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So, let's say that through a series of strange timey wimey events, I accidentally jump-start several technological revolutions in the early 1800's. So, at any given time, technology is ~60 years ahead of where it should be, sans nuclear weapons (nuclear power does exist though). Now let's say that WWI and WWII don't happen. Now, let's also say that, in 1930, America is provoked into a short but bloody war, culminating in a months-long blockade and bombardment of the enemy’s heavily fortified capital city. Beach landings are all but impossible, due to a series of anti-ship weapons under the water. The city can't perform an all out attack on the ships bombarding them, but they have supplies and weapons delivered to them from the land. The Americans can't get close enough to intercept the supply route, and this siege has been going on for months. In the port in Baltimore, the frame is being assembled for the largest ship ever built. "Super Dreadnought". 700 meters long, 3 nuclear reactors, and a retractable stabilization pylon on each side. Armaments:

10 31.5" guns
20 18" guns
20 16" guns
30 14" guns
40 3" AA guns
100 10" guns
300 .50 machine guns

It is decided that "nothing short of putting an entire battleship in the way could stop that damn supply route". Then an idea is pitched: put an actual battleship in the way. In particular, put the Super Dreadnought in the way. It's approved, and constructed with 7 sets of massive caterpillar tracks. Each set has one track directly under the ship, and one on either side. This massive ship is now amphibious.

Now, here are my questions:

  1. Is my proposed method of making this ship amphibious plausible?
  2. If so, what would the the approximate top speed?
  3. If not, what can I change to make it plausible?
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  • $\begingroup$ How do you even fortify a city against artillery? $\endgroup$ – CodesInChaos Nov 10 '16 at 12:35
  • $\begingroup$ You seem to be totally ignoring air power? $\endgroup$ – John Feltz Nov 10 '16 at 18:57
  • $\begingroup$ @JohnFeltz The thing is covered in AA guns... $\endgroup$ – CaptClockobob Nov 10 '16 at 19:03
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    $\begingroup$ No, I mean to use air power to enforce the blockade. You have the equivalent of what the US used in the Iraq/Kuwait conflict of 1991 - everything from B-52s to A-10s to F-15s. Wipe out the rail, road, and power links from the air. $\endgroup$ – John Feltz Nov 10 '16 at 19:07
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    $\begingroup$ @Tezra Is it wrong to want to have a giant battleship that can drive onto land? $\endgroup$ – CaptClockobob Nov 11 '16 at 20:14
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In a rather weird way, H.G. Wells wrote about the possible future of tanks and pessimistically envisioned monstrous battleship sized machines capable of carrying huge batteries of guns and plowing the landscape before them due to the immense weight.

What lies behind the Tank depends upon this fact; there is no definable upward limit of mass. Upon that I would lay all the stress possible, because everything turns upon that.

You cannot make a land ironclad so big and heavy but that you cannot make a caterpillar track wide enough and strong enough to carry it forward. Tanks are quite possible that will carry twenty-inch or twenty-five inch guns, besides minor armament. Such Tanks may be undesirable; the production may exceed the industrial resources of any empire to produce; but there is no inherent impossibility in such things. There are not even the same limitations as to draught and docking accommodation that sets bounds to the size of battleships. It follows, therefore, as a necessary deduction that if the world's affairs are so left at the end of the war that the race of armaments continues, that Tank will develop steadily into a tremendous instrument of warfare, driven by engines of scores of thousands of horse-power, tracking on a track scores of hundreds of yards wide and weighing hundreds or thousands of tons. Nothing but a world agreement not to do so can prevent this logical development of the land ironclad. Such a structure will make wheel-ruts scores of feet deep; it will plough up, devastate and destroy the country it passes over altogether.

enter image description here

Illustration from 1939

Of course, being a "linear projection", it takes a basic idea and inflates it to rather absurd dimensions. Wells was no crank, however. He had actually predicted armoured fighting vehicles in a 1903 story "The Land Ironclads" (technically, the Tripods from the War of the Worlds were also AFV's), and was an enthusiastic supporter of the development of real tanks when they were developed by the British.

enter image description here

A Land Ironclad

And this trope has carried on in Science Fiction and games with ideas like "Bolo" AI driven tanks and the Ogre war-game.

However, once you re read the description of the Wellsian super tank, you see the issues. Engines with "scores of thousands of horsepower" are absurdly huge (especially with 1930 era technology) regardless of what your power source is. The bulk of the machine will be made up of engine bays and transmissions. Since the engines will not convert 100% of your energy into motion, you need some sort of radiating mechanism. A ship at sea can dump its heat into the ocean, but on land it becomes a bit more difficult. You might be looking at a cooling system similar in size to the massive cooling towers at a nuclear power station.

The next issue is the mechanical strength of the chassis. A ship is fully supported by the water it displaces, but your vehicle will have hundreds or thousands of separate stress points in the suspension and track system. The body will be similar to a bridge standing on pylons, so there will be sections cantilevered between suspension elements. The body will be subject to stresses in multiple directions since the ground isn't flat, and firing stresses will complicate matters even more. When you consider a modern torpedo kills a ship by exploding under the keel and creating a cavitation bubble, snapping the ship where it is no longer supported, then consider the same effect will occur when the vehicle will be subject to similar stresses when crossing a stream, valley or even sufficiently large ditch.

Finally, this thing will be a target. It will be moving slowly enough that everything from long range artillery and bomber aircraft to tank hunting teams with explosive charges will be assembled and sent into action long before this thing can get into range of its target. Your multi million dollar investment will be smoking ruins, quite possibly before you even hit the beach (the Captains of the HMS Prince of Wales, IJN Yamato and the Bismarck can explain this more fully).

Given the parameters that you provided in the setup, it would be far more plausible for the attack to be made by carrier born bombers or even large seaplanes than to expend the time and energy needed to create the monstrosity you are describing.

enter image description here

USS Saratoga

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  • $\begingroup$ not directly related, but would you mind linking which USS Saratoga this is? $\endgroup$ – dot_Sp0T Nov 10 '16 at 8:29
  • $\begingroup$ Wells may have underestimated their impact. "Such a structure will make wheel-ruts scores of feet deep; it will plough up, devastate and destroy the country it passes over altogether." There's a good chance behemoth land ironclads' tracks will get bogged and unable to move. Soil has limits to the weight of structures it can support. The Super Dreadnought would certainly push its limits. $\endgroup$ – a4android Nov 10 '16 at 11:00
  • $\begingroup$ Click on the caption to link to the USS Saratoga CV-3 $\endgroup$ – Thucydides Nov 10 '16 at 18:43
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Generally speaking, this sort of approach has to be designed into a ship since day one. You need a very different structural setup when you can't just float the ship on water. Amphibious vehicles often make sacrifices to achieve their goals.

One thing you definitely will need to do is split up those 7 caterpillar tracks into several hundred tracks, or you will find that the dreadnought cannot turn at all!

Realistically speaking, there's nothing like it in all of engineering. The closest thing I can think of to what you are trying to do is the Crawler-Transporter NASA used to transport the shuttle, with a top speed of 1mph. That was 40m long and weighed in at about 2700 tons. The USS Iowa, one of the last of our battleships, was 270m and had a mass of 45,000 tonnes. Your ship is at least 3 times that big, and likely bigger, so that should give you a sense of how extreme the design is.

Also, expect this change to make the Super Dreadnought completely and utterly useless in the water. The drag from these tracks would make it the laughingstock of any navy in terms of top speed. Assume that what you created really was a single use device that will never find value in war again.

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  • $\begingroup$ It's also a huge and expensive single point of failure. If it gets stuck or is disabled in some way... $\endgroup$ – user10945 Nov 10 '16 at 7:07
  • $\begingroup$ On top of all that, NASA's Crawler only operated on a purpose-built road. Try driving it across everyday terrain, it will get stuck on the smallest hill or sink into even slightly soft earth. The OP's ship is at least equally doomed. $\endgroup$ – cobaltduck Nov 10 '16 at 18:34
  • $\begingroup$ It's also worth noting that the crawler-transporter carried the orbiter, external tank (possibly empty) and the two solid-fuel rocket boosters. Based on coolcosmos.ipac.caltech.edu/ask/… the total dry/empty weight as carried thus comes down to about 2.8 million lbs or about 1300 tons. It grows by nearly another thousand tons if the ET was carried full. In other words, if your numbers are correct (I haven't double-checked), even conservative estimates say that the crawler-transporter weighed more than the fully fueled spacecraft it carried. $\endgroup$ – a CVn Nov 11 '16 at 10:40
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    $\begingroup$ @MichaelKjörling It would not surprise me. Shuttle: "Space is hard... make it as light as possible!" Crawler: "You have one job... don't drop it." $\endgroup$ – Cort Ammon Nov 11 '16 at 16:15
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Other answers are good, but there is one more thing to it.

Sea is basically flat, with small distortions called waves, that still give pretty flat average. On the open ocean big waves are also long - so still flat. This means, you can dump stress really evenly. Construction is easier if it does not need to support mass on discrete number of points. Far less structural strength needed. With something long like a ship, change of road elevation (like start of an uphill ride) would mean that while front and rear are supported, middle is not. Ship as we know them would break.

Of course you could separate it into sections with flexible joints. Each of these should need own pair of tracks, own engine. Now, if you would only get rid of these joints, you would effectively have a column of tanks, artillery and support vehicles. Or you could leave one engine and joints, but then you would have to put it on the train tracks. Armed, armored trains was real,and looked somewhat like warships.

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    $\begingroup$ To expand on this (+1 by the way), this point is among the hypotheses for the fate of the Edmund Fitzgerald- two waves, exactly the length of the ship apart. One wave peak lifted the bow, the next peak lifted the stern, leaving the trough between them where the hull was unsupported. The ship broke in half, sank. $\endgroup$ – cobaltduck Nov 10 '16 at 18:38
  • $\begingroup$ Thanks @cobaltduck. I vaguely recalled something like that, but wasn't able to recall any details. $\endgroup$ – Mołot Nov 10 '16 at 20:45
  • $\begingroup$ Note that even plain old trains have almost exactly the same problem when turning, requiring very large turn radii for railroad tracks. $\endgroup$ – a CVn Nov 11 '16 at 10:47
  • $\begingroup$ At the time I posted my earlier comment, I had not known it was the 41st anniversary of the event in question. Spooky. $\endgroup$ – cobaltduck Nov 11 '16 at 13:43
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You should look into the Bagger 288.

Weight and size-wise, it is closest to what you are looking for, and somehow has all-terrain capabilities! This provides us with a captivating insight into the Bagger's weight distribution methods.

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No, and None

You asked for science based...

No, this sort of thing will never be feasible, at least not on Earth

As others have pointed out, the only reason we can make ships so big is because the ocean is a very/relatively easy medium to deal with. No matter the weight you can always "stand" on the ocean, as long as your average density is less than that of water. It does not matter how big you make something; as long as the density is less than that of water, it will float.

As a side note: this is also true of air, which is why we could/can make humongous airships. And both the ocean and the atmosphere are (relatively) kind to you in that they (mostly) distribute your load very evenly accross your hull.

This is not true on land, because of the square-cube law, and the fact that land is only pressing against one side of your craft. As the size increases, the pressure — i.e. weight per unit of area — on the ground will increase as well. If you scale something up 10 times, the area in contact with the ground will increase 100 times ($10 \cdot 10$) but the weight will increase 1 000 times ($10 \cdot 10 \cdot 10$). This means that the ground will give way and you will sink through it.

Among the largest land weapons systems mankind has tried to move around are the Panzer VIII Maus and the Heavy Gustav/Dora. The Heavy Gustav required dual railway tracks to help alleviate the square-cube problem. And the Maus never saw action, and even if it had it would have been a right pain to move it around since most bridges would be unable to carry its weight.

What kind of change would be needed to still try to do something like this? Well essentially you need less gravity: you need the battle to take place on the Moon, or on another, smaller planet. But since your question implicitly places the battle on Earth, sorry...

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You don't want a ship, you want an amphibious TRAIN. Your ship is too long for the sea, it would have to be very wide as well. TRhis would make it supremely unwieldy on land, how could it navigate even the gentlest hill crest? You can see here the various length-beam ratios and what ships use what. An Iowa class BB, for example, has a length of 860 feet and a beam of 108 feet for a ratio of 8. A Spruance class DD has 529/55=9.6 ratio. So your battleship, if it were scaled like a regular warship, would have a beam of at least 73 METERS, or 240 feet, which is the height of a TWENTY FOUR STORY BUILDING laid on it's side. Contemplate trying to maneuver that across the ground.

But a train, since it is flexible, can be much narrower since it is able to flex and can weave through geographic obstacles. The treads would have to be on each compartment of course.

For amphibious operation tanks and the like typically have rudimentary waterproofing, bilge pumps for seepage, and a dual locomotion system using water jets, not the treads. You could use the treads like giant paddle wheels if you could raise them halfway out of the water, or equip each compartment with jets. The linkage of multiple vehicles is advantageous because you can "lose" compartments to flooding without stopping the entire vehicle, and the linked vehicles can push/pull the others, so crossing small bodies of water would be pretty easy. For the deep ocean however, you would need substantial water proofing and high speed jets. It is possible, depending on your power source, to employ hydroplanes to raise the train compartments out of the water so they can run the treads of extend propellers/jets into the water. But this requires significant speed to work.

Another possibility is the deployment of a hovercraft skirt, so the entire train is just a hover train. This would work well if you could deploy treads when necessary to climb steep inclines, or perhaps alternate a treaded compartment with a hover one to allow for dual surface mobility.

Your armament mix is a bit suspect, as there isn't really a need for all the smaller rifled guns (the 16-14 inch ones) if you have beasts like the 31"er. How many targets can this thing expect to engage simultaneously, how many rifled guns can it shoot? Even the mighty Yamato BB just carried 18" guns and much smaller ones (mostly for anti-aircraft defense). The reason for this is that the bigger the bore, the longer the range. So the 31" (!!!!) and 18" guns presumably would have dealt with anything well before the 14 or 16" guns would have a chance to engage. Plus even with advanced electronics, simultaneously shelling dozens of moving targets would be very difficult (unless you had guided projectiles, I suppose). And all those different guns require different projectiles, powder bags, replacement parts, etc.

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  • $\begingroup$ The point of the overkill levels of firepower, is that The "Super Dreadnought" is meant to be able to single-handedly take on army's. It would be packed with troops and tanks. It is the ultimate mobile fortress. $\endgroup$ – CaptClockobob Nov 10 '16 at 18:59
  • $\begingroup$ @CaptClockobob sure, sure. My point is that they would be ALL heavy guns, not this odd mix of 14-18" guns. Historically at least a BB would carry all the same heavy guns, not have a turret of 16" and then one with 14". You have a lot of mixed batteries that don't make any sense. If the ship can mount 18" guns, then all the turrets would, the mount difference between 14" and 18" isn't that great, but the effective range and hitting power IS, so why not use the heaviest guns you got? $\endgroup$ – Jason K Nov 10 '16 at 21:38
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There are two very good reasons why tanks have never (successfully) grown to more than 70-odd tonnes.

  1. Mobility. For a tank to be useful, it needs to get around. One of the biggest limiting factors on modern AFV weight is the capacity of bridges - it's very difficult to get around if your vehicle is too heavy to cross any sort of bridge. Less important perhaps in a siege engine, but worth considering for such an enormous project - remember that battleships in that era were huge capital expenditures, and something that had only one role would probably not get approved.

  2. Usefulness. What can one giant tank with 10 guns do that ten tanks each with one gun do? Battleships only existed in the first place because they needed to be that big to carry the guns - on land, it would be far less necessary (and the requirement to carry fuel, food and crew to go thousands of miles wouldn't be there either). It's much the same reason as why battleships don't exist any more - you can fit weapons as big as you need on a 5 or 10,000 tonne ship, and one 50,000 tonne ship is far less useful than 5 10,000 tonne ships.

So even before you get to the scientific reasons why it couldn't work (and the other answers show this very well) there are good reasons why it wouldn't be very helpful even if it was possible.

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  • $\begingroup$ It is meant as a massive mobile fortress. carrying thousands of troops at once. It would be heavily armored, with massive multiple foot thick plates of Magnesium alloy (which is about as heavy as aluminum, but as strong as titanium). It would still be incredibly massive, but a hell of a force to be reckoned with. $\endgroup$ – CaptClockobob Nov 10 '16 at 18:56
  • $\begingroup$ It's still not really any more useful at anything than lots of tanks (which may be less armoured, but would be much harder to hit and you'd have to hit all of them to destroy them all). $\endgroup$ – Matt Bowyer Nov 10 '16 at 21:54
  • $\begingroup$ Additionally, there's a very good reason why AFVs don't have magnesium armour - it's really rather flammable. $\endgroup$ – Matt Bowyer Nov 10 '16 at 21:54
  • $\begingroup$ Not straight magnesium. It's an alloy of Magnesium and Silicon, and it's not flammable. But a bunch of small tanks, won't fire 31.5" shells... $\endgroup$ – CaptClockobob Nov 11 '16 at 2:43
  • $\begingroup$ NOTHING* can fire 31.5 shells - that's nearly an order of magnitude bigger than the biggest guns ever mounted to a warship However, guns roughly of the size of naval guns have been mounted on AFVs. You certainly wouldn't be looking at a small tank - a 16" - 18" assault gun would probably be the biggest and heaviest AFV ever to enter service. But you could still probably get to around ~100T, and you could make a huge number of those for the cost of one 'land-battleship', with far greater tactical utility *The biggest gun on a ship was 18.1", although 30"+ railway guns have been made $\endgroup$ – Matt Bowyer Nov 11 '16 at 15:20
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It's never going to make it out of the water, shorelines are either cliffs or soft ground, and this thing will sink in even hard packed soil. So the first time they try to land it, it will sink in the ground and become immobile.

The big question is why bother, you just need the artillery plus a support and defense units traveling as as individual units to get the same effect as your "super" while being far more mobile and they can replace units that get damaged. you need something like a better desinged Oka https://en.wikipedia.org/wiki/2B1_Oka for your largest guns. having all your guns as individual units gives much more flexability plus you can roll in replacements while the others are still firing. You use landing craft or amphibious units to get them to shore with a battleship supplying supporting fire. If you already have naval superiority why not use it.

You can deploy however many units you think it will take, plus support and defense units and keep replacing them for far less than your land titan will cost. Plus a mass of units will be a lot harder to destroy, one lucky hit stops your titan dead.

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