WI:Krigesmarine type xxI

Discussion in 'Alternate History Discussion: After 1900' started by HMS queen Elizabeth, Nov 9, 2018.

  1. Electricfox Omnishambler

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    HTP Submarines - Life's a bleach and then you dive.
     
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  2. McPherson McPherson; a guy who needs a shave.

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    I would rephrase that to: "life's a blanche and then you dye white with fear."
     
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  3. phx1138 Bocagiste troll

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    A pod of Hedgehog round? That's something that's never occurred to me.:oops: Sounds like it might be a good idea.
     
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  4. Astrodragon Coffee-seeking Dragon Donor

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    While eliminating the advantages of HF/DF, code breaking and centimetric radar will help the U-boats, it still wont let them win the Battle of the Atlantic.

    Without the informational advantage, the allies wont be able to route evasively as OTL. This will result in more convoy battles and more merchant ships sunk. But it will also result in more U-boats sunk.
    Radar was most efficient in Biscay, against subs entering and leaving port. With radar warning kit, those losses will be reduced (not eliminated, luck and errors also play a part). But it does mean a lot more time submerged, so shorter time on station for the U-boats.

    Regarding the efficiency of allied efforts against a better U-boat. Well, the Loch/Squid combination was coming in 44, it would be feasible to speed up the squid/sonar part and put it into River class escorts as a priority. That combo was an effective sub killer until the mid-50's, against boats which are better and quieter than a Type XXI. So the allies aren't as helpless as you may think.
    Remember that a Type XXI still has to get quite close to launch a torpedo, and the escorts are there listening for you. And the faster you go underwater, the noisier you are.
    More shipping losses, yes. A winning BoA, no.
     
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  5. lordroel Well-Known Member

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    Nope it would not matter, the whole point about the XXI was that it was invisible to radar. The 10 cm radar sets available in 1943 had a very hard time picking up the large ball valve snorkel head of the XXI. The smaller T-valve heads which were in development could not be seen by 1943 radar and were very hard to find with 1945 radar. The XXI was virtually invisible on the march.

    Now assume the XXI project is two years ahead of itself. This is not a simple premise since the 1943 XXI would not be the same as the 1945 XXI which was the product of the prevailing chaotic conditions. The workmanship would be better and the mess with the hydraulic system would probably not have happened since the 1943 XXI would still have used electric motors. It would have been a higher quality boat with a lot less problems. Further, the crew training program would have been undisturbed by enemy ASW in the Baltic. Also not that snorkel technology would have to be 2 years ahead of itself, so there was scope for a small, radar invisible T-valve snorkel down the road.

    What would have happened if about 100 of these 1943 XXI had been operational by the summer of 1943? They would have sunk a lot of ships and would probably have torn up the odd convoy. If we assume a production of 20 XXI/month and a loss rate of 10 - 15 per million tons sunk, we wind up being able to sink 1.3 - 2 million tons per month and still keep up the number of U-boats in the field. The loss rate of 10 - 15 per million tons is reasonable when one considers the way the XXI would operate. It would be invisible to radar since it never surfaces and the snorkel head is very hard to find, so losses while enroute to station would be minimal. It carried 23 torpedoes and had a fast reload system which would have allowed at least two attacks on a convoy before being found. So the XXI gets in something like 6 kills with 12 torpedoes before it has to dive away. With some luck, they could get off 18 torpedoes which would give around 9 kills. A single XXI attack would result in the sinking of 30,000 - 50,000 tons and the XXI probably has an even chance to get away. Note it can run for 11 hours at 10 knots, which is more than adequate for keeping up with a slow convoy. So far we are working with standard torpedoes, no Lerche.

    The big problem with winning the Battle of the Atlantic becomes finding the convoys. The XXI was capable of finding its own targets out to a distance of around 30 NM using sonar and it could probably hear a battle 60 or even 90 NM away. The best way to use them would have been under radio silence for the whole voyage and that would have been the end of ULTRA. However, it is doubtful that Doenitz would have done that. He would most likely have continued on with all the chit chat, although that may have tipped him off to ULTRA since a lot of XXI would have survived the attempts to sink them enroute and also they would have picked up the attempts to reroute convoys. I would think that given a year, Doenitz would have found ways to minimize the effect of both HF-DF and ULTRA. Since the XXI could have operated in a high threat area, it could have operated close to the western approaches and picked up its targets relatively easily.

    This does not answer the question of how many ships get sunk. In order to win the Battle of the Atlantic, the objective would have had to be 15 - 20 million tons per year, which was Allied production plus a modest reduction in the total pool. Historically, the U-boats sank 5.8 million tons in 1942, their best year, out of total Allied losses of 8.2 million tons. The XXI would have had to manage about 3 times that, rather unlikely given only the XXI. If we throw in wire guided torpedoes like Lerche, the numbers start to look better since the XXI can now bite back hard against pursuing ships. And so we find ourselves on that slippery slope of “What ifs”.

    The XXI by itself in 1943 would most likely not have resulted in a draw or a German win, but in a longer war. However, it was a vital ingredient in any German draw/win scenario. The other vital ingredients were an earlier appearance of jet aircraft, notably the Me 262, and the death of Hitler by 1943. With the Me262 in control of the air over the Reich in 1943, the XXI doing major damage in the Atlantic and the generals running the war without Hitler’s interference, a draw was quite possible. In this sort of scenario, the Americans would have had a tough time delivering an atomic bomb in the face of German air superiority.
     
  6. McPherson McPherson; a guy who needs a shave.

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    I agree.
    The German U-boaters pinned their hopes on their 1943 variant of pre WW II US deep sonar attack tactics. Creep into ambush, lie in wait for the target to overrun them and then launch a barrage of pattern seeking and acoustic torpedoes. This was the emergent U-boater convoy attack doctrine that comes into use with Type VIIs and Type IXs when the improved torpedoes arrive. GsG and GsF multi-channel sonar helps with the convoy location problem but the U-boaters are still at the mercy of their endurance limited G7 family of weapons. 140 degrees offset angle solution and 500 run seconds means a weapon functionally no better than the Mark XIV, and that is not good enough for "mobile minefield" tactics.
    Mr. Snort is not radar proof.
    Uhm… the British were terrible at ASW in the Falklands crisis. This is not because they were lacking in the skills. They did not have enough assets. Some people forget that the key aspect of the Battle of the North Atlantic and the allied victory is sensor saturation and sheer numbers of launch platforms with the needed profundity of weaponry to throw at each U-boat. By 1944, whole CVE task forces were deployed to chase 1 lousy U-boat. That is one (small) aircraft carrier with 25-30 aircraft, 4-6 destroyers and hundreds of depth charges and dozens of ASW mortars and plane dropped acoustic torpedoes, not to mention the air dropped sono-buoys, and the dozen or so active pingers and magnetic anomaly detectors, working like mad (pun) to develop a return off the 1 U-boat.
    It is a numbers war. Can the attacker saturate the defense? Nope. Too late.
     
  7. thaddeus Well-Known Member

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    thanks for putting that all together!

    if the KM had better discipline on communications, added keys to their encryption (?), and pursued the Kurier short radio burst concept? wonder how much longer they could have kept their clandestine surface fleet?

    you highlighted the fact that their departure zone (Bay of Biscay) was extensively targeted but without the support ships their target area by necessity shrinks? (a box inside of a box, the Allies know where you are departing from and the (likely) extent of your operational range)

    would add that they dealt away their Northern Sea Route (north of USSR) to the Pacific when they launched Barbarossa.
     
  8. Astrodragon Coffee-seeking Dragon Donor

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    And yet the RN had exactly zero ships damaged or sunk by submarines in the Falklands...

    Part of the problem is an A/S screen has quite a different configuration to an AA one. Given the losses, concentrating less on the A/S screen seems sensible.
     
  9. McPherson McPherson; a guy who needs a shave.

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    (^^^)

    As I explained in my immediate earlier post, I can agree with none of this assessment. The Germans were barking at the wrong development trees and their technical solutions would have failed against existing Allied saturations and systems in place. As for German air superiority provided that the Me262 had entered service mythically at the same time as the early Type 21? I respectfully disagree. The British and the Americans were about at jet engine performance parity with the Germans, way ahead in the esoteric materials science involved, and the allied plane designers were just so much better at their aircraft airframe trade-craft that aside from Kurt Tank it is ridiculous how bad the Germans were at it in 1943 on as they produced their paper designs and fantasies. Those "mythical" atomic bombes would have been delivered and there would be nothing the Luftwaffe could do to stop it. Luftwaffe 1946 was/is/has always been a myth.
     
  10. McPherson McPherson; a guy who needs a shave.

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    Against 1 German built coastal defense submarine with a "defective combat information system" and a partially trained Argentine crew that did not understand how their torpedoes worked and 1 de-rated GUPPY caught on the surface being misused in a supply / commando mission found by a lucky British ASW helo after that Argie captain broadcasted his position to the world on the radio? The point about not losing a ship to torpedo attack in this situation, AFAICT, is that it is positively based on sheer dumb luck and the fact that the Argentinians totally misused their paltry 2 assets. The British were / are never incompetent in ASW, but they were incredibly lucky that those sub drivers were not Russians.

    Air defense is an entirely different subject in this regard. If we want to refight the Falklands, it might be better if we take that to chat or perhaps visit one of the Falklands threads?

    In BOTNA terms, air defense of convoy means shooting down LRMPs. The Allies have Casablancas and Wildcats for that role. As for the LRMPs, the Germans never develop effective ones so it becomes an ASW exercise once the Condors are dead meat flying.
     
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  11. phx1138 Bocagiste troll

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    That's just it. With FIDO only capable of 12 kn for 10 min, you're looking at a Type XXI able to evade for over 8h: it only has to maintain 12kt to keep distance, & only do it for 10-12 min at a time...
    Am I being dense? Because I don't see anything "radical" about the idea of the Type XXI. Take a Type IX pressure hull, put in a 5m plug for more battery, sheathe it in a new casing (which sholdn't take too long to design), tank test a bit, & deploy. Knowing the Germans, the first batches probably have a lot of complicated & buggy gewgaws the crews will hate, & those will get deleted in the later batches, but maybe not, if you keep the internal gear to OEM Type IX.
     
    Last edited: Jan 6, 2019
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  12. McPherson McPherson; a guy who needs a shave.

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    One FIDO vs. 1 sub, maybe. US trials boats were capable of 5 m/s submerged and were battery sustainable at that speed for about 15 minutes. They could not outrun a pair. Type 21s are 1 m/s faster in theory. but if caught shallow are no faster than a US boat. The FIDO is still a success if the sub cannot execute a contact and sink.

    Good point. The Germans went to a sliced sausage assembled welded together hull sections method which was different from their usual keel, frame plates method for their previous U-boats' manufacture. Guess why I would not be a happy U-boater in that sausage? Would you trust some schmuck hastily retrained shoe salesman Walter from Stuttgart to know how to weld together an 8 meter in diameter barrel seam?
     
  13. Cryhavoc101 Well-Known Member

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    Some U-boat hunts took place over the course of a day or more till a successful prosecution with DC and Hedgehog - FIDO simply made attacking them easier

    And even if a U-boat did ultimately evade destruction and managed to escape - its low of battery charge and the crew are exhausted and any convoy they might have been targeting is 100-200 miles away!

    Ultimately winning the BotA wasn't about sinking U-boats - it was stopping U-boats sinking Merchants
     
  14. phx1138 Bocagiste troll

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    I entirely agree with the final proposition. Prosecute to kill wasn't required; I follow RN/RCN on that: keeping a U-boat down & away from the convoy will do nicely.

    I disagree somewhat with the ease of doing it being presumed. IMO, a faster boat will much more easily break contact with escorts &/or a/c, & more easily regain contact with a convoy. Yes, in time the Allies will have more *FIDOs & more improved *FIDOs, & IMO ultimately will defeat the *Type XXI--but what about in the meantime?:eek:

    Beyond that, & so far unanswered, is, what is RCN going to do with corvettes too slow to pursue dived *Type XXIs? What happens when you have hundreds of ships stacked up in Halifax & Boston without escorts? There aren't enough DEs as it is, are there? Nor enough crews. (And RCN hasn't the capacity to man them in any event: no suitably trained crews.) Neither will the new Supervictory be an answer; it can't replace the millions of tons of existing (slow) shipping, & sending these without escort is an obvious non-starter.

    So where are the notional escorts hunting these *Type XXIs to destruction coming from? And what isn't being escorted, to provide them?
    I continue to think breaking contact is easier than you do, & I don't think either of us is likely to be persuaded on it.
    True enough. However, the Type IX worked, & adding an identical section is a minimal change, so I'm not seeing the hazard spiking. Also Germany in wartime, so... Is there a chance of it? Maybe. Will it be uncovered in pre-operational trials? Maybe. Will BdU accept a (somewhat) higher loss rate for a higher performance? I would (tho it wouldn't be my default position).
     
    Last edited: Jan 7, 2019
  15. AJE Well-Known Member

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    It will not result in more U-boats sunk. Without the informational advantage, the Allies won't be routing evasively, but they also won't be routing dedicated ASW task forces offensively against the U-boats. U-boat losses will massively decrease as the U-boats are engaging less defended convoys when they are ready (or at least when the Allied convoys are as surprised as the U-boats are), and not engaging strong ASW task forces when they are caught by surprise.

    That is still a massive increase in time on station over OTL, as each ship whose station time is cut short by having to dive would have either been completely surprised and sunk OTL, or have had to make an emergency dive after being attacked anyway. Either one reduces time on station more than diving with warning from the radar warning receiver.

    That would work against the usual weapons used, but navies developed homing torpedoes like Cutie (US), Zaunkönig (Germany), and Zaunkönig II (Germany) to deal with those at around the same time. Germany screwed up its design and didn't get a torpedo that was immune to countermeasures like FIDO and Cutie, but a navy that doesn't won't have problems with Loch/Squid or any other WWII-era ASW technologies.

    But a submarine (of any kind) going fast is still quieter than surface ships going that fast. Outside of minehunters they have very little consideration given to underwater noise. It doesn't help much if the escort can hear a submarine but has to become an even bigger and noisier target than the submarine in order to catch up with and attack it.

    In short, if the Germans countered all 3 of those technologies, the Allies will still win the war but by brute force and simply being able to force more ships and materiel into the fray than the U-boats can hope to shoot down. Losses will remain very high until the end of the war with the Allies being unable to systematically find and destroy U-boats outside of those attacking convoys. Essentially the Battle of the Atlantic won't be decisively "won" in terms of systematically destroying U-boats while preventing them from having any significant effect on shipping, like what happened OTL. It would be a case of just taking big losses until Germany is invaded and defeated on land.

    As I said earlier, whether it's US submarines versus Japan's merchant fleet, British submarines versus Italy's merchant fleet, Germany's submarines versus the Allied merchant fleet, or any submarine force versus another navy, the submarine is superior to its countermeasures in cases of parity. If a country's submarine force is equal to its opponents in terms of technology, organization, and leadership, it will be able to operate unchecked by enemy countermeasures destroying its opponents' merchant fleet and navy. An ASW force can only defeat a submarine force through a sufficiently large technological, leadership, or organizational advantage to offset its inherent superiority. Just because the Battle of the Atlantic was won by thorough German incompetence and inferiority at all levels, does not mean that an ASW force as well-equipped and well-led as the Allied one would defeat any hypothetical WWII-era submarine force. It can be countered, and although the US' economic and industrial power would always win the war through brute force if necessary, such a force would be ineffective at limiting losses to a submarine force that was equally well-led and well-equipped.
     
  16. phx1138 Bocagiste troll

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    And we know that with the benefit of hindsight. What happens when the Brits are faced with very much faster U-boats that are, by all appearances, immune to any existing ASW? If they appear around May or June '43 (around the time of SC-229, IIRC), they're liable to be just enough to prod the Brits to actually do what they contemplated, but didn't: abandon convoy altogether.:eek::eek::eek: So are even less-effective, & less-numerous, *Type XXIs enough to do that?

    OTOH, as I think I said, if *Type XXIs lead to no Italian invasion, better in the long run...
     
  17. McPherson McPherson; a guy who needs a shave.

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    OP-art tempo and op-research. The British adapt what they have. If they have good mathematicians, and they do, they work out the tactical speeds equations and up their game that way. In the mean time they tighten belts and shift the bombing campaign and modify existing tech and doctrine.

    Cause? The Type 21 U-boats have to stick up snorts, leave wakes and they have to breath. The Type 21s are at that condition, slow, shallow and almost deaf and blind. Just as vulnerable as any battery recharging U-boat.

    Need better ASV obviously, MAD equipped Liberators obviously and either more Barracudas or Avengers as carrier borne ASW variants. Faster FIDO, contact grenades as we discussed, and grit teeth for six months until the quick fixes come on. Convoy is still the correct solution as log versus cube rule proves.
     
    Last edited: Jan 11, 2019 at 12:14 PM
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  18. phx1138 Bocagiste troll

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    You & I know that, but at the time, without even the shock of the higher-performance boats to face, the Brits were seriously considering abandoning it. So don't give me "op art & ops research", because the Brits used it, & still figured convoy might not be working--without facing the greater threat (real or not).

    On mining, the PTO Sub Force COs hated it, too. It actually worked nicely: one MV sunk & one damaged for every 26 mines laid, & no boats lost laying.
     
  19. PSL Information not passed on is lost.

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    That was actually proposed to modify the existing fleet of U-Boats , but it would have delayed XX-I by year. The speed advantage would have neutralized /offset late war ASW advantage.
     
  20. ennobee Well-Known Member

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    the biggest change I can see is that the Typ XXI class has a speed of 16 knots surfaced and 17 knots submerged. Versus only 7 knots submerged for the Typ VII who fought the battle of the Atlantic OTL. This means that a convoy would not be able to outrun a submerged Typ XXI the way it could a Typ VII. Thus the common strategy of long-range aircraft and minesweepers keeping the u-boat submerged while the convoy makes an evasive maneuver would no longer work. The U-boat has to be hunted and killed, not just 'nailed down'. I have no doubt that with the resources available the convoys would eventually succeed in detecting and killing even a continually submerged u-boat like the XXI, but it would still take them.several months to develop new tactics.

    Curiously, this makes it harder for the allies if the XXI were to replace the VII in 1941 then it would be if the XXI were available earlier and superseded the VII before the battle.