WI:Krigesmarine type xxI

[AJE]

a. FIDO drops were not singular. And when dropped were practically on top of the U-boat as her conning tower was awash, at least if doctrine was followed.
b. Acoustic torpedoes are farther away and can be decoyed or seduced by towed noisemakers.

Acoustic torpedoes can be decoyed, and launching one increases the chance of the U-boat being detected. Not as much as a conventional torpedo, but its still dangerous for the boat. Especially as the WW2 weapons weren't an all-aspect weapon, to get a decent chance of a hit you really needed to be in a good position. Of course, the escorts know this as well.

Submarine torpedoes were not fired singularly either, and acoustic torpedoes could not be decoyed when designed well. The US' own submarines found the only way to hide from FIDO in tests was to dive and stop all engines, no decoys or noisemakers worked. The Mark 27 had the same guidance, and the TXI was probably getting there although it was far too late and still likely over engineered.

c. Exactly! The Germans were deploying a weapon that got 1.6 freighters overall and then got promptly killed. They WERE incompetent. It was about 0.8 freighter for every dead U-boat at the end of it.

We agree on that.

The torpedo is the exclamation point that announces "Here I am, come kill me! I'm a U-boat." Of course the escorts will know. That is what a launch transient does with a short ranged torpedo.

If the U-boat is trying to escape an escort using its snorkel, its AWFULLY visible! And gets killed shortly afterwards.

Which is why the submarine would use batteries to quietly get to a safe distance from the escorts and then surface or use the snorkel.

Actually if the MAD gear designers know their physics... it cannot be defeated by that means. It is how magnetic influenced torpedoes actually work, ya, know?

Degaussing doesn't set the magnetic field to zero, it just reduces it so a magnetic mine has less chance of being set off. It was suspected (but not, iirc, actually proven) that it reduced the chance of a magnetic exploder on a torpedo going off. But it doesn't make you invisible.

MAD can be defeated by degaussing and, much like magnetic mines in WWII, in fact has been defeated for most of its existence. MAD systems have only ever been used as secondary systems to precisely locate submarines already roughly located, in the best case scenarios. No vehicle other than aircraft have ever used MAD (and even they don't use it much), and all available information indicates that modern MAD certainly has a range of under 10 km, and most likely less than 4 km. It cannot be used to search for submarines in general areas, and will not discover previously unknown submarines on the surface any better than visual searching, except in the very rare cases where a submarine gets unlucky.

 

[McPherson]

German torpedoes and usage.

Submarine torpedoes were not fired singularly either, and acoustic torpedoes could not be decoyed when designed well. The US' own submarines found the only way to hide from FIDO in tests was to dive and stop all engines, no decoys or noisemakers worked. The Mark 27 had the same guidance, and the TXI was probably getting there although it was far too late and still likely over engineered.

German heavy weight acoustic torpedoes had to be fired singly or at long intervals apart or they would start chasing each other in circles. That is why FIDO was itself released in hammer and anvil attacks, to keep the torpedoes from chasing each other.

FIDO tests showed that HUSL's shadow body architecture chase logic was correct, but the Germans put their sensors in the nose. Hence it was susceptible.

German competency.

We agree on that.

Which is why the submarine would use batteries to quietly get to a safe distance from the escorts and then surface or use the snorkel.

Creep speed. But if the DE is in hot pursuit, that flank run is about 40-60 minutes tops.

MAD can be defeated by degaussing and, much like magnetic mines in WWII, in fact has been defeated for most of its existence. MAD systems have only ever been used as secondary systems to precisely locate submarines already roughly located, in the best case scenarios. No vehicle other than aircraft have ever used MAD (and even they don't use it much), and all available information indicates that modern MAD certainly has a range of under 10 km, and most likely less than 4 km. It cannot be used to search for submarines in general areas, and will not discover previously unknown submarines on the surface any better than visual searching, except in the very rare cases where a submarine gets unlucky.

Not entirely true. It depends on hull metal, the degaussing methods used and whether the MAD uses one or two detector architectures. The Japanese used two and were dangerous. Detection (WW II) depending on atmospheric weather and ocean salinity (yes; salinity) was ~ 2000-4000 meters slant from altitudes no greater than 1,000 meters.

 

[pdf27]

Creep speed. But if the DE is in hot pursuit, that flank run is about 40-60 minutes tops.

Breaking contact isn’t that hard if they don’t know exactly where you are. The problem is getting back in contact again afterwards - the batteries don’t let you chase from outside suicidal snorkeling range, so you have to get in front and hope the convoy runs over you. That means you only get the one attack, realistically - the early war boats could keep a battle up for days

Not entirely true. It depends on hull metal, the degaussing methods used and whether the MAD uses one or two detector architectures. The Japanese used two and were dangerous. Detection (WW II) depending on atmospheric weather and ocean salinity (yes; salinity) was ~ 2000-4000 meters slant from altitudes no greater than 1,000 meters.

Anything I can use to read up on this? Very curious now...

 

[AJE]

Anything I can use to read up on this? Very curious now...

http://www.intrel.com/mea/mag/mea_app_mag_rng_sum.pdf
It's the best piece on calculating MAD detection range that I can find. Just adjust the degaussing efficiency and magnetometer sensitivity (boat size and base magnetic signature shouldn't be much different) downwards to appropriate WWII levels, and use the equations inside to calculate range.

 

[phx1138]

The issue of German resources got me thinking. Yes, Germany can't manufacture enough batteries for twice the capacity in the same number of boats. I'd say the *Type XXI would be built in smaller numbers, based on the amount of steel (in rough proportion of Type IX to Type VII), & would replace many of the Type VIIs built OTL. IMO, the numbers of Type VIIs OTL were in part because they were sunk with such abandon. The *Type XXI wouldn't be. It would be able to transit Biscay with less hazard, track & sink single ships more readily, escape LRMP a/c detection more readily (presuming detection isn't already confirmed, & mere contact isn't going to provoke a multi-ship, multi-a/c prosecute to kill, IMO). So, if German losses are lower, demand for batteries will be, & production can meet it.

In short, is it possible TTL sees a ramp up of losses in Allied shipping & U-boats both, until after Neptune.

Am I wrong?

 

[McPherson]

The issue of German resources got me thinking. Yes, Germany can't manufacture enough batteries for twice the capacity in the same number of boats. I'd say the *Type XXI would be built in smaller numbers, based on the amount of steel (in rough proportion of Type IX to Type VII), & would replace many of the Type VIIs built OTL. IMO, the numbers of Type VIIs OTL were in part because they were sunk with such abandon. The *Type XXI wouldn't be. It would be able to transit Biscay with less hazard, track & sink single ships more readily, escape LRMP a/c detection more readily (presuming detection isn't already confirmed, & mere contact isn't going to provoke a multi-ship, multi-a/c prosecute to kill, IMO). So, if German losses are lower, demand for batteries will be, & production can meet it.

In short, is it possible TTL sees a ramp up of losses in Allied shipping & U-boats both, until after Neptune.

Am I wrong?

Depends on lead, manganese, chlorine, and PLASTICS. Germany made her bullets out of steel for a reason. Her glass industry is also suspect. Lots of bottlenecks.