic wave’s effects. Metal boxes aren’t completely effective at reducing the magnetic part of the wave though.

A lot of utility equipment is protected with things called “halo grounds” or “ring grounds”, and “Ufer grounds”, in addition to Faraday cages (a metal box, effectively). The purpose of a halo/ring ground is you surround the building you want to protect with a ring of metal, and any incoming electromagnetic wave will induce currents into the ring and will shunt the energy directly to earth ground instead of inducing currents into your equipment. Ufer grounds are basically using grounded rebar in the building’s concrete foundation to provide an exceptionally solid earth ground connection. The main purpose of these halo grounds and Ufer grounds is to protect the building from lightning, but as a side effect they also protect the building from EMP strikes. A lot of data hubs used by phone companies, internet providers, cell phone companies, etc. will survive the EMP attack, although some of the communication lines between them will be fried. So they’ll go dark, but they can be fixed relatively quickly.

Yeah, I’m pretty sure the power utility folks aren’t anywhere near that helpless. I’d expect a majority of the population to have power restored by the 6 month mark.

Modern cars are more likely to be toasted than older cars. Tiny computers control everything these days.

A powerful EMP will induce current into the generator’s wiring. If enough current gets induced, the wiring or the connections fry. Most generators also have circuit breakers, and those could be damaged by the EMP. In an emergency, the breakers could be bypassed and melted connections could be fixed.

Yep. These doomsday scenarios generally rely on everyone being absolutely helpless morons.

Yep. Military command centers are hardened for EMP (and again, for lightning, because the same sort of protections work for both), and some vehicles are hardened as well, but many vehicles aren’t. Since you need a nuke to generate a decent EMP, I guess they figure the vehicles probably aren’t going to survive a nuke attack anyway, so why bother?

3

Yep. And I think they have to be running at the time of the EMP to be affected. Or at least completely taken out (some sub systems in new cars are always on). But please let me know if I’m misinformed.

4

It was a nuke, yes. I guess I should say no one noticed it until it happened, then…blam, US goes down in flaming ruin, basically. They don’t really get into what happens with the rest of the world much, but the US is essentially completely helpless.

Yeah, that was my thought exactly. I mean, hell, in a pinch I could make a freaking steam-powered generator myself with just parts around my house wrt the basic electronics. They make it like no one can do anything because of EMP!!!

Yes, but there are a lot of vehicles on the road still that are pre-computers. Also, I think you could circumvent a lot of the electronics if you had to. An engine is just an engine, after all, and while you might need to replace some of the wiring you could do that, in theory at least.

Exactly. It also relies on the government being completely clueless/corrupt/inept in this case. There is basically zero government (local, state and of course Federal) assistance given…even the local police are completely helpless after the EMP and basically just let law and order go completely.

I get that the cell and data networks would be down. And a lot of the radio as well (though I know for a fact a lot of counties in my state have a lot of really old radio equipment laying about in faraday cage type storage, though for other reasons than they think it will be an EMP attack).

Yeah, though I don’t know as much about what the Army/Air Force or the like have, I assumed it would be a mixed bag. But a lot of the US military is deployed overseas in bases around the world and I doubt you could cover that much of the world with high altitude nuke attacks to get even the majority of them…and I also doubt they would be sitting back thumb in ass and waiting for someone to tell them what to do while the US went down. Also, I’m fairly sure the President and Congress have contingencies for this, so they would still have at least some communications abilities as well as reserves of necessary supplies and equipment to keep the government going in the event of something like a North Korean attack such as happened in this book.

Anyway, thanks for the reply. It goes along pretty well with my own take, but figured I’d ask in case I’m missing something here.

5

Well, that’s flatly impossible, and has been since about 1960.

An EMP has to be extremely high-altitude, effectively exo-atmospheric. And that means missiles. No one can launch a long-range missile without some orbital sensor picking it up in real time. NORAD would see the launch, characterize it, predict its trajectory, and have a response tree on hand before the vehicle gets beyond the horizon of the launch site.

6

North Korea just looks and acts dumb, but they are not dumb enough to strike first, especially with one EMP attack or even one nuke and wait for their country to become a hole in the ground. If we strike first they of course will throw whatever is left at us from EMP to chemical to small nuc’s aimed as far as they can reach with the limited fire power they have now.

But to wait say five (5) more years for a new administration to take over would then have their nuclear capable arsenal ready to do some serious damage.
It’s a no win situation … EMP’s are bad and it’s not the damage report it’s the rebuilding question or more than likely the people moving problem away from the area that was hit.

Our only hope is an over throw of the present day ruling party in NK … 100 million spent now on that problem would save billions and countless lives later

7

As far as I know we don’t actually know a whole lot about EMPs and the only way to really know how bad one would be is to do a full-scale test. The worst case scenarios are usually being used to sell someone (individuals or the government) something (doomsday seeds or trillion dollar missile defense systems).

8

A bit outdated (nothing newer than 2003 models tested), but you can check this out. Pay attention to strength, of course.

9

Seems to me, that if it could happen, it already would have.

10

Moderator Note

While the OP specified North Korea, the factual GQ question here is focused on the actual known effects of EMP weapons of the type that a country with technology and resources similar to that of North Korea could produce.

How best to handle the real-world North Korean situation is a topic better suited to Great Debates. Feel free to create a thread there, if you’d like. There may also be existing threads there on this topic that you might be interested in.

GQ isn’t a good fit for this particular tangent, however.

11

It’s a MAD scenario. Mutually Assured Destruction.

If you do this to another nation, you can be assured they will retaliate in kind. You can also be sure that other nations (in our case, Canada and Mexico) will be also damaged and rather interested in making you pay.

12

Surely any EMP weapon would still follow the laws of physics relating to the propagation of electro-magnetic waves?

So how powerful would it have to be to take out all the continental US? (And that would get most of Canada & Mexico, too.) Where would you position it when firing?

The OP specifies the East coast of the US – that would still leave North Dakota at least partially intact, and that’s where most of our ICBM’s are located. (In Cold War days, North Dakota was the world’s 3rd most powerful nuclear power.) Plus there’s the west coast of the US. They are behind the shadow of the Rocky Mountains. And California alone is in the 10 largest economies of the world.

I agree the idea is ludicrous, but that’s common in works of fiction. But here in GQ, somebody ought to be able to give some rough calculations of needed strength & range of such a hypothetical EMP weapon.

13
14

Quoting myself here. I am curious if a new car would need to be running to be taken out by an EMP. Anyone know?

15

OK, so worst case scenario. North Korea manages to get its purported 250kton weapon on a missle and blows it up at an altitude for optimal EMP potential. How large an area is affected?

16

I’ve seen demonstrations of cars being hit by lightning to no ill effect, so on that basis, a metal-shelled car should be immune to EMP.

17

Didn’t really think of that. A car is just a big faraday cage.

18

I can’t really vouch for the accuracy of this source, but it does directly address the OP:

It certainly doesn’t sound as catastrophic as popular media portrays it, but then what do we expect from our popular media?

19

As for what area would be affected, it depends on the altitude of the blast, as indicated in the article I linked below. The higher the altitude (in mile or km), the larger the area affected. A blast at 400km (@ 250 miles) altitude over North Dakota would affect almost all of the continental US and most of Canada. Of course, that would also take out virtually all of the non-geosynchronous satellites over North America as well.

20

I’ve also seen cars that have had their electrical systems completely fried by lightning.

A car isn’t a perfect Faraday cage, and there are some cars that have plastic body panels. Still, a car’s body does tend to provide a great deal of shielding against an EMP. A lot of the protections they put into modern cars to prevent things like the engine computer being affected by cell phone signals also helps to shield the vehicle from EMPs.

I think the word “immune” there is a bit strong. Some cars will end up getting damaged by an EMP. Some will probably survive.

Ever since at least the 1970s (and maybe earlier), people have been promising EMP type devices for law enforcement to safely stop fleeing vehicles. Back in the 70s, they were able to demonstrate that their devices could stop vehicles. But they weren’t reliable. The manufacturers just said they had a few more things to work out to make them reliable. Even today, there are people still working on this, and they still say that they just have a few more things to work out to make them reliable. The thing they can’t seem to work out is that cars are just naturally resistant to EMP type effects. Sure, you can stop some of them some of the time, but you’re not going to stop all of them.

EMP weapons actually got their start back in WWII. It was the same sort of thing. They promised that they could stop enemy airplane engines, and the enemy planes would just drop out of the sky. They were able to stop engines in controlled tests on the ground, but when they actually tried it in the air, the weapons proved to be completely ineffective and they did not stop a single aircraft. It’s the same basic issue that you have with cars.

A lot of buildings these days use steel frame construction and metal roofs. This also tends to form a somewhat imperfect Faraday cage. The building that my company used to be in was notorious for this. Cell phones wouldn’t work in the interior of the building. If you needed to make a call, you needed to go out to the lobby or near one of the exit doors. These types of buildings also tend to naturally shield EMPs.