EMP Proof BOV's

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Nice links Colt,

The EMP creates electromagnetic radiation, micro and radio waves in nature that induce a voltage on electronic components. Depending on the intensity of the emp some, all or none of your electronics will be fried. Somethings can get partially damaged. It moves faster than circuit breakers. It likes antennas. You could emp proof by "beefing" up the circuits so they can handle larger voltages and not fry.

So after an emp you may need to replace anything electrical especially having transitstors, that is connected to wires, having wires or circuits inside it, or connected to an antenna. The wires should remain useable.

The problem appears to be radio wave related since the EMP behaves like radio and micro waves. Can one shield something from radio and microwaves? Would lead paint work? Since they are microwaves we all know a microwave oven shields the cook from them and it would work in reverse, if the waves were coming from the outside then stuff inside would be safe.

You could dissasemble a microwave oven and use it as an small em wave generator, if you could focus it maybe. And test your farrady cage. I wonder if you could test it by getting a portable radio. If you lose signal you'd be blocking the radio waves from entering the cage.

A farraday cage can be any metal enclosure that is grounded that doesn't have holes large enough for the waves to penetrate. 1mm or larger wavelenghts for micro wave to radio waves. The emp will travel around the shell and goes ground. Like lightening striking your car, you won't get struck as long as you stay in the sphere. You could use a metal ammo can as a farraday cage, hence night vision cans with the foam insulation, for shock and emp. The EMP can travel down a wire into your farraday cage.

Same principle for Nuclear radiation. Except other end of EM spectrum Nuke rad (gamma and x ray) is tiny wavelengths 0.00000000000001 meters ( a millimeter is 0.001 meter ) , thus you need layers of DENSE material so atoms are blocking the radiation and distance so the materials atoms can block them all. The waves go through any other, too pourous material, but on a massively small scale.

I'll check my shop manual for all electronic devices used on my truck, probably will be quite expensive and probably require a large metal box and the know how to install them, I'm sure the ford dealer won't be open.

 

I just read the threads listed above and they jive with info I found on another site that said if your vehicle isn't turned on you really have very little to worry about. Since I only drive my truck on weekends I'm in pretty good shape.

 

makes sense, because the circuits wouldn't have a load hence the load delivered by the emp wouldn't over load it. If it had a load on + the emp load, more likely to overload and fry.

 

You've got to be REALLY careful with this type of experiment.
1. Microwave transformers dole out about 2000v
2. Capacitors (though self draining) may still have a residual charge.
3. Unshielded microwaves could give you a quick case of cataracts.

BTW, there is some talk about the veracity of this threat on the AR15 board threads linked above, so I searched around and found this:

Electromagnetic pulse - Wikipedia, the free encyclopedia@@AMEPARAM@@/wiki/File:EMP_mechanism.GIF" class="image"><img alt="" src="http://upload.wikimedia.org/wikipedia/en/thumb/d/d3/EMP_mechanism.GIF/333px-EMP_mechanism.GIF"@@AMEPARAM@@en/thumb/d/d3/EMP_mechanism.GIF/333px-EMP_mechanism.GIF
and this:
Explosively pumped flux compression generator - Wikipedia, the free encyclopedia@@AMEPARAM@@/wiki/File:Flux_Compression_Generator_cutaway_view.jpg" class="image"><img alt="" src="http://upload.wikimedia.org/wikipedia/en/thumb/2/26/Flux_Compression_Generator_cutaway_view.jpg/300px-Flux_Compression_Generator_cutaway_view.jpg"@@AMEPARAM@@en/thumb/2/26/Flux_Compression_Generator_cutaway_view.jpg/300px-Flux_Compression_Generator_cutaway_view.jpg

Seems like there was some effort to weaponize this and it looks like a very sophisticated undertaking.

But who know? China, Russia, or (donning foil hat) a convenient way to initiate martial law. Think about it: no radio, tv, satellite, ham, cell phone, internet. Just knocking on neighbors doors... until the humvees roll down the street...
(taking off foil hat).

Anyway, I wouldn't put it high on my list, but on my list it goes.

 

Again I find myself on the same wavelength as you guys. (I read a lot, and would recommend Tainter's "Collapse of Complex Societies" here. I've rebelled against complexity in my life and find older vehicles that have no electronics to be a real comfort.) Mechanical diesels are absolutely charming in this regard, and diesel fuel stores indefinitely with the right preservatives. That's where I'm coming from.

OK - EMP is complicated. The Wikipedia article linked above is a good starting place. I may write several posts about this, but as to an EMP proof BOV, I think the early (89-93) first generation Dodge truck with the 12 valve mechanical injection 5.9 Cummins Diesel and a manual tranny beats them all. Here's why I say this:

1) The 5.9 12 valve Cummins is as close to a purely mechanical engine as you'll find. The only electrical part I have any concern about is the fuel shutoff solenoid, which is small and inexpensive. The starter solenoid's windings are robust enough I'm not concerned.

2) The 12 valve Cummins has no glow plugs, hence no glow plug controller. That's over $1000 less in parts than any other truck engine, and it's electrical parts to boot. I'd expect glow plugs to survive an EMP but the controller is a question mark. (Besides, you're going to be driving it, and maintenance costs matter.)

All the newer diesels - Powerstrokes, 24 valve Cummins, the Duramax - have not only computers but a bunch of sensors and electronically controlled transmissions. I've read that your average new vehicle has 15 microprocessors in it, and my guess is you'd need several of them just to start the dang things.

3) The Cummins has inexpensive injectors. The best set of performance injectors I know of for the 5.9 12 valve Cummins cost $500/set. I've heard of Powerstroke injectors at $200-$300 each. My set has six injectors - the Powerstroke needs eight!

4) Spare parts are everywhere, and cheap. You can look on Craigslist in any major city and you'll probably find at least one used 5.9 engine - complete and running - for less than $2000. Shop a while and you can buy for a lot less. It took me less than two months to find a nice one - complete with 120K on it for $1200 cash.

5) Another reason these engines are so common is they're found in a wide variety of medium duty trucks and buses. There's more to the equation than parts, though: did you ever think about one of them for an RV/BOV?

I found a nice front engine flat nose Bluebird school bus with low miles in excellent shape and am converting it into just that - an RV/BOV! It has the 5.9 Cummins and a stout Allison 4 speed automatic that's completely mechanical as well. Underneath, the front engine buses are nothing more than a medium duty truck chassis, which makes parts common and relatively cheap. (The rear engine buses and RV's are more complicated so I avoid them.) There's room for a heck of a lot of cargo and I can easily pull a 15,000 lb trailer behind it. Nice to have engine compatibility/parts interchangability with the pickup, too!

In the works are a 12 volt Sunfrost fridge (now cooling beer in the garage) AGM house batteries and a bit of PV solar to keep it running. I'm putting in a second identical fuel tank from a junkyard for 120 gal. total fuel capacity, which will get me from Colorado to Canada, Mexico or either coast without refueling. Also on tap is a little wood stove for heat and a used Viking gas cooktop I found on Craigslist. A kitchen sink is going in right away but won't be plumbed till later. Beds will be futons (anchored to the floor!) and even without firewood my Wiggy's bag will keep me warm wherever I go. If time permits I'll add the water tanks, plumb the kitchen sink and put in a bathroom.

The bus is paid for and I figure that I'll always have a roof over my head even if I lose my place to escalating property taxes or something. (Redundancy rules!) Here's how it works if I find myself living in it: In the city many Wal Marts let RV's park overnight. I've also noticed old school buses in a lot of church parking lots. (Park where people expect to see buses and you'll fly under the radar.) If things get really crunchy I'm too close to Denver's 3 million people so I plan to leave the state. Worst case, even if I can't make it across state lines to my intended retreat (a friend's place) I can always park it on someone's farm further out in the country and hire on with the farmer as security or something and do just fine. After all, I come with my own house and food - I just need water and parking!

A medium duty truck with a 24 foot box can also be parked almost anywhere. There are more of them out there than there are school buses, and with the economy in the tank you can pick up a nice one with a 5.9 Cummins for $5000 or less. People pay no attention to them because they're so common for deliveries. No cop will give one a second glance parked behind a shopping center or by a warehouse building, as long as you aren't grilling burgers beside it in the evening. One of these could become a nice RV/BOV as well. The only downside is you're going to need a CDL if you go this route whereas a bus can be titled and plated as a motorhome and your standard driver's license will work.

This leads me to:

6) It's cheap and simple to get real power out of the 5.9 and it stays reliable. Everyday fuel economy usually goes up a bit if you do the right mods. The bus was a little sluggish when I got it, so I upgraded injectors and put a fuel plate in the fuel pump. In normal driving, my fuel mileage went up 12%, but when I need it I now have 325 HP/750TQ on tap. That exceeds the rating of the tranny, so I don't use it often, but let me tell you: people really do a double take when a school bus pulls out and passes them going up a hill!

I strongly suggest the manual transmission for pickups. The first gen auto is entirely manual but starting in 1994 it's electronically controlled. The newer the truck, the more sophisticated and delicate the electronics. The autos can be rebuilt strong, but a manual is best. Many people replace the early 5-speed Getrag with a 5- or 6-speed New Venture which are said to be a lot tougher. (I recommend 4 wheel drive, but if the truck is two wheel drive you could easily put in an early Allison 4 speed automatic, which is entirely mechanical and rated for 30,000 GVW minimum.)

I've been very happy with these choices. Simplicity was my main consideration, and that worked out perfectly for EMP concerns as well. It so happens that I just started the bus tonight - it's really not necessary but I love sitting in the thing and listening to the engine. Sometimes when I'm out feeding the animals I'll go sit in it for a while and ponder the floor plan and space utilization. Once in a while I just have to start it up!

 

On the topic of EMP, I am fortunate to be my father's son. Although he taught electrical engineering most of his life, his PhD was in physics and he dabbled in defense and aerospace consulting his entire career. It's from that marvelous brain that I draw my knowledge.

As I said in the post above, EMP is a complicated topic to understand. The oft cited Starfish Prime atmospheric nuclear test in 1962 managed to turn off some lights in Hawaii nearly 1000 miles away. Since the first working metal oxide transistor was built Bell Labs in 1960, the use of transistors had to be very limited, yet - there was obviously already some vulnerability. What's missed here is that the magnetic field over that part of the planet is far LESS conducive to EMP propagation than it is over the continental United States. We would have had far more serious damage had that explosion occurred over our country in 1962, and I'm sure we'd take EMP real seriously today as a result.

There's a lot of info out there on this subject but a recent trustworthy article by a real expert (that doesn't get too technical) is at this address:

http://www.todaysengineer.org/2007/Sep/HEMP.asp

Due to the evolution of microprocessors (chips) and their widespread use, we are now far more vulnerable to EMP that at any time in the past. (Bad enough that our radios, computers, cars and phones would be wiped out, there are washers, dryers, microwaves and even toasters with chips in them now, for heaven's sake!) Every increase in processor clock speed came as a result of the ability to print transistors closer and closer together and thus lower operating voltages. Those advances make each new generation of chips even more vulnerable to damage by EMP than the last.

EMP is picked up on long runs of wire that serve as antennas. The power grid is just about ideal for this purpose and anything electronic that's plugged into the grid is likely to be destroyed by EMP.

Much shorter wires such as those in wiring looms in cars are sufficient to conduct an EMP and destroy automotive ECM's, and if you scroll down a few posts in my blog (www.invertebratenation.blogspot.com) you'll find a YouTube video of just such a test that stopped a car dead in it's tracks! I doubt the car would survive if it wasn't running, as the computers are plugged into the wiring harness regardless.

An excellent work of survival fiction ("doomer porn") centered around an EMP attack is Lights Out, which is downloadable as a PDF free of charge here:

http://www.survivalmonkey.com/Lights%20Out.htm

(I'm sure you guys know about this already, but I'm too new to have stumbled on that page yet.)

Another good fictional EMP read is "One Second After" by Fortschen, in bookstores now. I particularly like that there are no survivalists in this book - just everyday people in a small town coping with the collapse of society. It's probably the best book ever for introducing "civilians" to the concept of societal collapse.

I'll have more on this EMP subject, and moderators - feel free to move this if you want it turned into a separate thread on EMP. (I'm still not very familiar with the boards or I might have done that myself.) And PLEASE, if you move it, PM me so I know where it is!

 

Fireplaceguy,

Since you've obviously done a fair amount of research on the subject how about commenting on this post pulled from another site. This is where the interweb can get so confusing, the more you search the more different answers you get to the same question.

thanks

 

I read part of the above qouted report......the report was 160 or so pages I wanna say and it was commissioned by the government and as far as I know is the gov's official position..........here's the interesting part...even though the report says that there is nothing at all to worry about, but at the same time the report urges the gov to make a contingency plan to confiscate food supplies for orderly re-distribution to the populace in case food supply delivery is massively disrupted by EMP.

simply logic makes me highly skeptical of a report that makes both of those statements.....

 

So society will collapse because it's attached to the grid but my PDA will be fine? What was I ever worried about???

I read that report cover to cover.

You may be interested to know that the very government which is telling you "don't worry be happy" is quite concerned about itself. For example, they are busy deploying very expensive EMP proof equipment across their entire fiber optic network. An optical signal (beam of light) doesn't conduct EMP, so why are they bothering??

Your choice: Do as they say, or do as they do.

 

FIREPLACEGUY

it certainly seems you know damn good and well what you're talking about, and if ya wouldn't mind helping me out on this, it would save me some serious time and worry on wondering if I missed anything or not

what I recently bought is a 1993 Dodge Cummins W250 Club Cab with the 46RH Tranny and 269,000 miles....what all should be done to make it COMPLETELY EMP proof......as in, let's assume that the effects of EMP was as bad as the worst speculation out there, and an EMP attack was set off right over the top of my truck....what, in that extremely unlikely scenario, should be done now to make certain it'll get me home?

my understanding is that the tourque convertor wouldn't work, but that would only keep the over-drive from kicking in....???

what about the Neutral Safety Switch to keep it from being started in any gear other than Park? And how would I by-pass that? would I run a hot wire from a toggle switch to it?

fuel pump ok?

also, the locking hub went out, so I am gonna replace those and upgrade the splines and flange.....should I have them make it set up where I don't have to get out and lock in the hubs? I would see this as a huge benefit in a bug out situation (not having to get outta the truck to lock it into 4x4)....but would this make it like an older Bronco with full-time 4x4 where it gets horrible fuel MPG's? I may never need to actually use this in a bug out situation, but I will certainly be using this in a daily long commute to get my fat ass to work situation.

what else is there?

thank you for your time...seriously!

 

I'm seeing a lot of talk about diesels. What about the idea of buying an early '70s (pre eci) vehicle.
I'm just thinking that they're cheaper than any diesel and it really doesn't need to see a whole lot of action until TSHTF.

 

This is a perfectly good option. Just stock a set of spare ignition parts (condenser and coil) and you'd be good to go.

The advantages to diesel vehicles are many, though - among which are: 1) life of stored fuel, 2) power/torque - a consideration for a BOV, 3) durability, 4) fuel compatibility with other equipment and 5) fuel economy.

That's probably why everyone is talking about them so much.

 

I'll try, but I make no claim to know ALL the answers. My position on EMP is due in part to the fact that I'm a contrarian. Whatever the herd does, I usually do the opposite.

When the government says to not worry, I worry.

What I know about modern electronics and EMP leads me to believe there would be failures after an EMP event. If it were a HEMP I suspect they would be widespread and would lead to a collapse scenario that would probably play out along the lines of "Lights Out" or "One Second After" When I learn about some of the government's urgent preparations to function in the aftermath of EMP my concerns about it are amplified.

Those are great old trucks, aren't they? (I think it would be a home run if Dodge did a retro look like these for the next generation of trucks.)

I know very little about automatic transmissions and torque converters. I have a friend who builds trannies for all sorts of interesting applications (racing, mining vehicles, etc.) and has been at it for 30 years. I emailed a copy of this to him for comment and I'll post his not always so prompt response whenever it arrives.

I wouldn't think this would be vulnerable but they fail sometimes anyway. If you're not so stupid as to start your truck in gear, you might think about eliminating that circuit altogether. That would be one less thing to tempt Murphy.

You talking about the pump mounted on the engine? It's mechanical, isn't it? Should be fine, but that's another good thing to have a spare of anyway.

I'm no expert on 4wd systems. You'd be better off going talking to a good 4wd shop or onto a 4wd website or forum for answers.

In a bugout situation where the conditions are dubious, I would just lock the manual hubs and go. If I need 4wd I'll engage it. (My understanding is that the 4wd is not engaged unless you shift the transfer case into 4 high or 4 low, so this shouldn't do much to your fuel economy. I could easily be wrong on this, and I'll always stand corrected if I am...)

Around these parts, a lot of old timers leave them locked for a few months each winter, but then most of them drive something else unless it's snowy. Again, I'm not your best source on this, and would be interested in the answers you get from the pros.

The fuel shut-off solenoid is electrical. (It's mounted on the injection pump.) I suspect the windings are stout enough that they'd be ok, but I'd keep a spare of that on general principles anyway.

I don't know that I did that much good, but you're welcome. The way I see it is that we all contribute to this pool of knowledge, and I'm sure there are 4x4 people here who could teach me a lot about some of your questions.

 

Man, I'd like to see a "how to" guide on one of these vehicles.
IOW, "how to make a '91 ram 2500 EMP resistant."

because I just don't have the patience to do the research.

Any takers?

 

Couldn't you just park your vehicle in a metal building that is grounded, and ground the vehicle?

 

OzSt- your neutral switch is a mechanical switch, no worries. if its ever a problem just jumper it.

 

thanks fellas....been doing some research and still am doing some, I'll post back as I find things out

looking forward to seeing that reply from your friend when he finds time FPG

and yeah, I love the truck....although, gotta admit, I picked up a 78 Ford F150 SuperCab at the same time and haven't messed with it much at all, but the 78 would be my fav if it wasn't a gasser

 

Troubles with a decent metal building/garage:
1) Those nasty little emp waves are in a variety of wavelengths that can and will penetrate any larger opening than 1mm in any dimension.
The doors would have to danged near water tight.
Windows are a real problem. Use metal mesh, like aluminum window screen, and cover them entirely. (connect ground wires to them all, and run that to a grounded rod)
2) Large concentrations of metal, like a building, will absorb and "hold" an electrical discharge /"emp" . The time is undetermined, see the pacific test results: see "STARFISH",(Hawaii). Some instances, were 4 hours or more!
3) Concrete floors are not insulation from emp discharges. You'll need either a metal plate like aluminum diamond plate or something similar to connect a ground wire to. (still wouldn't help!) Easier to ground the vehicles body by the bumper, or chassis!
4) Most people really think their cars are grounded against lightning, some think they are insulated due to their rubber tires...
Now, consider the voltage of the lightning bolt, the distance they can travel, and usually ( not always) there is rain involved.
What insulation? Wet tires, that are only a mere few inches from their rims that are steel/aluminum/magnesium, connected to the rest of the vehicle? "Ground"? Uh....No. Definitely NOT insulated by a long shot! (for lightning anyway!)
5) A true ground (for emp purposes) is done by using heavy gauge solid copper electrical wire, and connected solidly, (usally by hot soldering) to a solid copper, or copper coated steel rod of 8 ft length, set into the ground as deep as is possible, OR, by burying the rods in a horizontal ditch no less than 3-4 foot depth. Making 2 rods in the shape of an "L" is the best found. (Best to have moist ground, or by using an electroyte chemical to ensure conductance)
(remember, electricity takes the path of least resistance, the shorter the path the better!)
DO NOT USE the water pipes! A big no no!

As for vehicles, we have a 1973 dodge van, a 1989 dodge van, and a 1986 chevy van, All are "safe" relatively.
My 1996 dodge would be meat for the grinder!
I have seen a lot of "movies" and video's, that tell you to disconnect BOTH battery leads....Prior to an emp!
I wonder IF anyone will call us and say we have 5 minutes to do that?
(Snort! Snicker!)
The battery has absolutely not a thing to do with what the EMP does.
Honestly!
It quite simply "overloads the circuitry" like mini- lightning bolts.
It fries the finer components, like those devices inside your home computer, cell phones, etc. That is WHY the people that work on those little gadgets wear those ankle and wrist bacelets in the work they do, to keep them "grounded", to prevent from having a "static build-up", resulting in any spark that will surely destroy those goodies! (notice that NEW hardrives come in those metallized foil sealed packets?) INSURANCE!
Kind like the shock you get from carpeting in cold dry weather, or from sweaters that are woolen, or on some (older) car seats!
It's a simple thing, and easy to understand, if you look at it as a big static shock!

How do I know of these things?
a) ADM in military service....
(atomic demolitions munitions) Also "SADM's" as well.
(Yeah, I know about them "neutron shells too!)
b) I worked for the Palo Verde Nuclear Generating Station outside of Phoenix.
c) AEC, NEC, and NRC, etc. clearances.

 

Add'l info...

Nuclear Weapon EMP Effects

A high-altitude nuclear detonation produces an immediate flux of gamma rays from the nuclear reactions within the device. These photons in turn produce high energy free electrons by Compton scattering at altitudes between (roughly) 20 and 40 km. These electrons are then trapped in the Earth’s magnetic field, giving rise to an oscillating electric current. This current is asymmetric in general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic pulse (EMP). Because the electrons are trapped essentially simultaneously, a very large electromagnetic source radiates coherently.
The pulse can easily span continent-sized areas, and this radiation can affect systems on land, sea, and air. The first recorded EMP incident accompanied a high-altitude nuclear test over the South Pacific and resulted in power system failures as far away as Hawaii. A large device detonated at 400–500 km over Kansas would affect all of CONUS. The signal from such an event extends to the visual horizon as seen from the burst point.
The EMP produced by the Compton electrons typically lasts for about 1 microsecond, and this signal is called HEMP. In addition to the prompt EMP, scattered gammas and inelastic gammas produced by weapon neutrons produce an “intermediate time” signal from about 1 microsecond to 1 second. The energetic debris entering the ionosphere produces ionization and heating of the E-region. In turn, this causes the geomagnetic field to “heave,” producing a “late-time” magnetohydrodynamic (MHD) EMP generally called a heave signal.
Initially, the plasma from the weapon is slightly conducting; the geomagnetic field cannot penetrate this volume and is displaced as a result. This impulsive distortion of the geomagnetic field was observed worldwide in the case of the STARFISH test. To be sure, the size of the signal from this process is not large, but systems connected to long lines (e.g., power lines, telephone wires, and tracking wire antennas) are at risk because of the large size of the induced current. The additive effects of the MHD-EMP can cause damage to unprotected civilian and military systems that depend on or use long-line cables. Small, isolated, systems tend to be unaffected.
Military systems must survive all aspects of the EMP, from the rapid spike of the early time events to the longer duration heave signal. One of the principal problems in assuring such survival is the lack of test data from actual high-altitude nuclear explosions. Only a few such experiments were carried out before the LTBT took effect, and at that time the theoretical understanding of the phenomenon of HEMP was relatively poor. No high-altitude tests have been conducted by the United States since 1963. In addition to the more familiar high-yield tests mentioned above, three small devices were exploded in the Van Allen belts as part of Project Argus. That experiment was intended to explore the methods by which electrons were trapped and traveled along magnetic field lines.
The “acid test” of the response of modern military systems to EMP is their performance in simulators, particularly where a large number of components are involved. So many cables, pins, connectors, and devices are to be found in real hardware that computation of the progress of the EMP signal cannot be predicted, even conceptually, after the field enters a real system. System failures or upsets will depend upon the most intricate details of current paths and interior electrical connections, and one cannot analyze these beforehand. Threat-level field illumination from simulators combined with pulsed-current injection are used to evaluate the survivability of a real system against an HEMP threat.
The technology to build simulators with risetimes on the order of 10 ns is well known. This risetime is, however, longer than that of a real HEMP signal. Since 1986 the United States has used a new EMP standard which requires waveforms at threat levels having risetimes under a few nanoseconds. Threat-level simulators provide the best technique for establishing the hardness of systems against early-time HEMP. They are, however, limited to finite volumes (aircraft, tanks, communications nodes) and cannot encompass an extended system. For these systems current injection must be used.
HEMP can pose a serious threat to military systems when even a single high-altitude nuclear explosion occurs. In principle, even a new nuclear proliferator could execute such a strike. In practice, however, it seems unlikely that such a state would use one of its scarce warheads to inflict damage which must be considered secondary to the primary effects of blast, shock, and thermal pulse. Furthermore, a HEMP attack must use a relatively large warhead to be effective (perhaps on the order of one mega-ton), and new proliferators are unlikely to be able to construct such a device, much less make it small enough to be lofted to high altitude by a ballistic missile or space launcher. Finally, in a tactical situation such as was encountered in the Gulf War, an attack by Iraq against Coalition forces would have also been an attack by Iraq against its own communications, radar, missile, and power systems. EMP cannot be confined to only one “side” of the burst.
Source Region Electro-magnetic Pulse [SREMP] is produced by low-altitude nuclear bursts. An effective net vertical electron current is formed by the asymmetric deposition of electrons in the atmosphere and the ground, and the formation and decay of this current emits a pulse of electromagnetic radiation in directions perpendicular to the current. The asymmetry from a low-altitude explosion occurs because some electrons emitted downward are trapped in the upper millimeter of the Earth’s surface while others, moving upward and outward, can travel long distances in the atmosphere, producing ionization and charge separation. A weaker asymmetry can exist for higher altitude explosions due to the density gradient of the atmosphere.
Within the source region, peak electric fields greater than 10<SUP> 5</SUP> V/m and peak magnetic fields greater than 4,000 A/m can exist. These are much larger than those from HEMP and pose a considerable threat to military or civilian systems in the affected region. The ground is also a conductor of electricity and provides a return path for electrons at the outer part of the deposition region toward the burst point. Positive ions, which travel shorter distances than electrons and at lower velocities, remain behind and recombine with the electrons returning through the ground. Thus, strong magnetic fields are produced in the region of ground zero. When the nuclear detonation occurs near to the ground, the SREMP target may not be located in the electromagnetic far field but may instead lie within the electro-magnetic induction region. In this regime the electric and magnetic fields of the radiation are no longer perpendicular to one another, and many of the analytic tools with which we understand EM coupling in the simple plane-wave case no longer apply. The radiated EM field falls off rapidly with increasing distance from the deposition region (near to the currents the EMP does not appear to come from a point source).
As a result, the region where the greatest damage can be produced is from about 3 to 8 km from ground zero. In this same region structures housing electrical equipment are also likely to be severely damaged by blast and shock. According to the third edition of The Effects of Nuclear Weapons, by S. Glasstone and P. Dolan, “the threat to electrical and electronic systems from a surface-burst EMP may extend as far as the distance at which the peak overpressure from a 1-megaton burst is 2 pounds per square inch.”
One of the unique features of SREMP is the high late-time voltage which can be produced on long lines in the first 0.1 second. This stress can produce large late-time currents on the exterior shields of systems, and shielding against the stress is very difficult. Components sensitive to magnetic fields may have to be specially hardened. SREMP effects are uniquely nuclear weapons effects. During the Cold War, SREMP was conceived primarily as a threat to the electronic and electrical systems within hardened targets such as missile launch facilities. Clearly, SREMP effects are only important if the targeted systems are expected to survive the primary damage-causing mechanisms of blast, shock, and thermal pulse. Because SREMP is uniquely associated with nuclear strikes, technology associated with SREMP generation has no commercial applications. However, technologies associated with SREMP measurement and mitigation are commercially interesting for lightning protection and electromagnetic compatibility applications. Basic physics models of SREMP generation and coupling to generic systems, as well as numerical calculation, use unclassified and generic weapon and target parameters. However, codes and coupling models which reveal the response and vulnerability of current or future military systems are militarily critical.
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