Bismarck Alternate Propulsion

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Dave Saxton
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Re: Bismarck Alternate Propulsion

Postby Dave Saxton » Fri Aug 26, 2016 7:23 pm

how so? most of the supply ships were discovered accidentally since KM conceded the N Atlantic and RN had many more cruisers to search with


During the period that mattered, when the round up occurred from June 1941 through Sept 30 1941, Ultra had the necessary Enigma keys and they knew where the supply ships were. They were careful to make it look like accidental discovery, but that was not really the case. The Germans investigated and deluded themselves into thinking it was accidental discovery.
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Re: Bismarck Alternate Propulsion

Postby Paul L » Fri Aug 26, 2016 8:11 pm

ultra only located 1/2, the rest had to be searched for by cruisers.

follow on supply network could have been established if needed. they had 40 tankers to draw from and 22 supply ships at the beginning of 1942.

trouble is KM was ruining Hitler's relatively untarnished war record and his efforts to isolate the UK, so he put a short leash on them.

had KM continued the hybrid program of diesel/turbine warships of the 1920s they might not have needed much of a supply net.
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Re: Bismarck Alternate Propulsion

Postby frontkampfer » Sat Aug 27, 2016 12:47 am

As long as they used Enigma then the RN was going to know about it no matter how many tankers they had.
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Re: Bismarck Alternate Propulsion

Postby Paul L » Sat Aug 27, 2016 5:04 am

frontkampfer wrote:As long as they used Enigma then the RN was going to know about it no matter how many tankers they had.


in 1941 KM lost 21 tankers/supply ships of which 7 were lost in the wake of Rheinubung which was 2 weeks [that's 14 per month compared to the annual rate of 1.75 per month], so yes it was bad but not irreplaceable. At the start of 1942 they had 40 tankers [average bunkerage 8800t each] and 22 supply ships . Rheinubung required 9 aux ships , which represented 13% of the available ships. A similar sortie in 1942 would require only 14% of these supply ships....very doable. To make matters worse they had scores of suitable merchants "laid up" had they been needed.

https://en.wikipedia.org/wiki/Operation_Rhein%C3%BCbung

In mid 1941 the ultra data decoded transmissions within days, but B-Dienst was also reading the daily RN reports of German U-Boat activities. The British didn't realize this until late 1942. By 1942 the tables had turned , when the four wheel was added to Enigma , preventing 95% of all Enigma traffic to be read...to make matters worse B-Dienst was reading 60% to 100% of all convoy radio traffic resulting in 1/3 of all 1942 convoys to be detected by decoding while U-Boats discovered another 18% by themselves.

US analysis estimated KM had a 50% chance of intercepting any 'detected convoy', provided the wolf pack was within two days sailing.




KM surface raiding missions in 1942 and into 1943 would have resembled operation Berlin more than operation Rheinubung.
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Re: Bismarck Alternate Propulsion

Postby Dave Saxton » Sat Aug 27, 2016 2:47 pm

Paul L wrote:KM surface raiding missions in 1942 and into 1943 would have resembled operation Berlin more than operation Rheinubung.


This was indeed the contention of the SKL. The SKL proposed resuming Atlantic surface raiding using the Tirpitz. It was Hitler that said no.

As for Naval Ultra, the keys they were using expired on Oct. 1st, 1941. The German Navy began using different keys, and the Naval Ultra was back to bits and pieces, taking considerable time to obtain. On Feb. 1st, 1942 the KM switched to the four rotor Enigma machines and Ultra was blacked out for most of 1942 ( the naval portion). Keys and rotor discs were recovered from a sinking U-boat in the Eastern Med late that year, and with the introduction of more capable crypto analysis computers, or Bombes, that eventually lead to the partial cracking of the newer Naval Enigma, and particularly the U-Boat Enigma, going into 1943.


So Ultra would not have been of great use against a renewed Atlantic surface offensive through most of 1942, it is true.
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Re: Bismarck Alternate Propulsion

Postby Dave Saxton » Sat Aug 27, 2016 3:05 pm

frontkampfer wrote:As long as they used Enigma then the RN was going to know about it no matter how many tankers they had.


This was certainly true during the summer and fall of 1941. The British had the Enigma keys in use during this period.
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Re: Bismarck Alternate Propulsion

Postby Dave Saxton » Sat Aug 27, 2016 3:16 pm

One thing working against the Germans successfully renewing an Atlantic surface offensive going into 1942 was the proliferation of Type 273 centimetric radar aboard British cruisers. Luetjens was mistaken in his report at the time that the enemy had surface search radar effective to 35km. By 1942 it was a fact. However, I'm drifting off topic.
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Re: Bismarck Alternate Propulsion

Postby Paul L » Sun Aug 28, 2016 4:25 am

Dave Saxton wrote:One thing working against the Germans successfully renewing an Atlantic surface offensive going into 1942 was the proliferation of Type 273 centimetric radar aboard British cruisers. Luetjens was mistaken in his report at the time that the enemy had surface search radar effective to 35km. By 1942 it was a fact. However, I'm drifting off topic.



no problem but even with 35km detection , sweep rates are going to be very poor indeed. The simplified calculation I remember was the detection range x 2 width [~ 40nm] was multiplied by the ship cruising speed. So a RN/USN cruiser is going to manage 15 knots x 40nm or about 600nm^2 per hour. A similar sweep for U-Boat would be 10nm x 15 knots or 150nm^2 per hour.

Next review target area to be searched GIUK . Nominally a 1000nm wide area, but more like 700nm- when you remove land. This is multiplied by day cruising speed of the target ; which was 20 knots x 24 hours or ~ 480nm x 700nm or 336,000nm^2 sea to be swept.

The RN cruiser can manage a day patrol of 24 x 600= ~ 14,400nm ^2 per day. So in short- based on ship detection alone - you need ~ 23 such cruisers sweeping spaced equidistant to have a 100% sweep success. If it was U-boats [252000nm/3600nm] you'd need about 70 search platforms to get 100% success .

If the weather is moderate to good you can sortie the sea planes which can sweep ~ 1250nm per hour against U boats and maybe 3 times this against larger ships. With a margin- they can patrol two planes for 3 hours each day adding > 22,000nm^2 to sweep area increasing the cruiser sweep to ~ 37,000nm^ 2 per day [weather permitting] . In that case the numbers required reduces to 9 search platforms for the GIUK gap. If a Rheinubung operation is attempted in May they will be detected [although historically the 1941 mission was only 5 cruisers], however if Operation Berlin is attempted in November -March the weather in this area is so bad the Raiders will likely not get detected in time and break through.
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Re: Bismarck Alternate Propulsion

Postby RF » Sun Aug 28, 2016 4:12 pm

Paul L wrote:
trouble is KM was ruining Hitler's relatively untarnished war record and his efforts to isolate the UK, so he put a short leash on them.


Not quite sure what this means - can you please elaborate, as a statement like that is very open to total misinterpretation. The bold section indicates my concern.

had KM continued the hybrid program of diesel/turbine warships of the 1920s they might not have needed much of a supply net.


For long range and long distance raiding you need supply ships - even the diesel engine hilfskreuzer needed to be resupplied.
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Re: Bismarck Alternate Propulsion

Postby Paul L » Sun Aug 28, 2016 7:55 pm

RF wrote:
Paul L wrote:
trouble is KM was ruining Hitler's relatively untarnished war record and his efforts to isolate the UK, so he put a short leash on them.


Not quite sure what this means - can you please elaborate, as a statement like that is very open to total misinterpretation. The bold section indicates my concern.

had KM continued the hybrid program of diesel/turbine warships of the 1920s they might not have needed much of a supply net.


For long range and long distance raiding you need supply ships - even the diesel engine hilfskreuzer needed to be resupplied.


Don't see any bold?

Yes if we are speaking of ATL for "Rheinubung" we are speaking about mid 1941 just before "Barbarossa". Hitler had conquered most of Europe and was about to rampage across Russia to Moscow. Hitler and his staff believed the war was almost won, since he had a string of victories that made the WW-I struggle pale in comparison. If he could kill Russia as a threat he would also remove any hope for UK to hold on.

Any failure of the KM would just be a fly in the ointment giving the British hope.


Re supply net. one would be needed and historically did exist until 1944. So establishing a follow on supply net was doable for follow on missions.
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Re: Bismarck Alternate Propulsion

Postby RF » Wed Aug 31, 2016 7:58 am

Paul L wrote:
RF wrote:
Paul L wrote:
trouble is KM was ruining Hitler's relatively untarnished war record and his efforts to isolate the UK, so he put a short leash on them.



Don't see any bold?


Relatively untarnished war record?

Brutal invasion and occupation of Poland?

Invasion of a succession of neutral countries whose only offence was their geographic position?

The list of war crimes and crimes against humanity is fairly long even at the time of Rheiubung.
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Re: Bismarck Alternate Propulsion

Postby Steve Crandell » Wed Aug 31, 2016 1:04 pm

RF wrote:
Relatively untarnished war record?

Brutal invasion and occupation of Poland?

Invasion of a succession of neutral countries whose only offence was their geographic position?

The list of war crimes and crimes against humanity is fairly long even at the time of Rheiubung.


I was under the impression that he was referring to success vs failure of military operations.

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Re: Bismarck Alternate Propulsion

Postby RF » Wed Aug 31, 2016 2:29 pm

I think the problem is over the word ''untarnished'' which is capable of all sorts of interpretation and misinterpretation as to context.
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Re: Bismarck Alternate Propulsion

Postby Paul L » Wed Aug 31, 2016 6:22 pm

Steve Crandell wrote:
RF wrote:
Relatively untarnished war record?

Brutal invasion and occupation of Poland?

Invasion of a succession of neutral countries whose only offence was their geographic position?

The list of war crimes and crimes against humanity is fairly long even at the time of Rheiubung.


I was under the impression that he was referring to success vs failure of military operations.



yes .
we were discussing Hitler's decision to halt risky raiding missions after Rheinubung he would not care about such negative images and most western powers didn't know about such stories or would not believe such stories until after the war.
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Re: Bismarck Alternate Propulsion

Postby JAG » Fri Sep 16, 2016 9:46 pm

Returning to the point in question, what could the KM have achieved had it decided to stick to Diesel and commerce warfare in 1934?

The powerplant would be heavier and occupy a larger volume while also needing a very long and thin ship (the P-class cruisers come to mind) in order to get the best posible speed out of the engines, everything else, weapons and armor would take a second seat to the powerplant needs in weight and volume....

So maybe a Bismarck-heavy ship, longer and thinner (30m maybe?), with 2x4x35/38cm in order to fit (and save weight) 16x12MZu42/58 large diesels on 4 shafts for 144.000hp? With triple 15cm superfiring over the main turrets achieving the same 6x15cm broadside as IRL.

Hopefully 30kts might be achieved with a huge range.

Feasible?


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