Lucky13
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.....and what was done to deal with these threats? How did the fighting countries (and others) mines and torpedoes compare to each other, how much damage did they cause?
How did torpedoes and anti shipping mines develope during WWII?
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vinnye
Senior Airman
One of the most serious threats to shipping around Britain during the early part of WW2 was the introduction of the magnetic mines by the LW dropping them at night into sea lanes.
It was a serious concern as ships were being lost and no reason could be determined - it was speculated that it was a new type of mine - but that was as far as it went. Fortunately for the British at least one mine was dropped onto mud flats and so was able to be examined bt bomb disposal teams. They removed all metal materials that they had - including coat buttons, and approached the mine. They took a rubbing of the shape of the fastening device and went away and had non magnetic tolls made. They dismantled the mechanisms and dicovered that the mines were activated by a magnetic field produced when the metal hull of a ship approached the mine.
This lead to the degaussing of ships - reducing their magnetic signature and giving them some protection from this type of mine,
It was a serious concern as ships were being lost and no reason could be determined - it was speculated that it was a new type of mine - but that was as far as it went. Fortunately for the British at least one mine was dropped onto mud flats and so was able to be examined bt bomb disposal teams. They removed all metal materials that they had - including coat buttons, and approached the mine. They took a rubbing of the shape of the fastening device and went away and had non magnetic tolls made. They dismantled the mechanisms and dicovered that the mines were activated by a magnetic field produced when the metal hull of a ship approached the mine.
This lead to the degaussing of ships - reducing their magnetic signature and giving them some protection from this type of mine,
mikewint
Captain
When the war started, the submarine force was immediately sent into action, with the order to wage "unrestricted submarine warfare" against Japan. However it would be 18 months before this really happened, and most of the problem during that time was torpedo related. The American problems with their torpedoes paralleled that of the Kriegsmarine, though the German depth keeping problem came from a leaky seal on a balance tank while the American problem originated with an engineer who based the settings on production torpedoes with data obtained from practice torpedoes with warheads that weighed 200 pounds less than the production version. Thus American torpedoes had a depth keeping problem. A torpedo set to run at fifteen feet would actually run as much as ten feet deeper. This problem was compounded by the blunt statement from the Bureau of Ordnance that there was nothing wrong with the depth keeping mechanism, and the commanders were obviously just missing their targets.
Eventually, it was no longer possible to ignore the commanders' complaints. Tests were run, using the relatively simple expedient of firing torpedoes at a fish net, and it was confirmed that the Mark-14 torpedo was running ten feet deeper than set. After this, BofO finally did their own tests, at last conceding that there was a depth problem. The commanders were ordered to adjust the depth settings to compensate for the error, and new torpedoes were modified to fix the problem. This having been accomplished, it was presumed that the success rate would now soar. It didn't.
Commanders were complaining that, even with the corrected depth settings, and perfect shots, the magnetic exploders were either, detonating prematurely, which only served to warn the target and alert the escorts, or they were passing under the target and not exploding at all.
Once again American torpedo problems ran along the same lines as German torpedo problems. The U-boats had experienced the same problems with prematures and failures, using their own magnetic exploders. The Germans quickly recognized the problem, ordered the magnetic exploders deactivated, and went back to blowing up targets. The Americans, on the other hand, insisted that the exploder worked, and that the problem had to be in the people using it.
Unfortunately for the Americans the Mark-6 magnetic feature was, based on a pair of false premises. First, that the earth's magnetic field was essentially the same everywhere and, second, that a steel-hulled ship is going to disturb that field. In fact, the earth's magnetic field varies considerably. An exploder that worked unfailingly off Newport could fail miserably in the Pacific. And it's a relatively simple process to degauss a ship's hull—something that was done routinely to warships and others going into combat areas once magnetic mines were introduced.
The American problem was compounded by two Rear Admirals, Robert English at Pearl Harbor and Ralph Christie, in Australia. Christie had worked on the Mark-6 exploder at Newport, and was convinced that it worked. He presumed that any problems came from poor maintenance or other user error. And it wasn't until English died in a California plane crash, and Lockwood took over at Pearl, that anyone would really listen to the commanders. Lockwood, like the Germans before him, allowed the magnetic exploders to be deactivated on Pearl Harbor boats, unfortunately Christie persisted in mandating their use.
But there was a third part of the problem that had been hidden by the magnetic exploder problem. Because the captains had been under orders to use the magnetic exploder, and had been setting their torpedoes to run the required five feet under their targets, few of them had had the opportunity to realize that that contact exploder was also defective.
Time after time, a perfect shot would send a torpedo squarely into the side of a target, only to have it fail to explode. It might punch a hole in the side of a freighter, but most likely not something that couldn't be repaired at sea. And with a warship, made of thicker steel, it might do nothing more than cause a small dent. At the same time, bad shots, made at extreme angles, where the torpedo hit the target at an oblique angle instead of square, resulted in the warhead detonating and the target going down.
Lockwood ordered more tests. Live torpedoes were fired at the cliffs on Kahoolawe. Three torpedoes were fired from U.S.S. Muskallunge, with the third failing to explode. Navy divers found the dud and it was returned to Pearl Harbor, where it was taken apart.
It was found that the contact mechanism, built to essentially the same standards as that in the slower Mark-10 torpedo, had failed under the greater impact of the much faster Mark-14. Instead of striking the primer, the firing pin had bent and jammed in the guides, which had also distorted. More tests were made, this time by dropping dummy warheads fitted with live exploders onto steel plates from a height of 90 feet, confirming the diagnosis. Once understood, the problem was fairly easy to fix. New firing pins were machined from a light, high-strength aluminum alloy (the metal reportedly came from the propellers of Japanese fighters shot down during the Pearl Harbor raid) and the guides were strengthened, so that they would hold up long enough for the firing pin to strike the primer and detonate the warhead. This "Pearl Harbor Modification" was fitted to all the torpedoes in the inventory, and the changes incorporated into new production. After that, the Mark-14 torpedo suddenly became a model of reliability, and sinkings finally did soar.
Eventually, it was no longer possible to ignore the commanders' complaints. Tests were run, using the relatively simple expedient of firing torpedoes at a fish net, and it was confirmed that the Mark-14 torpedo was running ten feet deeper than set. After this, BofO finally did their own tests, at last conceding that there was a depth problem. The commanders were ordered to adjust the depth settings to compensate for the error, and new torpedoes were modified to fix the problem. This having been accomplished, it was presumed that the success rate would now soar. It didn't.
Commanders were complaining that, even with the corrected depth settings, and perfect shots, the magnetic exploders were either, detonating prematurely, which only served to warn the target and alert the escorts, or they were passing under the target and not exploding at all.
Once again American torpedo problems ran along the same lines as German torpedo problems. The U-boats had experienced the same problems with prematures and failures, using their own magnetic exploders. The Germans quickly recognized the problem, ordered the magnetic exploders deactivated, and went back to blowing up targets. The Americans, on the other hand, insisted that the exploder worked, and that the problem had to be in the people using it.
Unfortunately for the Americans the Mark-6 magnetic feature was, based on a pair of false premises. First, that the earth's magnetic field was essentially the same everywhere and, second, that a steel-hulled ship is going to disturb that field. In fact, the earth's magnetic field varies considerably. An exploder that worked unfailingly off Newport could fail miserably in the Pacific. And it's a relatively simple process to degauss a ship's hull—something that was done routinely to warships and others going into combat areas once magnetic mines were introduced.
The American problem was compounded by two Rear Admirals, Robert English at Pearl Harbor and Ralph Christie, in Australia. Christie had worked on the Mark-6 exploder at Newport, and was convinced that it worked. He presumed that any problems came from poor maintenance or other user error. And it wasn't until English died in a California plane crash, and Lockwood took over at Pearl, that anyone would really listen to the commanders. Lockwood, like the Germans before him, allowed the magnetic exploders to be deactivated on Pearl Harbor boats, unfortunately Christie persisted in mandating their use.
But there was a third part of the problem that had been hidden by the magnetic exploder problem. Because the captains had been under orders to use the magnetic exploder, and had been setting their torpedoes to run the required five feet under their targets, few of them had had the opportunity to realize that that contact exploder was also defective.
Time after time, a perfect shot would send a torpedo squarely into the side of a target, only to have it fail to explode. It might punch a hole in the side of a freighter, but most likely not something that couldn't be repaired at sea. And with a warship, made of thicker steel, it might do nothing more than cause a small dent. At the same time, bad shots, made at extreme angles, where the torpedo hit the target at an oblique angle instead of square, resulted in the warhead detonating and the target going down.
Lockwood ordered more tests. Live torpedoes were fired at the cliffs on Kahoolawe. Three torpedoes were fired from U.S.S. Muskallunge, with the third failing to explode. Navy divers found the dud and it was returned to Pearl Harbor, where it was taken apart.
It was found that the contact mechanism, built to essentially the same standards as that in the slower Mark-10 torpedo, had failed under the greater impact of the much faster Mark-14. Instead of striking the primer, the firing pin had bent and jammed in the guides, which had also distorted. More tests were made, this time by dropping dummy warheads fitted with live exploders onto steel plates from a height of 90 feet, confirming the diagnosis. Once understood, the problem was fairly easy to fix. New firing pins were machined from a light, high-strength aluminum alloy (the metal reportedly came from the propellers of Japanese fighters shot down during the Pearl Harbor raid) and the guides were strengthened, so that they would hold up long enough for the firing pin to strike the primer and detonate the warhead. This "Pearl Harbor Modification" was fitted to all the torpedoes in the inventory, and the changes incorporated into new production. After that, the Mark-14 torpedo suddenly became a model of reliability, and sinkings finally did soar.
model299
Airman 1st Class
mikewint
Captain
Electric Torpedoes:
In addition to the three real problems with American torpedoes the was a fourth "perceived" problem, i.e. the large bubbling exhaust produced. American torpedoes, like the Japanese, were "steam" types. Alcohol was burned in a combustion chamber, using compressed air to supply oxygen (the largest part of the torpedo was the air flask) which produced a high-pressure "steam" exhaust that could be used to power a small turbine. This was geared to a pair of counter-rotating screws. The Japanese used pure oxygen instead of compressed air, which reduced exhaust (80% of air is incombustible nitrogen) and took up less room, allowing for the larger warheads in Japanese designs.
The bubbling exhaust produced by the Mark-14s left a trail of bubbles which marked the course of the torpedo as it ran in on the target. Not only did this potentially warn the target, but it could also give the escorts a starting point for their hunt.
Obviously the Americans needed to build a torpedo that didn't leave a bubble trail. As far as the BofO was concerned, obvious and accomplished were usually two different things. This was no exception. Newport experimented with electric torpedoes, but the basic design of the Mark-18 electric torpedo came from an entirely different source. The British supplied a captured German G7e torpedo, and this was copied, with the modifications needed to fit correctly in American torpedo tubes and interface with the TDC. With a maximum speed of 30 knots, the Mark-18 was slower than the Mark-14, but also much harder to spot in the water. It had a 575-pound warhead, and a maximum range of 4,000 yards. When the Torpedo Station couldn't build them fast enough, Westinghouse was contracted to build them.
As for the exhaust problem, studies after the war suggested that the bubble track was almost never spotted by Japanese lookouts. At least, not until the torpedo was too close to avoid. And as the Mark-14 ran much faster, it was actually more likely to get a hit.
Homing Torpedoes:
Enter the Mark-27 "Cutie" homing torpedo. This had a number of problems, but could be effective under the right circumstances. It was very slow, which limited its utility against anything doing more than 8.5 knots. It was also non-discriminating. The rules dictated firing no shallower that 150 feet, since the torpedo simply homed in on the loudest noise in the area. Too shallow, and that might just be the submarine that fired it.
The Mark-27 was a submarine version of the air-dropped Mark-24 "Fido" anti-submarine torpedo (referred to as a "mine" for security reasons) adapted for use against surface ships. One minor problem that sometimes cropped up occurred if two were dropped together. They would often forget to look for the submarine and chase each other around in a circle instead. After this was noticed, the torpedo release mechanism was modified to allow only single releases.
However sincs submarines would fire only one torpedo at a time, this problem didn't arise. These were 19-inch models, and carried a very small warhead (92 pounds for the Mark-24, 95 pounds for the Mark-27). In the original anti-submarine role this was enough, since it only needed to punch a small hole in the pressure hull and water pressure would take care of the rest. In the anti-escort role, the "Cutie" would home in on the escort's screws, and the small warhead was likely to be enough to blow off a screw and put the escort out of action. Submariners felt that wasn't necessary to kill an escort so long as you could get it stop trying to kill you.
In addition to the three real problems with American torpedoes the was a fourth "perceived" problem, i.e. the large bubbling exhaust produced. American torpedoes, like the Japanese, were "steam" types. Alcohol was burned in a combustion chamber, using compressed air to supply oxygen (the largest part of the torpedo was the air flask) which produced a high-pressure "steam" exhaust that could be used to power a small turbine. This was geared to a pair of counter-rotating screws. The Japanese used pure oxygen instead of compressed air, which reduced exhaust (80% of air is incombustible nitrogen) and took up less room, allowing for the larger warheads in Japanese designs.
The bubbling exhaust produced by the Mark-14s left a trail of bubbles which marked the course of the torpedo as it ran in on the target. Not only did this potentially warn the target, but it could also give the escorts a starting point for their hunt.
Obviously the Americans needed to build a torpedo that didn't leave a bubble trail. As far as the BofO was concerned, obvious and accomplished were usually two different things. This was no exception. Newport experimented with electric torpedoes, but the basic design of the Mark-18 electric torpedo came from an entirely different source. The British supplied a captured German G7e torpedo, and this was copied, with the modifications needed to fit correctly in American torpedo tubes and interface with the TDC. With a maximum speed of 30 knots, the Mark-18 was slower than the Mark-14, but also much harder to spot in the water. It had a 575-pound warhead, and a maximum range of 4,000 yards. When the Torpedo Station couldn't build them fast enough, Westinghouse was contracted to build them.
As for the exhaust problem, studies after the war suggested that the bubble track was almost never spotted by Japanese lookouts. At least, not until the torpedo was too close to avoid. And as the Mark-14 ran much faster, it was actually more likely to get a hit.
Homing Torpedoes:
Enter the Mark-27 "Cutie" homing torpedo. This had a number of problems, but could be effective under the right circumstances. It was very slow, which limited its utility against anything doing more than 8.5 knots. It was also non-discriminating. The rules dictated firing no shallower that 150 feet, since the torpedo simply homed in on the loudest noise in the area. Too shallow, and that might just be the submarine that fired it.
The Mark-27 was a submarine version of the air-dropped Mark-24 "Fido" anti-submarine torpedo (referred to as a "mine" for security reasons) adapted for use against surface ships. One minor problem that sometimes cropped up occurred if two were dropped together. They would often forget to look for the submarine and chase each other around in a circle instead. After this was noticed, the torpedo release mechanism was modified to allow only single releases.
However sincs submarines would fire only one torpedo at a time, this problem didn't arise. These were 19-inch models, and carried a very small warhead (92 pounds for the Mark-24, 95 pounds for the Mark-27). In the original anti-submarine role this was enough, since it only needed to punch a small hole in the pressure hull and water pressure would take care of the rest. In the anti-escort role, the "Cutie" would home in on the escort's screws, and the small warhead was likely to be enough to blow off a screw and put the escort out of action. Submariners felt that wasn't necessary to kill an escort so long as you could get it stop trying to kill you.
