Path: utzoo!attcan!utgpu!watmath!att!cbnews!military From: denbeste@BBN.COM (Steven Den Beste) Newsgroups: sci.military Subject: Re: mines Message-ID: <11644@cbnews.ATT.COM> Date: 22 Nov 89 04:13:56 GMT References: <11549@cbnews.ATT.COM> <11600@cbnews.ATT.COM> Sender: military@cbnews.ATT.COM Organization: Bolt Beranek and Newman Inc., Cambridge MA Lines: 60 Approved: military@att.att.com From: Steven Den Beste In article <11600@cbnews.ATT.COM> oakhill!serval!seningen@cs.utexas.edu (Michael Seningen) writes: > > >From: oakhill!serval!seningen@cs.utexas.edu (Michael Seningen) >If my fields classes are still with me. The hull of a sh >ip is such a sufficent cunductor plate for Electromagnet >ic waves that the magnetic field of the earth is altered > due to the hull and therefore the mine can detect this >change in magnetic flux and detonate. > >Mike Seningen >oakhill\!seningen\!serval It's been tried, and it doesn't work. Going into WWII, the U.S. submarines had a torpedo with a relatively small warhead (as compared to the Japanese or Germans). To sink a ship with such a small warhead would take many torpedoes, and for the first couple of years of the war torpedo production wasn't fast enough. The torpedos had been designed to use a "magnetic exploder". Thus instead of depending on multiple hits just below the surface to flood enough water-tight compartments to sink the ship, the idea was to let the torpedo run very deep, under the keel of the target. At such a depth the water pressure would act as a good damper for the warhead, and the resulting explosion would break the keel of the ship. Normal stresses would then break the ship in half. The problem with it is that the magnetic fields vary greatly from ship to ship, or even from place to place on the same ship. Early in the war, in '42 particularly, the sub commanders came back from patrol claiming to have sunk many Japanese ships because they lauched a spread of two or three torpedoes and a couple of them exploded (they heard them while going deep). What was ACTUALLY happening was that the torpedoes were exploding too soon, scaring the living hell out of the sailors on the target ship but not otherwise harming them. (This wasn't helped at all by the fact that the torpedoes routinely ran a couple of meters lower than they had been set to run.) There's no reason to believe that a mine using a magnetic fuse would work any better. On some ships it would explode too far away to do any damage, while it would ignore some others entirely. The other possible use of such a detector would be for the kind of mine that sits on the bottom of a shallow waterway (such as the Suez canal) and only releases to come to the surface when a ship passes. Thus such a mine would be immune to helicopter-based anti-mine activity. Presumably then the mine would use some other way of exploding such as a contact fuse. I'm not sure that this would be of any use, since the passing of a normal mine-sweeper would presumably cause release of the mines, which would bob to the surface after the mine-sweeper had already passed, and would be caught by the (I don't know the term - the things a mine-sweeper tows to catch and detonate the mines). Steven C. Den Beste || denbeste@bbn.com (ARPA/CSNET) BBN Communications Corp. || {apple, usc, husc6, csd4.milw.wisc.edu, 150 Cambridge Park Dr. || gatech, oliveb, mit-eddie, Cambridge, MA 02140 || ulowell}!bbn.com!denbeste (USENET)