budden@manta.nosc.mil (Rex A. Buddenberg) (11/21/89)
From: budden@manta.nosc.mil (Rex A. Buddenberg) Mark-Jason, A magnetic mine is one that contains a magnetometer (like you pocket compass, except when the needle moves it closes the firing circuit) that detects the magnetic signature of a passing ship. These mines, and magnetically exploded torpedos, were state of the art at the beginning of WWII. Other actuating mechanisms (for both mines and torpedoes) include: contact -- hull hitting the mine explodes it. See Iran Ajr in Persion Gulf along with USS Roberts. acoustic -- listens for propellor noises -- can be quite discriminating in telling the difference between different kinds of ships. pressure -- passing ships create pressure waves, like air pressure on your eardrums creating sound. various timing and remote control mechanisms. Minesweeping consists of simulating these signatures without actually hazarding the ships that normally make said signatures. So mines have gotten more intelligent over time -- it's hard to fake more than one of these signatures at a time. Controllers also have counters so that x ships pass over the top until everybody is sure the minefield has been cleared...then whammo. Rex Buddenberg
seningen@cs.utexas.edu (Michael Seningen) (11/21/89)
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. An interesting counter-measure was to run a wire or seri es of wires around the hull (i'm not kidding) and set up an electric field of just the right value such that its corresponding magnetic field (which is 90 degrees wrt th e electric field) that cancels the hull effect on the ear ths magnetic field. I know the general jist is right, my details and memory o f fields (the nightmares are still there) are fuzzy. May be someone who taps this area more often than I can give a better explanation. Mike Seningen oakhill\!seningen\!serval
pierson@cimnet.dec.com (11/21/89)
From: pierson@cimnet.dec.com In article <11549@cbnews.ATT.COM>, entropy@pawl.rpi.edu (Mark-Jason Dominus) writes, in part: .. > >What is a magnetic mine? How does it work? > A (sub sea) mine triggered by a change in the local magnetic field, assumed to be caused by a large mass of metal (a ship...) passing by. Initial units used (basically) a delicately balanced compass needle, free to swing on all axes. When it swung, it closed contacts to an electrically fused primer. Current ones are presumably more sophisticated. Until understood, hard to sweep. Later swept by wooden hulled ships, and low flying aircraft fitted with large electromagnets. Also "defeated" by degaussing (demagnetizing) the ships expecting to pass near such mines. Still in use. Another advantage is that they can't be swept by towed paravane gear. Also, can be laid in shallower water than tethered contact mines. Other mine fusing schemes: Contact: Traditional, requires mine to be close enough to surface for ship to hit it. Observation/Controlled: Earliest. Shore station fires mine when target ship is over it. Useful for coast defense. Sonic/Acoustic Triggered by waterborne sound Thanks dave pierson |The facts, as accurately as i can manage, Digital Equipment Corporation |The opinions, my own. 600 Nickerson Rd Marlboro, Mass 01752 pierson@cimnet.enet.dec.com
denbeste@BBN.COM (Steven Den Beste) (11/22/89)
From: Steven Den Beste <denbeste@BBN.COM> 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)
greg@ncelvax.UUCP (Gregory K. Ramsey) (11/23/89)
From: greg@ncelvax.UUCP (Gregory K. Ramsey) In article <11600@cbnews.ATT.COM>, oakhill!serval!seningen@cs.utexas.edu (Michael Seningen) writes: > > > From: oakhill!serval!seningen@cs.utexas.edu (Michael Seningen) > An interesting counter-measure was to run a wire or seri > es of wires around the hull (i'm not kidding) and set up > an electric field of just the right value such that its > corresponding magnetic field (which is 90 degrees wrt th > e electric field) that cancels the hull effect on the ear > ths magnetic field. > The Degaussing or deperming of Navy ships is of no small importance to the US Navy. All Navy ships (at least those considered "combat ships") are depermined soon after they are commissioned and after major overhauls. Depermining involves measuring the ships magnetic flux and then taking the ship to a facility where they wrap huge cables clear around the ship making a huge coil. This is a huge all hands effort on a destroyer (all hands on my last ship included all but the CO and XO), I shudder to think what is like on a carrier. (I've only seen pictures of that) Then the cables are charged in somesort of pattern. The intent is to reduce the ships normal field as much as possible. Then as Michael said, their are permanent cables wrapped around the inside the ship around each of the 3 axis (x,y,z). These can be energized by equipment on board the ship. The purpose is of course to nuetralize the ships field. These charges will be adjusted depending on a number of factors including the ships position relative the earth's magnetic fields, it's course and speed. And then you can multiply the complexity probably 10x if the ship is a minesweeper. Greg -- greg@ncelvax.uucp ___ Greg Ramsey _n_n_n____i_i ________ Naval Civil Engineering Lab (____________I I______I Code L54 805/ /ooOOOO OOOOoo oo oooo Port Hueneme, CA 93043 982-1272
mmm@apple.com (11/23/89)
From: portal!cup.portal.com!mmm@apple.com Ah, yes. Dr. Bush had a good story on this topic. Quoting from his autobiography: "An example of this latter kind of stumbling block appeared during the last war with the marine torpedo. An entrenched group in charge of this weapon not merely wished no civilian aid; it tolerated no interference by the rest of the Navy. So we shipped torpedoes to the Pacific, our submarines carried them on arduous and dangerous voyages and fired them at enemy ships, and the torpedoes would not go off. The torpedoes' speed had been increased, and the firing mechanism, having thus less time in which to function, became crushed before it operated. It was also improperly oriented--crosswise instead of end on. There had apparently been no tests to reveal the defect. Some of the mechanisms were altered at Hawaii by the Pacific fleet itself, and there were protests that this action was highly irregular. There is another story (I cannot vouch for this one) that magnetic torpedoes had been designed to explode under a ship by reason of the alteration of the vertical component of the earth's field, and that when used in low latitudes, they ran unexploded under the enemy ship because at low latitudes there was no vertical component to speak of." Vannevar Bush cites another reference on this topic: HISTORY OF U.S. NAVAL OPERATIONS IN WORLD WAR II, vol IV. by Samuel Eliot Morison, 1949.
Brian Ross (bxr307@coombs.anu.oz) (11/24/89)
From: Brian Ross (bxr307@coombs.anu.oz)
Whereas Steven Den Beste (denbeste@BBN.COM) believes
that magentic mines don't work the Allied experience with the
German ones in WWII indicates otherwise. However both magnetic
and acoustic influence detonated mines are generally only useful
in shallow water (lying as they do on the floor in most cases,
although I don't see why a tethered variant cannot be built,
although a minesweeper would then be able to cut the tether),
because they rely upon very weak forces to activate their fuses
which attenuate with distance.
There has been rather renaissance in mine warfare in
the last ten years. With the onset of considerably more computer
power with the micro-chip the mine has also tended to become a
more "smart weapon". In addition the mine's reach has been
increased with addition of a torpedo attach to it. The mine lies
on the seafloor (or tethered at depth, well below the surface)
and contains a computer which can be activated remotely. The
computer controls various sensors such as magnetic, acoustic or
pressure (a considerable change in pressure is associated with
the wake of a passing ship) and when these detect a target the
mine releases an acoustic or wire guided torpedo. This is then
guided to the target by computer. Such a mine could be enplaced
well before hostilities commence and could be activated when the
time is right. It is this sort of mine which bring shudders to
the minds of naval planners.
In reference to the use of Magnetic Pistols to fire
torpedo warheads, the Germans were quite successful by building
on their experience gained with the Magnetic influence mine. On
the otherhand the US Navy's efforts where as already related largely a
failure until late in the war. In addition the Germans actually
fielded such things as Acoustic homing torpedoes (I think they
were called "nixie" going by memory) and Acoustic influence
mines (nicknamed "oyster" mines by the Allies). Both of which
caused considerable trouble in the last year of the war.
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|
Brian Ross |Snail Mail:-
"Bill Bracket the self-made man who came|
in a a packet" | Brian Ross
----------------------------------------| Sociology Dept.R.S.S.S.
E-Mail Addresses:- bxr307@coombs.anu.oz | Australian National University
| CANBERRA,A.C.T.,2601,
bxr307@csc.anu.oz | AUSTRALIA
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-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-henry@zoo.toronto.edu (Henry Spencer) (11/27/89)
From: henry@zoo.toronto.edu (Henry Spencer) >From: Brian Ross (bxr307@coombs.anu.oz) > There has been rather renaissance in mine warfare in >the last ten years... Well, relatively speaking. There is still a major problem in getting funding or support for mine warfare, best expressed by the standard comment on the subject: "nobody ever got promoted for commanding a minefield". Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu
ferguson@maitai.src.honeywell.com (Dennis Ferguson) (11/28/89)
From: ferguson@maitai.src.honeywell.com (Dennis Ferguson) In article <11730@cbnews.ATT.COM> henry@zoo.toronto.edu (Henry Spencer) writes: > >>From: Brian Ross (bxr307@coombs.anu.oz) >> There has been rather renaissance in mine warfare in >>the last ten years... > >Well, relatively speaking. There is still a major problem in getting >funding or support for mine warfare, best expressed by the standard >comment on the subject: "nobody ever got promoted for commanding a >minefield". > I've been following the mine discussion for several days now and no one has mentioned the 'renaissance' in *land* mine warfare with programs such as Antihelo Mine and Wide Area Mine. In both cases these are very significant developments in mine warfare and may be the beginning of true autonomous (ie robot) weapons. The first has to be Tacit Rainbow which is a truly mobile autonomous mine. Dennis
mmm@cup.portal.com (12/04/89)
From: mmm@cup.portal.com I remember seeing pictures of nuclear mines, both for land and sea. (It was in an article about a nuclear weapons museum on a military base in New Mexico.) Can anyone enlighten me as to what these were intended to be used for? (Can you imagine a truck running over a mine, then a nuclear explosion takes place?) Were these things ever put into production?
pierson@cimnet.dec.com (12/05/89)
From: pierson@cimnet.dec.com In article <11917@cbnews.ATT.COM>, mmm@cup.portal.com writes... >From: mmm@cup.portal.com >I remember seeing pictures of nuclear mines, both for land and sea. (It was >in an article about a nuclear weapons museum on a military base in New >Mexico.) Can anyone enlighten me as to what these were intended to be used >for? For general interest, a book titled US Nuclear Weapons (Neil Hansen?) (About $30) goes over the entire (public) history of the US Nuclear weapons program, including device by device what the (known) characteristics are/were. Its in print, its also on discount at some book stores. Neil was involved in the defense of the "how to build an H-Bomb" case. The defense turned on the fact that all the allegedly classified info was, in fact, publicly available. While documenting this for the trial, he acquired quite a set of info. The book is _extensively_ footnoted for sources... The other nomenclature for the "land mines" is ADM, Atomic Demolition Munition, which describes their use (much) more accurately. As I understand it, the objective is to be able to thoroughly block/destroy battlefield access: tunnels, mountain passes, fortifications... >(Can you imagine a truck running over a mine, then a nuclear explosion >takes place?) Apparently, they were usually time fused... In any case, vehicles were not the target, per se. > Were these things ever put into production? Yes. I would have to look up the submarine N Mines... thanks dave pierson |The facts as accurately as I can manage, Digital Equipment Corporation |The opinions, my own 600 Nickerson Rd Marlboro, Mass 01752 pierson@cimnet.enet.dec.com
whh@PacBell.COM (Wilson Heydt) (12/08/89)
From: whh@PacBell.COM (Wilson Heydt) In article <11917@cbnews.ATT.COM> mmm@cup.portal.com writes: > > >From: mmm@cup.portal.com >I remember seeing pictures of nuclear mines, both for land and sea. (It was >in an article about a nuclear weapons museum on a military base in New >Mexico.) Can anyone enlighten me as to what these were intended to be used >for? (Can you imagine a truck running over a mine, then a nuclear explosion >takes place?) Were these things ever put into production? If my (admittedly unofficial) sources are correct, one place to find about 20 of them is in the Fulda Gap. --Hal ======================================================================= Hal Heydt |Surely the end of the world is at hand: Analyst, Pacific*Bell | Children no longer obey their parents 415-823-5447 | and *everyone* wants to write a book. whh@pbhya.PacBell.COM | --from a Babylonian clay tablet
cash@convex.com (Peter Cash) (02/05/91)
From: cash@convex.com (Peter Cash) In article <1991Feb4.060426.18067@cbnews.att.com> ccc_simon@waikato.ac.nz (Simon Travaglia) writes: ... >Has anyone ever developed a device to trigger mines. Something like a >HEAVILY armoured remote controlled device {like a tank say; that has about >5 inches of plate steel and is essentially only a remote controlled "car" that >drives a track thru a minefield?} >I'm unfamiliar with how technical mines are, so don't know what they are >capable of in the way of avoiding unuseful detonation. I'm sure such devices exist. However, some mines are quite sophisticated --they can be programmed to go off the nth time that they are subjected to a triggering stimulus. Thus, you could roll over the mine once with a steamroller, then have it go off when you drive over it with your jeep. -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | Die Welt ist alles, was Zerfall ist. | Peter Cash | (apologies to Ludwig Wittgenstein) |cash@convex.com ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~