The effects of EMP - Writers Forum

Code_Mage · 09-23-2007, 05:22 PM

What would happen if an otherworldly device caused a worldwide EMP (electro-magnetic pulse)? I have a few implications that I would like to consider:

1. What kind of mechanisms would be affected: would cars be able to start, for instance, or simply stop dead in their tracks? Would simple flashlights cease to function? How would plumbing and water services be affected?

2. Is it possible for such a massive EMP to be temporary in it's effect after the burst? Can cars start after the field has worn off? Can semiconductor chips be overloaded without melting down completely?

Shawn · 09-23-2007, 05:25 PM

Gamma ray burst - Wikipedia, the free encyclopedia

I don't think we'd worry about cars starting.

wmd · 09-23-2007, 06:21 PM

Electromagnetic pulse - Wikipedia, the free encyclopedia

an EMP is different than a gamma ray burst... I am pretty sure that you can have an EMP without radiation.

although with such a massive one as the op is suggesting, if there were radiation involved, Shawn is correct in saying that cars starting would be the last of our problems.

Shawn · 09-23-2007, 06:24 PM

I was thinking with the kind of power that's being talked about, the only event with enough energy is probably a gamma ray burst.

Nevertheless, if there ever is a large EMP event... it's probably because we're screwed one way or another.

mammamaia · 09-23-2007, 06:25 PM

fyi, wikipedia is not always the best source of valid info... here's a good article on the effects of emp on everday life, from the christian monitor:

Secure the US against bloodless terrorist warfare | csmonitor.com

halogen · 09-23-2007, 06:28 PM

Well, if the device was otherworldly you could just make it do whatever. Hell, make it do something completely unrealistic like turn trucks alive and use them to chase down and bludgeon survivors. It doesn't have to be an EMP. Is there some specific side effect you are looking for?

Code_Mage · 09-23-2007, 06:55 PM

So basically, for an EM-pulse to be so significant it cannot help be be ridden with gamma radiation?

@ halogen

LOL... I think you might have watched the latest Transformers movie.

MarkG · 09-23-2007, 08:16 PM

Cars wouldnt start, no, and flashlights wouldnt work. An EMP demagnetizes things. That means electic coils wouldnt work and batteries would have no charge. This is a physical thing, so no, theres no way an EMP could be temporary. Electrons are disspersed. Its bad. However, and I dont know how, the military claims to have all of its electronics armored against EMPs.

Rumrunner · 09-24-2007, 04:50 AM

Quote:

Originally posted by MarkG:
Cars wouldnt start, no, and flashlights wouldnt work. An EMP demagnetizes things. That means electic coils wouldnt work and batteries would have no charge. This is a physical thing, so no, theres no way an EMP could be temporary. Electrons are disspersed. Its bad.

Eh? No.

There is nothing inherently destructive or permanent about an EMP itself. What an EMP does that is destructive, is it induces stray electric currents in conducting materials. These electrical currents can destroy electronic circutry if they exceed the peak surge capabilities of the circuit in question, just like a lightning strike or other power surge will. This effect is immediate and instantaneous; there is no residual. Anything that survives the initial voltage spike will continue to function (provided there remains, for example, a power grid to connect it to).

Which raises an important point: just like in a electrical generator's dynamo, or in reverse, in an electromagnet, the relationship between the strength of the electromagnetic flux and the electrical field induced is directly related to the length of the conductor passing through the field. This means that small, non-voltage-sensitive things like individual battery-powered flashlights aren't likely to be affected unless the pulse is very, very massive. On the other hand, in a country like the US where you have a massive interconnected central powergrid containing hundreds of thousands of miles of linked transmission lines, even a relatively small pulse will generate a huge overall induction voltage which will fry most anything connected to it if the isolation circuit-breakers don't trip in time. I expect transformer substations and generating plants and such would be a mess; it would likely take years to repair that kind of damage.

It also means the more sensitive an item is to stray fields, the more susceptible it is to damage. Small, delicate electronics will be destroyed by pretty low peak voltages, so they're susceptible, to be sure. On the other hand, older analog technologies such as valves (vacuum tubes) are less susceptible. Modern cars with integral electronic control systems may be affected by a large enough pulse, but older vehicles I imagine would still run - though a big enough pulse might damage the alternator, which has a lot of length of wire in it, and would probably necessitate the replacement of fuses.

Disperses electrons? No. It excites them for a while, they move around a lot more than usual for a few milliseconds, then they settle right back down to how they were. There are not significantly more or less of them than there were originally.

Demagnitizes things? No. The presence of a massive peak current will create a temporary magnetic field (and vice-versa, that's how a generator works, after all) but as soon as the electrons settle down again the magnetic field goes away. A strong field can realign certain magnetic fields that are sensitive to easy realignment, like the particles of magnetic material that stores data on a disk platter.

Batteries present tiny conductive cross-sections overall, and electrochemical in nature. I can't see how an EMP could cause them to loose charge more than temporarily, either. Nothing is physically altered long-term by an EMP, so the chemical reactions might be briefly disrupted or reversed, but they would resume after.

Plumbing shouldn't really be affected, save to say that most municipal water systems rely at least partially on electrically-driven pumping stations; these pumps are big power hogs and connected to the grid by pretty solid cabling, so they'd most likely get toasted. Water pressure might vanish except in lowlying areas. Electrical arcs could ignite gas lines, I suppose, if there was a reason that oxygen was present inside the line, too - like an already broken pipe.

Hope that's of some use.

Cheers,
Rumrunner

Rumrunner · 09-24-2007, 05:03 AM

Quote:

Originally Posted by Code_Mage:
So basically, for an EM-pulse to be so significant it cannot help be be ridden with gamma radiation?

If you're trying to make it with current technology, pretty much yes. But I suppose its conceivable for some sufficiently advanced technology to find an alternative way of making one, or at least one in which the gamma rays might be redirected elsewhere.

In essence, there are two things that can cause what counts as an EMP. Very simplisticly, these are:

1) You can have a really, really massive magnetic field change orientation (i.e. north & south poles) a few times very quickly.

2) You can have a big cloud of electrons get massively energized and break free of their "home" atoms for a while. They then go zipping around until they find something nice and conductive to travel along, like a power line.

Option number 2 is what happens in a nuclear-blast induced EMP. It's the gamma rays produced by the detonation that knock the electrons loose when they smash into atoms in the upper atmosphere that are already kind of hyper due to the Earth's magnetic field and cosmic ray bombardment.

But, I guess if you can make a magnetic field like that, or a cloud of angry little electrons, without detonating a bomb, you might be able to bypass the gamma flare.

[Edit: A really, really big cathode ray tube might do it. Like a giant version of the electron gun in the back of an old-style tv or computer screen. But I'm thinking, like, Death Star sized.]

Mallignamius · 09-26-2007, 05:41 AM

Just tell me one thing. Will my refrigerator magnets be okay?

Rumrunner · 09-26-2007, 06:07 AM

Quote:

Originally posted by Mallignamius:
Just tell me one thing. Will my refrigerator magnets be okay?

I'm sorry, I originally intended to address that question in chapter 72 of my above response, but decided to omit it for the sake of brevity, which, as we all know, is my specialty.

In short, then: Yup, no problems there.

Hey... I wrote a readably short post for once.... I'm so proud of myself.

-Rumrunner

MarkG · 09-27-2007, 07:22 PM

Quote:

Originally Posted by Rumrunner

Eh? No.

There is nothing inherently destructive or permanent about an EMP itself. What an EMP does that is destructive, is it induces stray electric currents in conducting materials. These electrical currents can destroy electronic circutry if they exceed the peak surge capabilities of the circuit in question, just like a lightning strike or other power surge will. This effect is immediate and instantaneous; there is no residual. Anything that survives the initial voltage spike will continue to function (provided there remains, for example, a power grid to connect it to).

Which raises an important point: just like in a electrical generator's dynamo, or in reverse, in an electromagnet, the relationship between the strength of the electromagnetic flux and the electrical field induced is directly related to the length of the conductor passing through the field. This means that small, non-voltage-sensitive things like individual battery-powered flashlights aren't likely to be affected unless the pulse is very, very massive. On the other hand, in a country like the US where you have a massive interconnected central powergrid containing hundreds of thousands of miles of linked transmission lines, even a relatively small pulse will generate a huge overall induction voltage which will fry most anything connected to it if the isolation circuit-breakers don't trip in time. I expect transformer substations and generating plants and such would be a mess; it would likely take years to repair that kind of damage.

It also means the more sensitive an item is to stray fields, the more susceptible it is to damage. Small, delicate electronics will be destroyed by pretty low peak voltages, so they're susceptible, to be sure. On the other hand, older analog technologies such as valves (vacuum tubes) are less susceptible. Modern cars with integral electronic control systems may be affected by a large enough pulse, but older vehicles I imagine would still run - though a big enough pulse might damage the alternator, which has a lot of length of wire in it, and would probably necessitate the replacement of fuses.

Disperses electrons? No. It excites them for a while, they move around a lot more than usual for a few milliseconds, then they settle right back down to how they were. There are not significantly more or less of them than there were originally.

Demagnitizes things? No. The presence of a massive peak current will create a temporary magnetic field (and vice-versa, that's how a generator works, after all) but as soon as the electrons settle down again the magnetic field goes away. A strong field can realign certain magnetic fields that are sensitive to easy realignment, like the particles of magnetic material that stores data on a disk platter.

Batteries present tiny conductive cross-sections overall, and electrochemical in nature. I can't see how an EMP could cause them to loose charge more than temporarily, either. Nothing is physically altered long-term by an EMP, so the chemical reactions might be briefly disrupted or reversed, but they would resume after.

Plumbing shouldn't really be affected, save to say that most municipal water systems rely at least partially on electrically-driven pumping stations; these pumps are big power hogs and connected to the grid by pretty solid cabling, so they'd most likely get toasted. Water pressure might vanish except in lowlying areas. Electrical arcs could ignite gas lines, I suppose, if there was a reason that oxygen was present inside the line, too - like an already broken pipe.

Hope that's of some use.

Cheers,
Rumrunner

Wow. You really know what your talking about. Forgive my lack of details. I did think, as I understood it, that everything magnetic would fail. I thought the magnetized electrons were faulted in their symetry. but Im going to guess you know more about it than me or if not, be a politician. Nobody could ever suspect your lies.

Ilasir Maroa · 09-27-2007, 08:36 PM

Always trust rumrunner to have the details down.

of course, as this is probably science fiction, you could get away with anything you want provided you blame it on an alien device using some made-up particle.

Code_Mage · 09-28-2007, 08:08 PM

All of you have, in fact, been helpful. I come away knowing more than I did beforehand. Now I have one last question related to the first:

"What is meant by 'hardening' a device from EMP? Is is possible to make an electrical conductor immune if resistant? I know that there was once a computer invented that runs off fiber optics instead of semiconductors, and maybe that's the direction of technology that is also pleasantly immune. However, I have no idea how such a fiber-optic device would work and electricity would still be needed to light up the system itself."