Yonatan Zunger’s Blog

[politics filter]

Interesting article in the NY Times today about the dawning of a second nuclear age, characterized by a much broader (although not as deep) proliferation and the new challenges posed. There’s nothing particularly new or earth-shattering in it, but it does bring up a point which hasn’t been discussed an awful lot, namely the effort the US government is putting in right now towards the design of low- to medium-yield, deep-earth-penetrating nuclear weapons.

It’s interesting because it’s the first design push for a new kind of nuke since the Cold War, and many people are concerned that it could lead to a new arms race, or lower the bar to first use of nuclear weapons, and so on. I’m curious to know what people here are thinking about this issue. I’ve got my own — tentative — opinion, but in the interest of not pre-emptively biasing the conversation, I’ll hide it behind a

So my own thoughts: I actually think this is a good idea for a couple of reasons. First, the increasing popularity of bunkers as a place to hide one’s command and control and major military facilities (Libya, Iraq and North Korea are particularly famous in this regard) has the potential to create a deterrence gap no less serious than a nuclear weapons imbalance. If a country feels it’s immune to attack (and to detection by spy satellites!) it’s more likely to invade someone else, and so on. Deterrence works only if both sides know they have weapons to point at one another.

Implicitly, this only applies to countries with which we have some notion of mutual deterrence. This is actually a relevant way of thinking because the number of countries with which deterrence is a major manner of engagement is rising; if North Korea were to test a nuke publicly tomorrow, we would be playing in a very different game with them, and it would be one very familiar from the days of the Cold War. Even if they aren’t big enough to threaten all-out mutual anihilation, they don’t have to be; they just have to be able to aim at San Francisco. Or Tokyo. (Note that the latter is part of why ABM defense isn’t really worth as much as it sounds, even if it works)

Second, it responds to a genuine military necessity. One way or another, we are going to be involved in wars in the future, and these wars will almost certainly involve enemies sitting in hardened bunkers. I’ve sat down and done calculations on this, whether it’s possible to penetrate a bunker in any reasonable manner with non-nuclear explosives; the answer appears to be “yes, if you consider sending several B-52’s loaded to the gills with explosives, and dropping them all on precisely the same place to be reasonable.” This is still an option, and it’s still on the table; but it’s not practical for any large-scale situation. So yes, if people are going to be shooting at us from underground, we’d better have a way to shoot back.

(Implicit in that is the notion that not all wars we get involved in will be immoral. I say this because there’s an obvious response that simply wanting to be able to kill people more effectively isn’t a reasonable justification for anything. My response is that there may well be legitimate reasons for us to go to war in the future, and in those wars, people are likely to be hiding in bunkers. We need to have some preparation for that now, since these things can take several years to design properly)

Third, there’s a specific use of earth-penetrating nuclear weapons which nothing else can do: Destruction of nonconventional (particularly biological) weapons facilities. Striking these with conventional weapons, even if one hits them with enough to destroy them, has the nice extra effect of spraying their contents all over the place. In order to avoid doing this, the initial impact which strikes the building must deliver enough absorbed heat energy prior to the first shock wave (the one which will scatter all the contents) to effectively neutralize any biological agents. First of all, this means one needs a single big explosion instead of several small ones, unless by some magic all of the small ones are simultaneous to within a few milliseconds. Second, it’s not hard to calculate what sort of energy yield the explosion needs to achieve this – make an estimate of the facility size, consider the heat absorption of these biological molecules, and how much energy each one needs to neutralize it (say 3 or 4 eV per molecule, or maybe 100-200 eV for a complete cell) – and one quickly finds that the energy level is that of a nuclear weapon, and nothing else.

Finally, there’s the major criticisms of this: (1) It will lead to a new nuclear arms race; (2) It will lower the bar for first use of nuclear weapons; (3) Any design of new nukes is a bad thing.

(1): The new nuclear arms race already started. North Korea is working quickly on its bombs, Iran is working on its own, everybody and their mad bastard cousin seems to want their own nuclear weapons. As the NY Times article pointed out, these people have much lower bars to first use than we do. Us staying out of such a race would simply leave us with relying on Cold War-era weapons in a very different world; see (3) for why that’s bad.

(2): Not really. If simply having small-yield nukes would lower the bar, then we’re too late for that. We have remarkably small-yield nuclear weapons, ones that can be easily carried and set by an individual.

(3): Again, not really. Right now, our nuclear arsenal is in two categories: strategic and tactical. Strategic nukes are megaton+ thermonuclear warheads strapped to long-range missiles, designed to hit ICBM facilities and cities. Hardly a subtle weapon. Tac nukes are, if anything, worse; in the 10-100kton range, attached to artillery shells, designed to hit incoming troop formations and surface-level hardened facilities, and dirty as all hell. (It’s very hard to fit a “clean” bomb into an artillery shell form factor. The need for a shotgun design is part of that problem) If we’re going to need nukes for anything, I’d rather have purpose-designed ones that minimize side effects.

Of course, the really big things that have to be ensured about these designs is that they’re optimized to minimize immediate and delayed secondary destruction – fallout, soil contamination, and so on. This means designing bombs to do the maximum damage with the minimum force (explosion shaping, for example) and minimizing “dirt” in the reaction. The latter is technically achievable: Using high-boosting designs, trying to build what’s essentially a small H-bomb rather than an A-bomb, we can cut down radiation immensely. The US already has the (granted, somewhat dubious) honor of making far and away the cleanest nuclear weapons in the world.

Not that any of this is a good thing. But it’s going to be necessary sooner or later, and better to have the right tools prepared than to blunder in with nuclear artillery or some such.