AHQ: U-boat sinking rate to achieve victory?

[Vahktang]

I am figuring at this point that if the idea of a towed lift mine by a submarine was any way practical or reasonable somebody in history would have done it.
In a history of three sectional staffs, incendiary bats and aircraft carriers made of ice and saw dust, such of thing would have been tested and prototyped at least.
Thank you all.

 

[phx1138]

Sub gets in trouble, destroyer chasing them down, they release a mine on a tether, arming it when it is a safe distance away from the submarine.
Quick, thin hulled destroyer has to be quite close to get an effective depth charge hit.
While too close, mine goes off.

Well, the buoy at the end of the tether is attached to the sub and that cable is making a lot of noise and generating a wake. The destroyer will probably dogleg around the buoy , which may explode depending on whether or not the proximity fusing will work. If the buoy is about 50 or 100 meters away when it blows, the deck crew on the destroyer is going to get wet. The destroyer (unless it is built by Russians) will be fine.

The sub crew has two problems now: the cable has just fouled the screws and the destroyer is dropping depth charges

I was thinking the tether would be attached to the mine...but it has its own problems. One, you can't aim it; if you're going to shoot at a tincan, use a torpedo. Two, it's going to make rather a large bang rather close to the sub (unless the sub is quite deep), which is what depth charges are designed to do; that's a functional definition of suicidal. Three, it's a lot easier just to dodge the tincan (assuming you aren't Morton, O'Kane, or Dealey & just can't resist shooting at him ).

If you're going to cover the stern with sonar, I've wondered what's wrong with an array mounted above (& aft?) the screws; there's normally tankage there, AFAIK, in WW2-era boats.

 

[BlackDragon98]

Excuse my ignorance, why?
There are drift mines, after all, I understand.
And if you are mining shipping lanes mid-Atlantic than don’t they have to be drift mines?

yes, there are drifting mines but they can't be made into a minefield because they go where the currents and tides take them.
And drifting mines are dangerous to everything including your own ships, which is why it's a bad idea in general.

 

[McPherson]

I was thinking the tether would be attached to the mine...but it has its own problems. One, you can't aim it; if you're going to shoot at a tincan, use a torpedo. Two, it's going to make rather a large bang rather close to the sub (unless the sub is quite deep), which is what depth charges are designed to do; that's a functional definition of suicidal. Three, it's a lot easier just to dodge the tincan (assuming you aren't Morton, O'Kane, or Dealey & just can't resist shooting at him ).

If you're going to cover the stern with sonar, I've wondered what's wrong with an array mounted above (& aft?) the screws; there's normally tankage there, AFAIK, in WW2-era boats.

The screws put out a sound chord that sounds like popping popcorn that makes acoustics aft at least as as wide as a 30 degree cone and ten boat's length long impossible to use hydrophones passively. Active pinging just echoes back off a contact as a return into that popping noise and if it works also provides a home on signal cue to a torpedo headed up the props. BANG. Better to use a "worm".

 

[Vahktang]

I was thinking the tether would be attached to the mine...but it has its own problems. One, you can't aim it; if you're going to shoot at a tincan, use a torpedo. Two, it's going to make rather a large bang rather close to the sub (unless the sub is quite deep), which is what depth charges are designed to do; that's a functional definition of suicidal. Three, it's a lot easier just to dodge the tincan (assuming you aren't Morton, O'Kane, or Dealey & just can't resist shooting at him ).

Yes, the tether is attached to the mine and the submarine. The sub drags the mine and the mine is between sub and ship
One: you aim it by having the searching destroyer get close enough to the sub to be dangerous to the sub and it sets off the mine
Two: the very large bang is mitigated by distance, the tethered mine is far enough away from the sub that the big bang has no impact. 145’ in the example, that ought to be sufficient, right?
Three: this would be for the few times when the difficulty is near insurmountable. I understand that ‘faking your death’ oil, clothing, debris, floating to the surface was a thing. This would be used to bite them back instead.

 

[Vahktang]

yes, there are drifting mines but they can't be made into a minefield because they go where the currents and tides take them.
And drifting mines are dangerous to everything including your own ships, which is why it's a bad idea in general.

Well, sure, but, if you do not go there and the enemy does, it is a good idea to put some mines there.
Aerial mining an enemy harbor, for example, denying it to them until it is swept, I understand is very effective.
And after the war it is a pain to sweep them up, yes.

 

[BlackDragon98]

Well, sure, but, if you do not go there and the enemy does, it is a good idea to put some mines there.
Aerial mining an enemy harbor, for example, denying it to them until it is swept, I understand is very effective.
And after the war it is a pain to sweep them up, yes.

Yes, but a drifting mine is not anchored. It just follows the currents and therefore will hit and destroy anything it comes into contact with, including ships of the nation that released the drift mine.
The mines used in a harbor are stationary mines, they have an anchor of sorts.

For example, several years ago a live Japanese drift mine washed up on a BC coast. What if it hadn't and hit a cargo ship instead? See the point?

 

[phx1138]

Yes, the tether is attached to the mine and the submarine. The sub drags the mine and the mine is between sub and ship
One: you aim it by having the searching destroyer get close enough to the sub to be dangerous to the sub and it sets off the mine
Two: the very large bang is mitigated by distance, the tethered mine is far enough away from the sub that the big bang has no impact. 145’ in the example, that ought to be sufficient, right?

If you've got a can that close to you, you're probably dead already & just don't know it yet. (Hedgehog engaged at about 200yd.) Plus, a 600pd DC is lethal at 60'; a charge big enough to sink a tincan would be bigger, so you'll need to be further away than 150' or so.

This would be used to bite them back instead.

Develop an anti-escort homing torpedo, instead. It could be a simple calcium carbonate "rocket", launched from some kind of watertight deck tube perhaps (tho that would have to be absolutely watertight); if it's fast enough, the DD shouldn't be able to avoid it. Or a more conventional acoustic homer.

The screws put out a sound chord that sounds like popping popcorn that makes acoustics aft at least as as wide as a 30 degree cone and ten boat's length long impossible to use hydrophones passively.

I figured there was a good reason for the towed array. Thx.

 

[gatordad699]

As McP discussed, the towed array has two functions. Get a second data point to allow ranging and get an array away from own ships noise. Subs never rely on the array to hear things in their “baffles.” As Red October pointed out, subs always clear their baffles at unexpected times. I can neither confirm nor deny that the Soviets actually perform Crazy Ivans.

The noise from the propeller (propulsor or pump jet on modern boats) is flow noise. Any popping would be cavitation (vapor bubble forms at center of prop because it is turning too fast for the pressure it’s in. Vapor bubble travels to outer edge of prop where pressure is high enough to collapse it. This causes supersonic gas speeds, very loud noise, and causes erosion of the prop) Boats go to great lengths to prevent cavitation. One of the reasons they went to propulsors. Changes in throttle speed are limited by depth/pressure so you don’t cause cavitation.

There is no way a boat is going to tow a weapon or put one on its hull. The chances of it going off at the wrong time are way too high. There are many safeties built into torpedoes so they don’t explode inside a boat. Towing anything behind or above subs is dangerous. Modern subs have a few systems that do that and they cause all kinds of problems.

 

[Coulsdon Eagle]

Yes, the tether is attached to the mine and the submarine. The sub drags the mine and the mine is between sub and ship
One: you aim it by having the searching destroyer get close enough to the sub to be dangerous to the sub and it sets off the mine
Two: the very large bang is mitigated by distance, the tethered mine is far enough away from the sub that the big bang has no impact. 145’ in the example, that ought to be sufficient, right?
Three: this would be for the few times when the difficulty is near insurmountable. I understand that ‘faking your death’ oil, clothing, debris, floating to the surface was a thing. This would be used to bite them back instead.

You want the destroyer close enough to be dangerous to the sub?

Might be some crazy SOBs in the IJN who might appreciate that, but surely when the DD is hunting the SS, the SS wants to be out of danger?

 

[McPherson]

Might be some crazy SOBs in the IJN who might appreciate that, but surely when the DD is hunting the SS, the SS wants to be out of danger?

CDR Samuel Dealey .... Or as the IJN would say; " 聖なるサバ、あの男は非常識すぎて武士にはなれなくてすまい。彼はエイリアンに違いない。 バンザイ！"

(Holy Mackerel, he's too insane to be a samurai. He must be an alien. Banzai!)

 

[gatordad699]

I did some really cool “oceanographic research,” but those guys were without fear. Met Admiral O’Kane years ago. Pretty cool/scary/amazing stories. My first CO was like those guys. He could conduct “oceanographic research” by putting his had on the hull. Takes a different breed to stare down a destroyer.

 

[Vahktang]

You want the destroyer close enough to be dangerous to the sub?

Might be some crazy SOBs in the IJN who might appreciate that, but surely when the DD is hunting the SS, the SS wants to be out of danger?

Well, the point is that the Sub does not have a choice.
The destroyer is going to be that close anyway.
But, it can still endanger a destroyer.
And if the perception is that destroyers that get that close sometimes get hit, maybe some will hesitate to get that close.
Finally, I understand the submarine people in the IJN were considered near the bottom of the barrel, so they did not attract the best.

If you've got a can that close to you, you're probably dead already & just don't know it yet. (Hedgehog engaged at about 200yd.) Plus, a 600pd DC is lethal at 60'; a charge big enough to sink a tincan would be bigger, so you'll need to be further away than 150' or so.

In the example the sub is 145’ away. Further is possible.

Develop an anti-escort homing torpedo, i

How about an upward shooting Hedgehog ASW mortar variant?
But then one has the ‘do not put explosives on the deck of your submarine. Ever’ brought up by #gatordad699.
Also, targeting an anti escort mine would be a problem.

 

[McPherson]

How about an upward shooting Hedgehog ASW mortar variant?
But then one has the ‘do not put explosives on the deck of your submarine. Ever’ brought up by #gatordad699.
Also, targeting an anti escort mine would be a problem.

Read @gatordad699 in this thread. He answered that one for you. Float buoy bombs packed into the signal ejector is a BAD idea.

You want to lay a CAPTOR.

 

[Vahktang]

Yes, but a drifting mine is not anchored. It just follows the currents and therefore will hit and destroy anything it comes into contact with, including ships of the nation that released the drift mine.

iIf your country is already blockaded, putting mines in the enemy harbor would be good for you.
As a matter of fact (from wiki):

The U.S. effort against Japan, for instance, closed major ports, such as Hiroshima, for days,[33] and by the end of the Pacific War had cut the amount of freight passing through Kobe–Yokohama by 90%.

The mines used in a harbor are stationary mines, they have an anchor of sorts.

If placed by the owners of the harbor, sure.
An enemy dropping mines from a plane or using a sub to place them would hardly do that, would they?
It may behoove them to have the mines drift around the harbor and not sit in place, easily picked up and/or picked off.

For example, several years ago a live Japanese drift mine washed up on a BC coast. What if it hadn't and hit a cargo ship instead? See the point?

Yes, certainly.
Looked it up on wiki and found some stuff:

Offensive mines are placed in enemy waters, outside harbours and across important shipping routes to sink both merchant and military vessels.

So, not just a static defense. Usually, sure, but, could be used otherwise.
And:

By the beginning of World War II, most nations had developed mines that could be dropped from aircraft, some of which floated on the surface, making it possible to lay them in enemy harbours.

So, drift mines, used offensively.

Minefields designed for psychological effect are usually placed on trade routes to stop ships from reaching an enemy nation. They are often spread thinly, to create an impression of minefields existing across large areas. A single mine inserted strategically on a shipping route can stop maritime movements for days while the entire area is swept.

Again, if placed on a shipping route with a 100+ meters to the bottom it could hardly be anything but a drift mine.
And currents would be known, position for your ships to avoid them would be known, and possible position for the mines will get larger as time goes on.
Did they have mines that would deactivate after a time in WW2?

And, yes, cleanup is problematic.
During WW1 there was the North Sea Mine Barrage, where 70,000 mines were layed
Clearing the barrage after the war took 82 ships and five months, working around the clock.
Also:

When the war (II) ended, more than 25,000 U.S.-laid mines were still in place, and the Navy proved unable to sweep them all, limiting efforts to critical areas.[34] After sweeping for almost a year, in May 1946, the Navy abandoned the effort with 13,000 mines still unswept.[34] Over the next thirty years, more than 500 minesweepers (of a variety of types) were damaged or sunk clearing them.[34]

https://en.m.wikipedia.org/wiki/Naval_mine#cite_note-Gilbert,_p.5-34

 

[Vahktang]

Read @gatordad699 in this thread. He answered that one for you. Float buoy bombs packed into the signal ejector is a BAD idea.

You want to lay a CAPTOR.

I did indeed quote @gatordad699 in the post, agreeing with the post, but mistakenly used a # instead of a @ so it was unattributed.
And CAPTOR may be a bit too high tech for WW2.

 

[McPherson]

I did indeed quote @gatordad699 in the post, agreeing with the post, but mistakenly used a # instead of a @ so it was unattributed.
And CAPTOR may be a bit too high tech for WW2.

@phx1138 and I discussed it in a thread and it turns out, that if you have CUTIE, the right battery tech, the Mark 12 mine profile and the really dumb IJN, it is not only possible, it is a missed opportunity to play "whack a destroyer" off Chu'uk.

 

[Vahktang]

@phx1138 and I discussed it in a thread and it turns out, that if you have CUTIE, the right battery tech, the Mark 12 mine profile and the really dumb IJN, it is not only possible, it is a missed opportunity to play "whack a destroyer" off Chu'uk.

I am going to trust you on this and be suitably amused

 

[BlackDragon98]

iIf your country is already blockaded, putting mines in the enemy harbor would be good for you.
As a matter of fact (from wiki):


If placed by the owners of the harbor, sure.
An enemy dropping mines from a plane or using a sub to place them would hardly do that, would they?
It may behoove them to have the mines drift around the harbor and not sit in place, easily picked up and/or picked off.


Yes, certainly.
Looked it up on wiki and found some stuff:

So, not just a static defense. Usually, sure, but, could be used otherwise.
And:

So, drift mines, used offensively.


Again, if placed on a shipping route with a 100+ meters to the bottom it could hardly be anything but a drift mine.
And currents would be known, position for your ships to avoid them would be known, and possible position for the mines will get larger as time goes on.
Did they have mines that would deactivate after a time in WW2?

And, yes, cleanup is problematic.
During WW1 there was the North Sea Mine Barrage, where 70,000 mines were layed
Clearing the barrage after the war took 82 ships and five months, working around the clock.
Also:
https://en.m.wikipedia.org/wiki/Naval_mine#cite_note-Gilbert,_p.5-34

No, the problem is you argued for putting them in the middle of the north Atlantic, an area which is far too deep for anchored mines and the weather is also far too violent for anchored mines to stay in place.

 

[phx1138]

Takes a different breed to stare down a destroyer.

It sure does. Sam Dealey was one of the rare few. He's also a textbook case of how hard it is to pick good skippers, because he got bilged out of the Academy. (IDK why...) And there was somebody else (whose name I can't recall... ) who was bookish & mild-mannered, but one of the best the wartime Sub Force had. And O'Kane reportedly had a real braggadocio, but turned out to be ice cold under fire. Go figure.

Well, the point is that the Sub does not have a choice.
The destroyer is going to be that close anyway.

The idea is never to let the can get that close, unless you have no choice. There are safer options than this.

destroyers that get that close sometimes get hit, maybe some will hesitate to get that close.

I wouldn't count on it. @McPherson & I once went back & forth a bit over deck-mounted rockets being an anti-escort weapon, & he correctly pointed out the tincan skippers were willing to risk their ships--if they're any good at all. IJN ASW was awful, but don't think their crews & skippers lacked nerve--just skill at the job. RN, RCN, & USN had both, so this won't work against them.

In the example the sub is 145’ away. Further is possible.

You're making it harder to be successful... If that mine actually floats, it's going to swing on that tether like a kite, making it damned unlikely to hit the desired target, & more & more likely to foul the screws.

Also, targeting an anti escort mine would be a problem.

Which was one of the first objections raised...

I am going to trust you on this and be suitably amused

It's hard, but not impossible. The key issue is probably thinking of doing it to begin with.