It's really not. IMO, the battery capacity to make this credible means a boat that's enormous by WW2 standards. Besides, there's nothing in the Arctic: it only becomes useful when you've got SLBMs with nukes, or need to attack FBMs that do.
The Germans, if they had electro-boats and were smart would have used the area as a weather patrol zone. Play dodgem along the edges of the ice pack. Dangerous but doable.
Not to say a thread on a polar transit wouldn't be an interesting read...
Presuming the escorts see the launch. Presuming the attack isn't against one of the escorts. Presuming the escort is able to prosecute to kill--& you may be overestimating how easy that is.
Not gonna happen. Ranges for these WW II rocket barrages are short; <3000 meters. You wrote this yourself. ^^^^^^^^^^^^
Looking at your remarks on large solid lifters, it wasn't clear to me if you were arguing for it being insane or impossible (or both)... Either way, I just wanted to be clear I agree; OTOH, I don't think the smaller rockets are so stupid.
Which is why I've argued for a *Type XXI with pattern-runners & more tubes (& fish); the rockets are an AA (or anti-escort) addendum, not a replacement.
Shakes head. Does one know how hard it is to hit an escort in the North Atlantic with a barrage rocket salvo? The geniuses shooting back with the DE's deck guns and mortars stand a better chance of a hit on the now all too present and visible U-boat.
The Germans, if they had electro-boats and were smart would have used the area as a weather patrol zone. Play dodgem along the edges of the ice pack. Dangerous but doable.
of course my view Axis Germany should have tried to operate from Greenland so operating around the ice would be necessary ... albeit less ambitious than polar transit.
and as happy dividend to pact with Soviets they had use of Northern Sea Route https://en.wikipedia.org/wiki/Northern_Sea_Route with Soviets planning for German ships (raiders and others) to carry cargo on return voyage from Pacific (to alleviate strain on their railways.)
the Transpolar Route https://en.wikipedia.org/wiki/Transpolar_Sea_Route certainly saves on distance but at what hazard? rather than attempting clandestine use of Soviet coastal waters after (any) invasion of USSR.
of course my view Axis Germany should have tried to operate from Greenland so operating around the ice would be necessary ... albeit less ambitious than polar transit.
and as happy dividend to pact with Soviets they had use of Northern Sea Route https://en.wikipedia.org/wiki/Northern_Sea_Route with Soviets planning for German ships (raiders and others) to carry cargo on return voyage from Pacific (to alleviate strain on their railways.)
the Transpolar Route https://en.wikipedia.org/wiki/Transpolar_Sea_Route certainly saves on distance but at what hazard? rather than attempting clandestine use of Soviet coastal waters after (any) invasion of USSR.
The Germans, if they had electro-boats and were smart would have used the area as a weather patrol zone. Play dodgem along the edges of the ice pack. Dangerous but doable.
Some of them, yes. Having read a bit more, I'd suggest the 15cm (range around 8000yd) might be the best choice.
Even at 2000 or so (or less, in an emergency), hitting a DD with (say) 5x15cm rockets (never mind 5x32cm) will ruin his whole day. Even one isn't trivial. Nor is hitting a VLR with one...
And I am in no way suggesting anything bigger than the 32cm. (Better motor for improved range?) Anything bigger than that virtually demands a dedicated SSG, akin Growler, & that's getting nutty for 1940 tech.
Then again, a 15cm tube or two penetrating the hull, allowing reloads dived (& cold launching with something like calcium permanganate), wouldn't be a terrible idea. Two in the bow? Better still, 4-5 each beam? (TBH, tho, a WT deck mount is probably better, all considered; reload when you surface to charge batteries.)
Shakes head. Does one know how hard it is to hit an escort in the North Atlantic with a barrage rocket salvo? The geniuses shooting back with the DE's deck guns and mortars stand a better chance of a hit on the now all too present and visible U-boat.
It may be harder than I think; conceded. You seem to presume the firing boat is a) surfaced & b) static after firing. (I might also suggest c) Hedgehog-equipped escort isn't a given, either, in all cases. You've still got to locate him...)
So how long does it take an escort to close 2000yd (or 8000) at 16kt (presuming corvette, since DDs weren't common until late)? (My math sez 225sec minimum.) How far does (can) a *Type XXI travel in that time? (At 12kt dived, my math says over 1500yd.) So you've got an escort that has to search something like half a square nm around the firing point--presuming it was spotted, & they're not just chasing smoke trails...
Me? I might fire off one, move a few 100yd off the track to put an escort abeam, & wait for him to close enough I can give him 4 more, or a torpedo. How much can a corvette turn in 2sec (if I fire at around 500yd)? Not enough I'll miss, I don't think...
And if he has to search for me, as he approaches the firing point (& he does), his job gets harder (& mine easier), as he slows.
Bear in mind also, Hedgehog was limited to about 200m, so even if he localizes, I can shoot farther out, & I just need to put him abeam very briefly...
In fact, if I want him abeam, I might even deliberately cavitate to give him a "knuckle" to home on, "sprint & drift" to get abeam of him, then launch rockets.
Also bear in mind, that's not counting the possibility of *HARM: can SAR be fitted into a 15cm package in 1940? Into a 28-32cm space? I honestly don't know. It needn't be really sensitive, & NJGs did home on Monica with some variety of it.
of course my view Axis Germany should have tried to operate from Greenland so operating around the ice would be necessary ... albeit less ambitious than polar transit.
weather station outpost(s) on Greenland and Svalbard until 1944 and 1945 respectively? not projecting proper bases but enhanced version of OTL operations using OTL or enhanced u-boats.
this was kind of lost in your post ... did not think it should be and warranted highlighting, would make huge change, especially coupled with schnorkel.
YES but to be fair- the WARSHIPS 1 crew were unsure how difficult it would be to implement that and it certainly would require 'tuning' the E motor to increase submerged speed at the price of more efficient RPM for the diesel motors thus reducing surface speed and diesel endurance. How much difference to the diesels was unclear.
But the goal was worth the effort. if TYPE VII with VPP could reach 12 knots , then converting 1/2 flooding slits plus Walther style 'sail' should allow dash speeds of 14 knots or more. This in turn should reduce ballistic ASW attacks to 1/3 of attack value. Such ahead throwing ballistic ASW attacks vs 14 knots sub - should reduce effectiveness to levels of depth charge attack.
weather station outpost(s) on Greenland and Svalbard until 1944 and 1945 respectively? not projecting proper bases but enhanced version of OTL operations using OTL or enhanced u-boats.
Small note: The USS Flounder, which killed the U-537 (the one which put up weather station Kurt in Newfoundland), had a frustrating career, that was typical of the American silent service. She spent most of her time chasing elusive targets, being bombed by the Japanese, colliding with her wolf pack sisters or trying to dodge her own torpedoes (circular ones and erratics seems to be endemic in many of her attack reports.). Nevertheless she was where she was needed and made her own decisive contribution when required in the South China Sea to snuff out the German U-boat squadron operating in those waters.
The U-boat arm just was not fated to catch such lucky breaks.
Well, look at what happened to U-537. ^^^^^^^^ Along the ice pack playing dodge-em with an occasional Russian ship looks a lot safer than playing hide and seek with PacFlt and friends.
Stay away from the North American side, though. Those Canadians are dangerous.
Loaded (pun) questions.
About barrage rockets.
Some of them, yes. Having read a bit more, I'd suggest the 15cm (range around 8000yd) might be the best choice.
Okay. Some basics. When a Nebelwerfer is fired, (or any barrage rocket system say like HIMARS or MLRS) the rockets are rippled to prevent mutual interference in flight and fratricide at launch. This doesn't matter on land where the launcher vibration is insignificant and the rockets leave essentially with no recoil or shove forces imparted from that launcher, but at sea, there is roll, yaw and pitch and on a submarine that is a significant side force vector component on an already inaccurate ballistic projectile. Ye-old-rocket-launcher is not stabilized between shots and aim corrected like Mister Deck Gun. That ripple is going to be scattered to Hecuba and gone.
Also, the parabolas of our rocket projectiles are more like mortar shells so the chances of missing are just like with mortar bombs at sea. More on this in a moment.
Even at 2000 or so (or less, in an emergency), hitting a DD with (say) 5x15cm rockets (never mind 5x32cm) will ruin his whole day. Even one isn't trivial. Nor is hitting a VLR with one...
It will set fires but it won't sink him, and if it is a US tincan, the U-boat is dead meat. Just the AAA return fire will rip the German to shreds.
And I am in no way suggesting anything bigger than the 32cm. (Better motor for improved range?) Anything bigger than that virtually demands a dedicated SSG, akin Growler, & that's getting nutty for 1940 tech.
Then again, a 15cm tube or two penetrating the hull, allowing reloads dived (& cold launching with something like calcium permanganate), wouldn't be a terrible idea. Two in the bow? Better still, 4-5 each beam? (TBH, tho, a WT deck mount is probably better, all considered; reload when you surface to charge batteries.)
It may be harder than I think; conceded. You seem to presume the firing boat is a) surfaced & b) static after firing. (I might also suggest c) Hedgehog-equipped escort isn't a given, either, in all cases. You've still got to locate him...)
Given rocket firing U-boats, Hedgehogs will be pushed a lot harder. Long-ranged hedgehogs, more like Russian RBUs. The problem then becomes dispersion of fall going the other way. Here the surface ship has two edges. One, the surface ship mount is trainable (at least in the USN). Two the surface ship ironically is a better gun platform in that she has direct fire artillery as well as a depth charge thrower, mortar bomb discharger. So the U-boat has two flavors of death offered: a five inch shell through her pressure hull on the surface, or the time fused or inertia hammer fused mortar shell hits her as she tries to dive deep after she launched her rockets. Either way is about 30-60 seconds after she shows herself, depending on how good that escorts gun crews are. I am led to believe that Canadian ones were actually mighty good at hitting conning towers.
Did I mention that stabilized gun mounts matter?
So how long does it take an escort to close 2000yd (or 8000) at 16kt (presuming corvette, since DDs weren't common until late)? (My math sez 225sec minimum.) How far does (can) a *Type XXI travel in that time? (At 12kt dived, my math says over 1500yd.) So you've got an escort that has to search something like half a square nm around the firing point--presuming it was spotted, & they're not just chasing smoke trails...
Rapid fire at a launch flash; predict lead? 8 seconds for fire solution and 2-4 seconds for the shells to arrive and maybe 18-24 seconds for the first pattern of mortar bombs to splash. U-boat dead in 30? SAY GOODNIGHT, GRACIE.
Me? I might fire off one, move a few 100yd off the track to put an escort abeam, & wait for him to close enough I can give him 4 more, or a torpedo. How much can a corvette turn in 2sec (if I fire at around 500yd)? Not enough I'll miss, I don't think...
You are forced down being depth charged. He has radar, a firepower advantage... and buddies.
Bear in mind also, Hedgehog was limited to about 200m, so even if he localizes, I can shoot farther out, & I just need to put him abeam very briefly...
At this point improved MOUSETRAP (Rocket boosted underwater projectile~300 m but improvable by our Russian friends with tech little different from the USN first version to 6000 m) and US LIMBO look like the candidates for Wally's projected (pun) response. And with Canadian/USN (not British RN which was faulty) sonar doctrine, Mr. U-boat is being tag teamed by sprint-drift Able/Baker. He's dead, Jim,
In fact, if I want him abeam, I might even deliberately cavitate to give him a "knuckle" to home on, "sprint & drift" to get abeam of him, then launch rockets.
Baker will nail you as you knuckle while Able plays wag the tail at you.
Also bear in mind, that's not counting the possibility of *HARM: can SAR be fitted into a 15cm package in 1940? Into a 28-32cm space? I honestly don't know. It needn't be really sensitive, & NJGs did home on Monica with some variety of it.
What are you going to use as an illuminator or a home-on signal, here? Assuming that the Wally is not stupid, (and he isn't), he'll have dazzle (a balloon with a decoy transmitter as an aerostat) up to fox any home on radio signal scheme deployed in a German [ballistic?] rocket or guided glide bomb. Love those Canadian scientists.
"I say, Schmedly! Now I know why those Canucks gave us the party balloons!"
Some things that an attempt at a trans polar commerce submarine development program WILL develop:
1) A much larger definition of exactly what a BIG submarine is.
2) Longer submerged times.
3) More efficient submerged travel (streamlining) hulls.
Keep in mind, commerce/cargo, implies the bigger the better AFAIK, so nothing smaller that the ~6,500 ton I-400 class displacement should even be on the board for discussion of trans polar commerce submarines, as building a submarine aircraft carrier whose only 'cargo' is going to be a very small air wing (3 aircraft) and it's related materials, is in no way going to be able to turn a profit like a vessel designed for hauling freight could. Also, the exploration of the arctic ocean need not be done by submarines alone, nor do the initial explorers need be optimized for commerce, so think more in the lines of surface ships, ground/ice teams, seaplanes/amphibious aircraft all working as part of the project along with the submarine elements. Might we see something like custom designed engineering platforms included in such an effort?
Here is a picture of the hanger on an I-400 class submarine, during it's inspection after surrender.
So cargo submarines can (and would) have a much better handling capacity than any 'off the shelf' conversions, or slightly modified designs, like the Deutschland in WWI.
With the above in mind, just how big a submarine would a 1920's to 1940's nation be able to develop tonnage wise? History tells us only what WAS built, but function largely dictates form, and a trans polar commercial submarine hull form would be a far cry from what one would want to design for combat.
Could we see a cross between the type XXI/I 400 class, with high underwater duration combined with the ability to sail to any point on Earth with onboard fuel supply? Could we see something like 5 parallel cargo hangers, sitting atop 6 regular hulls, giving us something like what the I 400 class did with it's single hanger sitting atop 2 regular hulls?
Let's think outside the box, and see what we get. I want to set a goal of getting the OP for the trans polar submarine commerce route thread posted by the first week in Feb, so I need to get cracking and make some progress, lol...
Let's look at the physical geography and submarine history of both Germany and the USA in the time period from 1920-1950.
USA has the transcontinental railroads and the panama canal to use in the moving of freight around the country, and no way the USA's international trade can be easily cut off/blockaded. So the USA, in the realm of transpolar commercial submarines, has no need, and probably only slight interest, if that, in being a leader in this field.
Germany has access to international trade that can, and just recently has been, cut off by means of a distant blockade. If Germany wants to have trade that the UK cannot easily cut off, then surface ships don't work. Germany, OTOH, has both a real need for incoming raw materials and recent experience of not being able to get them, other than by slightly modified merchant submarines in WWI, due to British blockade. This situation is not going to change nor go away, so one cannot argue that a post WWI Germany cannot see the need for a cargo submarine (transpolar or not) in case/when she finds herself once again at war, that may or may not include a hostile UK.
Enter Japan/China, and the novel concept of a North-West passage kinda thing, but done by specially-designed-for-the-purpose, merchant submarines, and we get an idea of what the concept might be sold as. Of course, that would be the official, publicly given reason for such a program, that after all is only going to be paying off in the advent of a future war/blockade. And if one is both designing and building submarines for such a purpose, whether or not the transpolar submarine commercial route becomes a reality or not, design lessons and existing large submarine cargo vessels still give us the potential for some very interesting and enjoyable alternative history discussions.
So the short answer is, the USA has no real vested interest/need to develop merchant submarines, transpolar or not, as her regular (surface ship) merchant shipping can do whatever is needed, and at a fraction of the price. Germany cannot count on regular (surface ship) merchant shipping in wartime, so having a more expensive, yet still profit making, submarine merchant fleet, is not only viable, but perhaps vital.
Given rocket firing U-boats, Hedgehogs will be pushed a lot harder. Long-ranged hedgehogs, more like Russian RBUs. The problem then becomes dispersion of fall going the other way.
Given you've got enough escorts to do it with... How many wartime convoys had exactly 3 corvettes for escort? And you want to detail off two of them to prosecute to kill? To spend hours searching for a boat that's as fast dived as their maximum sonar search speed? (And capable of putting torpedoes in them...)
There's a reason drone helos were mooted for ASW, & the OTL Type XXI is it. It ain't nothing like so simple.
What are you going to use as an illuminator or a home-on signal, here? Assuming that the Wally is not stupid, (and he isn't), he'll have dazzle (a balloon with a decoy transmitter as an aerostat) up to fox any home on radio signal scheme deployed in a German [ballistic?] rocket or guided glide bomb. Love those Canadian scientists.
How many magnetrons do you think the WAllies could produce? Enough to make them expendable? That decoy will have to produce the same low-w/l signal as a radar set (presuming *HARM). Or an IR signal (which is easier). Maybe both (if the Germans are smart & use both options in separate rounds...).
How many captured U-boat crews were there? How, exactly, will Allied intel figure this out?
AFAIK, there wasn't a size limit, more a limitation of design knowledge: nobody knew how to build a sub any bigger, because there wasn't any need for one.
You're getting into limits of materials strength, too. Subs may be less susceptible, but the hazard of breaking in two due to wave action or other cause isn't trivial (& that was an issue for the early 1000'-long Lakes freighters). Can you safely double the length of I-400? Maybe. Stronger hull framing would be a really good idea.
And for Japan & Germany (especially), limitations on the amount of steel available probably govern more than anything: if you're using it for these big transport subs, what isn't getting built? IDK if they were capable of building with titanium (I doubt it); neither am I sure there was titanium ore available, nor how they'd pay for it if it was. (Buying from Canada would be my first suggestion, but...paying, & then, did Canada even mine it in the '30s? IDK offhand.)
Simplifying the design would be good, too. A dedicated transport wouldn't have to have many of the systems a war boat would, so fewer hull openings & easier operation (less chance of casualty), so fewer crewmen...
USA has the transcontinental railroads and the panama canal to use in the moving of freight around the country, and no way the USA's international trade can be easily cut off/blockaded. So the USA, in the realm of transpolar commercial submarines, has no need, and probably only slight interest, if that, in being a leader in this field.[/quote]
Chief enemies before LNC; Japan, Germany, Great Britain, and RUSSIA.
Note blockade lines?
Germany has access to international trade that can, and just recently has been, cut off by means of a distant blockade. If Germany wants to have trade that the UK cannot easily cut off, then surface ships don't work. Germany, OTOH, has both a real need for incoming raw materials and recent experience of not being able to get them, other than by slightly modified merchant submarines in WWI, due to British blockade. This situation is not going to change nor go away, so one cannot argue that a post WWI Germany cannot see the need for a cargo submarine (transpolar or not) in case/when she finds herself once again at war, that may or may not include a hostile UK.
Enter Japan/China, and the novel concept of a North-West passage kinda thing, but done by specially-designed-for-the-purpose, merchant submarines, and we get an idea of what the concept might be sold as. Of course, that would be the official, publicly given reason for such a program, that after all is only going to be paying off in the advent of a future war/blockade. And if one is both designing and building submarines for such a purpose, whether or not the transpolar submarine commercial route becomes a reality or not, design lessons and existing large submarine cargo vessels still give us the potential for some very interesting and enjoyable alternative history discussions.
And the USN has to stop them. Makes for an interesting game of dodge-em along the edges of the pack ice.
So the short answer is, the USA has no real vested interest/need to develop merchant submarines, transpolar or not, as her regular (surface ship) merchant shipping can do whatever is needed, and at a fraction of the price. Germany cannot count on regular (surface ship) merchant shipping in wartime, so having a more expensive, yet still profit making, submarine merchant fleet, is not only viable, but perhaps vital.
As soon as WW II ended, the USN started running missions against the Russians. The USN was running missions into the Arctic as soon as America acquired Alaska. That included submarines.
Then you have to have torpedoes. The thing about escort ships is that the crews tend to take their job seriously. As long as they float they fight. Rawalpindi comes to mind.
Flow noise? From a mount folding into the deck, except on firing? (And I'm less than convinced Allied sonar in WW2 could hear it.)
Deploy the launcher, as the Germans actually proposed, and you have a series of grinds and crackles that a deaf sonar operator can hear through earmuffs.
Given you've got enough escorts to do it with... How many wartime convoys had exactly 3 corvettes for escort? And you want to detail off two of them to prosecute to kill? To spend hours searching for a boat that's as fast dived as their maximum sonar search speed? (And capable of putting torpedoes in them...)
Too many were under-escorted. But now the Germans are making it easy and yes, two per sub. That is doctrine once the Able/Baker tactics are worked out.
There's a reason drone helos were mooted for ASW, & the OTL Type XXI is it. It ain't nothing like so simple.
Who says anything about drone helos? (DASH) USN is dropping sonobuoys in 43, and homing torpedoes. This is not ATL when this happens, this is RTL. And it works against fast subs.
How many magnetrons do you think the WAllies could produce? Enough to make them expendable? That decoy will have to produce the same low-w/l signal as a radar set (presuming *HARM). Or an IR signal (which is easier). Maybe both (if the Germans are smart & use both options in separate rounds...).
Enough to equip every artillery mount director in American army and navy AAA director sets with enough left over the USAAF and the allies. Decoys? Pfft. Canada can produce enough. They did.
How many captured U-boat crews were there? How, exactly, will Allied intel figure this out?
^^^^^^^^^^^^^^^ The British had enough of them that they set up a special bugged "hotel" to process them.
['quote]AFAIK, there wasn't a size limit, more a limitation of design knowledge: nobody knew how to build a sub any bigger, because there wasn't any need for one.[/quote]
US, Japan and France.
You're getting into limits of materials strength, too. Subs may be less susceptible, but the hazard of breaking in two due to wave action or other cause isn't trivial (& that was an issue for the early 1000'-long Lakes freighters). Can you safely double the length of I-400? Maybe. Stronger hull framing would be a really good idea.
And for Japan & Germany (especially), limitations on the amount of steel available probably govern more than anything: if you're using it for these big transport subs, what isn't getting built? IDK if they were capable of building with titanium (I doubt it); neither am I sure there was titanium ore available, nor how they'd pay for it if it was. (Buying from Canada would be my first suggestion, but...paying, & then, did Canada even mine it in the '30s? IDK offhand.)
That ACTUALLY depends on Australia (for the US) and Russia (for the Germans).
Simplifying the design would be good, too. A dedicated transport wouldn't have to have many of the systems a war boat would, so fewer hull openings & easier operation (less chance of casualty), so fewer crewmen...
It's about a 2" target, at the waterline, & you don't need to leave it up.
And do you have any notion how hard it was to see it? AFAIK, radar couldn't even do it for most of the war: by the time the Allied escorts have that capability, Germany has lost anyhow.
Providing the fast, heavily-armed *Type XXIs haven't slaughtered enough shipping to win...because they would be having a field day, while we argue about whether their rockets would work or not.
Deploy the launcher, as the Germans actually proposed, and you have a series of grinds and crackles that a deaf sonar operator can hear through earmuffs.
Too many were under-escorted. But now the Germans are making it easy and yes, two per sub. That is doctrine once the Able/Baker tactics are worked out.
So you're going to strip the convoy of its escort to chase one target & leave it completely exposed to half a dozen others? When the target boat can be nearly a mile away from any transient in the time it takes a corvette to get to it? You really think it's so easy to catch a fast boat? The Type XXIs were a nightmare for OTL escorts, & that was given DDs.
Who says anything about drone helos? (DASH) USN is dropping sonobuoys in 43, and homing torpedoes. This is not ATL when this happens, this is RTL. And it works against fast subs.
Enough to equip every artillery mount director in American army and navy AAA director sets with enough left over the USAAF and the allies. Decoys? Pfft. Canada can produce enough. They did.
When I mean "penetrations", I had in mind torpedo tubes & Kingston valves & such; since fast diving wouldn't be an issue, large numbers of vents wouldn't be needed. A good, tight main induction, conn hatches, & a couple of escape trunks would do it.
Loading inboard (if done) can be with large WT deck hatches; make them as big as you need. (The inboard WT hatches were about 60"; would they need to be bigger to load anything?) I picture 1 each fore & aft, but maybe in pairs (port & starboard)? Or in tandem? How much freight space is there aboard?
And then there's the question of cargo. Putting bulk freight, like grain, aboard makes sense; ditto liquids (oil, gasoline). "Box" freight (assembled TVs or something) would be a bad idea. Spare parts? Smallarms ammo? Crates of rifles or pistols? Food (maybe)? It would have to be high value & fairly urgent to warrant using such an expensive delivery method.
The large hatches are a scary idea in a war boat, but since (if you have half a lick of sense) you don't send these in harm's way, cracking open the deck hatches with DCs shouldn't be an issue.
You lost me. Are these supposed to be blockades of US trade, or blockades by USN? USA can pretty much trade with all of the western hemisphere (N & S America) without anything anyone could really do about it, and Japan/China is likely to remain open for US business as well.
Nice image, but not really useful, at least it does show a good image of the Arctic Ocean. Remember my earlier post #39? The hidden link there tells the whole tale of the ice covering the north pole.
See the picture up thread of the hanger on the I 400 class. IIRC, the hanger was circular in cross section, and something like 12' in diameter, plenty big enough for cargo, but I have to wonder, is that really the biggest a cargo submarine of the times could have?
Oh heck, here it is again...
Note the USN figures standing off to the right, on an upraised platform, and how their heads are well below the top of the hanger. I would indeed call this a big hole, and we know from OTL that it worked, so fast cargo loading/unloading would be the norm.
I'd like to look at training and mass production.
In order to ramp up in peacetime you need a large number of small (Baltic) training subs.
To fit within the naval treaties. To keep costs down. To create demand for a mass of units. To train the cadre for many boats.
Type II (259t) made in a modular assembly hall or three. Option to add an snorkel later in secret. The RN S-class are over 800t per boat and they are building loads on top of a few out size minelayers (Grampus) and specialists.
So three locations building a dozen each in 1935 and 1936 isn't impossible. Given development of modular assembly you could expect training of new crews in over a hundred boats by the time a long range war fighting model is started into mass production.
Most HEDGE HOG attacks resulted in 10% chance of sinking U-Boat that was evading, while attacks on unsuspecting U-Boats were ~ 30% effective. But those were subs @ 2-4 knots. If the U-Boat speed was 12 knots then the figures are more like 4% vs evading U-Boats compared to 12-14% vs unsuspecting targets.
Basic depth charge attacks were 5% vs normal U-Boats and should be 1-2% vs fast U-Boats. This is why every one switched to ASW torps post war.
The conning tower and navigation bridge that comes with it is not two inches. More like the side of a barn.
And do you have any notion how hard it was to see it? AFAIK, radar couldn't even do it for most of the war: by the time the Allied escorts have that capability, Germany has lost anyhow.
Detectable by 1942 radar at a range of ~ 8,000 meters.
PRO document ADM 219/537, Radar equipment for ASW use on aircraft, published on 23 Jun 1942.
Two ASV radars are described. The British ASV-II uses fixed antennas covering a 30° arc, and has separate "search" and "homing" arrays. It works on a wavelength of 1.7 metres (175 MHz). The American ASV-10 uses a small dipole antenna with a 30-inch paraboloid reflector which has a 10° arc and sweeps 90° each side of the aircraft. It has a PPI display, and operates on a wavelength of 10cm (3000 MHz).
The range performance under optimum conditions of each set is given as:
Target ASV-10 ASV-II
Periscope, 1 ft exposed 2 miles —
Periscope, 4 ft exposed 4 miles —
Submarine (750 tons) surfaced 18 miles 6 miles
Destroyer 45 miles 25 miles
10,000 ton ship 60 miles 45 miles
Land 100 miles 75 miles
"Tactics should be based on maximum ranges considerably less than these, say 12.5 on a submarine for ASV-10."
ADM 219/549, Analysis of US aircraft attacks on U-boats, which is a copy of USN ASWORG memorandum no. 20, published on 07 Dec 1942.
The following table gives average sighting distances and visibilities for visual and radar searches. Army and Navy aircraft carry different radar equipment, and so are listed separately.
Type of search Average Average Ratio
contact visibility
distance
Visual 4.3 mi 7.6 mi 0.57
Army radar 10.6 mi 4.7 mi 2.26
Navy radar 4.3 mi 3.9 mi 1.10
Providing the fast, heavily-armed *Type XXIs haven't slaughtered enough shipping to win...because they would be having a field day, while we argue about whether their rockets would work or not.
What does that matter? Depth to conning tower, 12' to 18' Max speed with mast up < 6 knots (any faster and the periscope shaft bends, jamming it in the UP position.) = dead U-boat. Also you have to slow down to almost hover to fire rockets or launch torpedoes in a WW II boat.
Fair enough. I do think you might discourage some, but I'll concede.
You mean the flame diverters and exhaust baffles bubbling away like mad as the launcher is raised from its shelter? Of course it is flow noise. It is popcorn in the headphones.
And how quickly can you close the range to that transient? Faster than the sub can change position? Not if it's doing even 6kt, let alone 12.
Can't launch at 6 knots. More like < 2 knots (rockets are fragile things), and THAT takes time to slow down and speed up. Escort is faster and it doesn't have to guess.
Of course I know that story, but the USS Growler I was discussing is a GRAYBACK I know about. a sub that can launch a Regulus missile. She is is SSG 577 and she was never bombed or strafed. Did you not know this? SS 215 was a GATO that was presumably sunk by her own fish on her last patrol. She was not killed by that ramming and machine rake incident from the Japanese gunboat that killed "Take her down." Gilmore.
Incidentally that ramming is exactly the kind of result I would expect from a lunatic rocket attack on a convoy escort.
Could they? Ever hear of the hammer and anvil? And why was CUTIE successful against Japanese destroyers?
So you're going to strip the convoy of its escort to chase one target & leave it completely exposed to half a dozen others? When the target boat can be nearly a mile away from any transient in the time it takes a corvette to get to it? You really think it's so easy to catch a fast boat? The Type XXIs were a nightmare for OTL escorts, & that was given DDs.
It is not the speed of the launch platform, it is the speed and reach of the weapon. Why assume that the Wallies will not learn afresh: bracketing, sonar lashing, drive down and persistence? Adapt to the faster escape speeds and keep after them. And besides with rockets the dumb sub has signed its death warrant with a bullseye and a sitting duck posture anyway.
Not with what the Allies had OTL. It worked against the Type VIIs & Type IXs, neither capable of the high dived speed the Type XXI was.
Here is the hint; how fast can the Type XXI U-boat accelerate and dive from 2 knots and 40' to keel after rocket launch to its final op-depth and speed versus how fast the depth charges and torpedoes arrive? About 2 minutes. That ='s dead boat in 1943. FAT torpedoes are safer. THAT is what the Germans were actually planning RTL, Get in front of the convoy, blind fire a dozen FATs by sound bearing from 100 feet, then go deep quietly and creep off.
It's looking like this is a Hitlerian idea: flashy, but impractical...
Nautilus SS 168; about 3800 tonnes submerged
Surcouf; NN3 about about 4200 tonnes submerged.
I-400, about 6000 tonnes submerged.
Incidentally, depending on either the Americans (investigation of the Thompson Lykes) or the French (another investigation), Surcouf was lost at sea when she was rammed by a US banana boat, or she was bombed by the US Navyfor being where she had no business being. (an "accident" apparently.)
Auphan, Paul; Mordal, Jacques (1959). The French Navy in World War II. Annapolis, MD: Naval Institute Press
Here.And here. The US probably got some titanium from somewhere, but here is the hint. To build the SR-71 Lockheed had to get the US government post WW II to run a scam on the Russians to steal the ore from them. If Canada is supplying, it is to the British Empire.
I was thinking deck-mounted pods, for a start.
When I mean "penetrations", I had in mind torpedo tubes & Kingston valves & such; since fast diving wouldn't be an issue, large numbers of vents wouldn't be needed. A good, tight main induction, conn hatches, & a couple of escape trunks would do it.
Loading inboard (if done) can be with large WT deck hatches; make them as big as you need. (The inboard WT hatches were about 60"; would they need to be bigger to load anything?) I picture 1 each fore & aft, but maybe in pairs (port & starboard)? Or in tandem? How much freight space is there aboard?
And then there's the question of cargo. Putting bulk freight, like grain, aboard makes sense; ditto liquids (oil, gasoline). "Box" freight (assembled TVs or something) would be a bad idea. Spare parts? Smallarms ammo? Crates of rifles or pistols? Food (maybe)? It would have to be high value & fairly urgent to warrant using such an expensive delivery method.
The large hatches are a scary idea in a war boat, but since (if you have half a lick of sense) you don't send these in harm's way, cracking open the deck hatches with DCs shouldn't be an issue.
Here is your problem. The best way to load cargo on a sub is containerize it. No cargo hatches. Put the
stuff in pressure resistant cans and mount it externally. This way, one solves the internal volume limits and reduces vulnerability to yaw and pitch from unsecured and mis-ballasted mass. It is also easier to load and crane off. Problem. Where do you put it? See what the Japanese did with the I-400? (See below and wait for it, I'll get there to discuss that problem in a moment.). Strongback is the logical place.
You lost me. Are these supposed to be blockades of US trade, or blockades by USN? USA can pretty much trade with all of the western hemisphere (N & S America) without anything anyone could really do about it, and Japan/China is likely to remain open for US business as well.
Since it is the US conducting operations, those are the blockade lines the US has to establish and maintain. Notice where the transits from US ports to those blockade stations occur? Shortest safest routes are kind of obvious. If I were a farseeing RAINBOW planner and looking at a defeated Britain in the fascist pocket, I would be very energetic about getting freighter killers into service that can fight along the GIUK.
Nice image, but not really useful, at least it does show a good image of the Arctic Ocean. Remember my earlier post #39? The hidden link there tells the whole tale of the ice covering the north pole.
Then why is it necessary for me to explain why AIP boats don't work as transiters and why snort boats can and do work along the edges of the ice pack?
See the picture up thread of the hanger on the I 400 class. IIRC, the hanger was circular in cross section, and something like 12' in diameter, plenty big enough for cargo, but I have to wonder, is that really the biggest a cargo submarine of the times could have?
The I-400 was a pig to handle underwater. Her hanger leaked. There was a special automatic trim and ballast system fitted for aircraft operations which is also useful for cargo shifting purposes (these subs could be used as freighters), but the system was noisy, distinct and very recognizable as a "here I am, come here and kill me." trackback. In addition, that superstructure acted like a wind rudder, making the sub hard to steer on a baseline course.
Oh heck, here it is again...
Note the USN figures standing off to the right, on an upraised platform, and how their heads are well below the top of the hanger. I would indeed call this a big hole, and we know from OTL that it worked, so fast cargo loading/unloading would be the norm.
I'd like to look at training and mass production.
In order to ramp up in peacetime you need a large number of small (Baltic) training subs.
To fit within the naval treaties. To keep costs down. To create demand for a mass of units. To train the cadre for many boats.
Type II (259t) made in a modular assembly hall or three. Option to add an snorkel later in secret. The RN S-class are over 800t per boat and they are building loads on top of a few out size minelayers (Grampus) and specialists.
So three locations building a dozen each in 1935 and 1936 isn't impossible. Given development of modular assembly you could expect training of new crews in over a hundred boats by the time a long range war fighting model is started into mass production.
Most HEDGE HOG attacks resulted in 10% chance of sinking U-Boat that was evading, while attacks on unsuspecting U-Boats were ~ 30% effective. But those were subs @ 2-4 knots. If the U-Boat speed was 12 knots then the figures are more like 4% vs evading U-Boats compared to 12-14% vs unsuspecting targets.
A short U-boat war would have to be a decisive blow. Hundreds of U-boats wiping the seas of British merchant shipping before counter measures and replacements can come into place. I agree that a long siege of the British Isles is a failure. It must be a rapid and complete defeat of sea communications. Starve or capitulate.