2012/09/05

Nuke modernisation gone stupid

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From the journal Foreign Policy about a U.S. modernisation program for free-falling nuclear bombs:

Consolidating four modifications into a streamlined bomb is a pretty ambitious work plan. But, as if that weren't enough, the Air Force wanted the proposed B61 Mod 12 to be more accurate than the original B61. The major limitation on accuracy has always been the parachute that slows the bomb's descent, largely to prevent the bomb from splattering when it hits the ground. Parachutes, though, mean the bomb drifts a bit in the wind. The Air Force wanted to replace the parachute with a guided tail kit, like that used on precision munitions. But removing the parachute introduced a new complication: An atomic bomb dropped without a parachute will explode before the airplane is safely away. That means NNSA must also redesign much of the packaging and components to survive "laydown" -- i.e., thudding into the ground and then exploding a few moments later.

This made me think "idiotic idea" immediately. 
I wonder why?

There are two main considerations for the location of an explosion: height and surface composition. A nuclear weapon detonated in the air, called an air burst, produces less fallout than a comparable explosion near the ground. [...]
For subsurface bursts, there is an additional phenomenon present called "base surge". The base surge is a cloud that rolls outward from the bottom of the subsiding column, which is caused by an excessive density of dust or water droplets in the air. [...]
For subsurface land bursts, the surge is made up of small solid particles, but it still behaves like a fluid. A soil earth medium favors base surge formation in an underground burst. Although the base surge typically contains only about 10% of the total bomb debris in a subsurface burst, it can create larger radiation doses than fallout near the detonation, because it arrives sooner than fallout, before much radioactive decay has occurred.

The militarily "useful" effects of a nuke are its overpressure wave, heat radiation and the first few seconds of nuclear radiation. All that comes afterwards is unwanted dirt. This 'upgrade' seems destined to make the nukes dirtier, more troublesome.
An airburst is not only less dirty, but also more effective. Hilly and rolling terrain diminishes ground burst effects on ground troops and surface objects and doesn't create the constructive interference blastwave that  airbursts can produce.

S Ortmann
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5 comments:

  1. But a "less effective" nuke, closer to the target, is (in some circumstances) more effective.

    I believe the US retired some airdropped landers a few years ago, designed to land on top of deeply buried soviet bunkers, and collapse the caverns on top of them.

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  2. They could have made steerable chutes or simply have stuck with wind-correcting glide bombs.

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  3. The U.S. tactical nuclear "arsenal" is a mess. And the concentration on that free falling bomb is dangerous as it limits operation flexibility.

    Re the modifications: Don't forget that there is a whole huge organisation plus industry behind that effort with Mod12 the only job in sight ... Of course they milk it to the max!

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  4. The question I have is it's a nuke how many targets out there that if it misses by a few meters will not be destroyed. I would say very few and in that case maybe a gps guided one would be better. The real problem has been congress not wanting to make "new" weapons and saying only so many updates can be done before it is considered a new weapon so they can say we haven't made any new nukes in years.

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  5. All this nuke modernization makes me wonder about a conventional approach. The explosive destruction radius of a nuke is not great and gets diminished by cubic law over distance. The grape bombs were a conventional idea to create a similar destroyed area. If you take grape bombs to the extreme you arrive at thermobaric weapons that create lots of energy emitting particles spread in a volume.
    Improving the blast to be more directed in energy transfer on the surface and not dissipating much energy upwards into a mushroom and the gap between uncontrolled massive energy flow nukes and designed conventional explosions will narrow down. Add some radioactive material as part of conventional strikes and you have enough dirtyness to act as force de frappe. Nukes become increasingly dated and expensive with uses limited to taking out bunkers and scaring territorial invaders.
    The problem is that wars can be fought over network access and intellectual properties with territory devoid of natural resources, such as Europe having little meaning except for housing humans with know-how. Occupation of that territory would be only one means of acquiring that know-how.

    Kurt

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