American militarism pre-WW2 and the Ultimate Battleship

Discussions on alternate history, including events up to 20 years before today. Hosted by Terry Duncan.
TheMarcksPlan
Member
Posts: 918
Joined: 15 Jan 2019 22:32
Location: USA

American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 22 Oct 2019 04:00

We all know that the U.S. went from isolationist to global hegemon in a short span encompassing WW2. The political reasons for this transformation are complex and I don't want to focus on discussing them here; I want to discuss what a U.S. Navy committed to world domination from the 1930's at the latest might have produced.

Specifically, it's kind of cool to this history nerd to imagine the "maximal battleship" that could have been produced pre-WW2. OTL we have the Tilman Battleship studies from the post-WW1, pre-Washington Treaty era. https://en.wikipedia.org/wiki/Maximum_battleship

But IMO this doesn't exhaust the economies of scale inherent in the design of larger ships. And the interwar U.S. would have been poised to exploit these economies of scale to a greater degree than any other power, as it was the world's largest economy by far and had excess industrial capacity due to the Great Depression. To summarize a few points on these economies of scale:
  • A ship's drag, and therefore its required horsepower for a given speed, varies primarily with its surface area and its wave drag.
  • Surface area scales with the square of linear dimensions while displacement scales cubically.
  • Wave drag (at a given speed) scales with displacement and the square root of length.
  • Bigger ships have lower Reynolds coefficients, meaning that drag for a given size decreases further.
  • Battleships generally show a greater proportion of displacement devoted to armor and guns with scale.
  • Ships generally show a lower ratio of hull weight to deadweight as their displacement increases.
  • Larger propellers are generally more efficient than smaller for large ships.
  • Larger power plants are generally more efficient than smaller.
Taking all of these factor together, I can imagine an interwar U.S. determined to maintain a navy "second to none" that could and would build super-battleships on a scale not generally imagined, at a price that would preserve economies of scale.
For example, imagine a ship 2400ft waterline length, 360ft beam, and 140ft in hull depth (empty draft of 40ft and empty displacement of ~700k tons, maximum draft of 120ft to maintain 20ft of freeboard - this would require ballast and/or unusually heavy ammunition/fuel load).

The first obstacle to this cubic escalation of battleship scale is harbor depth. Luckily, the U.S. possessed on both coasts at least one sheltered harbor that could resupply a gargantuan ship up to 100ft draught: Puget Sound and Tacoma Harbor on the West Coast and Massachusetts Bay and Provincetown in the East. Because a ship of the dimensions I'm envisioning has a basically unlimited range/endurance, one harbor on each coast is all that's needed. In addition, the Lahaina Roads used by the U.S. Pacific Fleet as an anchorage has a depth of several hundred feet. The outer harbor of Manila Bay around Corregidor and Mariveles has a depth of over 100ft. So an enormous ship could deploy operationally from Pearl, Seattle, Manila Bay, or Massachusetts, and could enter any of the normal U.S. anchorages for routine maintenance (SF Bay, Hampton Roads) after offloading ammunition and excess fuel either at the aforementioned deep-water ports or via resupply ships (as its draught would be less than 40ft).

A ship of this size could devote a hitherto-unimagined portion of its total empty weight to guns and ammunition. Basically it could devote the entirety of the differential between cubic (displacement) and quadratic (dimensional) escalation of its scale to greater firepower. One could sketch, for example, a ship with ~400 18in guns in the main battery and ~1,500+ 9.5in guns in the secondary battery. This would, however, require turrets firing over each other in broadside and therefore restricting some of the armament's angle of fire. That's addressed, however, by the ability to elevate guns to more than 45 degrees via "burying" gunhouses in a uniform deck-level armament belt: with that ability, guns incapable of depressing below a certain angle due to neighboring turrets can simply fire high-angle arcs against opponents' weaker deck armor.

Here's a first-draft approximation of a layout for such a mega-battleship:

Image

...where large circles represent main battery armament and small circles secondary.

This is drawn at a smaller scale than the 2400x360 battleship I mention above but it conveys the general idea: 1/2 to 1/3 of the armament is always available for low-angle fire against close-in targets (that won't survive more than a few minutes) while the rest of the armament can fire high-angle arcs against aerial or land targets.

A note on propulsion:
While a 2400/360 ratio of LWL-Beam is lower than for most modern battleships, the overall propulsion requirements - and therefore the tradeoff between expense and displacement implications of speed versus structure - are radically different for a giant ship versus a normal ship. The 2400/360 ship with a 100ft battle draft (again achieved after leaving port via ballast instead of structural weight) has only ~8x the surface area, and thus 8x the friction at equal speeds, of an Iowa-class battleship. It also has a similar ratio of friction-caused vs. wave-making-caused drag at 33 knots. It could use 30ft propellers in two vertical rows, meaning far ~50% higher propulsive efficiency from a given HP generated by the ship (HP: Thrust being determined linearly from RPM for ships, generally speaking). Finally, the enormous hull volume would allow usage of industrial-level efficiency for electricity generation to E-turbines (as in BB Nevada) without exceeding 10% of hull volume.

EDIT:
In following posts I'll expand on the details of propulsion, armor, gunnery, etc. for these ships.

At base is a contention that a mega-BB of this type could have mounted the firepower of ~200 normal BB's and ~500 cruisers, while being too deadly to air attack for carrier-based (or any) aerial attack.

TheMarcksPlan
Member
Posts: 918
Joined: 15 Jan 2019 22:32
Location: USA

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 22 Oct 2019 06:12

A bit more quantitatively on propulsion:

Compared to an Iowa-class BB, a mega-BB of 2400x360x100ft (battle draft) would have approximately 8.6x the underwater surface area, as an Iowa-class BB is 860x108x37ft at deep load [I'll leave the arithmetic to those following along rather than burdening the post with it]. Thus at 33kn top speed, it would have ~10x the friction drag and require 10x the propeller thrust of BB Iowa.

The next major component of ship drag (and thus propeller thrust and HP) is wave drag. Wave drag shows a non-smooth function with lots of "kinks" depending on hull length and speed. http://brennen.caltech.edu/fluidbook/ex ... vedrag.pdf One good high-level approximation of wave drag, however, relates the square-root of a ship's waterline length to its speed: https://en.wikipedia.org/wiki/Froude_number. A longer ship generates less wave drag than a shorter ship for a given displacement. For the purposes of this thought-experiment, I'll suppose that the wave-drag coefficient (amount of drag per ton of displacement) relates to (1) the Froude number for a given length and (2) the cube of speed.

From the foregoing fundamentals, the MegaBB would have 8.6x the friction/area of BB-Iowa and 6.7x the wave drag. Assuming that Iowa's wave/friction drag breakdown is 50/50, this would imply ~1,600,000HP for the MegaBB to achieve 33kn at 100ft draft and 1,780,000t displacement. Or a little short of 8x the HP generation.

But HP isn't just a matter of drag, it's also a matter of how efficiently HP is turned into propeller thrust. In this domain, larger propellers and lower RPM are generally more efficient than smaller and faster-spinning propellers. http://web.mit.edu/13.012/www/handouts/ ... eading.pdf Maximum propeller size is and was limited by tip rotational speeds; exceeding a certain angular velocity at a given ambient water pressure and for a given technology level brings one into the domain of counter-productive cavitation where spinning faster produces less thrust and/or damages propellers. https://en.wikipedia.org/wiki/Cavitation

A larger propeller, however, generates thrust in proportion to the square of its diameter (i.e. it imparts a velocity delta to a mass water in proportion to the square of its diameter) while its tip-speed increases linearly with its diameter. Thus at a given technology level and water pressure, a propeller should be able to generate more thrust in proportion to its increase in diameter, assuming its RPM decreases inversely with its diameter as well.

One illustration of this basic physics/engineering principle is the seemingly inexhaustible economies of scale for container ships, which travel at high speeds for cargo ships and have been growing inexorably. The Emma Maersk, for instance, requires 109,000 HP to attain 25.5kn at ~200,000t displacement. https://en.wikipedia.org/wiki/Emma_M%C3%A6rsk [deadweight tonnage of 157k-t and light-ship displacement of ~50k-t]. Compare that to BB-Yamato's 27kn at ~150k HP and ~71k displacement. To achieve this economy, the Emma Maersk uses the largest propeller in history at nearly 34ft diameter (compared to ~18ft for BB-Iowa). https://gizmodo.com/this-five-bladed-be ... 1546432773

While the WW2 battleships used largest propellers of their time, they were still limited by hull form and draft. Image

Using larger propellers would have required extending their protection further aft - with associated weight implications - or changing the hull form in the rear - with associated hydrodynamic and weight implications. As buillt, each of the Iowa's shafts carried 53,000HP from its turbines using ~18ft propellers.

A MegaBB using ~30ft propellers could have used ~90k HP (30/18*53) at lower RPM without hitting cavitation limits for a given water pressure, but also could have been deployed in deeper water (higher tip-speed cavitation limits) at battle draughts - meaning even higher HP loading per shaft. With ~3x the beam and ~2x the draught at battle depths, a Mega-BB could have easily deployed 10x the HP of BB-Iowa. But it would have done so at ~50% greater propulsive efficiency, meaning only ~6x the horsepower of BB-Iowa for the 33kn or a much-higher top speed (I'll address the form/friction effects of a "fatter" hull in following posts).

If we assume cubic escalation of power with speed, a MegaBB top speed of 37kn at 100ft draught would require ~1.5mn HP or ~7x the Iowa's powerplant. As described hereafter, it could generate that HP more efficiently given its commodious hull.

TheMarcksPlan
Member
Posts: 918
Joined: 15 Jan 2019 22:32
Location: USA

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 22 Oct 2019 06:43

A preliminary note on armor for MegaBB.

Assuming steel density of 490lbs/ft3 and:
  • A citadel of length 1600ft, width 300ft, and deck armor of 2ft(!), that's 210k-t for deck armor
  • For a citadel-belt 2ft thick, 50ft high [from 10ft below water to 40ft above given 140ft hull depth and 100ft battle draught] we have 70k-t belt armor
  • Bulkheads of 200ft, 50ft high and 2ft-thick are ~9k-t
  • Total citadel armor is ~300k-t
Our target displacement at 2400x360x40 and .7 block coefficient is ~700k-t so we're well within the limit with 100's of k-t for armament and turrets.

User avatar
T. A. Gardner
Member
Posts: 1954
Joined: 02 Feb 2006 00:23
Location: Arizona

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by T. A. Gardner » 22 Oct 2019 07:33

I doubt it could be built. The sheer length would be an issue with the bending moment of the ship and strength of materials. If you look at modern super tankers, they have to account for this bending moment, and even the curvature of the Earth in design.
Then there's the issue of ports and maintenance services.
In the pre-WW 2 years, the USN built new drydocks at most US naval bases on both coasts. These were usually designated the #4 drydock or graving dock. They were about 1100 feet long and around 150 feet wide. This was then considered sufficiently large for any projected future ships and they are still within the size to dock an aircraft carrier.
This would mean that the ship couldn't be drydocked anywhere on the planet.
With a 100 foot draft, the ship couldn't enter most, almost any, harbor in existence. Few harbors are 50 to 75 feet deep let alone over 100. This would mean mega dredging at every harbor the ship was intended to use. For example, such a ship couldn't deploy from Pearl Harbor which is only about 40 to 50 feet deep for the most part. San Francisco is the same way. The ship couldn't tie up at Hunter's Point for example for the same reason. The harbor is too shallow.

Image

Image

Piers and docks would have to be greatly enlarged to handle such a ship as well.

Then there's ship handling in these harbors. I severely doubt that would be easy to do.

And lightening the ship to reduce the draft by half would likely induce serious stability issues not to mention the time and effort involved in doing this before entering and after leaving port.

I'd say on the whole, like the H44 this is simply too much ship to make it worthwhile.

maltesefalcon
Member
Posts: 1811
Joined: 03 Sep 2003 18:15
Location: Canada

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by maltesefalcon » 22 Oct 2019 11:40

The points above on dry dock facility are spot on. Also look at manouvering at speed. A ship this size at war speed would be a juggernaut, very difficult to correct course.

IMHO US would be better served by making more carriers, Iowa Class and (maybe) Montana Class.

OpanaPointer
Member
Posts: 4137
Joined: 16 May 2010 14:12
Location: United States of America

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by OpanaPointer » 22 Oct 2019 11:44

The law was that no US military ship could be more than 108 feet wide. This was to allow them transit the Panama Canal. (Cheap two ocean navy idea.)
Come visit our sites:
hyperwarHyperwar
World War II Resources

Bellum se ipsum alet, mostly Doritos.

TheMarcksPlan
Member
Posts: 918
Joined: 15 Jan 2019 22:32
Location: USA

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 22 Oct 2019 18:18

T.A. Gardiner wrote:With a 100 foot draft, the ship couldn't enter most, almost any, harbor in existence. Few harbors are 50 to 75 feet deep let alone over 100.
The empty draft is 40ft. 100ft is BATTLE DRAFT ONLY. Typical full load draft would be ~60ft with ~500k tons of ammo/powder and fuel.

Why such a deep battle draft? Because as you note the ship's hull depth has to increase for the bending moment [more on that below]. But armoring 80ft of freeboard would be wasteful if not necessary. Therefore, the ship would take on ballast when entering battle to reduce its freeboard to ~40ft, enabling only the top 50ft of the hull to be covered by the main belt. Because the ship is so huge and because its machinery and crewing requirements don't scale cubically, it needs less than half its internal volume to accommodate magazines, machinery, accommodations, plotting rooms, storage, etc. Here's a quick sketch of the cross-section amidships:

Image

The torpedo bulges are 45ft wide on each side; the bottom 30ft of the hull is void space as well. The green-labeled cross section is 60x270ft. Across a 1600ft citadel its volume would be ~260,000 GRT or over three times the total volume of RMS Queen Mary: plenty of room to house all the crew and ship functions within the citadel. Non-citadel space could be void as well - probably you'd flood that space to avoid fires in battle and keep your torpedo bulges empty.
T.A. Gardiner wrote:The sheer length would be an issue with the bending moment of the ship and strength of materials.
Moment of inertia for a rectangular beam increases cubically with thickness and linearly with width. https://www.engineeringtoolbox.com/area ... _1328.html
This is one reason that large ships have better structural efficiency than smaller ships - i.e. their empty weight is a lower portion of their total displacement or deadweight. Empty weight of the largest-ever oil tanker, for example, was only ~1/8 of its max displacement. https://en.wikipedia.org/wiki/Seawise_Giant

At 140ft hull depth and 2400ft length, this ship's length/depth ratio of 17.14 is only slightly higher than BB Montana's 16.4 (921/56ft). If anything, it would be possible to make it a bit longer. But I'll keep these dimensions for now.
For example, such a ship couldn't deploy from Pearl Harbor which is only about 40 to 50 feet deep for the most part. San Francisco is the same way. The ship couldn't tie up at Hunter's Point for example for the same reason. The harbor is too shallow.
To repeat, empty draft is only 40ft and loaded draft 60ft. Draft becomes 100ft DURING BATTLE ONLY via internal flooding.
As I stated in OP, the ship would be loaded with shells at only a few ports - Provincetown and Tacoma being my suggestions. Here are depth charts for those two ports:

Image

Image

As you can see, Tacoma harbor is at least 140ft deep everywhere. Provincetown harbor is ~100ft deep near the outer spit - putting a giant wharf for loading shells etc would be perfect there.

Everywhere else, the ship's 40ft empty draft would allow access to, e.g., Hampton Roads and SF Bay for overhaul or repairs if necessary.

Once loaded with shells and fuel to 60ft draft, the ship could operate from many harbors.

Mariveles Harbor at the mouth of Manila Bay is over 100ft deep:

Image

Scapa Flow is over 100ft deep. The USN used Lahaina Roads as an anchorage during/before WW2, which is several hundred feet deep. https://en.wikipedia.org/wiki/Lahaina_Roads
T.A. Gardiner wrote:Piers and docks would have to be greatly enlarged to handle such a ship as well.
Yes. And drydocks. But again, only a few. The ship's practically unlimited range and extreme fuel efficiency per fighting power means it only needs a few places to load, then can cruise without resupply for months.

And a situation in which this ship has spent all its ammo - 500k tons of shells - is a situation in which any enemies have been destroyed, so it's not a huge issue that it might have to return to Tacoma from the Philippines to restock ammo. And given its fuel efficiency, it could make that run at 30kn both ways, meaning only a couple weeks' absence from the theater.
maltesefalcon wrote:IMHO US would be better served by making more carriers, Iowa Class and (maybe) Montana Class.
One of these ships could carry the broadside weight of over 200 Iowa class ships: say 400+ 18in guns firing at over twice the Iowa's RoF, plus 1,000+ 9.5in guns firing at 8/min.

And it's basically unsinkable: You can't penetrate the decks with anything but maybe a Grand Slam bomb from a four-engine bomber (maybe). With 45ft torpedo bulges and 30ft of void at the hull bottom, there's no way to hit the vitals from underwater.

Its secondary and even primary guns would make attacking it from the air a suicide mission, especially for carrier-based planes that can't carry anything but door-knockers against 2ft armor.

The construction cost would likely not exceed ~10x the Iowa class, as it uses only 7x the power plant and has economies of scale on hull and armor construction.
OpanaPointer wrote:The law was that no US military ship could be more than 108 feet wide. This was to allow them transit the Panama Canal.
Montana-class BB's and Midway-class ignored the Panama Canal restriction; this ship would have to as well. At 30kn, a trip around Cape Horn would take only a couple weeks.

maltesefalcon
Member
Posts: 1811
Joined: 03 Sep 2003 18:15
Location: Canada

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by maltesefalcon » 22 Oct 2019 23:48

The biggest operational issues I see are:

You cannot have just one or two. You'd need several in each area of ops to provide relief units for repair and rest of crews.

There would also be numerous waterways where enemy ships could skulk out if range of its guns but in water too shallow for it to venture.

TheMarcksPlan
Member
Posts: 918
Joined: 15 Jan 2019 22:32
Location: USA

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 23 Oct 2019 00:09

maltesefalcon wrote:You'd need several in each area of ops to provide relief units for repair and rest of crews.
Not sure what you mean by that. The ship/ships (I'd say plan for four) would deploy only for decisive actions.
maltesefalcon wrote:There would also be numerous waterways where enemy ships could skulk out if range of its guns but in water too shallow for it to venture.
Sure, they wouldn't be able to enter "The Slot" around Guadalcanal, for example.
But you'd use these ships to force decisive action in deeper water. Sail it right up to Rabaul, for example, in the Guadalcanal scenario. Or right up to Truk Lagoon. You'd shoot down 80% of planes dispatched to stop it, kill any naval forces challenging it, and still have ammo left to lay waste to the naval bases.

Similarly, a ship like this could deter any invasion of the Philippines even if stationed in Seattle. It would take ~6 days to steam from Seattle to Luzon, at which point the sea lanes supporting the invasion are closed for Japan. The ship could shell any landing sites into the oblivion while there.

User avatar
T. A. Gardner
Member
Posts: 1954
Joined: 02 Feb 2006 00:23
Location: Arizona

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by T. A. Gardner » 23 Oct 2019 01:12

TheMarcksPlan wrote:
23 Oct 2019 00:09
maltesefalcon wrote:You'd need several in each area of ops to provide relief units for repair and rest of crews.
Not sure what you mean by that. The ship/ships (I'd say plan for four) would deploy only for decisive actions.
maltesefalcon wrote:There would also be numerous waterways where enemy ships could skulk out if range of its guns but in water too shallow for it to venture.
Sure, they wouldn't be able to enter "The Slot" around Guadalcanal, for example.
But you'd use these ships to force decisive action in deeper water. Sail it right up to Rabaul, for example, in the Guadalcanal scenario. Or right up to Truk Lagoon. You'd shoot down 80% of planes dispatched to stop it, kill any naval forces challenging it, and still have ammo left to lay waste to the naval bases.

Similarly, a ship like this could deter any invasion of the Philippines even if stationed in Seattle. It would take ~6 days to steam from Seattle to Luzon, at which point the sea lanes supporting the invasion are closed for Japan. The ship could shell any landing sites into the oblivion while there.
Or have a couple of these torpedo it repeatedly and send it to the yards for a decade of repair...

Image

TheMarcksPlan
Member
Posts: 918
Joined: 15 Jan 2019 22:32
Location: USA

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 23 Oct 2019 01:52

T.A. Gardiner wrote:Or have a couple of these torpedo it repeatedly and send it to the yards for a decade of repair...
First, the ship can sustain 30kn+ for weeks on end so good luck to that submarine hunting it.

Second, with 45ft torpedo bulges and ~1mil tons reserve buoyancy, even a dozen torpedo hits won't send the ship to the yard. This isn't like hitting a SoDak/Iowa BB with 20ft bulges, where a single torpedo can undermine the integrity of the magazine and other essential ship functions. You'd need to "hole in one" another torpedo through a pre-existing torpedo hole to get through the bulges. Even then you're not hitting the magazines, which are all above the waterline, and you'd need exemplary luck to hit the engines.

User avatar
T. A. Gardner
Member
Posts: 1954
Joined: 02 Feb 2006 00:23
Location: Arizona

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by T. A. Gardner » 23 Oct 2019 06:03

For this ship to "sustain 30 kn+ for weeks" it would have to carry somewhere around 300,000 tons of fuel, possibly as much as 350,000. That's based on the fuel efficiency of the Iowa class scaled up. Refueling it would become a serious issue. No existing tanker could come close. It'd take a fleet of these one after another emptying their load into this monstrosity probably over several days to refuel it.

I think the other issue would be the ship would have radical shifts in buoyancy, metacentric height, and stability as it went from light ship to full load and back. I think that would be a serious issue too.

User avatar
Robert Rojas
Member
Posts: 2658
Joined: 19 Nov 2002 04:29
Location: Pleasant Hill, California - U.S.A.

RE: American Militarism Pre-WW2 And The Ultimate Battleship

Post by Robert Rojas » 23 Oct 2019 07:19

Greetings to both brother "THE-MARCKS-PLAN" and the community as a whole. Howdy T.M.P (or Erich if you so prefer). Well Herr General Oberst, I see you've traded in your ground pounding field gray Army Uniform for the blue uniform of the United States Navy - that's quite a significant change! Since I am neither a naval architect nor a naval engineer by professional training, I will refrain from interjecting my woeful technical ignorance into your colorful introductory posting of Tuesday - October 22, 2019 - 2:44am. Generally speaking, brother T.A. Gardner appears to be performing Yeoman's work shooting holes into your fanciful notion of what I would christen as the BEHEMOTH CLASS of battlewagons. Incidentally, I believe that you might be doing yourself a disservice IF you gloss over brother Opana Pointer's technical observations about the Panama Canal within his sage posting of Monday - October 21 - 2019 - 7:00pm. However, with all of that said, I was WONDERING how YOU were going to "sell" this monstrosity to the American naval bureaucracy - more specifically to the Chief of Naval Operations FLEET ADMIRAL ERNEST J. KING. In short, that is where YOUR theoretical battleship will undoubtedly conduct the majority of its figurative "combat". Well. that's my initial two Yankee two cents worth on this bizarre exercise into the absurd - for now anyway. As always, I would like to bid you an especially copacetic day from sea to shining sea.

Best Regards,
Uncle Bob :idea: :|
"It is well that war is so terrible, or we should grow too fond of it" - Robert E. Lee

User avatar
Terry Duncan
Forum Staff
Posts: 5701
Joined: 13 Jun 2008 22:54
Location: Kent

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by Terry Duncan » 23 Oct 2019 11:20

TheMarcksPlan wrote:
22 Oct 2019 04:00
We all know that the U.S. went from isolationist to global hegemon in a short span encompassing WW2. The political reasons for this transformation are complex and I don't want to focus on discussing them here; I want to discuss what a U.S. Navy committed to world domination from the 1930's at the latest might have produced.

Specifically, it's kind of cool to this history nerd to imagine the "maximal battleship" that could have been produced pre-WW2. OTL we have the Tilman Battleship studies from the post-WW1, pre-Washington Treaty era. https://en.wikipedia.org/wiki/Maximum_battleship

But IMO this doesn't exhaust the economies of scale inherent in the design of larger ships. And the interwar U.S. would have been poised to exploit these economies of scale to a greater degree than any other power, as it was the world's largest economy by far and had excess industrial capacity due to the Great Depression. To summarize a few points on these economies of scale:
  • A ship's drag, and therefore its required horsepower for a given speed, varies primarily with its surface area and its wave drag.
  • Surface area scales with the square of linear dimensions while displacement scales cubically.
  • Wave drag (at a given speed) scales with displacement and the square root of length.
  • Bigger ships have lower Reynolds coefficients, meaning that drag for a given size decreases further.
  • Battleships generally show a greater proportion of displacement devoted to armor and guns with scale.
  • Ships generally show a lower ratio of hull weight to deadweight as their displacement increases.
  • Larger propellers are generally more efficient than smaller for large ships.
  • Larger power plants are generally more efficient than smaller.
Taking all of these factor together, I can imagine an interwar U.S. determined to maintain a navy "second to none" that could and would build super-battleships on a scale not generally imagined, at a price that would preserve economies of scale.
For example, imagine a ship 2400ft waterline length, 360ft beam, and 140ft in hull depth (empty draft of 40ft and empty displacement of ~700k tons, maximum draft of 120ft to maintain 20ft of freeboard - this would require ballast and/or unusually heavy ammunition/fuel load).

The first obstacle to this cubic escalation of battleship scale is harbor depth. Luckily, the U.S. possessed on both coasts at least one sheltered harbor that could resupply a gargantuan ship up to 100ft draught: Puget Sound and Tacoma Harbor on the West Coast and Massachusetts Bay and Provincetown in the East. Because a ship of the dimensions I'm envisioning has a basically unlimited range/endurance, one harbor on each coast is all that's needed. In addition, the Lahaina Roads used by the U.S. Pacific Fleet as an anchorage has a depth of several hundred feet. The outer harbor of Manila Bay around Corregidor and Mariveles has a depth of over 100ft. So an enormous ship could deploy operationally from Pearl, Seattle, Manila Bay, or Massachusetts, and could enter any of the normal U.S. anchorages for routine maintenance (SF Bay, Hampton Roads) after offloading ammunition and excess fuel either at the aforementioned deep-water ports or via resupply ships (as its draught would be less than 40ft).

A ship of this size could devote a hitherto-unimagined portion of its total empty weight to guns and ammunition. Basically it could devote the entirety of the differential between cubic (displacement) and quadratic (dimensional) escalation of its scale to greater firepower. One could sketch, for example, a ship with ~400 18in guns in the main battery and ~1,500+ 9.5in guns in the secondary battery. This would, however, require turrets firing over each other in broadside and therefore restricting some of the armament's angle of fire. That's addressed, however, by the ability to elevate guns to more than 45 degrees via "burying" gunhouses in a uniform deck-level armament belt: with that ability, guns incapable of depressing below a certain angle due to neighboring turrets can simply fire high-angle arcs against opponents' weaker deck armor.

Here's a first-draft approximation of a layout for such a mega-battleship:

Image

...where large circles represent main battery armament and small circles secondary.

This is drawn at a smaller scale than the 2400x360 battleship I mention above but it conveys the general idea: 1/2 to 1/3 of the armament is always available for low-angle fire against close-in targets (that won't survive more than a few minutes) while the rest of the armament can fire high-angle arcs against aerial or land targets.

A note on propulsion:
While a 2400/360 ratio of LWL-Beam is lower than for most modern battleships, the overall propulsion requirements - and therefore the tradeoff between expense and displacement implications of speed versus structure - are radically different for a giant ship versus a normal ship. The 2400/360 ship with a 100ft battle draft (again achieved after leaving port via ballast instead of structural weight) has only ~8x the surface area, and thus 8x the friction at equal speeds, of an Iowa-class battleship. It also has a similar ratio of friction-caused vs. wave-making-caused drag at 33 knots. It could use 30ft propellers in two vertical rows, meaning far ~50% higher propulsive efficiency from a given HP generated by the ship (HP: Thrust being determined linearly from RPM for ships, generally speaking). Finally, the enormous hull volume would allow usage of industrial-level efficiency for electricity generation to E-turbines (as in BB Nevada) without exceeding 10% of hull volume.

EDIT:
In following posts I'll expand on the details of propulsion, armor, gunnery, etc. for these ships.

At base is a contention that a mega-BB of this type could have mounted the firepower of ~200 normal BB's and ~500 cruisers, while being too deadly to air attack for carrier-based (or any) aerial attack.
To be honest, a quote from the German admiralty about one of the Kaisers sketch designs for a cruiser comes to mind here "Yes, it is lovelly. If only it could float." There is a photo of a model going around where 16" turrets number close to 100 that this reminds me of, but I have not been able to find it again.

The fueling issues have already been pointed out, but a single magnetic mine will be enough to sink this idea, as will the later torpedoes that explode under the hull rather than in contact with it. The other problem is ths sheer amount of resources it will take up. You could build a dozen or so mixed battleship and carrier groups in its place, and their ability to be in more than one tiny spot in the ocean at a time makes them infinitely more useful. There is a cut off point where increasing the size ceases to be of much use, the guns are puny compared to the size even if they are in great numbers. Is a Montana or Yamato as good as two South Dakotas? If there are unlimited resources then maybe, but they can still only be in one place at a time so you end up building 4 x 70k ton ships as opposed to 4 x 35k ton ships. In the case of the design proposed, if an enemy nation builds a comparable ship but arms it with less but better laid out 80cm guns like the Schwerer Gustave but can fully automate the loading to achieve maybe a round per gun per two mins, you now have no advantage at all.

You would be better going down the Habbakuk line, making the facility effectively unsinkable and accepting limited mobility as some kind of bombarment/coast protection monitor, then maybe it is less of a waste, but making such a ship from steel is not cost effective.

User avatar
Takao
Member
Posts: 2932
Joined: 10 Mar 2002 19:27
Location: Reading, Pa

Re: American militarism pre-WW2 and the Ultimate Battleship

Post by Takao » 23 Oct 2019 12:44

Port use for provisioning is immaterial. What none of the ports so far mentioned have is a drydock capable of handling such a ship. There is no place to go for hull repairs or bottom scraping. Marine growth Wil start lowering the speed in a month's time. In 6-9 months you have already lost 3-4 knots.

Nor is there any yard capable of constructing such a behemoth without an incredible amount of improvement.

Is there any armor manufacturer capable of producing armor plate in the thickness you require, or is the armor going to be layered?

Then there is construction time which no one has mentioned yet. The hull can be put together fairly quickly, the armor and especially the turrets will be the bottleneck. How long is it going to take to produce 140 triple 18-inch turrets? And that is just for one ship...Not to mention all the secondary turrets of 8 and 5 inch guns.

Sink it? Disable those barn door props and building sized rudder and its immobile. The behemoth cannot turn to avoid torpedoes, nor is it able to outrun them.

Return to “What if”