January 12, 2016

Thoughts About That Unexpectedly Underwhelming Blast

As we mentioned earlier, the North Korean government announced that they had successfully detonated a fusion warhead. Given the apparent small yield of the warhead, (6-10 kilotons) there has been considerable skepticism expressed. This skepticism is not unfounded especially given that getting such small yields are hard to get from what we normally think of as an H-bomb. There has been further speculation that the weapon is what is called a "boosted fission weapon". This does not get the majority of its explosive force from fusion, but it does set off a fusion reaction which causes the fission reaction to burn much more completely. This can as much as triple yields on fission warheads, or reduce the amount of fissionable material necessary for any given yield. This alone would be a big breakthrough as it would allow North Korea to make more bombs for the same amount of fissile material. An increase of 2 or 3 times the number of bombs in the arsenal is a very substantial benefit. 


Of course there is the problem of the very low yield. which has led many to conclude that this was a fizzle. That's possible, but the last three North Korean bombs have had very similar yields, in the 6-9 kiloton range. Small nuclear explosions are actually HARD. This was a problem the US had with the W-54 program, where some of the intended the applications (a bazooka!and short range AAM) called for a sub kiloton yield but the tests kept overshooting it. 

The North Korean's first test was very small and may well have been a fizzle, but the subsequent three have been very comparable in yields. Given the difficulties of getting a reliable nuclear yield below 10 kilotons this indicates extraordinarily consistent incompetence....or that it's by design.

It is possible that the North Koreans have had a string of fizzles, but this would mean that they thrice duplicated a design flaw that did not befall the Americans, Russians, Brits, Frenchmen, Chinese, Indians, Pakistanis South Africans* and (presumably)Israelis.

Furthermore, given that a good deal of this program is aimed at chest thumping and deterrence, it seems logical that the North Korean's, if they were experiencing difficulties with an implosion system, would, have at least one very simple gun type weapon like Little Boy. Such weapons are so reliable as to not strictly need testing, so a respectable 10-20 kiloton blast could have been had for propaganda purposes easily.
They have not done this, and after their first detonations their tests have been fairly consistent in yield. 

Doctor Jerry Pournelle has a discussion of this on his site...
There’s some speculation that this is an attempted enhanced EMP weapon. There’s other speculation. Add to that that I have never worked in weapon design, and the last time I seriously needed to know about the minutia of nuclear weapons was more than thirty years ago, and you will understand that I am not going to speculate. We know that North Korea tested something, and they call it a sophisticated fission weapon; what they tested was low yield, and the last time I looked, low yield was harder to do than higher yields: particularly lower than 10 kt....[/quote] 
Pournelle, caries on a discussion with Stephanie Osbourne (a retired rocket scientist who also worked on nuclear planning in the cold war) and they both reference, but do not link to speculation that this is fission boosted weapon designed to utilize the Compton Effect in conjunction with the Earth's magnetic field to produce a powerful electromagnetic pulse.

The Compton Effect

The yield of the tests is actually in the ballpark of the yields that are expected from a first generation EMP optimized nuke. Jerry Emanuelson, who appears to be an electrical engineer, has a very extensive page on what is publicly known about EMP optimization in nuclear weapons. This is part of his larger site on EMP in general. His conclusions seem to be quite consistent with those of Nigel Cook, a former physics professor who has a very heavily researched blog on the effects of nuclear weapons. Mr. Cook posted an extensive (to the point of rambling) post on this possibility after the North Korean tests and included patent data as well as multiple links. He has an earlier more general overview of the problem here.

Note that both sources indicate that this kind of small fusion assisted warhead could allow a 10 kiloton warhead to produce comparable EMP effects to a more conventional warhead in the megaton range (with the tradeoff that it would have to be detonated lower and therefore cover a smaller area). 

This tradeoff would double the number of weapons needed to blackout most of the U.S.A. and southern Canada.




"Well, maybe the Norks just want us to appreciate the night sky like they do."

This of course solves their targeting problems as the target area for this weapon is measured in states rather than meters. Additionally, it would make a small device of the type they can already deliver anywhere on earth (they can launch small satellites) an actual strategic threat. 

A total power failure involving hundreds of transformers blowing up (that requires replacement from France, Finland or China)  would take years to recover from. Add to that occasional widespread fires from overloaded wires and the collapse of the internet as well as the ancillary effects of no power, refrigeration, or heat and this could become a very bad thing. 

If this is in fact what the DPRK is doing (and we have little way of knowing)  it would be quite logical as it would give them a credible counter-value strategic capability that a few nukes, even very big ones would not provide. 

Fortunately, the North Koreans have modest goals (clinging to power by the throats of their citizenry, possibly conquering the south, and killing every Japanese male on earth) . While the regime is odious, it's not like they want to return the whole planet to the 6th century...like some people.

Amongst the ranks of THOSE PEOPLE naturally are included the Iranians, who are working very closely wth the DPRK in the advancement of SCIENCE as part of their general pattern of good behavior in the wake of the nuclear deal that solved everything. One probably ought to assume assume that much of the North Korean nuclear expertise is shared by Tehran now. 

  
Of course the notion that a nation using slave labor to put together a nuclear bomb might bollox it repeatedly should not be utterly dismissed, but the consistency of the yields and the potential payoffs, mean that this option ought to not be rejected out of hand.


more...

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October 29, 2014

Not Really Effective, but Surprisingly Good

While looking for info on the Ukranian situation I blundered into this, 
 It's an interesting post on penetration tests that the Soviets did matching their 14.5mm anti-tank rifles against captured German tanks. 

 
First is a "heavy tank". I have no idea what it is, aside from that it's German. Here are the results with a 14.5 mm AT rifle:
  • Lower front plate (45 mm at 10 degrees): does not penetrate
  • Turret rear (28-30 mm at 10 degrees): penetrates at 200 meters, 100 meters at a 30 degree angle
  • Turret platform side (28-30 mm): penetrates at over 300 meters, 100 meters at a 30 degree angle
  • Lower hull side (28-30 mm): penetrates at over 400 meters, 100 meters at a 30 degree angle

This is a bit better than I would have thought. 

The performance against what are described as medium and light tanks is correspondingly better. I would not want to face these in a Panzer2 or even some modern APCs, and certainly not in a Humvee.

The"rifles" are beasts of course, with the lighter, single shot version weighing nearly 41 pounds and being 79 inches long. I suppose if one put a bayonet on one it would be a serviceable pike. These were obsolescent later in the war, but it is apparent that they were still quite effective weapons if used well.  I knew these guns were still in use around the world as antimaterial rifles, but the linked post gives a much greater appreciation of how fearsome they can be.






 "That just ain't right!".

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April 07, 2013

Asking the Important Questions




I did not realize they were so resilient.

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March 27, 2012

The Medicine Gun

I blundered into information on Meriwether Lewis's air rifle.

The gun is important to U.S. history because it served to deter attacks on the Lewis and Clarke expedition (they demonstrated it to the tribes they met...and implied that they had quite a few more than they did). It also reportedly took down a Grizzly bear at one point, though its unclear how many shots this took.

I had known vaguely about the Austrian use of repeating air guns, but I had not realized just how impressive their performance was.


It was equivalent to a .45ACP carbine, had 22 shots and carried enough air for ~30 shots in each flask! (There were generally three flasks per soldier) The flasks could be charged by hand with an ingenious pump the soldier carried with him (although it took 1500-1800 pumps to do so).

This is seriously impressive performance for 1790. Something like this would be a really cool survival gun today.

More here and info on the whole family of weapons can be found here here. The second link is particularly thorough and has this interesting tidbit as well.

Made in the 1940s during WW2, this gun doesn't look like a Girandoni, but examination shows that it clearly was built by someone familiar with the Girandoni repeating airgun system. Purchased in Europe, the story is that this gun was built somewhere in occupied Europe by a partisan bicycle maker during the Nazi occupation in WW2



Cool!

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February 17, 2011

TRANSFORMATIONAL!

This takes 'Optimal Manning' to a whole new level.


I'm sure nothing whatsoever can go wrong.


Nothing at all...

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