Research Thread - USN vs. KM

[joea]

Right to go along with the ASW warfare thread (btw both will have ramifications for continuing SH3 mods I hope as well as benefiting from the SH3 modding experience) in order to tweak things from the sub side to get a more realistic and historical I thought it useful to compare and contrast the USN and the Kreigsmarine (though looking at say the RN sub branch or other navies is certainly not excluded).

Again we can look at:

1) Pre-war sub doctrine

2) Wartime development and experience

3) Weapons and tech (ie. the different ways the USN and KM dealt with torpedo problems)

That's just to start.

[bigboywooly]

Here a nice brief summary of the KM torpedo problems and how Donitz tried to shake up an answer can be found on Uboat Aces

http://www.uboataces.com/articles-wooden-torpedoes.shtml

BDU's own KTB contain many references to converstions and dealings with the Torpedo Inspectorate

From http://www.uboatarchive.net/BDUKTB30256.htm

Donitz wrote in Jan 40


The Director of the Torpedo Inspectorate telephoned me today. Trial shots have been made against T 123, which did not fire, and magnetic measurements have been made on torpedoes in store, with the result that the Torpedo Inspectorate considers the possibility of torpedoes not firing is proven.
The fact that its main weapon, the torpedo, has to a large extent proved useless in operation has been the greatest difficulty with which the U-boat Arm has had to contend with since the beginning of the war and it has had a most serious effect on results. At least 25% of all shots fired have been torpedo failures. According to statistics covering all shots up to 6.1., 40.9% of unsuccessful shots were torpedo failures.

1) In August 1939, before the boats left port during the emergency period, a conference held in the Torpedo Trials Department during which the doubts expressed by B.d.U. with regard to the proper functioning of the pistol were dismissed as unfounded by Rear Admiral Wehr, Director of Torpedo Trials Department.

2) On 14.9 U 29 reported by radio that 2 torpedoes had fired prematurely after covering the safety distance. The Torpedo Inspectorate first wished to make out that the U-boats had made an error in position of 30-60 miles. I would not accept this explanation. The Torpedo Inspectorate then recommended setting the pistol 2 zones lower, in order to lessen its sensitivity. This meant that they would not be certain to fire against merchant ships under 3,000 BRT if shot under and such ships would therefore have to be attacked with impact firing. An order was accordingly given to the U-boats by B.d.U. on 14.9.

3) Failures were not eliminated however. Further premature detonations were reported.(U 27 reported that the explosion caused slight damage to the boat). Until the cause was discovered, the Torpedo Inspectorate arranged for the torpedoes to be fitted with an "A" setting of the switch, which made it possible to cut out electric firing.

4) After the "A" setting of the switch had been fitted, B.d.U. ordered on 2.10 that only impact shots were to be fired. This meant that for the present the danger of premature detonation was eliminated. The step was taken for the sake of safety of the boats, until such time as the cause of premature detonation was discovered.

5) At the beginning of October the Torpedo Inspectorate stated that the cause of premature detonation in the G7e had been traced to a bad cable lay-out. The cables had now been laid differently and the G7e could once more be fired under. In the case of the G7a mechanical disturbances were causing premature detonation and the G7a could therefore still not be fired under until the question was finally cleared up.

I expressed doubts on these different explanations for premature detonations, but as the Director of the Torpedo Inspectorate assured me that the G7e was now safe, I decided to try and I released the G7e for firing under with "MZ".

6) On 18.10 U 46 reported a premature detonation of a G7e in an attack on a convoy. It was therefore established beyond question that the pistol was not safe in the G7e despite the adaptation made. I again ordered impact firing only also for the G7e, with electric firing cut out (switch setting "A").
We were thus back where we were in 1914/18. But I had to make this difficult decision to abandon the much-vaunted, much-discussed magnetic firing in order to avoid losing boats, directly or indirectly, through our own weapons and in the interests of U-boat successes.

7) On 20.10 the Director of the Torpedo Inspectorate informed me by telephone that he had discovered that day that the torpedo (G7a and G7e) was keeping a depth 2 meters below that indicated. Numerous reports from boats, stating that the torpedoes had failed to fire with impact firing units despite good firing data, also indicated that the torpedoes were running deeper than their setting and therefore passing under the target. I therefore ordered on 20.10 that torpedoes with impact firing were to be set at a maximum depth of 4 meters.
At the suggestion of the Torpedo Inspectorate, I ordered further that torpedoes with impact firing were to be set at 2 meters or less than the draft of the target. But in order to avoid surface breaking and consequent cold running the minimum depth setting had to be fixed at 3 meters, and 4 meters in an Atlantic swell. This meant that torpedoes could not be fires at targets with a draft of less than 5 or 6 meters, e.g. destroyers could not be attacked.

8) On 23.10 a conference was held in Wilhelmshaven between B.d.U., Director of Torpedo Inspectorate and Director of Torpedo Trials Department and Torpedo Experimental Command, in which the following points were confirmed:

a) variations in depth considerably greater than hitherto assumed were to be expected.

b) that the cause of premature detonation had not yet been established.

c) at B.d.U.'s request, it was agreed that at least the explosion at the end of the run which had also frequently occurred, should be eliminated in the near future.

It was thus established that the effective functioning of the torpedo was very limited indeed:
with impact firing, danger of passing under with "MZ" shot, danger of premature detonation.

9) On 5.11 a new (adapted) pistol was brought out and it was hoped that, by stabilization of the needle, it would be proof against premature detonation. The pistol was designated Pi(A-B). With this pistol use of magnetic firing was again permitted. Depth was to be set at draft of target plus 1 meter. All our hopes were now centered on this pistol and further reports received of failures of the present pistol seemed less important.

10) U 28 and U 49 were the first boats to sail with Pi(A-B), on 8.11 and 9.11 respectively. On 19.11 U 49 reported one G7a premature detonator after the safety distance had been covered, one G7e probably failed to fire, 2 G7a detonated after covering 2000 meters. This was a bitter disappointment and our best hopes were dashed in one blow. Apparently there was no improvement on previous conditions. Further reports followed from other boats of premature detonations and failures to fire.

11) Some of the specialists in the Torpedo Inspectorate suggested that the pistols should be set 2 zones below the setting shown in the chart in order to reduce sensitivity and so avoid premature detonation. The depth setting should be the same as the draft of the target and the torpedo thus brought closer to the ship so that the firing field would be effective even at the reduced pistol sensitivity. I was against this and the Director of the Torpedo Inspectorate and the remaining specialists agreed with me.

12) Small alterations to the pistol (insulation of the copper cap, smoothing a thrust collar) did not bring any improvement. Every now and then premature detonations seemed to become fewer for a time and firing under was adhered to, because firing with impact firing units would again have meant many failures due to passing under.

13) Report of shots, in which the pistol failed to fire, despite certain firing data, became more and more numerous. The Torpedo Inspectorate believed that the pistol could not fail to fire if shot under and refused to accept any idea that failures could be caused by this section of the pistol. I had all shots, which the commanding officers believed to be failures to fire examined by the Torpedo Inspectorate. They thought that these must be due to misses or be regarded as unexplained. I can no longer accept this explanation. in view of the large number of reports of shots failing to fire with certain firing data. I consider that in many cases the failure of the pistol to fire is proven and I made this quite clear in a conference with Torpedo Experimental Command on 19.1 (see War Log of 17.1).

14) Experimental firing at T 123 afterwards showed that in fact several pistols failed to fire when shot under. The Torpedo Inspectorate now admits the possibility of failures to fire and issued the following instructions, to be passed on to the boats, on 21.1:

1. For targets under 4,000 BRT, destroyers and surfaced S/M's, depth setting 4 meters.

2. The pistol may fail to fire against targets under 1,000 BRT.

3. For all other targets, depth setting draft plus 1 meter, even in bad weather.
The results remain to be seen.

15) In addition to the negative results of trial firing at T 123, recent magnetic measurements of the body of the torpedo and the battery compartment have shown that these exercise an irregular, unstable magnetic effect on the pistol and may cause a strengthening (premature detonators) or a weakening (firing failures) of the magnetic unit. The torpedoes in store are to be demagnetized. The Torpedo Inspectorate doubts if this will be successful. The causes of the failures have therefore by no means been mastered.

16) The Commanding Officers' and crews' confidence in the torpedo is very much shaken. Again and again the boats have tried, in the face of strong enemy activity, to fire their torpedoes under the best possible conditions and often when they have made a daring attack they have been rewarded with failures and even danger to themselves. At least 300,000 tons, which might have been sunk, can be reckoned lost through torpedo failures. I think it is certain, for instance, that U 47 Lieut.(s.g.) Prein's shot at the London class cruiser was a premature detonator. It is very bitter for Commanding Officers and the executive control to find that the U-boat Arm cannot achieve the success expected of it, in spite of a thorough peacetime training, because of torpedo failures.
I will continue to do all I can to keep up the fighting spirits of the U-boats in the face of all the setbacks. We must continue to fire torpedoes in order to discover the causes of the defects and remove them. But commanding officers and crews will only gradually regain full confidence in the torpedo if lasting technical improvements can be made.


More from the BDU KTB's

http://www.uboatarchive.net/BDUKTB30262.htm - Norway Campaign

http://www.uboatarchive.net/BDUKTB30263.htm - Norway Campaign

http://www.uboatarchive.net/BDUKTB30264.htm First half of May 40 and Donitz continues


I have therefore demanded, as set out in a T/P to the Torpedo Inspectorate, that the English pistol be copied as quickly as possible. A faultless functioning of this pistol may be expected by reason of its simple construction.

[Bilge_Rat]

should this thread be stickied like the other one? I have a lot of material on U.S. sub doctrine in WW2.

dealing first with the U.S. torpedo problems, here is a good article which summarizes the problem:

http://www.historynet.com/air_sea/naval_weaponry/3037866.html?featured=y&c=y

There were basically three problems:

1. the magnetic exploder did not work as advertised. Because it was top secret, U.S. skippers were not told of its existence until a few months before the war and were given only cursory details on how it worked. Most turned it off and relied exclusived on contact exploder 2-3 months into the war;

2. the torpedoes ran much deeper (i.e. 6 feet or more ) than set. This was only really figured out in the summer of 1942;

3. the contact pin was too weak, it would break if the torpedo hit a ship at a 90 degree angle without exploding. This was only figured out in the summer of 1943;

So it was not until the fall of 1943 that U.S. skippers had a fully reliable torpedo. The attitude was also different, when Donitz was informed of german torpedo problems by his skippers, he believed them and the problems were solved quickly. When reports started coming in from U.S. skippers about torpedo problems, the torpedo bureau and flag officers took the position that the skippers were not using the torpedo properly, which delayed a resolution of the problems.

[Sailor Steve]

Sorry, but that last is just not true. The German problems very closely paralleled the Americans'. In the Norway campaign they estimated that they lost the opportunity to sink several cruisers and merchants, along with three separate chances to sink the Warspite. At one point Prien complained that he fired everything he had at an anchored merchant group. All torpedoes ran deep and the British never even knew they had been attacked.

Yes, Doenitz did respond quickly by ordering the removal of magnetic pistols immediately, but they didn't have a good working magnetic torpedo until early 1943, just ahead of the Americans and two years after the problems were identified.

[Bilge_Rat]

By relatively quickly, I meant the summer of 1940 when they had a reliable torpedo, which means about 10 months into the war rather than 20 months for the U.S., but its clear the KM also had its share of torpedo problems as well.

[bigboywooly]

Yes the Germans missed some BIG targets due to torpedo failure


11.4 T.O.R. 1350:
W/T message T.O.O. 1246........2 destroyers torpedoed on the evening of April 10th. Effect of explosion not observed. U 25.

11.4 T.O.R. 2340:
W/T message 2115. Triple spread miss on Cumberland, one detonation at end of run. Triple spread on York cruiser in grid 5617 at 2115. Spread fused prematurely. Depth 7 meters, zone - 4. Position grid 5672. U 48.

12.4 T.O.R. 0305:
W/T message 2250. 2 failures, one detonated at safety distance, one after 30 seconds, 100 meters off large destroyer. U 51.



The first sub sunk in the war was due to such a failure

U 39 attacked the Ark Royal on the 14th Sept 39
Magnetic torps detonated early alerting the escorts
The sub was DC to the bottom
All hands survived though

The Norway campaign bought out further problems with the Mag pistols in so far as it was belived the the Earths magnetics in that region made the problem worse ( not sure if explained that right )

U 48 reported 2 triple spreads in the evening on a large cruiser, no hits scored, 4 self detonators. THis report of failure, together with those of U 51 and U 25 give rise to extreme doubts as to the effectiveness of magnetic fuse in Zone O. The question of torpedo failure appears to threaten the success of the entire operation.

The torpedo Inspectorate tried to claim the British were using degaussing equip on most of their ships to explain the mag failures
Obviously not true in early war

Basically at the start of the war the German torpedos were no better than at the end of WW1 apart from the splashless entry