Fact Check UCS Nuclear Bunker Buster Anti-Aurgment

[Mr Bean]

First off the Union of Concerned Scientists put togther a slick animation aginst using Nuclear Bunker buster stype weapons.

I watched it, on first past it seemed good and was well on it's way to swaying me... except the primary assertion of the entire aurgment is that Bunker buster style weapons can only penetrate dozen's of meters down.

Except... our conventional bunker busters were supposed to be able to penetrate hundreds of meters and I've heard stories of several destroyed bunkers from Saddam's era when our inspectors went in to do post assesment on the weapons we droped on the night of the invasion when we attempted to kill Saddam and his boys before the war started.

So how deep can we drop a bomb before it goes off?

[kheegster]

I'm personally surprised that they're talking about MT yield weapons. I thought that RNEP warheads would be within the 10s of kT range?

[SirNitram]

Depends on the make of the bomb. There's new ones being developed now. The Army is apparently up to something called the 'Deep Digger', down to 30 feet. Lockheed wants to make one which uses a sheath of gas to somehow get far superior penetration, ten times the norm. I guess it's some kind of supercavitating missile?

The RNEP's been cancelled, as well. I think the animation, while sensible and accurate by the numbers, is based on the prattle about nuking Natanz. Yea, sure you are. THat's why the RNEP was junked, right? For those who might want a pic, Link to one of the League of Atomic Scientist's blogs... Specifically, a pic of Natanz.

Yes, the centrifuges are underground. I see plenty we could ruin without nukes, to say nothing of the effects of explosions going off while centrifuges being pumped full of uranium in gas form are being spun at top speed.

[Lord of the Abyss]

Except... our conventional bunker busters were supposed to be able to penetrate hundreds of meters and I've heard stories of several destroyed bunkers from Saddam's era when our inspectors went in to do post assesment on the weapons we droped on the night of the invasion when we attempted to kill Saddam and his boys before the war started.

I'm no expert, but I've heard it claimed that nukes are simply more delicate than non-nuclear explosives. A tiny deformation in the shaped charges around the fissionables means a fizzle instead of an nuclear explosion.

[AMX]

Except... our conventional bunker busters were supposed to be able to penetrate hundreds of meters...

Except, of course, they don't.

Thanks to Nit for reminding me of the correct search term to google it:

Deep Digger is different. It does not depend on the kinetic energy of the warhead at all – in fact, it parachutes down. Then it stars drilling. The weapon is limited only by how deep the drilling process can go, which is a matter of how deep it can ‘muck’ (clear debris from the shaft). And although the details are classified, that is much, much deeper than any kinetic weapon will ever go. In the tests last year, it demonstrated a tunneled down ten meters -- about 50% more than the BLU-113, which is the current record holder.

Checking the included link, we find this:

The Guided Bomb Unit-28 (GBU-28) bomb is designed to penetrate hardened targets before exploding, capable of penetrating 100 feet of earth or 20 feet of concrete.

So, no "hundreds of meters".
In fact, it barely qualifies for "hundreds of feet".

[The Yosemite Bear]

so where's a "tall boy" when we need one?

[AMX]

so where's a "tall boy" when we need one?

In the museum, where it belongs.
Tallboy could only penetrate 16 feet of concrete.

What you want is Grand Slam (at least 23ft).

[SirNitram]

A penetrating nuke is fundamentally a bad idea. You must reach a given depth, or the fallout is immense and destructive(Unlike an Airburst). And this depth is ridiculously hard to reach with the current designs, because as mentioned, a nuke is more fragile than other bombs.

Now, if Lockheed's Supercavitating earth-burrower(A concept which still baffles me, but I'll let the boffins work it out) mounted a small nuke, it might work. But then, why? Why burrow down and waste a nuclear explosion?

[phongn]

Now, if Lockheed's Supercavitating earth-burrower(A concept which still baffles me, but I'll let the boffins work it out) mounted a small nuke, it might work. But then, why? Why burrow down and waste a nuclear explosion?

Greater radius of destruction than a conventional bomb? The shockwave effects will propagate much further and perhaps destroy a large complex, whereas a smaller conventional bomb may not.

Yes, the centrifuges are underground. I see plenty we could ruin without nukes, to say nothing of the effects of explosions going off while centrifuges being pumped full of uranium in gas form are being spun at top speed.

But what if the centrifuges are off and only damaged? The US seems to want assured destruction of those facilities.

[SirNitram]

Now, if Lockheed's Supercavitating earth-burrower(A concept which still baffles me, but I'll let the boffins work it out) mounted a small nuke, it might work. But then, why? Why burrow down and waste a nuclear explosion?

Greater radius of destruction than a conventional bomb? The shockwave effects will propagate much further and perhaps destroy a large complex, whereas a smaller conventional bomb may not.

Presumably, if it's underground, it's going to be of a limited size. Being underground. Though don't air fuel bombs have that lovely overpressure shockwave without the small problem of lots of fallout?

Yes, the centrifuges are underground. I see plenty we could ruin without nukes, to say nothing of the effects of explosions going off while centrifuges being pumped full of uranium in gas form are being spun at top speed.

But what if the centrifuges are off and only damaged? The US seems to want assured destruction of those facilities.

I somehow doubt the entrance would be all that useable after a conventional flattening. But yes, they could be turned off and merely damaged. Which just sets them back all the further.

Shit, even if Natanz was completely obliterated, they could just rebuild. That won't change if we nuke 'em or conventional bomb 'em.

[Sea Skimmer]

So how deep can we drop a bomb before it goes off?

The best penetration we can get is about 40 meters though hard soil or clay and by that point even a tungsten bomb casing will be in the process of liquefying. Its no reason to object to this sort of weapon though, because the only other option is to drop multi megaton nuclear device fused for a surface burst. The 300kt max B-61-11 is more effective against a bunker then the 9 megaton B-53 device it replaced. End of argument.

The people who object to these things are usually the sort who object to the very idea of a nuke but they'll use any tactic they can to go against them. They of course never have better options. I love the fallout radius part, which provides absolutely no quantification and the assertion that its useless against many bunkers also with zero backing and no basis in reality. Those bunkers in Iran are perhapes within the scope of the 20,000 pound bomb the USAF is working on, any kind of burrowing nuke would crush them like a bug.

I'm no expert, but I've heard it claimed that nukes are simply more delicate than non-nuclear explosives. A tiny deformation in the shaped charges around the fissionables means a fizzle instead of an nuclear explosion.

That is true and is a problume, but its mostly dealt with by suspending the nuclear device on a shock absorbing framework inside the bomb casing.

[Sea Skimmer]

A penetrating nuke is fundamentally a bad idea. You must reach a given depth, or the fallout is immense and destructive(Unlike an Airburst). And this depth is ridiculously hard to reach with the current designs, because as mentioned, a nuke is more fragile than other bombs.

So what? The alternative is to just use a FAR larger nuclear bomb and burst it on the surface, which will still create a huge amount of fallout and throw that fallout higher into the atmosphere. Anyway, we set off the Sedan test without killing everyone in North America, sure did suck for one or two towns downrange though.

Now, if Lockheed's Supercavitating earth-burrower(A concept which still baffles me, but I'll let the boffins work it out) mounted a small nuke, it might work.

Nothing too complex about it in concept. The weapon is supercavitating because its to be surrounded by a thin shroud of gas as it penetrates, which substantially reduces friction.

But then, why? Why burrow down and waste a nuclear explosion?

Because there are bunkers in the world which are proof against anything less then a modest yield earth penetrate or an enormous surface burst. A few Russian bunkers are proof against even direct hits form high yield devices but we don’t need to worry about them that much. Also keep in mind that while its not that hard to find tunnel and bunker complexes, figuring out the internal layout can be a bitch. Iran was nice, its bunkers at Natanz are built with the cut and cover method, so we could still exactly what they built. However some other Iranian nuclear facilities are in tunnels and any really deep bunkers is going to be a tunnel. No good way exists to tell the layout, you can only get a rough idea of the size based on how much dirt gets dug out. Without precise data on the tunnel layout conventional bombs wont work, and even if you do get a hit you’ll only destroy part of the facility. The fun thing is, once you decide to dig deep enough that tunneling is more cost effective then cut and cover, there is little additional cost to go down 500 meters vs. the cost of digging just barely deep enough to warrant the tunnel. So some bunkers are absurdly deep and often tunneled under mountains as opposed to inside the mountain as the US foolishly built Cheyenne Mountain.

[phongn]

Presumably, if it's underground, it's going to be of a limited size. Being underground. Though don't air fuel bombs have that lovely overpressure shockwave without the small problem of lots of fallout?

Not neccessarily. Facilities like Zhiguli are quite large underground. FAEs are also somewhat fragile and require an optimal air mixture that might not be easy to attain in an underground environment. Currently the hope is that the superpenetrator nukes (if they work) will be able to burrow deep enough so that no fallout will occur - but as you noted, there is some controversy if they can get a nuke deep enough.

I somehow doubt the entrance would be all that useable after a conventional flattening. But yes, they could be turned off and merely damaged. Which just sets them back all the further.

Yes, but how fast to recover if the machinery is merely damaged versus totally destroyed?

Shit, even if Natanz was completely obliterated, they could just rebuild. That won't change if we nuke 'em or conventional bomb 'em.

Well, presumably this will be used in a general war scenario where they won't be able to rebuild anytime soon.

[WyrdNyrd]

I think a lot of the problem some people have with bunker-busting nukes is related to them not trusting The Powers That Be.

Sometimes there may well be no other way to destroy a bunker than to use an even dirtier high-yeild above-surface bomb. So then you do need a smaller "digger".

But I think what they're really worried about, is that the following mindset might develop: "These things are safe and clean! No fallout! So let's just use them every time we need to blow shit up!" It's the "if all you have is a hammer, everything looks like a nail" complex, with nukes!

This may seem like a ridiculous fear, but sometimes TPTB do make some scarily bad decisions, so that people will suspect them of being capable of any degree of stupidity.

[Sea Skimmer]

Presumably, if it's underground, it's going to be of a limited size. Being underground. Though don't air fuel bombs have that lovely overpressure shockwave without the small problem of lots of fallout?

An FAE dropped on the surface is useless against a bunker with decent blast doors. They are good for destroying a terrorist cave in the mountains, not properly built military facilities. The amount of power released is in any case much less then the punch of even a very small nuclear device, and there is no way to dig in the FAE warhead before it explodes to increase effectiveness.

I somehow doubt the entrance would be all that useable after a conventional flattening. But yes, they could be turned off and merely damaged. Which just sets them back all the further.

Smashing the entrance would just mean they have to dig it out, that's not going to be an overally long delay.

Shit, even if Natanz was completely obliterated, they could just rebuild. That won't change if we nuke 'em or conventional bomb 'em.

Which is why as I've said many times, any attack would have to be a full scale on aimed at crippling the entire Iranian military and industrial state.

[Illuminatus Primus]

Presumably, if it's underground, it's going to be of a limited size. Being underground. Though don't air fuel bombs have that lovely overpressure shockwave without the small problem of lots of fallout?

How is the fuel going to be spread through the air to be ignited and generated that shock wave...underground?

[MKSheppard]

Whatever points they made are pointless and not worthy of consideration after the trick they pulled with their graphic.

Yes, they thought that nobody would notice them inflating RNEP from a 5~ kiloton to a 1.2 megaton device in their web site; and then inflating the cratering radius and fallout in their nice flash animation to one equal to a 20 megaton device.

[MKSheppard]

Also, Nantaz, their example in the flash animation, was built by the cut/cover method of piling dirt on top of concrete bunkers.

I recall an early test of BLU-28 Deepthroat, the one we used in 1991 made of 8" barrels; we dropped it out in nellis; and after digging 100~ feet down and not coming close to the bomb; we gave up on retreiving it for damage analysis.