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SOLariss
Post subject: Re: Midway class battlecruiserPosted: December 29th, 2020, 1:30 am
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erik_t wrote: *
As a very rough rule of thumb, modern warships are pretty carefully designed for operability and maintainability. Improvements can be nibbled away on the margins, but if one finds oneself sketching out a super badass cruiser of doom that is a dramatic advance on existing ships in nearly every respect, there's probably something you're missing. In this case, the chief shortcoming is the new artist's common mistake of trying to fit ten tons of equipment into a three-ton bucket.
As for cruiser of doom, and why hasn't anyone implemented it yet: it is based around a new class of cannons (that seem to be currently in development) that were originally intended to be a loophole around an intermediate range ballistic missiles treaty. Here you can find a more comprehensive article about it. It is actually intended to be transported on land via a trailer truck (albeit very large one):
[ img ]
sorry for the potato image, but it seems to be taken from some exposition stand.
Neither China (that have never participated in the treaty), nor Russia (that made Iskander, that actually brought the treaty to its end) posses technologies required to accomplish such an endeavor. Particularly electronics able to withstand extreme g-forces of the shot from such a weapon.

Same goes for it's CIWS, Hyper Velocity Projectiles (for cannons), is another experimental American technology, that was first tested in September of 2020 and managed to shut down cruise missile imitator. Again, nobody but the US seem to have anything similar.

Actually I'm not nearly the first to propose putting Strategic Long Range Cannon on a ship, here Popular Mechanics speculates about the possibility of battleships armed with this weapon. I just don't like battleships IMHO, they are too much eggs in one basket, just remember Yamato, that Japanese feared to put into battle.
acelanceloet wrote: *
The rear guns and VLS fitting 'just barely' is exactly the issue: with the personnel access, ammunition elevator, reinforcements against shocks (as a gun happends to provide shocks to a ships structure) the amount of space required is about 2 or 3 times the amount of space you currently have. The VLS either has no hatch at the bottom, in which case seawater ingress (in heavy wave conditions) will result in damaged missiles and systems or requires a hatch down there that will require maintenance and is also still a risk in heavy weather. All in all, this will not reduce the required space (the maintenance access might even increase the required space) while offering just the very minor advantage of having a lower infrared signature.... while the infrared signature of the orignal system is only there when firing missiles out of the top, in which case there will be a lot of heat above the deck anyways.
As for the rear guns, the intent was to have horizontal ammo conveyor instead of the vertical lift. The ammunition storage can be put under the helipad, by the sides of the boat hangar. There is no need to bury their ammunition deeply into the ship, provided that the powder is incredibly hard to ignite and most of rounds don't contain explosives (they are "hit to kill").
As for VLS, I didn't mean the hatch at the bottom, but a horizontal flame channel flame channel diverting flame between the hulls:
[ img ]

Lover IR signature wasn't the main goal unlike crew safety. See, most of ships equipped with VLS have them both fore and aft of the superstructure, but for the purpose of at sea rearming Midway has all of its missiles at the back. Thus I'm worried about a situation, where somebody is working on the helipad and there is immediate need to launch a missile. Actually I don't know what is the safe distance for human to be from Mk41 when the missile is launched, that's why I wanted to be as safe as possible. From the videos I've seen the exhaust does look terrifying.
acelanceloet wrote: *
I agree nuclear would not fit the concept, but then you should wonder, if the goal is to have this ship in numbers, does high speed make sense? if you have enough of them to station them around the world, there is no need to have very high speed long range relocations.
There were four reasons for putting ludicrous powerplant on the ship, two logical and two silly:
1.Replenishment time, to the nearest port and back (when Midway is used not as a part of big strike group).
2. Fast deployment in solo mode to support special ops or in case if rapid unexpected escalation.
3.I could't come up with ship's class and name, from standpoint of history, unarmored ship with ludicrously big guns is Battlecruiser (but than it must be fast), and naming was much easier than for cruisers or destroyers, as the US had very few of them.
4.Upon lurking on GE's site I tried to find something with high efficiency and combined cycle, the problem is all their new and more efficient designs are large powerplant turbines, hence I've chosen the smallest air derivative among them. Additionally its power allows the ship to be a fast battlecruiser indeed.
acelanceloet wrote: *
Also, note that the ticonderoga was build on a hull originally designed to take less systems. You add the big gun, high speed (and all the required power for that), 50% more VLS on a hull the same length on a hull shape that will likely result in less displacement. In other words: displacement wise, this hull is in my opinion between 30 and 50% of the displacement I would expect for the weapon systems you are listing. And that is without taking into account the amount of fuel required for an high speed ocean crossing.
As for the displacement: the main hull should have roughly the same displacement as Ticonderoga (similar length, width and draft) + some additional displacement from pontoons. The hull itself can be made from lighter materials, so less dead weight. The powerplant might be even lighter(one large turbine instead of four smaller), however the electric part gonna be heavy indeed, as well as all the needed fuel. As for VLS, I made a mistake, I wanted the ship to have less missiles than Ticonderoga (actually, for some reason I thought it had way more) as it gonna be capable of rearming at sea, so there is no reason to carry several billion dollars of dead weight. Will update the drawing and the description.

As for electric motors, I actually thought about Zumwalt's 39MW motors (have no idea how much they weight) (4x35.5 MW, not 4x142 MW, that's just silly).


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acelanceloet
Post subject: Re: Midway class battlecruiserPosted: December 29th, 2020, 3:41 pm
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Even if the ammo does not go down but sideways, the ammo conveyor still needs space you don't really have.

And I understood that you meant it as such, but my point still stands. Note on the image, there is a hatch at the bottom. If that hatch doesn't open, you cook up VLS block. If it opens at the wrong moment, you drown out your missiles with salt water. There are VLS systems with a hatch that opens sideways, but as far as I have seen such VLS systems are always above main deck level where said hatch can be inspected and maintained and the risk of water ingression is low.

I suspect crew safety would not be impacted a lot: if missiles are leaving your deck, you should not be near it, and if some more flames and heat are coming with it.... You're in trouble anyways. For crew safety, a cold launch system might be more like what you are looking for.

as for the ludicrous powerplant (as you called it :P) : A tico has a range at 20 knots of 6000 nm. This is with the tico using about 50% of the ships propulsive power. Let's assume you have the same amount of space on board for fuel as a tico and you also use 50% of your power for the long range. Let's also assume (for this rough estimation) that your propulsion has the same efficiency as the tico's. So, you would have 100% more power then the tico, so you would have only have 50% of the range of the tico, so just 3000 nm. Is this enough for your mission?
That said, are you sure only 100% more power then a tico would get you 60% more speed? Resistance drag goes up with the speed squared, and wavemaking resistance even more, so I would expect the power increase for said speed to be over 250% then the 200% you have now.

The displacement: the additional displacement of the pontoons isn't a lot compared to that main hull, while the structure to keep those pontoons attached adds quite a bit of weight high up. While this hull shape allows for more volume and some more topweight, it is not very weight efficient: the hull itself will always be heavier then an conventional hull of the same displacement. You could go for alternate materials, but those make the ship expenonentially more expensive and complicated (example: LCS) and on actual combatants we have seen a move away from aluminium for any habitable structure. That said, aluminium could save you a percentage (10%, maybe even 20% if really done well) but that doesn't save you from the hull being less then half the size it would have to be for these systems.
The weight of the electric motors I estimated based on a weight of 80 tons of an 20MW electric motor, So I estimated 4 tons per MW of electric power on your waterjets. Note that you need a generator that provides said power to the waterjets motors, so you would need an 142MW generator as well, and then you haven't even added the diesels and the waterjet itself and the gasturbine.....

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erik_t
Post subject: Re: Midway class battlecruiserPosted: December 29th, 2020, 4:29 pm
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Of course anybody can draw anything they want, it's a free internet. That said...

If you want to sketch things that are closer to the realm of plausibility, I would encourage beginning with more minor alterations to and departures from existing warship designs (or serious proposals from NAVSEA and its equivalents). Then, try to use that study to try to better understand how and why current ships are designed, built, and operated the way they are. Only through this understanding of the literal state of the art can we ever imagine we could improve upon it (in the pixel-bashing sense... I am under no illusion I am remotely qualified to pretend to be a naval architect).

As an example, citing gas turbine thermal (?) efficiency down to the tenth of a percent (!) but shipping only a single grossly overpowered main powerplant... this is very much putting the cart before the horse. No damage tolerance, awful efficiency at partial load, no maintenance downtime... this is a fundamental operability problem that would become more obvious with some fairly basic study of anything currently afloat.


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SOLariss
Post subject: Re: Midway class battlecruiserPosted: December 29th, 2020, 9:36 pm
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Slightly changed the design:
Reduced amount of missiles to 80 (all in MK57s). After stumbling upon Mk41 specs. Didn't expect the thing to be THAT heavy.
Replaced one LMS100 with two LM6000 PF+ (53MW each). Combined output still 142 MW (with added steam cycle).
Reduced max speed to 40 knots. (The more I think about it, the more I come to conclusion, that there won't be enough power for 50, and there is no need for such speed).

Currently I'm thinking if it would be beneficial to drive two waterjets directly from one of the turbines (no gear box), and other two-by electric motors (for more control).

As for cold start missiles, unfortunately, the US doesn't seem to have any. And is not going to, and after watching video of S300 falling on its own launcher, I now understand why.

I wonder what generation of LM2500 are installed on Ticos as the newest iteration of this turbines is 40% more powerful then the first one?


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heuhen
Post subject: Re: Midway class battlecruiserPosted: December 29th, 2020, 10:44 pm
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78Snipe84
Post subject: Re: Midway class battlecruiserPosted: December 30th, 2020, 7:21 am
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You might try to draw your engineering plant and see if it fits. For example the width of the engineering space for a DD-1000 is about 60' the length is about 205'. It has about ten feet of additional hull surrounding the space on each side (The hull is 80 ft wide). In that space are two MT30s with generators, two aux generators (LM500s), and the two main drive motors.
A top view might help with layout also.
Your hull is much too narrow for a engineering plant of that power.
I do like your idea of putting missiles in the outrigger, I'm just not so sure in this case how well it would work.


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heuhen
Post subject: Re: Midway class battlecruiserPosted: December 30th, 2020, 2:44 pm
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and for better survivability, you want to dived the engine room into separate water tight room, each room of the same size.

Unless you want to build after commercial standards...


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SOLariss
Post subject: Re: Midway class battlecruiserPosted: December 30th, 2020, 8:33 pm
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The more I look at my drawing, the more I'm tempted to redo it drastically. Maybe gonna ditch Zumwalt style superstructure (to save some displacement), there is enough space in wide upper portion of the hull anyway, and maybe replace helo hangar with aircraft carrier style elevators (by my estimation, after ditching Mk41s, even two CH47s can easily fit by the sides of the boat hangar).

BTW, found a brochure for marine version of LM6000, it's 4.3x16.5x4.9m for entire turbine/generator assembly, and the width of my main hull is ~16m, so two will perfectly fit in even side-by-side with plenty of space around. I want to fit them somewhere in the middle part of the main hull in order to gain additional protection from sponsons. Although I want to go for combined cycle, so heat exchangers and steam turbine still has to go somewhere. However the problem I see with the combined cycle, is the fact, that it is desirable for exhaust manifolds of both turbines to be close together in order to use a single heat exchanger, but as far as I understand, this is bad from a survivability standpoint.

PS. It seems I figured out how to safely rearm Mk41s at sea (the ship with extra stability would be helpful anyway). Basically make something akin fuel reloading machine for an RBMK reactor:
[ img ]
But much smaller, and obviously without bulky radiation protection.


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heuhen
Post subject: Re: Midway class battlecruiserPosted: December 30th, 2020, 9:03 pm
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Mk41 VLS, have an a canister system, with it's own crane for reloading missiles at sea, the crane would take up the space for three of the silos, but I think US Navy drooped it, Erik-t can probably answer if they are still in use or not.


[ img ]

[ img ]
[ img ]


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SOLariss
Post subject: Re: Midway class battlecruiserPosted: December 30th, 2020, 9:11 pm
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heuhen wrote: *
Mk41 VLS, have an a canister system, with it's own crane for reloading missiles at sea, the crane would take up the space for two of the silos, but I think US Navy drooped it after I while, I think they concluded that it wasn't needed anyway, they just go back to port.
As far as I understood, the problem with that crane was that the container was suspended from it, and thus unstable at sea. I've seen videos of Mk41 rearming, have no idea, how they were supposed to tho this at sea with that collapsible crane. The thing I'm suggesting is fully rigid and rides on rails, that are laid along the VLS.


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