[107789] in Cypherpunks
CDR: Re: [Fwd: C-Subs, a very scary thought] (fwd)
daemon@ATHENA.MIT.EDU (Jim Choate)
Sat Jan 23 21:12:51 1999
From: Jim Choate <ravage@EINSTEIN.ssz.com>
To: cypherpunks@EINSTEIN.ssz.com
Date: Sat, 23 Jan 1999 20:00:50 -0600 (CST)
Reply-To: Jim Choate <ravage@EINSTEIN.ssz.com>
----- Forwarded message from Steve Schear -----
Date: Sat, 23 Jan 1999 09:11:55 -0800
From: Steve Schear <schear@lvcm.com>
Subject: CDR: Re: [Fwd: C-Subs, a very scary thought]
>
>Not that steel vs. concrete has anything to do with showing up on sonar:
Perhaps they plan to include air bubbles to increase the sound absorbtive
properties, though voids are generally not a good thing in composites.
----- End of forwarded message from Steve Schear -----
Actualy it isn't absorption so much as dispersion. The bubbles cause the
sonar wave to be broken up by reflection and refraction. This is the theory
behind the Prairie Masking technique. The submarine releases a very fine
mist of bubbles about itself. As the sonar wavefront comes into them it is
broken up and the reflections are non-coherent and nor correlatable to the
original ping. The problems is that it's quite detectable on passive sonar
and it plays hell with the ballast air supply.
If you have access to a compressor, an air hose, a swimming pool, some sort
of target, and a sport sonar you can experiment. Put the sonar in the deep
end. Then move the target around in the shallow end and you'll see a
reflection. Connect hose to compressor and poke small holes into it, lots of
them. I used a small drill bit and power drill. Now lay the hose across the
pool bottem (I had to use weights to keep mine down). Turn on the compressor
and give it a few minutes, you will have to adjust the pressure. At some
point you should see a bubble wall form and the reflection from the shallow
end stop at the bubble fence. I've always felt it would would make for a good
sonic 'fence'across the mouth of a harbor.
It may be worth noting that several of the anti-sub techniques begin with
the codeword Prairie.
____________________________________________________________________
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The Armadillo Group ,::////;::-. James Choate
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