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  #1  
Old 07-06-2012, 07:02 AM
gotpasswords gotpasswords is offline
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EMP, power systems and fuses

In today's column about EMP it was noted that some things such as high-voltage transformers are not exactly stockpiled in abundance and that re-creating them would take some time. Would this delay bringing power systems back up after being damaged by an EMP? Sure, but...

Would an EMP really turn every transformer into a smoldering lump? Or would an EMP just blow out the weak spots in the system? What weak spots? Oh, how about the intentionally weak spots known as fuses? Granted, the task of having to replace thousands of fuses would take a good while, but we probably have more fuses on hand than transformers, and in a dire emergency, fuses can be bypassed.
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  #2  
Old 07-06-2012, 09:21 AM
davekhps davekhps is offline
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The two largest problems with EMP, in my mind, are these:

1. The system is only as strong as the weakest link. Meaning, so what if the "entire" grid isn't brought down? Bring enough of it down, all at once, and you're left in a "close enough for golf" situation.

We had one one-hour storm here in the D.C. area and people were out of power for days. Replicate this on the entire Eastern seaboard but make it effect *every* element of the grid all at once-- and things not on the grid, like vehicles, gas generators, you name it-- and then see how quickly the system can come back.

2. EMP is a wonderfully assymetric threat. Meaning, even a backwards country like North Korea can "fight above its weight" as long as it has the means to do so. You don't need a thousand warheads incinerating America to bring it down a bunch of pegs-- you only need a few. Crazy act of war, sure; but far more obtainable than the Cold War-era MAD-level arsenals were.

Anyway, my guess is that an EMP attack would be Very Bad News. No, we wouldn't be propelled back into the Stone Age, and no, we wouldn't spend forever dealing with the problem. The concern is, however, that we'd spend *long enough* dealing with the problem that the second- and third-order effects would be nigh catastrophic-- modern civilization can put up with major urban blackouts in a single metro area for a week at a time with just relatively minor kvetching, but try doing that on a massive geographical scale for *months* at a time, where *no* electrical stuff works, not just the power plug.

A modern 21st century society hasn't had to deal with that kind of shock. No one can say for sure how, let alone if, it could cope with that.

Last edited by davekhps; 07-06-2012 at 09:21 AM.
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Old 07-06-2012, 09:23 AM
gnoitall gnoitall is offline
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Originally Posted by gotpasswords View Post
In today's column about EMP it was noted that some things such as high-voltage transformers are not exactly stockpiled in abundance and that re-creating them would take some time. Would this delay bringing power systems back up after being damaged by an EMP? Sure, but...

Would an EMP really turn every transformer into a smoldering lump? Or would an EMP just blow out the weak spots in the system? What weak spots? Oh, how about the intentionally weak spots known as fuses? Granted, the task of having to replace thousands of fuses would take a good while, but we probably have more fuses on hand than transformers, and in a dire emergency, fuses can be bypassed.
Ancient Chinese Electrical Engineer Adage: A $50 transistor (or $500,000 transformer) will happily sacrifice its life to save a 5-cent fuse.

More to the point, fuses can't save a transformer if the electromagnetic pulse induces destructive voltages directly within the coils of the transformer itself, which is how that actually happens.
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  #4  
Old 07-06-2012, 09:27 AM
Una Persson Una Persson is offline
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Originally Posted by gnoitall View Post
Ancient Chinese Electrical Engineer Adage: A $50 transistor (or $500,000 transformer) will happily sacrifice its life to save a 5-cent fuse.
I love this quote.
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  #5  
Old 07-06-2012, 09:30 AM
chappachula chappachula is offline
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Originally Posted by gotpasswords View Post
Would an EMP really turn every transformer into a smoldering lump? . but we probably have more fuses on hand .
Well let's see what one source says:
A solar storm as powerful as the one in 1859
Quote:
"could fry more transformers than the power companies keep stockpiled, leaving millions without light, potable water, sewage treatment, heating, airconditioning, fuel. phone service,or perishable food and medicine during the months it would take to manufacture new transformers."
This is not from the National Enquirer or the Daily Sun
It is from National Georgrahic Magazine.(The most recent issue-June 2012, page 42.The cover article is about solar storms.)
Now, Natl Geo is a not a peer-reviewed science journal...but it's a pretty respectable publication that definitely does not aim for "woo" appeal.

Maybe we should be a little more seriously concerned with the physical reality of Mother Nature, and less with Cecil's cynical bashing of Newt.

Last edited by chappachula; 07-06-2012 at 09:33 AM.
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  #6  
Old 07-06-2012, 09:36 AM
chappachula chappachula is offline
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(deleted a double post. Sorry).
I was just trying to correct a typo in my previous post: I meant "National Geographic" Magazine

Last edited by chappachula; 07-06-2012 at 09:38 AM.
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  #7  
Old 07-06-2012, 10:03 AM
Irishman Irishman is offline
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We have a national magazine by and for Georges?
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  #8  
Old 07-06-2012, 12:19 PM
ftg ftg is offline
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How long is it going to take to manufacture all the replacement parts to get basic services going again? That is going to be difficult and then some. Given that:

1. The plants themselves are going to be down. A really tricky bootstrap process. And too many core parts are not easily orderable from overseas.

2. There are going to hordes of hungry, angry people roaming around causing problems. Once the food runs out in the cities, rebuilding stuff is going to get really, really hard.

Moving and processing food will be the main bottleneck. And even if you could get bags of flour to people, how many are going to know how to and be able to do anything with it?

Even if we got lucky and got basic things running in 2 years, that's about 1.9 years too long to keep society stable.

It's pretty much your standard movie apocalypse if this ever happens.
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  #9  
Old 07-06-2012, 01:44 PM
davekhps davekhps is offline
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Originally Posted by ftg View Post
Even if we got lucky and got basic things running in 2 years, that's about 1.9 years too long to keep society stable.

It's pretty much your standard movie apocalypse if this ever happens.
This. Even if the infrastructure to rebuild remains intact, supporting and exploiting that infrastructure is going to be one heckuva challenge.

Meaning, even if you could build replacement equipment-- no sure thing-- you no longer have the modern support infrastructure in place to distribute, install, maintain, etc.

We live in a "just in time" society. An EMP eliminates the "just in time" part-- what then happens to that society?

Again, it's one thing to hunker down for days (storms, power failures), or even weeks (epidemiological crises). But we're talking months at a minimum.

EMP is a nasty thing. I'd almost rather have traditional nuclear war-- at least then there's no worry about the aftermath, we'd all be screwed.
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Old 07-06-2012, 02:19 PM
Michael63129 Michael63129 is offline
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Fuses won't work if the induced voltages are high enough; the current will just arc across the gap, which would especially be a concern with long-distance transmission lines. Although I would think that an isolated transformer (e.g. a spare just sitting there) wouldn't be damaged since there isn't much space for current to be induced (longer lines = more voltage and current induced; note also that it is current more than voltage that causes damage).
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  #11  
Old 07-06-2012, 02:28 PM
Fool in the Rain Fool in the Rain is offline
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Working for a utility, I can tell you the electrical infrastructure it is a lot more delicate then it first appears.

I've been involved in many storm restorations and it still amazes me to this day how simple it is to cause a power failure.

It takes approximately 3-6 months to order and have delivered any transformer over the size of 3000kva. Granted we have 'some in supply', but obviously not enough to replace all of them in the system we own.

Fuses can be bypassed, sure, but it puts the system following the fuse in danger of overload, especially people's homes/businesses. Another problem is incorrectly installed generators that can back-feed into the system, overloading it in that way.

How easy is it to have a system failure:

The Great Northeast Blackout of 1965 all began when a relay (about the size of a fist) failed, diverted electricity through other feeders, overloading them, which in turn forced other systems to 'dump' their power to other feeders, causing massive back-feed and overloading them, until the entire system simply collapsed, and was forced to be shut down.

Time to system failure ~ 5 minutes.

Southern New England, New York State and southern Quebec were out for up to 12 hours

Cause: Human error - relay settings were set too low.

Last edited by Fool in the Rain; 07-06-2012 at 02:29 PM.
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  #12  
Old 07-06-2012, 08:34 PM
Senegoid Senegoid is offline
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This whole thread, OP included, is ALL off-topic!

Cecil's above-cited EMP column was itself a follow-up on his earlier 1993 column, in which Jonathan Jensen of Baltimore simply asked: Is there a way to silence those Og-damn obnoxious boom-cars? In that earlier column, Cecil promptly went off-topic, writing about large-scale EMP events that take massive energy bursts (like nuclear blasts or sun storms), whereupon they take out a whole city like Honolulu from 800 miles away. Hardly likely your average city-dwelling peace-and-quiet-loving citizen is going to have access to that.

All's that Jonathan Jensen ever wanted was some small-scale weapon that one person could wield to take out that Og-damn boom-car from, say, across the street.

And that's all I want too, and I'm still waiting for Cecil, or someone, to expound on that. Forget global EMP's that fry our transformers back to the stone age. I still just want a way to shut down those boom-cars!

It took a response from B. J. Merholz of Los Angeles to point out the discrepancy in Cecil's response:
Quote:
Your reply referred to something like nuclear bombs or cosmic forces or some other sad expression of comic overkill rather than taking your correspondent's question seriously and answering it accordingly. You could have advised the gentleman that several such devices have already been invented and are already available on the open market. One good example is the very handy Smith and Wesson .38 caliber Police Special.
Dang it, I (like Mr. Merholz) just want a small-scale personal boom-car silencer, capable of operating on one vehicle at at time, at a range of, say, 0.25 mile or less. THAT was the real OP of this discussion! And Cecil goes off the deep end with his EMP talk which, interesting though it may be, doesn't help.

ETA: I mean, I want something high-tech and electronic and more subtle than the suggested Smith and Wesson anti-boom-car device.

Last edited by Senegoid; 07-06-2012 at 08:38 PM.
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  #13  
Old 07-07-2012, 09:14 AM
Hagen Hagen is offline
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@Senegoid
Google has come up with this: http://m.wikihow.com/Build-an-Emp-Generator
However, here's what I'd prefer to use and I know that it would work: http://www.youtube.com/watch?v=QrgTt...e_gdata_player

Explosively fired vortex ring generator. No way he going to be able to trace it back to you. Just blow the car into a tree.

Other little known facts about google is that it takes just as long to find what you're looking for as it does to write a complaint message. YouTube is also good for this


I've heard that the great majority of our infrastructure was specifically protected from emp during the cold war, but that this is not the case anymore because we no longer consider it as likely. I am cynical about the statement that cold-war era infrastructure was specially hardened on a large scale.

On that note: how do you harden your infrastructure on a large scale? Decentralize it? Insulate it?
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  #14  
Old 07-07-2012, 10:07 AM
Heracles Heracles is offline
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What is not clear to me is what parts of electronics will fail. Is the individual transistor fried? Or does it just malfunction for a few seconds, which means the surrouding circuits are overloaded or submitted to currents, voltages, stresses they're not designed to handle, which quickly fries out capacitors and such?

One thing that hasn't been mentioned up to now is that, once people have their food and shelter back, they still won't have a job. If electronics became inoperable tomorrow morning, I as a programmer wouldn't have anything to do, and neither would most office workers. As has been demonstrated in recent years, it's difficult to keep an economy afloat without workers.

A few other aspects to consider:

- Individual money is mostly in electronic form, to the point where many people don't even have paper proof of their financial assets. Yes, all banks have remote backup sites for their computing infrastructure, and presumably so do the NYSE and NASDAQ, but these are co-location services which are not designed to host all institutions at the same time. And there's no point having a backup computer center on the other coast if the long-distance communications networks don't work.

- Speaking of communications, how much long-distance phone service is still analog? 0%?

- If hard drives and magnetic tapes get damaged or erased (would they?), even the backups are fried. Better archive your stuff to DVD, people!

- Landline phones, for those who still have them, are mostly cordless electronic gizmos themselves. Old ladies would get burglarised for their Model 500 rotary-dial phones. Oh, and their electro-mechanical washing machines, ovens, refrigerators, etc. And their phone books.

Last edited by Heracles; 07-07-2012 at 10:09 AM.
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  #15  
Old 07-07-2012, 11:54 AM
Iggy Iggy is online now
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More than just transformers, we don't even have enough utility poles stockpiled for even a modestly widespread disruption.

In 2004 four hurricanes hit the state of Florida in short succession. One of those, Ivan, had laid waste to the island of Grand Cayman on its way to the Florida panhandle. Power companies were scrounging power poles and transformers to rebuild downed systems.

Much of Grand Cayman was without power for two months. Power was only restored that soon because Fortis, the parent company of the Cayman power company, already had assembled in Canada a shipment of power poles destined for their operations in Belize to build out new systems there. The shipment was diverted to Cayman. Without that shipment it would have been a few more months to get enough poles to do the job.
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Old 07-07-2012, 12:08 PM
Patch Patch is offline
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So how could a standard homeowner shield his generator to block that big solar EMP and keep temporary power up?
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  #17  
Old 07-07-2012, 02:27 PM
chappachula chappachula is offline
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Quote:
Originally Posted by Heracles View Post
once people have their food and shelter back, they still won't have a job. I as a programmer wouldn't have anything to do .
There's a problem with your logic here:
If you as a programmer have nothing to do, then people won't be able to get their food and shelter back.
Food can't be distributed to supermarkets without electronics. Sure, it worked fine in 1940, and 1950 and even later. But nowadays,it's all electroinic-- the finances behind the farming, the logistics of trucking, the check-out registers at the store and the salaries of the consumers who pay for it .
Which means you need the programmers to get back to work before the food and shelter can be restored. But you can't put the programmers to work if there's no food and shelter.

Lather, Rinse, Repeat.
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Old 07-07-2012, 03:40 PM
Michael63129 Michael63129 is offline
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Originally Posted by Heracles View Post
What is not clear to me is what parts of electronics will fail. Is the individual transistor fried? Or does it just malfunction for a few seconds, which means the surrouding circuits are overloaded or submitted to currents, voltages, stresses they're not designed to handle, which quickly fries out capacitors and such?
It's usually the opposite; transistors are usually damaged by external overloads or failed components, either due to overvoltage or overcurrent (as would come from an EMP, but the current has to find its way into the circuit first). I also suspect that modern electronics may be less susceptible to EMP effects because they are much smaller (remember, loop area determines how much voltage and current can be induced), and many IC chips and transistors are rated to withstand ESD (not the same, but it also involves high current/voltage spikes, typically several thousand volts or more through a limiting impedance) or avalanche breakdown.
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Old 07-07-2012, 04:39 PM
ftg ftg is offline
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Originally Posted by Patch View Post
So how could a standard homeowner shield his generator to block that big solar EMP and keep temporary power up?
Have everything off line when it hits. Generator off, as much unplugged as possible. Nothing connected to the grid at all.

If you are connected to the grid when it hits, a lot of your stuff is fried. The generator (not running) won't help. A basic whole house surge protector might mitigate a few things, but it isn't going to be rated for a full nuke EMP.

If your generator and what you want to power survives the hit, the big issue is going to be what is the generator going to use for fuel after your supply is used up? The local gas stations aren't going to open for a good long time.

Note that wires and such act as the antennas for absorbing the EMP pulse and sending it down the line into transformers, your house, etc. So the longer the better and a utility grid makes a great antenna.

For the disabling the local jerk situation, you don't have miles of wire and a huge pulse but you are a whole lot closer. The wiring in the car will pick it up and send it to all the nice little computer parts in a modern car and fry them.

While it all looks very doom and gloom for the nuke pulse scenario, there is a silver lining behind that mushroom cloud. Well, it probably won't be as bad all over.

First of all, not all nukes are created equally. H-bombs do a really great job, ones like the North Koreans blasted are not anywhere in the same league by orders of magnitude.

Furthermore, you need an air burst. Preferably very high up in the atmosphere for an H-bomb. For a fission bomb, you go too high and it eventually becomes less effective. A ground burst will only fry part of a large city. Very few countries have the capability to burst H-bombs at high altitude over the US. Really just China and Russia in terms of enemies. At that point, it's WWIII and EMP is the least of every human's problems.

N. Korea or Iran setting off a smuggled in bomb in a city is "just" going to take out that city's electronics for a few miles around. Hardly anything to worry about. Except for the blast, radiation, zombies, etc.
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Old 07-07-2012, 06:56 PM
Flyer Flyer is offline
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This may be somewhat sensationalized, but it's distinctly scary, nonetheless.

Quote:
The Earth has a roughly 12 percent chance of experiencing an enormous megaflare erupting from the sun in the next decade. This event could potentially cause trillions of dollars’ worth of damage and take up to a decade to recover from.
http://www.wired.com/wiredscience/20...ve-solar-flare


If that estimate is anywhere near accurate, then a re-do of the Carrington Event is probably more likely than somebody attacking us with an EMP.

The silver lining is that today, we can see it coming. A last-ditch defense would be for the grid operators to shut things down before the worst of the CME reached us.

Quote:
Even now, the center's Bogdan said, the most damaging emissions from big storms travel slowly enough to be detected by sun-watching satellites well before the particles strike Earth. "That gives us [about] 20 hours to determine what actions we need to take," Viereck said.

In a pinch, power companies could protect valuable transformers by taking them offline before the storm strikes. That would produce local blackouts, but they wouldn't last for long.
http://news.nationalgeographic.com/n...event-science/
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  #21  
Old 07-08-2012, 10:23 AM
gamerunknown gamerunknown is offline
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People would return to subsistence farming while working on infrastructure. Presumably there'd be an anarchist "digger" era. Cabbage has a pretty high yield if seeds could be distributed fast enough to limit widespread starvation (in the growing period, perishable goods could be consumed). Presumably there'd be widescale looting and deaths anyway - there's not enough space to grow enough food to sustain inner city folk and outer city folk probably wouldn't be too happy accommodating the new influx.
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Old 07-09-2012, 09:10 AM
postpic200 postpic200 is offline
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EMP

A few year back Popular Mechanics went over this,

http://books.google.com/books?id=e88...%20EMP&f=false

they said it would cost about $400 to build. If they were put in the right places you could cause a lot of trouble. It's not like you would have to take down the entire country to cause major disruptions. Hit the all of our coasts at the same time and take power away from 50% of the people would be enough to cause trouble for years. Imagine the New York blackout in 1977 scaled up. You would still have many of the same problems, parts, food, transportation and it would take many years and cost billions to fix everything.
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Old 07-09-2012, 03:53 PM
PaterDeus PaterDeus is offline
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After living through the '03 blackout, I think going a week or two without power would be more of an inconvenience than an apocalyptic catastrophe. Reading up on the sequence of failures that led to that blackout shows how fragile the system is, but also how protective measures limited the damage.

I'm not saying it would be pleasant, but far from the doomsday scenario that some would make it out to be. The only way I can envision such a scenario would be the majority of the nation to be without power for more than a few months. So the question then becomes, how likely is it for a large CME to cause that amount of damage? In my mind, the most likely doomsday scenario is a widespread pandemic like the ones that played out in movies (e.g Contagion) or throughout history (e.g. the spanish flu & black death.)

Last edited by PaterDeus; 07-09-2012 at 03:54 PM.
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Old 07-16-2012, 05:20 PM
sfbiker sfbiker is offline
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Originally Posted by PaterDeus View Post
After living through the '03 blackout, I think going a week or two without power would be more of an inconvenience than an apocalyptic catastrophe. Reading up on the sequence of failures that led to that blackout shows how fragile the system is, but also how protective measures limited the damage.


I'm not saying it would be pleasant, but far from the doomsday scenario that some would make it out to be. The only way I can envision such a scenario would be the majority of the nation to be without power for more than a few months. So the question then becomes, how likely is it for a large CME to cause that amount of damage? In my mind, the most likely doomsday scenario is a widespread pandemic like the ones that played out in movies (e.g Contagion) or throughout history (e.g. the spanish flu & black death.)
The difference between a "normal" power system failure blackout and an EMP induced blackout is that after the EMP blackout, few backup power sources will be running.

Look at the nighttime pictures in the URL you gave - a fair number of lights (especially in large urban areas) remained lit despite the power outage. Hospitals, local, state, and federal facilities, many large supermarkets, some larger businesses and industrial facilities, etc all have backup generators so as long as they could keep fuel in the generators, they could keep the lights on.

But image what would have happened had there been a large EMP induced power failure, and few backup generators were still functioning. Hospitals would have to close within days if not hours, even if fire trucks and police cars were still functioning they'd lose central radio coordination, industrial processes that require power to shut down safely would be apruptly terminated leading to damage and possibly hazardous materials release (oil refineries could be down for months due to improper shutdowns), water pumping/filtration and sewage systems would be offline, no refrigeration means that even if people have food, much of it can't be stored for long, food cooking becomes impossible for many people cut off from electricity and natural gas, etc.

Short term power problems can be compensated for by generators at key places, but if an EMP damages generators and local building wiring and equipment, it really would be a huge disaster. For a modern example, look what happened at Fukushima -- after they lost utility power, they relied on their backup generators to keep cooling pumps running. After the backup generators were destroyed, there was nothing they could do to safely shut down the reactors.
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Old 07-17-2012, 03:13 AM
enmity01 enmity01 is offline
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Originally Posted by Patch View Post
So how could a standard homeowner shield his generator to block that big solar EMP and keep temporary power up?
Well, it could conceivably be done, but it'll take a LOT more tenacity than the "standard homeowner" is likely to muster.

First, you're going to have to have these preventive measures in place well before a massive CME or EMP occurs. NOAA or NASA may be able to offer a week or two head's up on a potential CME. But it's unlikely that even if NORAD or other national defense agency learned of a pending nuclear attack, that they'd be willing and able to share much more information than perhaps an EAS signal telling you to seek shelter in a basement or reinforced area away from windows immediately.

So, you better be getting started this weekend EMP-proofing your home. A Faraday cage enveloping your residence would be a good start. This will be problematic if you watch OTA/sattelite television, listen to radio, or have a cell phone, as none of these will work inside your home once it's in place. However, no matter how good of a Faraday cage you build around your property, attracting the ire of your neighbors and HOA; anything plugged in to the grid is probably going to get fried anyway. So you would be well served keeping a a radio, lights, medical equipment, and so on unplugged if you'd like to be able to use it afterward.

However, larger items such as your car, refrigerator, and the generator itself might be big enough antennae of their own to not be protected by your Faraday cage, so they should be stored underground. Hopefully there's still room for you and your loved ones down there in if you need to take cover. No need to worry too much about keeping a spare cell phone or computer though. They'd be pretty much useless for quite some time except for maybe satisfying your Angry Birds or solitaire fix.

But you'll need to have a heavy duty block and tackle type hoist to retrieve these items afterward, an electric winch will most certainly be useless at this point. Your house wiring may or may not still be usable, but you should probably have plenty of extension cords on hand just in case. Don't expect a transfer switch set up to work with the generator to still be functional. So you're bound to be causing a backfeed situation further complicating utility restoration. You're still going to have to figure out how to provide your family with food and water for the next couple months at least, likewise, as others have pointed out, don't expect to find gasoline for your car or generator for a long while after the fact. Which leads to the biggest problem you'll face even after conquering all these obstacles... The Prepper's Paradox.

By taking such extensive measures to maintain a modest degree of modern convenience after a cataclysmic event, you'll have painted a huge target on yourself to those not so well prepared. You'll be besieged with pleas for help to transport people to shelters, medical facilities, share your food, water, and other resources.. and that's just the first day or two. As people deplete the own supplies of food and water, and see that government and charitable assistance are in extremely short supply. These people will face the grim realities, and they'll become far more desperate... and dangerous! Never mind how expert a marksman you may be, how much of an arsenal of shotguns and assault rifles, and ammunition you may have hoarded.. The sound of your generator, your lights, and the scent of food cooking is going to attract scores of people seeking to deprive you of your fortitude by any means necessary.
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Old 07-17-2012, 01:53 PM
Michael63129 Michael63129 is offline
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Originally Posted by enmity01 View Post
However, larger items such as your car, refrigerator, and the generator itself might be big enough antennae of their own to not be protected by your Faraday cage, so they should be stored underground. Hopefully there's still room for you and your loved ones down there in if you need to take cover. No need to worry too much about keeping a spare cell phone or computer though. They'd be pretty much useless for quite some time except for maybe satisfying your Angry Birds or solitaire fix.
At least from a CME, you aren't going to have to worry about your car and appliances (unplugged) getting fried even if a repeat of the 1859 Carrington event occurred; the induced voltages simply won't be high enough, according to this paper:

Quote:
That is, for example, assuming for simplicity an induced,
approximately uniform geoelectric field of 100 V/km along
the length of one power line whose length is 100 km, this
would produce a voltage of 10 kV in that power line.
100 volts per kilometer, so induced voltages in your house (assuming you turned off the main breaker) or appliances will be much, much lower, only a volt for a 10 meter long wire (even inside of a computer that wouldn't do any damage, since the lowest voltage ICs still use about 1 volt; malfunction (if on) possibly but not permanent damage, and wires inside of computers are much shorter than 10 meters), so I think you would be pretty safe as long as you had forewarning of the event. Not sure about a nuclear EMP, but if they are similar, even if the nuclear EMP was 10 times, or even 100 times (i.e 10 volts per meter), stronger, it still shouldn't be a serious problem aside from utility lines; of course, even if your house and appliances are undamaged you still have a total meltdown of the utility grid (and good luck getting more fuel for your generator).
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