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Here's the explanation

These are the structural questions about my "Super Dreadnought".

  1. How wide would the ship have to be to be stable on the water?
  2. Would the Caterpillar treads hold the weight of the ship?
  3. What would be the approximate weight of the ship (without crew and ammunition).
  4. What would the water displacement of the ship be?
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    $\begingroup$ Avoid using external links that are required for questions or answers. Paste the relevant sections of the link as quotations in your question. $\endgroup$ – Ranger Nov 9 '16 at 17:58
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    $\begingroup$ It's not a Dreadnaught if it has different sized guns. It's kind of the definition of a Dreadnaught. $\endgroup$ – Aron Aug 17 '18 at 6:41
  • $\begingroup$ You list quite a few batteries that are each much larger than any put on a historical ship. A length of 700m would be completely unrealistic (it might work for just one of those batteries). The largest projected ships I know of would mount fifteen 18" guns or eight 20" guns, and no other guns larger than 6". There is no basis for extrapolation to that imaginary bunch of ship stats you put together. $\endgroup$ – David Thornley Aug 17 '18 at 18:26
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Your "a priori"s are ... dubious. For the no nuclear bombs, I guess you'd need to require that they know more about the effects of radiation and fall-out, and are morally opposed to using them - even though it will cost their own son's lives. Yeah, better we send our sons to die, than risk one of those pesky enemy lives! If they have some "underwater weapons" that prevent ships from getting close, then you have to explain how the supership is going to get close - it would be an even bigger and easier target. You didn't mention air power, but clearly, control of the sea depends on whether airplanes or dirigibles exist. These "underwater weapons" would need to have their ammunition replenished. If via tunnels, then destroy the tunnels; if via submarines, then destroy the subs (using your own "underwater weapons"). Weight is proportional to volume which is the third power of length. Support for the treads is proportional to the second power of length. Meaning as you increase the size of the ship, the tread area scales at the 3/2 power. (meaning it goes exponential). You seem to be assuming your ship will be perfectly rigid. It won't. How you'd actually support the ship over its treads would be enormously difficult (although you're probably aware of how NASA does a similar thing). I find the idea that you're going to get these treads onto a sufficiently hard surface implausible - they'll get stuck in the muck. (As the shore batteries destroy the ship...). A little physics/mechanics: the hull of a ship supports its weight over a massive surface area, you'd have to support that same weight with arms (pylons?) on top of the tread dollies. This would require the entire redesign of a ship. Basically, it's not a ship, its a building. On wheels (treads) I know of no building which would survive bombardment for more than a couple of minutes. Feel free to investigate the weights of your cannons. It's easy to find it. You also need to explain why you'd need different sizes of guns.(I understand the need for protecting against small boarding parties), but not the 6 sizes you mention. They say defense is easier than offense. That is only true for a point location. When you have to defend an entire coastline (or any other type of border), then the advantage is heavily tilted to the offense, which can pick its point(s) to attack (as well as time).

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  • $\begingroup$ It's more along the lines of "Nukes are too dangerous", and not wanting to disclose that they have the ability to level entire city's until it is absolutely necessary. The underwater weapons are basically hull shredders. Basically underwater barber wire, except much larger. The "pylons" are stabilization for the ship while firing from the water. The entire ship is meant as the worlds largest siege weapon, thus the copious amounts of firepower. It would be heavily armored. $\endgroup$ – CaptClockobob Nov 10 '16 at 3:28
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Well...

From a historical perspective, the solution would be to land ground forces far away from the city where the coastal guns can't reach, and then advance on the supply route. If this is impossible then paratroopers, if this is impossible, airstrikes.

The thing is, a battleship of the dimenshions you describe would firstly eat up half the navy's annual budget to build, and a 10th of the budget to maintain, next it would indeed be technically possible to build an amphibious craft with such size, but you would have to cut down weaponry, armour and speed drastically to achieve it. This means you would have to drop the 31.5 in guns, and probably also accept a decrease from 20 18 in barrels to maybe 10 or 12. (By the way, when you say guns, do you then mean barrels, or gun mantlets? if mantlets, how many barrels pr. mantlet?) you would have to accept armour that compares to an ordinary battleship, or alternatively accept a speed of only 10 knots (less than a third of, for example, an Iowa class) but i'm guessing, if you intend to use it like an armoured fortress, speed is of little imprortance, and would thus preffer to sacrifice speed for armour. You should also bump up the amount of reactors to 6 at least, and prefferably 8 or 10, as the track mountings will create MASSIVE drag, and slow the ship to half it's speed without the tracks no matter how you slice it.

The most important factor however, is that the country this ship is supposed to attack has either no airforce, or complete air superiority has already been established by the US air force, as even a few well placed bombs could still sink the entire thing, no matter how well you armour it up, or alternatively, blow off a track and render it immobile, with (i'm assuming) no chance of recovery once on enemy soil.

Also, you should read this, it has every parallel with your narrative, except maybe that yours is believed to have a chance of success by it's own commanders. https://en.wikipedia.org/wiki/Operation_Ten-Go

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Comparing with this large ship: https://en.wikipedia.org/wiki/Gerald_R._Ford-class_aircraft_carrier

we see that your ship is about twice as big.

  1. Width at waterline 41 * 2 = ~80m.

  2. No, Either they are too weak to hold it or it would make it too heavy to float (common sense speculation). Making it amphibious is going far overboard. If this was practically doable then we would see lots of aircraft-carrier-supertanks in reality.. we do not.

  3. & 4. Assuming it scales relatively evenly (I checked a few ships and it matches roughly) it would make it displace about 800,000 tonnes, but as it carries a lot of other stuff it would probably be a bit heavier than the carrier so say 1,000,000 tonnes. The weight of the ship is equal to the displacement (or it would sink or pop up).

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While not a ship the way you describe, H.G Wells did write about "Land Ironclads" (a book published in 1903), and later on predicted massive armoured fighting vehicles the size of WWI Destroyers crawling across country and laying waste not only to the enemy, but to the very land they drove over (War and the Future, 1917).

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.

snip

The machine will be perhaps as big as a destroyer and more heavily armed and equipped. It will swim over and through the soil at a pace of ten or twelve miles an hour. In front of it will be corn, land, neat woods, orchards, pasture, gardens, villages and towns. It will advance upon its belly with a swaying motion, devouring the ground beneath it. Behind it masses of soil and rock, lumps of turf, splintered wood, bits of houses, occasional streaks of red, will drop from its track, and it will leave a wake, six or seven times as wide as a high road, from which all soil, all cultivation, all semblance to cultivated or cultivatable land will have disappeared. It will not even be a track of soil. It will be a track of subsoil laid bare. It will be a flayed strip of nature. In the course of its fighting the monster may have to turnabout. It will then halt and spin slowly round, grinding out an arena of desolation with a diameter equal to its length. If it has to retreat and advance again these streaks and holes of destruction will increase and multiply. Behind the fighting line these monsters will manoeuvre to and fro, destroying the land for all ordinary agricultural purposes for ages to come. The first imaginative account of the land ironclad that was ever written concluded with the words, “They are the reductio ad absurdum of war.” They are, and it is to the engineers, the ironmasters, the workers and the inventive talent of Great Britain and France that we must look to ensure that it is in Germany, the great teacher of war, that this demonstration of war's ultimate absurdity is completed.

The need for massive engines and track mechanisms to drive such machines suggests to me that an amphibious version, although not impossible, would be simply impractical (or more impractical, if you will) simply because of the massive amount of space needed to ensure buoyancy. Compare, for example a US Army M-2 Bradly and a Marine AAV-7. The AAV-7 is much larger in order to ensure it is bouyant enough to swim ashore. Even more impressive is the difference between the Stryker and the new Marine ACV, while similar 8X8 wheeled vehicles, once again the ACV is far larger to allow it to swim safely.

So while potentially enormous vehicles like the Landkreuzer P. 1000 Ratte have been proposed as fighting platforms, and even larger land vehicles have been built (such as the crawler used to transport Saturn rockets and Space Shuttles, or huge draglines or bucket wheel excavators used for coal mining), the sheer engineering challenges to make them work on land are hard enough, the additional work required to make them amphibious would likely be a deal breaker in terms of effort and resources expended.

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