removing (disarming?) naval mines

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Hi all. I'm writing a fantasy story where the tech does not exceed 1959. One of the MCs is training to learn to disarm naval mines. I chose this based on the son of a friend of my mother's (not someone I can call and just ask questions to, unfortunately) who I was told worked for a period as a diver disarming naval mines. That sounded very brave and admirable to me and I wanted to have my MC do training to do something similar. However now, try as I might, I can't find anything about how people do that. I've read about ships that are minesweepers and detonations from the air. But what about divers that disarm mines? Does anyone know anything about that?
Apparently Jacques Cousteau's group used to remove or detonate mines (that's how it's phrased on the wiki page about naval mines) which to me implies that it is, in fact, possible to remove mines without detonating them. Can anyone tell me more about that?
I'd like to be able to describe the process of disarming naval mines in the book. As there are many types of mines, it would be great to be able to describe more than one, if possible, but I'll take what I can get. The tech level of the mines would ideally not exceed WW2 era, because the mines the MC is disarming are left over from a conflict that happened a couple of decades before the start of the book.
Thank you in advance for any help.
 

TulipMama

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To the best of my knowledge, which I'll admit is limited, mines were almost always detonated. The only reason to disarm a mine would be to study the detonation mechanism, which was the case for the 'magnetic trigger' mines popular in the mid-late WW2 naval scene. Once the allied forces had dissected one of these mines, they started developing ways for their ships to detonate them safely or to avoid them (such as large scale de-gaussing to minimize the magnetic field of the ship).

It's very resource intensive to 'capture' a mine. You need to locate one, train somebody to disarm it, and they still have a better than not chance of getting blown to heck even if they did everything right. After that you're down and expert, have to locate another mine and potentially down a ship since these proximity mines could do irreparable damage in a very large radius.

Basically, the reason you don't find 'mine-disarmer' as a steady job description is because it's a lot cheaper/less time consuming to blow mines up and in a war every resource counts. Even post-war the only reason not to blow up a nautical mine would be to save it for a museum or something.

Otherwise, you'd need the same training as a diver and a bomb-disposal unit.
 

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Cousteau was dealing with a very unusual situation. The Germans, as they left French territory, including numerous harbors, mined the harbors to render them unusable by the Allies. After the war was over, it became necessary to remove those mines that were in the midst of the French harbors and towns. Exploding them was not a good option, as the debris could hurt surrounding people and structures. Hence many were disarmed, while some were removed to safer areas to corrode and render themselves harmless that way.

Normally letting them go BOOM! is the easiest way of dealing with them.

Basically a mine will have a hatch that needs to be opened to disarm it. You need some way to transport it safely (i.e., in a disarmed state) before you place it. Disarming the mine is basically a reverse of the process of arming it, with some secret ways to trip up the enemy and cause it to go boom. Problem with naval mines, as opposed to land mines, is that naval mines are in an unstable environment (water) making it a lot harder to work on them.

Jim Clark-Dawe
 

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Thanks everyone.

And thanks, Jim, for your response as it's getting at what I'm trying to find out.

Exploding them was not a good option, as the debris could hurt surrounding people and structures. Hence many were disarmed, while some were removed to safer areas to corrode and render themselves harmless that way.

I'm glad to know that disarming naval mines is actually a thing at all, even if it is unusual.

Basically a mine will have a hatch that needs to be opened to disarm it. You need some way to transport it safely (i.e., in a disarmed state) before you place it. Disarming the mine is basically a reverse of the process of arming it, with some secret ways to trip up the enemy and cause it to go boom.

This is what I'd like to learn more about. The how-to-arm-it vs. how-to-disarm-it, plus the tricky stuff that might trip someone up. Do you have any ideas on sources I could read about it? Or maybe a specific type of mine I could look up?

I've looked at some diagrams of simple naval mines that were activated with a chemical inside. Basically the mine had a piece that suck out, and within this there was a vial of chemical. When the piece got broken due to being banged against by a ship, the vial would break and release the liquid, triggering the mine. But my problem with this is that it seems like it was a lot more common for mines by WW2 to have a magnetic fuse, and I haven't found anything that really spells out how those would work. From what I understand it had to do with the metal of the ship interacting with the magnetism of the earth, but to be honest I don't really understand that, especially since apparently people trying to approach a mine like that would remove all metal from their clothing, and I don't understand how metal on one's clothing would have the same effect as a huge metal ship. Plus I don't know how one would arm/disarm such a mine.

And I gather there were other designs, too. I'd like, ideally, to come to understand how to arm/disarm at least two designs, so I can describe my MC learning about each. Anyway, thanks for the explanation about Cousteau. I'll see if I can find out more about what his group did with removing mines.
 

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Movies and television always go with cutting the green wire. It might work with military grade weapons, but the average terrorist bomb-maker doesn't worry about the colors of the wires. He or she grabs what's ever is available and goes from there. Notice that they never discuss what the wire connects to, which is the important fact.

In other words, there are a lot of limits on how much anyone with any knowledge will discuss detonators. I don't know a whole lot, but still know way more than I should.

Naval mines in WW2 were of several different types. You seem to be interested in contact mines and magnetic mines. Contact mines are very simple to understand. Pins on the outside are compressed on contact and set off a detonator, which could be a vial of chemicals.

Magnetic mines use a detonator that is set off by metal passing close to it. The metal of a ship causes a distortion of the earth's magnetic field causing a magnetic needle within the mine to move and set off the detonator. The bigger the piece of metal, the further from the mine it will go off. But if you get close enough with a smaller amount of metal, the magnet will also move.

Basically disarming an explosive involves making sure the two parts of the detonator don't come together. In a magnetic mine, stopping the magnetic needle from moving would disarm it. Simple instructions are opening the cover and somehow blocking the needle from moving.

Jim Clark-Dawe
 

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Thank you, Jim! That's extremely helpful. The only question I have now is how the makers of the mine might make it more difficult for someone to disarm it. If the process is relatively simple, like blocking or removing the needle, what would they do to make that more difficult? Some sort of boob trap, no doubt, but what do those look like? Wires? Pressure plates (which would have to be small I would think)? You open the panel on the mine and the movement of the door is connected to the needle, making it move?
And how would someone circumvent the complication?
 

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Thank you, Jim! That's extremely helpful. The only question I have now is how the makers of the mine might make it more difficult for someone to disarm it. If the process is relatively simple, like blocking or removing the needle, what would they do to make that more difficult? Some sort of boob trap, no doubt, but what do those look like? Wires? Pressure plates (which would have to be small I would think)? You open the panel on the mine and the movement of the door is connected to the needle, making it move?
And how would someone circumvent the complication?

I'm no WW2 Nazi scientist, so I can't tell you the secret sauce that would be historically accurate. I did take some time to look at some WW2 nautical mine diagrams though, and it doesn't look like they had any anti-tamper equipment come standard. Most of them seem to be armed with gun-cotton or a TNT variant known as Amatol, and both denature in salt-water becoming inert over time. The simplest way to kill one would be to use a brass, anti-sparking drill tip to puncture the sphere and let the ocean disarm the bomb for you.

Now, it's possible that a run of mines with anti-tampering devices were ordered to really mess with the allies if they knew the mines would be put in delicate, non-blow-up-able areas.

I can give some best guesses and possible design options that MAY have been used. Probably the best way to make sure they can't be disarmed is to booby trap the hatch you need to open. Personally I'd equip it with a latch that tugs the detonator unless you slip a key into some innocuous port by the hatch door. It'd be too much effort to make them unique keys, so probably something as rudimentary as a screwdriver slipped into the port to stop the latch from tripping the detonator would be enough. It's simple, cheap and effective assuming the allies haven't managed to capture and dissect one. Most mines that I've looked at over the last day-ish of time seem to have the detonator RIGHT at that hatch anyway, so it'd be easy as pie to just make that hatch impossible to open after arming without blowing the thing right to heck. They could also include a small battery with an incomplete circuit set in the outer shell (tether mines had a two shell system, one filled with air, and one closer to the center crammed with explosion-filling) and drilling the outer shell would flood it with salt water, completing the circuit and making for the bang-bang. Magnetic mines could be set to go off with minuscule magnetic fields, I'm talking micro-Gauss, the kind of magnetic field you'd find around a wrist watch. The fact that the person disarming the thing would have to free-dive with wooden or brass tools may have been enough of a middle finger to the allies. Simple mechanical booby-traps would work with these 'influence' mines as well though too, but Churchhill did successfully order one that had been dropped from a plane be dismantled. It had landed on a military base at low tide, so instead of splashing it just thunked into the mud. They ordered all metal removed from the engineers who worked on it and they successfully reverse-engineered the design. If there was going to be any mines with anti-tamper devices set in it, I'd put money on it being the ones dropped into the London Harbour near it's naval bases.

FYI, the contact mines, or 'horn-trigger' mines did have a vial of acid in the horn at the start of the war on the British side. The horn would compress, shatter the vial of acid, make a small battery with a cathode/anode set into the base of the horn (think that lemon battery science experiment from high-school) and the electrical signal would set off the detonator. The vial of acid was later replaced with an induction coil copied off a German design because it was more reliable.

Hope that helps!

Tulip Mama <3
 

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Wow, Tulip Mama! I'm so grateful you took so much time to help me. Really really thank you, you've been an immense help, and I will be using this in my story.
 

jclarkdawe

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It's a balancing act between the likelihood of someone wanting to disarm the bomb versus the need to render a bomb safe from harming yourself. It could be something like requiring the bolts on the hatch to be opened in a specific order, it could be duplicates so you don't know which one is the right one, it could be the green wire from movies. It could be incredibly difficult by requiring the insertion of something like a key. (Lose the key and there's no way to disarm your bomb. It's happened.)(By the way, the "key" might not even look anything like a key.)

But naval mines aren't that likely to be tampered with, so the safety devices would probably be fairly simple. And the simple solution would be to drill a hole in them and let them flood. Especially with salt water, it would probably work fairly well. This is a variation on dumping the bomb in a bucket of water.

Understand that the simplest solution for mines is to explode the sucker.

But understand the drama of bomb disposal. You've just arrived at your 100th magnetic mine. You know magnetic mines inside and out, and could build one in your sleep. It doesn't matter. With this mine, suppose they did something different? There's no way of knowing this until the rest of the world hears a loud boom. (The mine disposal guy won't hear the bomb explode -- he'll be dead.) Disarming a mine is an adventure in the unknown, no matter how much one knows. And what happen if the enemy has added a timer to the mine? Even if it is as simple as opening the hatch, and turning a switch or two, you don't know this when you arrive on the scene. You only know it afterwards when the bomb doesn't explode.

Don't overthink this. The scene is dramatic because of the what-ifs. This is the reason you remove everyone for hundreds of meters, or maybe, if the bomb is big enough, several kilometers. Although I know explosives guys who will juggle detonators with the safety in place, a live bomb is always something to treat with caution. Bombs have been known to go off with a minor little jiggle.

Jim Clark-Dawe
 

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I'm no expert on the subject, but if it were me, I would capture the anchor chain from a safe distance, which would require securing a tow line to the chain and probably cutting it, and then tow it to a place where it could be safely detonated.
 

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Get your hands on the old BBC series,"Danger UXB". It is about a bomb disposal unit and does spend some time on German Sea mines. It will really explain what is involved to disarm something and the steps taken by the Germans to keep them from being disarmed.
 

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I'm no expert on the subject, but if it were me, I would capture the anchor chain from a safe distance, which would require securing a tow line to the chain and probably cutting it, and then tow it to a place where it could be safely detonated.

I'm no expert in disarming naval mines either, but I'm not sure I'd want to be on a vessel attached to a large, unsteerable subsurface explosive device that is pushed around by currents.
 

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I'm no expert in disarming naval mines either, but I'm not sure I'd want to be on a vessel attached to a large, unsteerable subsurface explosive device that is pushed around by currents.

I'm saying tow it with a very long rope. If the anchor chain is severed, it will then rise to the surface. No, I don't want to be the guy that hooks the rope up and cuts the chain.
 

jclarkdawe

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Normal process for sweeping naval mines involves a specially designed ship that tows paravanes on either side. The paravanes are connected to the ship by cables and are designed to float below the surface and the probable depth of the mines. The cables will frequently cut the anchor line of the mine, and if not, the mine will slide down the cable until it hits the paravane and goes boom. The cut mines come to the surface and the ship uses small arms fire on the mine until it goes boom.

My impression is that the first few mines are rather exciting and after that it becomes a rather ho-hum duty. There isn't a whole lot of debris that goes up with the mine and water reduces the blast range. But you make sure you explode the mine far enough away so it does not damage.

Sometimes you can't do things the normal way. One example during WWII would be beaches for landings. In the US Navy, you'd call in what eventually became the seals. At that time, it was UDTs and NCDUs. They were trained in both disarming and arming explosives underwater.

It's relatively simple to slice the cable to a mine and attach a long one from a ship. Currents are relatively predictable so can be calculated into the known hazards. Risks are very manageable and the UDTs and NCDUs got a fair amount of volunteers. Young people, especially men, are known for making stupid decisions.

Good story on mine sweeping in WWII is THE CAINE MUTINY. Not that there's much in there about mine sweeping, but that was the norm for a mine sweeper in WWII.

Jim Clark-Dawe
 

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FWIW, most WWII sea mines were not booby trapped because there could always be that circumstance where you need to disarm your own mine. Mines left as troops were retreating could have been, and there are a number of areas where they were known to have been.

Many sea mines had an external detonator mechanism that was simply screwed into the mine when it was placed. Unscrew the detonator and the mine was disarmed. There were lots of designs, contact, magnetic, etc. and a lot of mechanisms for placing the mines, from anchors with chains to attached to objects like ships or docks to simply left floating around. You'll need to do some serious research if your story depends on exact processes, or it could be as simple as:

"After disarming the mines in the harbor, the Navy's demolition teams took the mines to a secure location for disposal."

Jeff
 
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My Dad was the gunnery officer and diver on a WW2 minesweeper. For diving training review the movie Men of Honor. There are TWO reasons for disarming mines, 1) you want to learn about the mine, and 2) the mine in permanently affixed to a structure and need it gone. US Navy SeeBee engineers had to prepare the D-Day sites for our troop landing by sneaking in every night for a month before the attack to disarm the S-mines (aka Bouncing Betties), which were more of a fixed booby trap than a true marine mine, and also to disarm the Teller Mines (T-Mine 35, T-Mine 42, and T-Mine 43), these were affixed to anti-tank obstacles and were the ones sought by, and disarmed, by the SeeBees. They had to be disarmed and not blown-up to keep the Nazis un-apprised of the mines change in operability. If a view with binoculars showed the mine was still there then all was well, or so they thought.

My 2 cents.

DrDoc