"Dave Eadsforth" wrote
Paul F Austin writes

"Dave Eadsforth" wrote


Was that because the blast hit the tunnel head on? If so, I could
imagine the VERY hot gases etc going straight down the tube. However,
if the complex were built of tunnels that zig-zagged sharply, the nuke
would move enough rock to crush tunnels at 90 degrees to the explosion
and any hot stuff entering a tunnel head on to begin with should be
blocked when a section at 90 degrees to it collapsed.

The test galleries for UGTs were layed out herringbone fashion along a
main
tunnel. Each test gallery could "see" the nuclear explosion so that the
test
articles could be exposed to both thermal and nuclear (the two blur
together
somewhat) radiation.

So; exposed on purpose. If thin tunnels were zig-zagged like a WWI
trench system with bulkheads between, I guess that might help a bit.

That's direct nuclear and thermal radiation, more or less direct line of
sight. There's also the fireball, which can expand around corners. I think
that if a nuke is _in_ the bunker with you, that you're in trouble. Blast
doors may contain the effect but life's hard. The problem is to _get_ the
nuke onto the target. Underground targeting is pretty much impossible. There
are some signatures from shallow excavation but they're subject to spoofing
and maskirovka. How many nuclear munitions are you going to be allowed to
use in a hunt n' peck strategy?


The blast doors were build to withstand the
overpressures that the bomb would generate. In the UGT where they failed,
it
was the closing mechanism that failed to operate rather than the doors
being
breached.

Bet that annoyed some designer...

As I understand it, the argument for building penetrating nuclear weapons
is
that the weapon will volatilize any agents (chemical or biological) that
are
present before they can leak out.. That seems iffy to me. As far as
"crushing" tunnels, there won't be much crushing going on much outside
the
facture zone, which for a full yeild B61 (300KT) is about 900 feet
radius.
Any bunker more than a few multiples of that distance away will get a
hellacious shock but if competently designed, should remain intact.

Hmm, nuke has to be accurately targeted then - I suppose they might run
to the cost of GPS guidance for this type of bomb...

No, it's not so much the accuracy required of the weapons as it is accuracy
in target detection. From Glassstone, "relatively small, heavy, well
designed structures" suffer light damage at 2 1/2 times the apparent crater
radius (2200 feet in this case). This is damage to the bunker itself and not
the contents.


But the shock of the explosion would cause those bunkers safely beyond
the fracture zone to rock and roll like hell. I read somewhere that the
interior facilities at Cheyenne Mountain were resting on humungous sized
springs - is that the only option for resilience?

There will be two zones around a nuclear explosion: the area near the
fracture zone where any bunker will collapse and and area around that where
the contents of the bunker won't survive. The outside that, dust trickles
out of the ceiling, everyone hunches their shoulders and then straightens up
and carries on.

Again, from Glasstone, internal equipment will be destroyed by a 7g shock if
not shock mounted and about 60g if it is. The modelling of shocks on
equipment is complex and outside a USENET discussion.


Enthusiasts keep ignoring these unpleasant facts and suppose that
ground-penetrating RADAR or some other MagicTech will give the attackers
x-ray glasses so that they can see more or less where the bunkers really
are. Fat chance. I mentioned up-thread that modern tunneling equipment
can
drive a shaft 200 feet a day. With a year to prepare, without superb
HUMINT
it's all going to be a mystery to the targeters, even with nukes at their
disposal.

So, what to we conclude when a country orders a set of tunnelling
equipment, ostensibly to build a metropolitan subway, and then gives up
'because the geology is all wrong' (um, wouldn't that have come out of
the original survey?)? Is the kit sitting in a junkyard - or is it now
underground, doing something else?

North Korea for instance doesn't even pretend to be building subways.
They've been tunneling for fifty years and the area near the DMZ (and under
it) is honeycombed with tunnels.

This is a hard problem and one that the puissance of nuclear weapons doesn't
solve.