So can the mad Korean bring us to our knees with EMP?

[Magiver]

@electronbee

Never say never. Lotsa sanctions, limited resources, starvation, it’ll all catch up to them eventually.

Launch a nuke and that all goes away as your country gets mowed over.

The upper echelon has to know if there’s a rebellion they’ll be tortured as well as their families. The populace will go full circle on them.

And the last desperate act of crazy man during a rebellion is? You know, when it all catches up to him eventually?

You keep acting as if the nukes and rockets don’t exist. They exist.

[Gray_Ghost]

@Magiver

yes and I cited otherwise with a source other than an internet poster.

If it’s the “10kT can generate significant EMP,” quote from wiki, it comes from this testimony. Specifically, Dr, Lowell Wood’s and Dr. William Graham’s testimony before the House Armed Services Committee, October 7, 1999, at Pages 46-49. Dr. Wood was a senior scientist at the Lawrence Livermore National Laboratory, and Dr. Graham was Reagan’s Science Adviser from 1986 to 1989. Here’s the quote (it’s long) “Mr. Weldon”, refers to Representative Curt Weldon:

Mr. WELDON. Let’s increase that to 10- to 20-kiloton.

Dr. GRAHAM. Either way it turns out the fields more or less are logarithmic in the nuclear weapons yield, so they vary fairly slowly with the yield, and I don't believe the analysis has been done which would give a definitive answer to that question.

Page 47 PREV PAGE TOP OF DOC
However, pieces of the analysis have been done and other systems looked at that while I think the United States would survive such an event, there are such a large number of capabilities, both in our military forces directly and even more in our civilian, supporting infrastructure that we need, that it is quite possible that the effects could provide a major disruption and delay in our activities.

As you know, to deploy military forces in an expeditionary fashion overseas, we require massive logistics to get them there, equip them and sustain them there, and that requires a heavy use of the civilian infrastructure, air transport, surface transport, telecommunications, computing capability. Monetary flows in the United States are primarily electronic today and throughout the world. All of those capabilities depend heavily upon civilian electronics and somewhat military electronics. All of those would be subject to disruption and confusion. None of the civilian infrastructure that I know of has been designed with EMP threats in mind, and, therefore, is likely to experience some degree of disruption. So if we were in a time-critical situation where we have to get men and women to a theater rapidly, such an attack could cause us a significant delay and, therefore, a military problem.

Mr. WELDON. Dr. Wood.

Dr. WOOD. Mr. Chairman, the question or the set of questions that you posed are certainly the most pertinent ones. They also elicit answers which not only are a bit extended, but really is—some portions of them would have to be made in closed session.

But to speak to the issue as much as feasible in open session, the North Koreans certainly have the ability to deliver a small nuclear explosive to the U.S. at the present time. The ballistic missile capability which they have demonstrated could deliver a warhead weighing substantially more than a tenth of a ton and substantially less than one ton anyplace that they chose to in the United States, including any height of burst that they choose over the continental United States.

Page 48 PREV PAGE TOP OF DOC

So that is something which I think the Rumsfeld Commission predicted would happen. It is something of which the test of last August 31, 1998, indicated they indeed had that capability.

The press reports are saying that they could strike Alaska or they could strike Hawaii. That is striking in reference to a 1-ton warhead. With a fractional-ton warhead, that same missile could deliver that warhead to any point over the continental United States, over the 48 contiguous states. It is not necessarily the case that the referenced 1-ton warhead is what the North Koreans would use. It is very well known that U.S. strategic warheads that are in stockpile at the present time have masses of tenths of a ton, and not very many tenths of a ton. So if the North Koreans had access to a single sheet of paper, whether it could come to them in a fax from a Soviet nuclear weapons laboratory, they could use the materials that they are known to have in hand to create a warhead, not, Mr. Chairman, that was one kiloton or even ten kilotons, but substantially higher yield than that.

My colleague Dr. Graham has said that the EMP yield of a warhead is very weakly dependent on its energy yield. That is true, but it is true in spades. **Special purpose nuclear warheads, on a kiloton scale, can have much more of EMP effect than ordinary nuclear warheads on the megaton scale. Less than ten kilotons properly employed in the type of warheads which have actually been examined, both in the Soviet Union and in the United States experimentally, warheads of less than 10-kiloton yields can put out very large EMP signals. So it is necessary to understand that it doesn't take a megaton to do an awful lot of damage. You can do an awful lot of damage in ten kilotons or less.** [EMPHASIS ADDED]

Page 49 PREV PAGE TOP OF DOC
Mr. WELDON. What would be the damage done by that, in your opinion? That is what I am trying to get at, and I know there are all kinds of variations. Are we prepared, militarily and civilian, for the kind of capabilities North Korea has?

Dr. WOOD. In order to be noncontroversial, I will just quote a CIA estimate that has been briefed by a senior cognizant CIA national intelligence officer on the Hill here during the last year, on an unclassified basis, where he considered a hypothetical laydown of the type that could be posed by a Taepo Dong missile over the central United States and presented the unclassified calculations of what the EMP yield or the EMP consequences would be at the coasts of the United States; in other words, most distant from the explosion. The EMP field strengths that were calculated there—and nobody seriously questions these calculations, they are with tool sets that are community tool sets that have been around for decades—with the field strengths that were demonstrated at the coasts, the maximum distance, you would see upset or damage to a wide variety of civilian equipment that has been documented to fail at these field strengths, and you would see some damage to military equipment.

The consequences of such a laydown are very strongly dependent on what you assume is the nature of the explosive, as well as what you assume is the vulnerability of the equipment, but with documented equipment vulnerability of the type that has been measured for sensitivity to these threat spectra during the last two to three decades, you would see major damage as far out as the coasts to civilian gear. You would also see it to a substantial amount of military gear.

What Dr. Weldon wasn’t telling you there is that the E1 component to EMP is strongly dependent on gamma flux from a nuclear explosion, and most nuclear devices aren’t designed to emphasize gamma flux. Even with, e.g., Starfish Prime’s 1.4 Mt yield, only 1.4 kt of that was in the kind of gamma radiation necessary to generate a strong E1 component. You can make devices that emphasize hard gamma output, but it takes a sophisticated understanding of bomb hydrodynamics and radiation management that would also allow you to make multi-stage thermonuclear devices (and efficient ones at that). Which is something the Norks haven’t shown they’ve been able to do.

An interesting question I have is, if an EMP device is launched by NK against Japan and detonated at very high altitude, does that mean that a nuclear or conventional response from the US or Japan would necessarily follow? After all, only computer chips and power stations would get fried in this hypothetical; comparatively few people or none would die as a result. It’d just be hideously expensive to fix. And NK would still have the option to escalate to direct nuclear attacks against Japan/SK/US. Or shell the living daylights out of Seoul.

[Gray_Ghost]

And it’s Dr. Wood, not Weldon. Sigh.

But the answer to the OP in the title is No. Right now, anyway, for the US. No guarantees about the Kwanto Plain or Seoul.

[Magiver]

@Gray_Ghost

An interesting question I have is, if an EMP device is launched by NK against Japan and detonated at very high altitude, does that mean that a nuclear or conventional response from the US or Japan would necessarily follow? After all, only computer chips and power stations would get fried in this hypothetical; comparatively few people or none would die as a result. It’d just be hideously expensive to fix. And NK would still have the option to escalate to direct nuclear attacks against Japan/SK/US. Or shell the living daylights out of Seoul.

hideously expensive is a gross understatement.

[SenorBeef]

@Trinopus

It’s like someone points a gun at you, and you worry about hearing loss if it gets fired.

If they can explode a nuclear weapon high over our country…then they could explode it on our country, and wipe out a major city, doing far more harm to us than any EMP.

How do you figure? If we’re talking about a realistically weaponized EMP of US/Russia capability (which NK can’t match), a significant fraction of the country losing power and electronics is way more damage than losing a city. Losing a city wouldn’t shut down the whole US logistical network. People would die, but it would be fairly isolated. Whereas with the EMP, we’d lose transport networks for food, gasoline, clean water would stop working, almost everything comes grinding to a halt.

It would hurt much less to lose 5 million people in NYC than to lose power and electronics in a way that would require decades to recover from over even a quarter of the US.

[Whack-a-Mole]

@SenorBeef

How do you figure? If we’re talking about a realistically weaponized EMP of US/Russia capability (which NK can’t match), a significant fraction of the country losing power and electronics is way more damage than losing a city. Losing a city wouldn’t shut down the whole US logistical network. People would die, but it would be fairly isolated. Whereas with the EMP, we’d lose transport networks for food, gasoline, clean water would stop working, almost everything comes grinding to a halt.

It would hurt much less to lose 5 million people in NYC than to lose power and electronics in a way that would require decades to recover from over even a quarter of the US.

How damaging is an EMP? What is its range?

I used to install PCs in hospitals and when we did it in the MRI rooms we had a map with the magnetic field lines to be sure we stayed far enough away that the PCs would not be affected by the magnet (or erase the credit cards in our wallet).

These are very big magnets and (I forget exactly) everything was fine 10’ or more away from the machine.

I realize an MRI is different than an nuclear induced EMP but still…these things don’t have stupendous range.

Also, while some bits may be broken the infrastructure remains. Not sure it would take decades to recover.

But again, I have never seen anyone lay out exactly the damage an EMP would wreak and at what distances.

[Francis_Vaughan]

An EMP isn’t a static magnetic field, which is what you have with an MRI scanner. What does the damage is the very high gradient of the EM field. Being a dipole the MRI magnet’s field falls off with the 4th power of the distance. Which is why you can easily get far enough away. An EMP isn’t, and as it is a phenomenon that is an extended plane in the atmosphere, the fall off with distance may actually be zero for anyone under the extent of the nuke, and fall off as a mix of linear and eventually inverse square as you get many hundreds of miles away.

It would be interesting to know what the gradient of the field would be next to a quenching MRI scanner magnet, but I suspect that it would be damped by the reactance of the now non-superconducting magnet windings.