Earlier Type XXI - informed by Cold War developments

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TheMarcksPlan
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Re: Earlier Type XXI - informed by Cold War developments

Post by TheMarcksPlan » 18 Aug 2020 03:20

Lars wrote:I would add: Is there a risk that the U-boats sink one of their own in such a torpedo rich environment?
Regarding the pattern-running torpedoes no. These would be running near the surface, the U-Boats well beneath. A U-boat forced to surface amidst the convoy would likely get hit by a torpedo but such a U-boat is screwed anyway.

The homing torpedoes did pose a threat to Uboats:
After at least two unconfirmed instances of U-boats (U-972 and U-377) sinking after being allegedly hit by their own torpedoes, the BdU ordered the submarines to dive to 60 metres (200 ft) and go completely silent after launching acoustic torpedoes to minimize the risk.
https://en.wikipedia.org/wiki/G7es_torpedo (haven't checked the article's cites but they're provided in article).

It'd be unlikely for two submerged boats to be so close together that their fish would home on another sub but I suppose it's a risk.

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Re: Earlier Type XXI - informed by Cold War developments

Post by gurn » 18 Aug 2020 06:18

little bit about torpedoes from U.boat.net
https://uboat.net/technical/torpedoes.htm
"Variants
All the German U-boat torpedoes were 53.3cm (21 inch) in diameter and had a warhead of 280kg (The T5 had 274kg). There were also two important pattern-running devices which could be applied to various torpedo types. These were FAT and LUT.

The FAT (Federapparat Torpedo) ran a wandering course with regular 180-degree turns, was useful against convoys, and was fitted to both G7a and G7e T3s. From the end of 1942 onwards it was manufactured at the rate of roughly 100 per month.

LUT was a more sophisticated version of the FAT, with more variable patterns, but was only used operationally towards the end of the war."

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Re: Earlier Type XXI - informed by Cold War developments

Post by TheMarcksPlan » 18 Aug 2020 06:33

...and a bit more from the internet:

LuT

In March 1944, a new torpedo guidance device appear, the LuT (Lagenunabhängiger Torpedo), which was developed from the FaT design, but that incorporated someimprovements in the search pattern.Now it was possible to set a new course, after a primary run, this new course, allowed thetorpedo to follow the course of the convoy, to then start a zigzag search pattern. Thiszigzag distance, would be set to be anything from 0 to 1600 meters, while on the originalFaT, only 2 options were available.The velocity of the torpedo was alsoimproved, and its speed could be setbetween 5 to 21 knots. The LuT wasinstalled in the G7a (TI LuTI G7a), andin the electric version of the same (TILuTI G7e), with increased autonomy. A new version, the LuTII, allowedchanges of course, of 180°. The LuTwasn't used in combat until 1944, andonly some 70 of them were usedoperationally.
https://fdocuments.in/document/dangerde ... rev10.html

Image


Image


@Carl Schwamberger I still haven't relocated my earlier-referenced source stating the pattern-running torpedoes would have >90% hit rate. But IIRC it was just an opinion statement.

That said, the above diagrams show the basic sense, IMO, in judging an exceptionally high hit rate for the pattern-running torpedoes. Just envision 90 of the red patterns on the second diagram overlaying a convoy and it's difficult to imagine much of it surviving.

The LuT in particular would be deadly. As its name suggests ("position-independent"), it could be launched at any bearing and run a pre-set path across a convoy (used a gyroscope to determine its post-launch bearing and another to run its pre-set course). So a sub could fire an LuT while running away from the convoy or whatever.
Last edited by TheMarcksPlan on 18 Aug 2020 07:33, edited 1 time in total.

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Re: Earlier Type XXI - informed by Cold War developments

Post by TheMarcksPlan » 18 Aug 2020 07:25

Tom from Cornwall wrote:How well do you think your "wolf pod" can co-ordinate their attack?
This is definitely a weakness of the true submarine, which can't use its radio, versus a surfaced submersible which can.

That said, two points:

1. The Germans developed a "burst transmission" system for broadcasting convoy locations in the later war. See Llewellyn at 132 for discussion of its implications. Among other things, this meant a sub had only to poke above water briefly to "download" a long radio transmission containing all relevant operational info.

2. Depending on which version of an "Earlier T21" ATL we're discussing, it's possible for the Germans to have hundreds of boats at sea at once. The USN's downside scenario, after all, was based on the SU building subs as fast as the Germans and therefore fielding 2,000 boats. In that circumstance, you could have 5-boat pods always remaining within a mile or so of each other. Such a pod ~simultaneously picks up radar/visual/hydrophone/sonar contact on a convoy and, pursuant to tactical policy, embarks on a simultaneous attack without needing to coordinate (all pod members would assume that all others would be attacking once contact was made). The pod would also leverage the burst transmission system to position itself for maximum likelihood of encountering a convoy.
I'm certainly not a statistician, but doesn't your calculation rely on a rather unlikely perfect spread of torpedoes fired from a perfectly placed set of submarines against a perfectly positioned set of targets?
I don't think so. See the diagrams in the preceding post. IMJ any pattern-running torpedo aimed at the convoy (a target several miles in length and breadth) would have trouble not hitting something. ...unless the convoy has been mostly sunk, in which case there's a lot of gaps in the diagram. But obviously that's a feature, not a bug.
How many dud warheads or dud fuzes or defective "pattern running" mechanisms or defective electrical circuits, etc, etc.
The warheads were no different from the normal German warheads which, by later-war, were fairly dependable.

Good question re the guidance systems - idk.

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Re: Earlier Type XXI - informed by Cold War developments

Post by TheMarcksPlan » 18 Aug 2020 08:36

TheMarcksPlan wrote:Depending on which version of an "Earlier T21" ATL we're discussing, it's possible for the Germans to have hundreds of boats at sea at once. The USN's downside scenario, after all, was based on the SU building subs as fast as the Germans and therefore fielding 2,000 boats.
As I've said from the start of this thread, IMO there's no feasible story in which the T21 alone can win the war. If the Red Army kicks the Ostheer's teeth in, there's nothing to be done at sea for the Nazis.

But given the common view that Hitler should have - and could have - avoided war with the SU, it might interest some to consider an earlier T21 in a no-Barbarossa context. And it's interesting to me, of course, to consider T21 in a post-Barbarossa context where the Germans have won in the East (as I think they should have).

In OTL 1944, Germany spent ~5% of its munitions budget on Uboats:

Image

If there's no Eastern Front, moving just half of the of the ~half of German Heer munitions spending to Uboats - i.e. increasing Uboat share to 30% - would result in 6x the historical Uboat production. Speer's OTL program was for 30/mo in 1944; 6x that program is 180/mo.

Now of course the Allies would freak the F out over 180 T21's per month and start bombing anything with a whiff of Uboat. But even if they cut Uboat production in half that's 90/month or say 1,000 per year.

...which is an absolute nightmare for the Wallies.

Of course there are short/medium-term bottlenecks to expanded U-boat production such as shipyard space. But in the longer term - especially in a "No Eastern Front" ATL - Germany can expand shipyard space. Heck it nearly built enough shipyard space for all T21 final assembly under 20 feet of concrete. https://en.wikipedia.org/wiki/Valentin_submarine_pens

The OTL Uboat campaign imposed ~10x the economic costs on the Wallies as Germany herself bore for Uboat production. https://web.archive.org/web/20080409052 ... aigns.html

Had T21 been merely as successful as T7/9 were until '43, the Wallies' economic resources edge would have disappeared against a thousand T21's.

The point isn't that the T21 was some wunderwaffe - it wasn't. It was simply the rational adaptation of 20th century guerre de course strategy to 20th century realities.

The point is that the '43-'45 equilibrium in which submarines were decisively defeated is a historical anomaly. In every period besides '43-'45, the submarine enabled an inferior seapower to impose asymmetrical costs in conventional global warfare. Those asymmetrical costs would have heavily favored the USSR in the Cold War had warfare not turned into reciprocal nuclear holocaust. It was humanity's good luck, IMJ, that the brief interregnum between submersible and submarine coincided with Germany's defeat.

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Re: Earlier Type XXI - informed by Cold War developments

Post by Carl Schwamberger » 23 Aug 2020 22:33

TheMarcksPlan wrote:
18 Aug 2020 07:25

2. Depending on which version of an "Earlier T21" ATL we're discussing, it's possible for the Germans to have hundreds of boats at sea at once. The USN's downside scenario, after all, was based on the SU building subs as fast as the Germans and therefore fielding 2,000 boats. In that circumstance, you could have 5-boat pods always remaining within a mile or so of each other. Such a pod ~simultaneously picks up radar/visual/hydrophone/sonar contact on a convoy and, pursuant to tactical policy, embarks on a simultaneous attack without needing to coordinate (all pod members would assume that all others would be attacking once contact was made). The pod would also leverage the burst transmission system to position itself for maximum likelihood of encountering a convoy.
This would be impressive. Hughes & Costellos Battle of the Atlantic has quarterly numbers & shows operational boats peaked at 100 during Oct-Dec 1942 & held to that number Jan-March 1943. Thats for the North Atlantic and North America waters. Adding in the Mediterranean, South Atlantic, & Indian Ocean increases that slightly. This fell back town to 1942 levels of 60 operational boats in July-Sept 1943 & 35 Oct-Dec 43. Note that in this case H & C refer to boats actually able to patrol. Repair, refit, and training numbers are separate even tho counted as operational by other methods.

During this peak six months from October 1942 thru March 1943 attack groups of ten to fifteen boats were possible with 2-4 such groups available on the average in the north Atlantic. Some larger groups were occasionally managed, tho typically half or less of a group actually sighted a convoy. In the autum of 1942 these groups were able to intercept a convoy better than 50% of the time. After the Brits discovered the convoy radio code had been compromised & closed it to German penetration the intercept rate fell off significantly. A increase in the penetration of the KM radio signals allowed a increase in enroute course changes to dodge the suspected lines of the attack groups. Montifiores 'Enigma. The Battle for the Code' & Budianskys 'Battle of Wits' have some passages describing how that worked.

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Re: Earlier Type XXI - informed by Cold War developments

Post by T. A. Gardner » 23 Aug 2020 23:28

Type XXI production would have been limited most by the ability of Germany to produce batteries for the boats, both new ones and replacements for ones in service. Since each boat would require twice the batteries (at a minimum) as a Type VII or IX, this would mean that about half the number of boats of those two types could have been produced as battery production was limited in Germany throughout the war.
If the Allies were really freaking out about the Type XXI, the bombing and destruction of the Akkumulatoren Fabrik Aktiengesellschaft Berlin-Hagen plant in Hagen on the outskirts of the Ruhr would have effectively put a near complete end to production just as the bombing of the Tego film glue factory did to the Ta 154.
This single plant produced roughly 90% of the batteries used in U-boats and torpedoes through 1942 when AFA opened a new factory in Hanover. While the Germans could rebuild the factory and regain capacity, that would have taken time and not just U-boat but torpedo production would have suffered while that happened.

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Re: Earlier Type XXI - informed by Cold War developments

Post by TheMarcksPlan » 24 Aug 2020 04:03

Carl Schwamberger wrote:
23 Aug 2020 22:33
Hughes & Costellos Battle of the Atlantic has quarterly numbers & shows operational boats peaked at 100
GSWW v.6 has a great table for these stats:

Image
T.A. Gardner wrote: Since each boat would require twice the batteries (at a minimum) as a Type VII or IX, this would mean that about half the number of boats of those two types could have been produced as battery production was limited in Germany throughout the war.
Oh so then Germany must have built T21's at a slower rate than they built T7/9.

Oh wait, they didn't? They must have increased their battery production then.

This is a typical AHF response in that it has a whiff of insight by pointing up a relatively obscure production constraint, but meanwhile can't imagine the possibility of different investment paths creating different output mixes.

Just as Germany invested more to produce more batteries later, they could have done so earlier - with tradeoffs of course. Were the T21 actually available earlier, very heavy tradeoffs in its favor would have been wise.

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Re: Earlier Type XXI - informed by Cold War developments

Post by TheMarcksPlan » 24 Aug 2020 04:33

TheMarcksPlan wrote:GSWW v.6 has a great table for these stats:
Some more basic math...

Say our hypothetical T21 force averages 18 boat-days-at-sea per front-line Atlantic boat (about the KM's average in March '43).

A fleet of 1,000 T21's gets you 18,000 boat-seadays.

Now suppose the T21 is only as effective as the average early-'43 Uboats and sank 100 GRT per boat-seaday.

That's 1.8 million tons sunk every month or 21.6mil per year. The W.Allies maxed at building 14.4mil tons in 1943.

Of course one might guess that T21 would be more effective than early-'43 T7/9; I'd guess 10x more effective on the attrition stats and 3-5x more effective on the GRT/boat-day stats (T21 would, I concede, have more trouble congregating around spotted convoys).

If T21 is only 3x more effective per day than T7/9 then a 1,000-boat fleet sinks 65mil tons annually - more tonnage than existed worldwide in 1946.

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Re: Earlier Type XXI - informed by Cold War developments

Post by T. A. Gardner » 24 Aug 2020 06:00

TheMarcksPlan wrote:
24 Aug 2020 04:03

Oh so then Germany must have built T21's at a slower rate than they built T7/9.

Oh wait, they didn't? They must have increased their battery production then.

This is a typical AHF response in that it has a whiff of insight by pointing up a relatively obscure production constraint, but meanwhile can't imagine the possibility of different investment paths creating different output mixes.

Just as Germany invested more to produce more batteries later, they could have done so earlier - with tradeoffs of course. Were the T21 actually available earlier, very heavy tradeoffs in its favor would have been wise.
They did in 1942, 43, and 44. The Allies also didn't bother to bomb any of the battery plants until the beginning of 1944 even though they knew exactly where they were. When they hit the AKA plant at Hagen in 1944 they pretty much wiped the plant out cutting U-boat production roughly in half due to a lack of batteries available to install in them.
So, if the Allies bomb these plants earlier and more thoroughly they will definitely put a crimp in production.

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Re: Earlier Type XXI - informed by Cold War developments

Post by T. A. Gardner » 24 Aug 2020 17:28

TheMarcksPlan wrote:
24 Aug 2020 04:33
TheMarcksPlan wrote:GSWW v.6 has a great table for these stats:
Some more basic math...

Say our hypothetical T21 force averages 18 boat-days-at-sea per front-line Atlantic boat (about the KM's average in March '43).

A fleet of 1,000 T21's gets you 18,000 boat-seadays.

Now suppose the T21 is only as effective as the average early-'43 Uboats and sank 100 GRT per boat-seaday.

That's 1.8 million tons sunk every month or 21.6mil per year. The W.Allies maxed at building 14.4mil tons in 1943.

Of course one might guess that T21 would be more effective than early-'43 T7/9; I'd guess 10x more effective on the attrition stats and 3-5x more effective on the GRT/boat-day stats (T21 would, I concede, have more trouble congregating around spotted convoys).

If T21 is only 3x more effective per day than T7/9 then a 1,000-boat fleet sinks 65mil tons annually - more tonnage than existed worldwide in 1946.
This completely violates the Law of Diminishing Marginal Utility. As sinking rise, the Allies WILL take increasing action to counter the cause(s). That in turn will result in the Type XXI becoming less and less effective, just as the Type VII and IX became historically. In addition, as sinkings rise, the number of remaining valid targets will decrease resulting in a decrease in sinkings simply because there are fewer targets to be had.

So, while an earlier Type XXI would be more effective than the Type VII or IX, the end result would be the same. The Allies likely paying a somewhat higher price will still win the battle of the Atlantic and the German U-boat fleet will be hunted down and sunk just like virtually every other unsupported commerce raider naval war in history ended. Commerce raiding is a spoiler, not a war winner. It is best done on the cheap as that gives the best return for the investment.

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Re: Earlier Type XXI - informed by Cold War developments

Post by TheMarcksPlan » 24 Aug 2020 20:12

T.A. Gardner wrote:while an earlier Type XXI would be more effective than the Type VII or IX, the end result would be the same.
This is like a mantra repeated to soothe anxiety.

The "law" of diminishing marginal utility applies (to the extent social sciences have any valid laws) to individual utility consumption curves. Elsewhere it doesn't work: try building a 7-foot stairway to a 9-foot second story and contemplate the marginal utility of those last two feet.

"The Allies will be out of ships" is not as good a retort as you seem to think it is.

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Re: Earlier Type XXI - informed by Cold War developments

Post by Tom from Cornwall » 24 Aug 2020 20:41

Hi TMP,

Any scale on that second diagram of pattern running torpedo? I’m not sure what normal spacing was between convoy columns and between ships in each column. Nor whether standard practice was to ‘close up’ due to sinkings or to leave bigger gaps, etc.

Could the U-boats transmit to each other when dived? Or would a synchronised attack on a convoy have to be choreographed from shore in both time and space (operationally and tactically)?

Regards

Tom

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Re: Earlier Type XXI - informed by Cold War developments

Post by T. A. Gardner » 24 Aug 2020 21:13

TheMarcksPlan wrote:
24 Aug 2020 20:12
T.A. Gardner wrote:while an earlier Type XXI would be more effective than the Type VII or IX, the end result would be the same.
This is like a mantra repeated to soothe anxiety.

The "law" of diminishing marginal utility applies (to the extent social sciences have any valid laws) to individual utility consumption curves. Elsewhere it doesn't work: try building a 7-foot stairway to a 9-foot second story and contemplate the marginal utility of those last two feet.

"The Allies will be out of ships" is not as good a retort as you seem to think it is.
Actually it works quite well. If you start out with say 1000 ships and 100 escorts and you sink 500 ships an 10 escorts the remaining ships will:

1. Be far better escorted and hence harder to approach and sink
2. With fewer ships in fewer convoys finding those convoys and ships will take longer therefore you are sinking fewer ships per unit time than before.
3. The Allies will take and develop countermeasures just as they did historically. This is just a matter of how long it takes them to do that. As they do the efficiency of the Type XXI will diminish.

Using a direct example from that law, one might consider a pizza and someone who is hungry. As they consume each slice of pizza, each additional slice has less and less value in staying their hunger. Same thing here.

What you stated in your earlier post was that each U-boat sank X number of tons per unit of time Y. Type XXI's would be Z times more effective so XYZ = tons now sunk per unit Y to infinity.

Historically, the Allies got more effective much faster than the Germans could come up with new tactics and technologies to use with their U-boats. It also didn't help the Germans that most of what they came up with wasn't a means of greater offensive power but rather means of trying to stay undetected and unattacked. ESM for radar so the U-boat could submerge when a ship or plane with radar approached. Snorkels to allow underwater transits making it harder for aircraft in particular to find a boat. Coatings for boats to reduce the effectiveness of sonar.
What they didn't do was increase the offensive power of the boats themselves much. They did invent and deploy several types of torpedo, the most effective probably being the acoustic homing torpedo. They didn't really employ other types of systems at sea either. Sure, the Luftwaffe did devote small numbers of aircraft to attacking shipping but these were few in number and often erratic in results produced. There was also little cooperation between the LW and KM.

None of that changes the fact the KM was conducting a Guerre de Course of merchant raiding without a supporting navy that could take on the enemy's navy.

Sure, the Type XXI would have improved German results in the short run, but in the long run they still lose.

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Re: Earlier Type XXI - informed by Cold War developments

Post by T. A. Gardner » 24 Aug 2020 21:56

Tom from Cornwall wrote:
24 Aug 2020 20:41
Hi TMP,

Any scale on that second diagram of pattern running torpedo? I’m not sure what normal spacing was between convoy columns and between ships in each column. Nor whether standard practice was to ‘close up’ due to sinkings or to leave bigger gaps, etc.

Could the U-boats transmit to each other when dived? Or would a synchronised attack on a convoy have to be choreographed from shore in both time and space (operationally and tactically)?

Regards

Tom
Everything you wanted to know about Allied convoys in WW 2

https://www.ibiblio.org/hyperwar/USN/re ... index.html

While the paper Results of the German and American Submarine Campaigns of World War II by Michel T. Poirier, CDR, USN, dated 20 Oct 1999 appears to no longer be available on-line I did find his conclusions used here:

https://history.stackexchange.com/quest ... age-of-qua

His conclusions show that the Allies could and did outspend and outproduce the Germans to a point where they were never going to win. The Type XXI wouldn't change that. It was evolutionary, not revolutionary in design. Sure it was faster under water, but it used the same sensors, same tactics, same weapons, as its predecessors. Some of his conclusions are kind of iffy, but the overall gist is the Allies simply overwhelmed the Germans using cubic dollars (pounds) and industry.
What they couldn't beat with brilliance, they bludgeoned with brute force and numbers.

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