Inspired by the thread How long could we last w/o electricity?
What is the mechanism that destroys exlectrical systems? Is this simply a matter of overloading electrical systems by induction? Do the wires and/or circuits just melt? Would systems not in operation be damaged or destroyed?
Gonna WAG this, mainly to bump it, cuz I want to hear from someone who actually knows this stuff.
[WAG] An EMP, electro-magnetic pulse, would come from a H-bomb fired off high enough to blast its powerful “spike” charge over a wide area. Everything that can receive the charge by induction gets charged up momentarily and strongly.
The EMP is a brief burst of intense electro-magnetic static, so one end of a wire is briefly positive and the other isn’t, resulting in a current in the wire, which the equipment would not be designed for. All the worse as the EMP fluctuates in voltage and wavelength, like static. The charges and currents would be high, and vary and reverse themselves. The result would be like the sparking you get in a microwave oven when the items being heated can arc across from one to the next.
My memory of reading about this, in some popular fear-spreading source, made it sound as if you would get multiple frequencies, and therefore it could fry everything from small electronics to power transmission lines.
I think individual objects closed inside steel cases would not be affected.
Here’s an article from “Popualr Science” about EMP’s:
http://popularmechanics.com/science/military/2001/9/e-bomb/print.phtml
As MaryEFoo said, maybe this is just “fear-spreading” but since the article is from “Popular Science”, the source has some credibility. I was surprised to learn that an EMP does not require an H-Bomb and the article mentions that an EMP bomb could be built for as little as $400.
To me it seems that we should seriously study how to guard against these.
Unfortunately, EMP and its effects are very real, as shown discovered in Hawaii after a nuclear weapons test in the Pacific.
I’ve always considered a relatively easy way for a nation to put the United States into a very bad situation. If North Korea developed a missile capable of putting a nuclear weapon over the US high enough and detonated it, what would be the appropriate response? Do we destroy their cities when they have not directly killed Americans? A response in kind would not be effective against a society less dependent on computers and other electronics.
Basically an EMP flux with computers.
Military electronics are supposed to be immune to EMP damage due to “tempest hardening.” How does this work? Are the devices really immune, or are they just slightly better than normal?
wolf_meister & ricksummon,
EMP, like any other electromagnetic phenomenon, obeys the inverse square law. Intensity is inversely proportional to the square of the distance from the source.
You can build an EMP bomb with just a few hundred dollars worth of gizmos and it’ll fry any electronics with 3 feet of itself when it goes off. Big deal. A sledge hammer has a greater lethal radius against electronics.
The whole point of H-bomb based EMP was that the power source was strong enough that the effects would reach out for hundreds of miles against unshielded electronics.
Said another way, for any given EMP power source and distance, whether any particular target device will be damaged or not depends on how resistant it is to damage. Military gear can absorb a LOT more of a spike that your cellphone can. that doesn’t mean it’s invincible, merely that it can be closer to the EMP source and still survive.
The DOD is currently working on non-nuclear EMP weapons that will have a lethal readius of a couple hundred feet against military-grade gear.
“Tempest” is something totally unrelated to EMP. That’s the code term for sheilding electronics so they don’t broadcast spurious signals that enemy bugs might pick up & be able to make sense of. The shielding technology is similar in some ways, and very different in others, but the motivation is totally different.
The wires and circuit traces of electrical systems act as antennas, and pick up the electromagnetic pulse. This causes high voltages and currents to be present in areas that were not designed for them. Circuit traces and wires can melt. The itty bitty wires inside of chips that connect the silicon to the outside world can melt. The semiconductors inside of chips that are operating can be sort of short circuited, which even if the EMP doesn’t destroy them, can cause them to destroy themselves.
Quite possibly.
We do. The basic defense against an EMP is called a Faraday Cage. Basically, any time you have a conductive cage around something, the electricity will flow over its surface and won’t go inside. Googling “faraday cage” will give you lots more details.
By the way, EMP weapons aren’t just for terrorists and the military. Police have been experimenting with portable EMP devices that work kinda like the spike strips they use now. You slide a little square thing out on the road, and when the car drives over it, it fires an EMP upward, frying the electronics that control the engine. This brings the car to a much safer stop than puncturing the tires. So far it’s only in the experimental stage though. I’m not aware of anyone actually using the device.
LSLGuy and Engineer_Comp_Geek
I wish that an EMP bomb were that easy to guard against or that its effects were only confined to a small area. However, from the Popular Science article:
The Indian military has studied Flux Compression Generator (FCG) devices in detail because it fears that Pakistan, with which it has ongoing conflicts, might use E-bombs against the city of Bangalore, a sort of Indian Silicon Valley. An Indian Institute for Defense Studies and Analysis study of E-bombs points to two problems that have been largely overlooked by the West. The first is that very-high-frequency pulses, in the microwave range, can worm their way around vents in Faraday Cages. The second concern is known as the “late-time EMP effect,” and may be the most worrisome aspect of FCG devices. It occurs in the 15 minutes after detonation. During this period, the EMP that surged through electrical systems creates localized magnetic fields. When these magnetic fields collapse, they cause electric surges to travel through the power and telecommunication infrastructure. This string-of-firecrackers effect means that terrorists would not have to drop their homemade E-bombs directly on the targets they wish to destroy. Heavily guarded sites, such as telephone switching centers and electronic funds-transfer exchanges, could be attacked through their electric and telecommunication connections.
(Emphasis mine)
So, it seems that Faraday Cages might not be very effective protection and “EMP bombs” could be effective over long distances.
I’m trying to get a sense of how effective a large scale EMP attack might be. For instance, even aside from power plants, power lines and computer chips, America has… er, gee, HOW many hundred million gasoline and diesel engines? From lawn mowers to Mack trucks, and IIRC, diesel hardly needs much of an electrical system at all to run.
Faraday cages are a lot more effective than that article might lead you to believe. However, you don’t really know if you’ve got all the holes plugged until the first EMP weapon goes off. There are a lot of “hardened” sites that might have problems. Plus, faraday cages are big and expensive. You aren’t going to shield everything in sight. How many people have faraday cages around their offices? How many ATMs are built inside of faraday cages?
A lawnmower, due to its simplicity, might still work. You’d have to get a heck of a jolt to render it useless. Likewise, my kit car (essentially a 1960 beetle) will survive a much stronger jolt than any of the newer cars in my driveway. Most modern cars, even diesels, have gobs of computers inside of them.
The inverse square law also limits how effective an EMP weapon can be. The EMP level decreases with the square of the distance from the source, which means that the danger drops off rather dramatically with distance.