High-Altitude EMP Effects in a Computer Age Nuclear War

So, over in the thread Atomic War In The 80s, there was some discussion of EMP, which I think merits its own thread, as it's so often brought up in these sorts of threads. I've quoted a post by SergeantHeretic as an example of what gripes me, though I swear I'm not trying to pick on anyone). My responses/concerns are appended.

No sir, it causes a short term interference with solid state electronics and that's all.

I am highly skeptical of the pooh-poohing of EMP. It isn't as if there haven't been instances where high-altitude EMP has caused significant damage. The damage caused would vary considerably depending on the size of the weapon, the altitude at which it was detonated, and its location relative to the Earth's magnetic field. For an example, I would direct you to the Soviets' Operation K tests in 1962, which did indeed cause considerable havoc:

The worst effects of a Russian high altitude test occurred on 22 October 1962 (during the Cuban missile crisis), in Operation K when a 300 kiloton missile-warhead detonated west of Dzhezkazgan (also called Zhezqazghan) at an altitude of 290 km (180 mi). The Soviet scientists instrumented a 570-kilometer (350 mi) section of telephone line in the area affected by the detonation in order to measure electromagnetic pulse effects.[2]
The EMP fused all of the 570-kilometer monitored overhead telephone line with measured currents of 1500 to 3400 amperes during the 22 October 1962 test.[3] The monitored telephone line was divided into sub-lines of 40 to 80 kilometers (about 25 to 50 miles) in length, separated by repeaters. Each sub-line was protected by fuses and by gas-filled overvoltage protectors. The EMP from the 22 October (K-3) nuclear test caused all of the fuses to blow and all of the overvoltage protectors to fire in all of the sub-lines of the 570 km telephone line.[2] The EMP from the same test started a fire that burned down the Karaganda power plant, and shut down 1,000 km (620 mi) of shallow-buried power cables between Astana (then called Aqmola) and Almaty.[3]



This, and the Starfish Prime tests earlier that year, indeed suggest that a high-altitude EMP burst could be a significant problem for the targetted area. (An accurate understanding of the Starfish Prime test's effects is difficult to obtain partly because little was done contemporarily to assess its effects, and partly because the burst was so far from the affected area.) How significant a problem it would be is certainly debatable...but I think it's very difficult to sustain an argument that it wouldn't be a major problem or a problem at all.

By itself, a HAEMP wouldn't necessarily be crippling. But such a burst or bursts, combined with the havoc wrought by a full-on nuclear strike, would be crippling, both in the short and long term.

Here are a couple papers on the subject (I'll admit right now that a lot of the math went right over my head):

The Early-Time (E1) High-Altitude Electromagnetic Pulse (HEMP) and Its Impact on the U.S. Power Grid
A Russian Assessment of Several U.S.S.R. and U.S. HEMP Tests (PDF - see Page 33. There are also a couple interesting articles on battlefield nukes following, including the Pershing missile.)
 
When I served i nthe United States Army as an Aviation Maintenence technitian (Attack and utility helicopters) I was directly and rigorously trained on what to do in regard to a possible electromagnetic pulse.

The mathematics of the issue did NOT go over my head.

Have you ever heard of a PINCH?

It is a device that generates an electromagnetic pulse.

When it is activated, insted of total devastation, you get the 18th century, for about fifteen to twenty minutes.

In any regard military government and emergency systems are already hardened against the effects.
 
It's a gimmick, not a weapon, only really good for training.

Maybe it has potential. I once read a sci-fi steampunk novel called "Fitzpatrick's War" by Theodore Judson, where one of the weapons that enabled the the dominant society to seize power in the world is a man-portable EMP generator, against which no defense exists.
 
Maybe it has potential. I once read a sci-fi steampunk novel called "Fitzpatrick's War" by Theodore Judson, where one of the weapons that enabled the the dominant society to seize power in the world is a man-portable EMP generator, against which no defense exists.
Yeah, the fictional version probably has a lot more punch than a real PINCH.
 
When I served i nthe United States Army as an Aviation Maintenence technitian (Attack and utility helicopters) I was directly and rigorously trained on what to do in regard to a possible electromagnetic pulse.

The mathematics of the issue did NOT go over my head.

Have you ever heard of a PINCH?

It is a device that generates an electromagnetic pulse.

When it is activated, insted of total devastation, you get the 18th century, for about fifteen to twenty minutes.

In any regard military government and emergency systems are already hardened against the effects.

I should clarify...I was referring to the effects on civilian systems, particularly power distribution and computers. I'm aware that most military/government assets are hardened to one degree or another.
 
I should clarify...I was referring to the effects on civilian systems, particularly power distribution and computers. I'm aware that most military/government assets are hardened to one degree or another.
Oh, well of course, yes, that's another story entirly, yes, Civilian and commercial systems would probably get the crap kicked out of them by an EMP but ony if there was power running through them at the time of the EMP.
 
Oh, well of course, yes, that's another story entirly, yes, Civilian and commercial systems would probably get the crap kicked out of them by an EMP but ony if there was power running through them at the time of the EMP.

That's my concern.

Incidentally, I was reading a bit on the PINCH devices and came across this link, wherein the folks at Sandia National Lab are discussing their PINCH device, apparently the most powerful in the world (the article is in reference to the Ocean's Eleven remake.) It's a damned interesting article.

The article does, however, contain this bit...

Sandia researchers have still more news: even their colossal Z-pinch doesn't generate a very strong electromagnetic pulse. The pinch is "a poor EMP source," says Quintenz. "We have on occasion interfered with the sensitive electronics in cameras and computers located in the same laboratory space," he says, but "to my knowledge we have never caused a problem with any electronics or electrical system outside the accelerator building itself."

...which pretty much reinforces what you said - that it's a gimmick. Take it for what it's worth, I guess.

Jason
 

MSZ

Banned
EMP is more of a Hollywood boogeyman than an actual threat to state infrastructure. The mathematics behind it isn't very complex. An EMP occurs every time a nuclear device is initiated. It is however absorbed by the atmosphere relativly easily. Hence, at ground or near-ground bursts the area affected by the EMP is almost the same as that covered by the fireball, as the energy released is immiediatly converted into heat. To create a large EMP effect bursts have to occur higher from ground. This in turn makes it a victim to the cube-law effect - the higher it is detonated, the atmosphere is thinner, the "pulse" has to travel a further distance adnd "spreads out" over a larger area, thus dropping in intensity. Remember that for spheres, the surface area is proportional to the cube of the radius - triple the radius, the intensity of the pulse will drop by a factor of 27. So while ground initiations would more likely melt any electronics than turn it off, high altitude initiations would end up giving out the same EMP output as a lightning bolt striking outside your home. It might turn on your car alarm; it might blow the fuses at your home; but it will not blow up your computer, cause massive short circuits leading to massive fires or render your microchip-based electronics useless.
 
That's my concern.

Incidentally, I was reading a bit on the PINCH devices and came across this link, wherein the folks at Sandia National Lab are discussing their PINCH device, apparently the most powerful in the world (the article is in reference to the Ocean's Eleven remake.) It's a damned interesting article.

The article does, however, contain this bit...

[/i]
...which pretty much reinforces what you said - that it's a gimmick. Take it for what it's worth, I guess.

Jason
Well, like I said. :/
 
Hence, at ground or near-ground bursts the area affected by the EMP is almost the same as that covered by the fireball, as the energy released is immiediatly converted into heat. To create a large EMP effect bursts have to occur higher from ground.

I am aware of this, which is why I was careful to specify high-altitude EMP.

This in turn makes it a victim to the cube-law effect - the higher it is detonated, the atmosphere is thinner, the "pulse" has to travel a further distance adnd "spreads out" over a larger area, thus dropping in intensity.

This conforms with the reading I've done on the subject. Sort of. One paper I've read (see pg. D-7) suggests that a large burst at 400km altitude would cover the majority of CONUS with a field strength of 25,000 V/m. That is certainly more than enough to gork most consumer electronics. The induced current in even a 10cm power cord attached to an electronic device would produce a current of 5000V (most ICs can't handle more than 1000V).

Also, I would love to understand why the 1962 Soviet test I linked to in my original post is inapplicable. Assuming the accounts are correct, it seems to indicate that induced currents in long power lines would render much of the infrastructure completely fuxxored. Frankly, that's all that would be required for serious societal effects; you could skip nuking the other aimpoints altogether.

Remember that for spheres, the surface area is proportional to the cube of the radius - triple the radius, the intensity of the pulse will drop by a factor of 27. So while ground initiations would more likely melt any electronics than turn it off, high altitude initiations would end up giving out the same EMP output as a lightning bolt striking outside your home. It might turn on your car alarm; it might blow the fuses at your home; but it will not blow up your computer, cause massive short circuits leading to massive fires or render your microchip-based electronics useless.

AIUI, the problem with comparing EMP vs. lightning is not just field strength (as I mentioned above), but the rise in amplitude. EMP is not only stronger, but also rises more quickly. Circuit breakers, fuses, etc. aren't built to cope with those sorts of current rises.

You should really read the ORNL report I linked in the OP. It isn't a fear-mongering piece at all - quite even-handed, really. But it does reinforce my suspicion that damage from a high-altitude EMP burst, while not necessarily a world-ender by itself, would be a Bad Thing (TM). Yeah, the car might run after, but good luck with anything else.
 

MSZ

Banned
Well, I'm no physicist. I have a general understanding of it, which leads be to having some doubts for example:

One paper I've read (see pg. D-7) suggests that a large burst at 400km altitude would cover the majority of CONUS with a field strength of 25,000 V/m.

The paper didn't specify the yield of the initiated device at 400 km altitude. Mathematicaly speaking, yes, an EMP generated at such a distance could cause damage if it was powerful enough, but for it to be that powerful, it requires a lot of energy. But let's say that we are talking about a nuke just that powerful - why does the E-field rise in strength with the the growth of the area it covers? It should weaken I think.

And that powerful induced current? Once the fuse goes, the circuit is broken and it can't be induced. The energy spike lasts for only about a nanosecond, it doesn't have a "lasting effect" like radiation. Domestic appliances can survive that, since the damage to it isn't caused by the electricity itself, but by the heat generated through resistance. If it only is in effect for a short period of time, most of them won't be damaged - lightbulbs will, some microprocessors as well. But the fridge and vacuum cleaner will keep on working.

And is a nuke-induced EMP more powerful than lighting-induced one? Lightings carry a current of a few hundred thousand ampers and can strike directly next to any potentially affected objects. The distance traveled would be significantly shorter than a few hundred kilometers. So it seems to me that a comparision is possible.

But again, I'm not a electrical engineer. I did read some articles on the matter some time ago, scientific monthly magazines mostly. I don't really have an anwser why the Soviet experiments are inaplicable - it is just doubts, I don't see it as a catastrophy that fuses would blow countrywide - they are just fuses, they cost a few cents and every house has spares, as do power companies. So I'm not saying an EMP could be completly ignored with nobody even realizing it, but it wouldn't be a world-ender either. A minor to average inconvienience at most. And a waste of a nuke.
 
The surface area of a sphere is 4*pi*r^2, so three times the radius means nine times the surface area, or in the case of electromagnetic radiation, 1/9 of the intensity.
 

Thanos6

Banned
There's a Spider-Man novel trilogy, where the baddie's plan ends up being "hit Manhattan with an EMP" and then let his riches skyrocket in value in the chaos. I'll have to post it.
 
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