Saturday, October 02, 2004

Bunker buster bombs: boom or bust?

John Kerry announced he would unilaterally forego research and development into "bunker buster" nuclear weapons. These are weapons specifically designed to penetrate deep into rock or concrete before detonating.

We know that enemies like Saddam, Kim Jong-il, and whichever illiterate old Ayatollah is leading the mad Iranian mullahs at present, have reacted to the advances of American precision air and missile power by constructing deep underground facilities which cannot be destroyed by current crop of conventional "bunker busters" {which operate on the same principle as the proposed nukes, but with less explosive power}. It is uncertain whether such redoubts could be compromised by even large nuclear explosions on or near the surface.

It's simple physics: the force of the shock wave from an above-ground explosion will travel primarily out and up from the target, because the ground below is denser than air. Even if a huge bomb or warhead were exploded directly over a deep bunker, that bunker might survive. This is the reality which led to construction of deep bunkers for our key government officials in the West Virginia mountains fifty years ago.

We do know that a massive above-ground explosion would have devastating results on the ground, however, killing hundreds of thousands and spreading radioactive fallout over a wide area. Since our targets in such an attack would not be the Iranian or North Korean people, but their leaders and weapons, we could only be sure of the collateral damage, and not the desired effect.

The bunker-busting nuclear warhead would be designed to penetrate deeply into the ground, rock, or concrete over the bunker before detonation. Thus surrounded by solid material, the shock wave would have many times the force underground than an above-ground detonation, with the objective of collapsing the bunker.

The arguments AGAINST developing such weapons fall into three basic categories: 1) practical physics, 2) diplomatic and treaty implications for proliferation, and 3) increasing the likelihood of actual use of nuclear weapons.

1. The physics argument. In order to penetrate deeply, a warhead must impact the ground at high speed. The higher the speed, the deeper it goes. However, current materials and technologies limit the possible speed at impact, because if the warhead is going too fast, it will lose structural integrity before reaching the desired depth for detonation. Some claim the maximum possible depth would be no more than 20 meters or so, which might not be deep enough to destroy a given bunker - but would still probably throw a significant amount of fallout into the atmosphere.

This argument presumes no advances in technology. It is similar to the objections to missile defense in the early '80s: "We can't do it right now, so it's impossible." Of course, our missile defense technology has advanced since then, to the point we are nearing practical deployment. Had this mindset been prevailing in the '50s and '60s, we might never have reached the moon.

Of course, the development of a new weapon entails innovation and technical advances, and always has. The bow and arrow was a new technology in the age of the spear. Had we not researched and developed stealth aircraft or missile defense, they would not have been "possible," either. The objection is fallacious.

2. The testing-treaty-proliferation argument. It is argued that we might have to test these weapons underground, which would violate the spirit of the test ban treaty {which we didn't ratify, but adhere to} and inspire or excuse other nations to seek nuclear capacity and/or do their own testing.

The experience of the last half-century is that other nations will acquire nuclear weapons whether we want them to, or not. Nations who have sought to do so either withdraw from treaties prohibiting it, or just ignore them. Non-proliferation agreements failed to prevent India, Pakistan, Israel, South Africa, and North Korea from going nuclear, or others from trying.

Neither is it certain that developing BBB would require underground nuclear testing. We would surely have to test penetration into the ground, to ensure structural integrity of the materials, but computer modelling is so advanced it might be able to satisfactorily evaluate the effect of a blast, once we know how deep we can deliver the weapon.

One thing is certain: our self-imposed abstaining from testing will not deter the PRK, Iran, or any other enemy from their own testing if they believe they can achieve nuclear insurance from American military force.

3. Lower-yield weapons make nuclear war more likely. This argument projects that by diminishing collateral damage by developing bunker-busting or battlefield nukes, they are more likely to be used in war.

This is essentially the same argument used against the neutron bomb, but in a different world. When our primary threat came from large enemies like the USSR and China, whose ambitions were for dominance and influence, Mutually Assured Destruction was a plausible and effective deterrent. The face and nature of the enemy has changed, though.

Using our huge warheads designed for Cold War MAD against smaller nations would be a horrific decision, and one that would not guarantee success against bunkered enemy leadership or weapons. They are therefore far less likely to be deployed, so in this respect the objection has some validity.

But, deterrence relies upon the enemy's uncertainty of our response. If a Kim Jong-il or Khameini think we won't dare strike, or can't reach their bunkers, our "deterrent" becomes a paper tiger. If instead we have the capability to surgically destroy them and their WMD facilities with limited nuclear blasts, it provides a far greater deterrent to them. MAD is a meaningless concept against an enemy who can't totally destroy us, and who knows we won't totally destroy them.

The fact is the more options in our arsenal, the greater the deterrent. To cut off even discussion of developing bunker-busting weapons, as John Kerry proposes, makes a WMD attack against us by a rogue nation more likely, not less. The uncertainty of our capabilities that BBB would add to their calculations would be the only realistic and effective deterrent against them.

Also, in cases like Iran, where fanatics might sacrifice themselves and their nations to attack us, the bunker busters give us an additional preemptive option, which could be used to deter them from proceeding with developing underground facilities for WMD. The only true deterrent is a credible threat, which these weapons constitute.

In sum, we can and ought to proceed with the necessary R & D expeditiously. The Cold War is long ended, and our nuclear strategy must adapt to the new geopolitical situation, just as our diplomacy has.

Hugh Hewitt is assembling a virtual symposium on this subject. Visit his site to follow the progress, or for the insightful posts and helpful links he provides every day. I do.


Blogger Grumpy Old Man said...

Very interesting and thoughtful analysis. The "enemy uncertainty" argument is really a good one. Wish I knew more about the physics.

My response to Hugh here,

October 2, 2004 at 4:42 PM  
Blogger Matthew Heidt said...

I am no physicist, but I have extensive practical experience with the demolition of explosives. Your postulation is correct with regard to surface detonation following the path of least resistance and away from a subterranean target. I think that a Nuke BBB would be effective for another reason. A shaped charge which detonates around a hollow cone creates a superheated jet and a molten slug that is directed toward the base of the cone. I believe that the tremendous heat generated by a Nuke imbedded in concrete would also create a superheated jet and turn the concrete into a molten slug that follows the trajectory of the weapon impact with devastating effect.


October 2, 2004 at 11:26 PM  
Blogger Jesse said...

I posted this on Foggy Ruminations:

Hey Matt: I agree, explosives are wonderful things and when used in a manner to correctly direct their force, can be deadly. I had a good job when I was a young Sgt working with explosives for battle simulation purposes. The job was free reign (for you non military types that means minimal supervision i.e. I would sometimes not talk to a superior directly for weeks on end, just be expected to show up with my kit and set off the show), I spent a lot of time on the range 'playing' with explosives to see what they would do, to create flash results, but not put nearby soldiers or equipment in unnecessary danger, and minimize the use of pre-packaged explosives. Awesome job! I made a shaped charge out of a 2 liter wine bottle (I found the idea in a book somewhere), you know the ones with the concave part on the bottom. I nicked the top off the bottle with det cord (clean cut) and filled the bottom with C4 (about a pound). It blew through a door on a truck like it wasn't there and another one put a hole in the frozen ground to a depth of a couple of feet. I used it with liquid fuel to simulate napalm strikes among other things, very effective, and conservative use of my explosives. It is amazing and sometimes unbelievable what a 'shaped' charge can do, and how easy they are to make. This is why these nuc’s are necessary, selective use of nuclear power without the collateral damage that dropping a big one would cause. Makes sense to me, but hey I'm just a retired ex airborne / infantrymen. I would rather see the commander taken out on a position than slaughter the soldiers until he gave up. js

October 3, 2004 at 6:44 AM  
Blogger PureData said...

The real question is what is the energy of the nuke used to do? Blast effects or radiation? What about both?A radiation nuke that produced an energetic x-ray laser would heat a large tube of material for a long way into the earth. A follow-on blast strike a few seconds later would drive a shockwave down this tube. Just a thought.

Concrete does not melt. It decomposes into its chemical parts. Most rocks will melt, but some won't.

Would a simple shaped charge Nuke produce a kinetic molten slug? Where will you get the momentum to drive this slug? Will the slug work in such a hypershock environment? Could the underground bunker be designed to deflect this slug around it? Or could a carefully chosen geological stratum over it act like the composite armor does on tanks?

The Russians have developed small non-fission nukes recently that have little radiation. We have them, too.

The Russians also (conveniently) have a lot of handy codes around for estimating effects of nuclear packages on natural and man-made substances. Here is a peaceful application.

And then, there are the pure-fusion devices. VERY hard to detect. Think 9/11 was bad? Someone could construct this in a warehouse and leave.

October 4, 2004 at 2:28 PM  
Blogger PureData said...

Very interesting articles. The necessary condition for a non-fissionable nuke is the high-energy explosive.

The blast pressure is a square of the density of the explosive. If you double the density of the explosive, the blast pressure quadruples.

Imagine if you could replace carbon, oxygen, and nitrogen with elements further up the periodic chart with the same chemical properties as those in Cubane?

So, instead of 500 kbar, you go with something 20 times denser and you now have 500 * ( 20x20 ) = 20,000 kbar or 20 million bar. This is half the way to spontanous fusion at 45,000 kbar. (?)

Add in a trigger to kick off fusion at a lower pressure (temperature ) and you are done.

Of course, if you could make the explosives, why not just use them. A pound of this stuff would be like 1000 pounds of TNT. A few pounds in a shaped charge could bring down just about any structure.

October 4, 2004 at 3:01 PM  
Blogger PureData said...

Bingo. Very dense explosive.

Red Mercury

All you need is a highly motivated, brilliant Sociopath and a bit of infrastructure.

October 4, 2004 at 3:11 PM  

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