Five Hours Before

RATTLESNAKE said:
I agree with this assessment, but in all reality would power companies,utilities, ever get back up and running to today standards? If an EMP event was to ever happen man made or nature(Solar Flares) to the magnitude which we are talking about it would be game over, Stone ages.. Getting power restored would be the least of our worries for sure.
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Disagree. That's "magic talisman" type thinking. We KNOW that this sort of thing can be done, and there are lots of books and printed reference materials out there. It'll get rebuilt. Might take some time due to the sheer magnitude, but we have an advantage our ancestors did not: WE know it can be done and it was done.
 
dwarven1 said:
Disagree. That's "magic talisman" type thinking. We KNOW that this sort of thing can be done, and there are lots of books and printed reference materials out there. It'll get rebuilt. Might take some time due to the sheer magnitude, but we have an advantage our ancestors did not: WE know it can be done and it was done.
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I sure hope your scenario is right and mine would be wrong, I would not disagree with your statement that "we have an advantage that our ancestors did not" due to the facts of today's technology. But the longer it would take to rebuild the least likely hood of getting things back to the way where IMO would be harder with each year that passes. Society will go on, but in what capacity is the question.?
 
We have a number of advantages over our stone age ancesters:

1) We know what to do
2) We know how to do it
3) We know just how valuable doing it is.
4) A great deal of the infrastructure is in place, it just needs to be repaired. (Wires, Dynamos, Turbines, etc) they mostly would need control components.

Don't get me wrong, the first 2-3 weeks will be terrifying for most, since the government will need to establish martial law and emergency powers to control and direct industry for a consorted recovery effort, but it will happen.
 
The real problem is that when the cities become essentially uninhabitale (imagine a big city without A/C) , and the Roving Hordes will be heading for more-open areas, there will be conflict if the people in the more-open areas are not forthcoming with charity.

I've said before that most SHTF / TEOTWAWKI scenarios are predicated on a large, sudden population reduction, where the survivors have some breathing space to get the prepped stuff ready, or to "get a clue" WRT survival.

I think that in an EMP scenario, the cities will be more like "Make Room, Make Room," by Harry Harrison (which is what "Soylent Green" was based on).
 
Romeosierra616 said:
You can ground out your car so it won't be affected by EMP you know...
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No grounding that you could do to your car would be more effective against an EMP event than the existing faraday cage of the metal body of the car. The effectiveness of a ground is limited by its resistance. If the EMP event can induce a sufficient voltage field from the top to bottom of the car to damage the computer, grounding the body of the car will be useless. If anything, inducing a current path from the car body to ground would induce electric current and nulify the faraday cage effect of the body.

You're much better off removing the battery and shorting the positive and negative battery cables to minimize the voltage that can be induced on the electrical systems of the car and removing the car's computer and placing it in a shielding box.
 
I think I'll rely on the method thats been tested/used for decades and works lol

Plus if the EMP is delivered by high altitude Nuclear detonation, well... protecting electrical systems will be the least of our concerns.
 
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Romeosierra616 said:
I think I'll rely on the method thats been tested/used for decades and works lol

Plus if the EMP is delivered by high altitude Nuclear detonation, well... protecting electrical systems will be the least of our concerns.
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And what method is that? How has it been tried and tested?

Grounding is not an effective protection against EMP, its actually counter productive by providing an electrical path through the shielding, allowing the shielding to establish an internal e-field. While more effective than nothing, it's less effective and leaving the shielding floating. "Grounding" is used in EMI protection (different from EMP) to prevent the shield from becoming an antenna with respect to the electronics "reference ground" which is not necessarily earth ground.

The most extensive testing of Nuclear EMP effects on automobiles was limited because the agency conducting the test was financial responsible for the vechiles but had no funding in their testing budget to pay for any of the vehicles, so rather than test vehicles anywhere near nuclear EMP E-field levels, they slowly raised the E-field levels until some malfunction occured, and then discontinued testing.

They tested 37 different makes and models of cars for E-fields upto 50kV/m (limit of their equipment). No non-running vehcile exhibited any damage (none had their body's grounded either) and only 1 running vehicle exhibited damage that required component replacement, 3 stalled and needed to be restarted while 25 exhibited "nusence" failures that did not interfer with the car's function. 50kV/m is the estimates 'Ground Zero" e-field strength for a 100km arial burst of a 1.4 Megaton fusion bomb. Maximum E-field strength is obtained at about 300km, where the field strength increases to 60kV/m
 
ShadeWPI said:
...
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I'm not disputing what you are saying, especially where I am a know-nothing when it comes to anything electrical, but since you seem to be very knowledgeable on the subject...

Faraday cages I've never understood to be "ungrounded"? (If that is even a proper term?) Just saying I've never seen an example of a Faraday cage set off the ground or on some insulator. Now, assuming the sheet-metal of a vehicle acts as a Faraday cage, why is a vehicle a different animal?

Honestly, not trying to be argumentative with anyone, I'm just trying to learn and I (and surely others) probably need an "talk to me like I'm 5" explanation. If you could be so kind as to explain that I would appreciate it.

Thanks.
 
Hiltonizer,

That's going to take a little more time than I have at the moment, but I promise I will.

Demonstration faraday cages (onces that are built to show the faraday cage effect) are grounded to prevent them from building up a potential difference from their local ground. If they are floating, the cage could become charged well above the local ground with no path for discharge untl someone touched it, provided that path through their body and the charge passed through them as current, potentially hurting or killing them. That would be a very scaled up version of you dragging stocks on a carpet on a dry day, which builds up a charge on your body, then touching something metal, which discharges it. Without moisture in the air, your body is insulated from the ground and unble to dissipate that build up of charge. When you touch something grounded, your body is no longer insulated and the charge moves from your body to the grounded object and we say it "shocks" you.
 
ShadeWPI said:
And what method is that? How has it been tried and tested?

Grounding is not an effective protection against EMP, its actually counter productive by providing an electrical path through the shielding, allowing the shielding to establish an internal e-field. While more effective than nothing, it's less effective and leaving the shielding floating. "Grounding" is used in EMI protection (different from EMP) to prevent the shield from becoming an antenna with respect to the electronics "reference ground" which is not necessarily earth ground.

The most extensive testing of Nuclear EMP effects on automobiles was limited because the agency conducting the test was financial responsible for the vechiles but had no funding in their testing budget to pay for any of the vehicles, so rather than test vehicles anywhere near nuclear EMP E-field levels, they slowly raised the E-field levels until some malfunction occured, and then discontinued testing.

They tested 37 different makes and models of cars for E-fields upto 50kV/m (limit of their equipment). No non-running vehcile exhibited any damage (none had their body's grounded either) and only 1 running vehicle exhibited damage that required component replacement, 3 stalled and needed to be restarted while 25 exhibited "nusence" failures that did not interfer with the car's function. 50kV/m is the estimates 'Ground Zero" e-field strength for a 100km arial burst of a 1.4 Megaton fusion bomb. Maximum E-field strength is obtained at about 300km, where the field strength increases to 60kV/m
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This is good info, Shade. Reference please on the car testing by .gov.
 
P-14 said:
This is good info, Shade. Reference please on the car testing by .gov.
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It's on page 115 of the EMP Commission's Report to Assess the Threat to the United States from EMP Attack: Critical National Infrastructure (Page 131 of the PDF - http://www.empcommission.org/docs/A2473-EMP_Commission-7MB.pdf from their website - http://www.empcommission.org/

The commission was part of the National Defense Authorization Act of 2001 following the attacks on Sept 11.

It's been summerized on other sites. The assement is, even at ground zero (directly below) a high-altitude arial burst nuclear detonation intentially designed to induce EMP, non-running motor vechiles would remain operational and most running vehicles would continue to work after they had been restarted. The real threat to automotive transportation is the damage it would do to the power grid and the ability to continue to operate oil recovery, transportation, refining and distribution systems, effectively terminating the renewal of supplies.
 
Hiltonizer,

Let’s see if I can cover how this works without sailing over too many heads in the process.

Electro-Magnetic Pulse (EMP) is a short duration, high amplitude electro-magnetic field. The Electric field induced high differential voltages between various points within an electrical system, if this voltage is high enough to break-down the insulation between those points, they conduct current and damage the circuit. The magnetic field induces high currents through conductors, which can cause them to heat-up and damage them or their insulators.

Faraday Cage is a closed conductive system (sphere is ideal, but shape is not critical. The faraday cage works because when an electric field is applied a conductor, it induces a current, this current forces charges (electrons) within the conductor to flow with the electric field. Without a loop for the current to flow though, the current quickly returns to zero and the electric field within the conductor is uniform and equal. If there is a hollow area within the conductor (the inside of the faraday cage) with a uniform and equal electric field surrounding it, there is a uniform and equal electric field within.
When faraday cage is floating (not connected to “ground”) and it is exposed to an EMP, the voltage of the cage tracks the highest field strength its exposed to, effectively recreating that field strength over its entire surface. Anything within the cage is also floating, like a person standing on a ship. If the ocean rises, the ship and the person rise together, and the buoyancy of the boat, is relative to the conductivity of the conductor of the faraday cage.
When a faraday cage is “grounded” and its exposed to an EMP, the voltage of the E-field and the voltage of the ground connection are fighting and the ground connection must carry enough charge to cancel the full voltage difference between the peak field exposure and the “ground” reference it’s grounded to.
If we point this back to a car in a 50kV/m EMP field – the car’s roof is about 1.5m above the surface of the earth (which isn’t ground until you get to material of sufficient conductivity, usually the water table) So, here in New England, there’s usually ground moisture 1-3 meters from the surface, so the E-field exposed to the car is about 175kV above the “ground” that it’s trying to be forced to maintain. Now we have a temporary situation where the car and ground need to equalize, and this will impose a short direction E-field within the car, whose field strength is determined by the resistance of the car body verse the resistance of the “ground” conductor. The lower the resistance of the ground conductor, the higher the temporary field inside the car. The higher the resistance of the ground conductor, the lower the temporary field inside the car. The “floating” car (no ground) effectively has an infinite ground resistance, so has virtually no temporary internal field.
If we go back to that boat example, it’s like having the boat attached to the bottom of the ocean with a spring. When the ocean rises, the spring (conductivity of the ground strap) and the buoyancy of the boat (conductivity of the metal in the car) fight enough other, and how deep the boat ends up depends on which one is stronger.

So, why are faraday cages used for demonstration grounded? The simple answer is safety and easy of demonstration. Most demonstration cages are used for displaying lightning strikes, which require the E-field to break-down the air and the current to flow through the resulting plasma (About 3,000kV/m). If you don’t ground this kind of faraday cage, it works for the first strike, but now you’ve charged the cage and you need an ever-higher e-field (with respect to the earth) to generate new strikes, until the cage is charged far enough above the ground to induce a strike from the cage to ground (much like dragging your socks on a carpet on a dry day and “shocking” yourself, but on a MUCH larger scale) In addition, if you didn’t ground the cage after the demonstration to match its voltage to the ground, anyone touching the cage after the demonstration would provide a lower resistance path than the air, and the cage would discharge through them, injuring or killing them.


I'm sorry if that's still too technical, it's really hard to do this effectively without graphics or being in person to judge when I'm getting too technical and losing someone.
 
Like I said, I'll rely on what I know and have seen with my own eyes to work, I'm not gonna get dragged into a debate lol, private company have tested cars with the very same method I use on my car with success against EMP. Nuclear weapons aren't the only thing that produce EMP after all.

but regardless, unless we get hit by a weapon that only produces EMP, there's gonna be much larger issues at hand than your laptop or car not working lol
 
Romeosierra616 said:
Like I said, I'll rely on what I know and have seen with my own eyes to work, I'm not gonna get dragged into a debate lol, private company have tested cars with the very same method I use on my car with success against EMP. Nuclear weapons aren't the only thing that produce EMP after all.

but regardless, unless we get hit by a weapon that only produces EMP, there's gonna be much larger issues at hand than your laptop or car not working lol
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Give us some details. Everything I have been able to find about EMP is basically that what gets toasted would be the grid and other long lines. THings like your car, cell phone etc. will be fine. What studies are you refering to? Not trying to stir the pot. I am curious.
 
Since you tested this method on your car

What kind of damage did your car sustain when you didn't grounding it?
What was the E-field level you used?
What was the orientation of the E-field to target vehicle?
Was the E-field generated near field or far field?
Was the car running during the test or stationary?
What was the grounding method used?
 
As a layperson, the best info I've read is in the 2008 EMP Commission report: http://www.empcommission.org/docs/A2473-EMP_Commission-7MB.pdf

It states that something like 10 percent of vehicles would be affected and most of those could simply be restarted following engine stall. Then again, I'm not an expert and can't speak to the validity of their tests/info.
 
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MisterHappy said:
Build a Faraday cage ( I have plenty of screening) for my generator, them become the New Tom Edison selling amps to the neighbors.

The point about the CC Companies noticing a run on business is a good one - assuming that they're not on the top of of the "call me" list and clamp down pro-actively.

Seriously, you'll have no more than 2 hours or so, I'd say, before the news is out and the roads are completely jammed and such, as your buddy was not the only one to text, and news will spread faster than you can hit the "forward" button.

IN that time: Canned food....lots of it. Gasoline, as much as can be got. Mantles for the Colemans, extra propane, extra kero and candles. Water is not a problem, I have 13,000 gallons (pool) and usable-with some tratment water down the street.

PLenty of salt, to season the long pig barbecue.
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I was thinking "bug out to your place" until that last line...
 
MisterHappy said:
only one way to be sure....group buy on a nuke, or should we consult Mythbusters?
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I like it! "Today on Mythbusters: Can you really buy a Ukrainian tactical nuke on the black market for $20 Million? And more importantly, will it work? Let's find out!"
 
Post to Mythbusters:

There are lots of claims of the the damage wide spread EMP from various sources would do. The two main sources are high-altitude nuclear detonation and mass corona ejection from the sun. Both function by inonising the upper atmosphere, which triggers and EM pulse from the earth magnetic field (picture the Earth's M-field as a tuning fork and other two events as a hammer hitting it)

In the Early Sixies, Project Starfish Prime detonated a 1.4 megaton nuclear bomb over the Pacific ocean and the EMP damaged 300 street lights 700 miles away in Hawaii, and the EM field generated by Starfish Prime was 1/10th the capability of a correctly placed and well designed bomb - which theoretically could affect all of the continential US with it's radius of effect.

In 2002, a US government commission (EMP COMMISSION) "studied" the effects of EMP on various infrastructure, cars, military and civilian components. They concluded non-running cars were unaffected, but 10% of running cars stalled, most with no lasting effects and 25% experiences some "nucience" (non-critical) failures. But their testing methods were poor at best.

I'd love it if Mythbusters could take on the challenge of what would work after an EMP burst from a Mass Corona Ejection or high altitude nuclear detonation.
 

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