Senator Pete Domenici (R-NM) sent out a press release announcing that the Appropriations Conferees “have agreed to drop funding for continued research on the Robust Nuclear Earth Penetrator (RNEP) project…” The House had eliminated DOE funds for RNEP, while the Senate recommended $4.0 million.
The real shock: NNSA asked the conferees to do it.
Apparently, there has been some sort of policy change to focus on conventional weapons. (DOD will apparently continue its earth penetrator work, focusing on conventional earth pentrators. Here is one suggestion.)
F. Josef Hebert at AP managed to get an “administration official” to confirm “that a decision had been made to concentrate on a nonnuclear bunker-buster.”
It may just be a coincidence, but David Ruppe at Global Security Newswire recently revealed the forthcoming Doctrine on Joint Nuclear Operations might omit some controversial language regarding the use of nuclear weapons.
A sudden burst of sensibility all around.
Oh, and some moron at the BBC called RNEP a “mini nuke.” Sigh.
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http://www.spiegel.de/wissenschaft/mensch/0,1518,druck-381788,00.html
— anon. · Oct 26, 06:38 AM ·
— Leslie · Oct 26, 09:44 AM ·
I was under the impression that the GBU-28 already worked like this – at least in the ‘stable mode’.
The servo controls they describe to stabilize the path of this ‘unstable munition’ are nontrivial. I don’t think it would work in anything but extremely uniform soil – and countermeasures herein would be possible.
Perhaps a passive stabilization scheme of some sort using the fins would be better.
Rock or concrete would be a much more difficult application as well.
I am dubious that the improvements will be dramatic – perhaps under ideal conditions.
— John Field · Oct 26, 09:54 PM ·
The reason why many [subsonic] projectiles have slender pointy noses is that it creates tensile stresses somewhat in front of the nose. These tensile stresses cause fracture allowing further penetration. Think of a nail.
For materials without fracture – e.g. fluids – this is unnecessary, and a greater concern is doing work on the fluid from inertial forces – such as boundary layer drag or boiling due to cavitation. In this case, a thinner and shorter boundary layer is desirable. More like a submarine’s nose.
The two effects result in competing design objectives – sharper or blunter. Supercavitating shapes are designed to be blunt in a sort of optimal way to minimize boundary layer.
In sand, of course, fracture is unimportant, and layer drag needs to be minimized, so these supercavitating blunt shapes make sense.
For rock, it is a different story. A bomb falling from 30,000 feet will land at about 422 m/s not including drag – that corresponds to an inertial pressure in rock of about 36,000 psi. Good rock will shear somewhere up around this pressure as well, and break in tension quite a bit lower. So, for rock and free falling projectiles, we want sharp noses. Supercavitating shapes are not used, for example, for powder driven concrete nails.
Now, if there is a rocket on the end of the penetrator, and the speeds go way up – maybe above mach 3 or so – then inertial pressures become more important again and we might want to go back to blunt[in rock]. There are some problems in doing this, however – but that is another story.
Anyway, perhaps this is what they are up to.
— John Field · Oct 27, 09:12 AM ·
I don’t know how to calculate that, but perhaps someone here can help.
In any event, I’m very, very skeptical that a conventional weapon can be made effective against a bunker even 100 meters deep in competent rock, let alone ones deeper or protected with burster slabs and the like.
— Allen Thomson · Oct 27, 05:03 PM ·
I am simply relating that the depth of penetration can depend significantly on design – and in subtle ways.
To me, 100 feet in sand is about the upper end of what seems conceivable.
I think deep bunkers in rock are pretty much off limits – unless we change the rules somehow.
Nonetheless, there is a still big capability difference between 50 feet of hardened concrete and 20 feet.
Fundamentally, there is not really an energy constraint on the penetration. In theory, a sharp chisel blow can drive a crack all the way down through the rock. In reality, the penetrator pulverizes everything in its path – and that does take lots of energy.
You see, the answer depends on the design of the penetrator, and the result can vary by an order of magnitude or more. If the rock breaks up into golf ball sized lumps, that’s a lot better than if it turns to dust. Also, if the damage zone is only as wide as the bomb, that’s a lot better than if it’s 3 feet around.
A heavy bomb can make a swimming pool sized hole in the ground. That volume in the ground – if projected into a slender tube deep into the earth – can go pretty deep.
The $64 million question is: How wide an area gets pulverized? And how big are the pieces?
— John Field · Oct 27, 09:45 PM ·
Supercavitaballisticexplodeocious
— mark gubrud · Oct 29, 01:54 PM ·