First off, the idea for dispersed communications, hull antennae, and radar kites. Building antennae into the deck and railing really doesn't solve anything, in terms of shock damage, since they still have to be exposed to operate (burying them in the deck armor would result in lack of function, becoming self defeating), and thus would be damaged, or destroyed, by even a near miss... The kite really isn't even a question to me. What makes it less likely that the array itself wouldn't be hit by chance? Specifically targeted? Cable sheared off? It's another unarmored item that can be shot off, in the end.
The 'hull antennae' idea is easily answered by looking at the design of ships in general... There is a reason all that gear is located at the top of the superstructure, away from highly conductive seawater. It's not that your signal would be impaired... You wouldn't get one. It would simply bleed off into the surrounding ocean, and even if you did, however unlikely it is, get a faint signal connection, any modicum of EW would render it moot.
In order to perform a gunnery mission on today's highly fluid battlefield, you will need more than a walkie-talkie and functioning guns... Unless you don't mind dropping shells on your own men, or on civilians. Radars, rangefinders and modern communications do far more than give you coordinates. They offer to-the-meter calculations for a firing solution, give a first shot hit probability that is absolutely crucial when providing fire support, and offer a networked viewpoint that is completely lacking with the bare bones approach from the 1940's... One look at the hit ratios of such guns in action without modern communications is all the proof of that concept that most anyone needs, methinks. They weren't even that good at hitting each other, and thats what they were supposed to do to start with. More sucess was achieved at lobbing shells at shore targets that couldn't move... But what about modern battlefields where the enemy is more often on the move, rarely dug in, and likely to be mechanized?
Unless he's profoundly stupid, the 'Bad Guy' isn't going to line up nice and neat for your guns. And he doesn't have to go that far inland to avoid them.
All of that said, I feel some clarification is in order regarding a few bones of contention in this thread...
First, a disclaimer... If the automatic response is 'But there will be new advances!', then the automatic answer is 'I've got a Silver Bullet for your Magic Armor.' I'm using what we have today, not what we might have twenty years from now, and history goes a long way towards explaining, by itself, that every advancement in defensive ability is temporary, and the weapon to defeat it is often both cheaper and easier to make.
That said, let's start with some basics, and the basic I will start with is what 'Semi-Armor Piercing' actually means. After doing a little digging, I found that the term actually dates back to the days of the Dreadnought and other ships like her, referring to shells that were quite capable of penetrating light to medium armor, but not the heaviest stuff out there.
It means the same thing regarding ship to ship missiles. 'Semi-armor piercing' doesn't mean it can't penetrate more than a basic hull, it merely means that the missile isn't meant to fly through more than a modest amount of shipboard armor before detonating... Now, finding absolute facts in terms of this armor defeating ability isn't easy, but I have dug up a few estimates over the last week or so that paint a picture for comparison. And I don't even have to jump to 'but it could be developed' from here.
I'll open with the AGM-84 Harpoon, the lightest of the threat missiles that this fictional warship would have to defeat. It's just about 15 feet long (4.6 meters), weighs in at 1,523 pounds (691 kilograms, with booster), and flies at a 'measly' 537 miles per hour (864 kph/ 240 meters/second). This is pretty much the standard anti ship missile of the US Navy, discounting the possibility of tossing Tomahawks at a target. The original, un-upgraded, Block I Harpoon is estimated to have a penetration of 2.7-4 inches (6.9-17.4 cm) of RHA. It is, by absolutely all definitions, an armor piercing weapon, designed to defeat light to medium shipboard armor, but not foot thick plate.
Now, upping the ante to another missile discounted as a threat (for some reason)... The SS-N-19 'Shipwreck' (otherwise known as the P-700 Granit). This is a bit of a big boy, designed by the Soviets in the 1970's to attack US carrier battle groups. It's 33 feet (10 m) long, and weighs a whopping 15,000 pounds (7,000 kg), with an estimated speed of at LEAST Mach 1.6, but an upper estimated speed of GREATER than Mach 2.5, in it's operational envelope, which is an altitude of about 30 feet above the water... And they work in swarms of 4-8, with one missile performing short 'pop-up' periods to feed targeting data to the others. Nifty, I think, for a weapon that's been in service at least 34 years. It's estimated penetration is a minimum of 7 inches of RHA... And a maximum of 10 inches of RHA. 10 inches. Nearly a foot of solid steel, and this is still classified as a 'semi-armor piercing' weapon.
So, no, 'semi-armor piercing' doesn't mean that it can't penetrate armor. On the contrary, it's meant to, just not massive amounts of it.
Now then, another thing that cropped up before is the belief that a shell from a large (16 inch) gun is a better armor piercing weapon than a ship to ship missile, even a monster like the Granit... It's time we take a close look at both devices, and how armor piercing weapons ACTUALLY become armor piercing. While we're at it, I think that getting an idea of the actual joules delivered on impact might be a thought, too.
The Mark 8 'Super Heavy' shell, fired by the Mark 7 16 inch/50 caliber (the barrel length is 50 times the diameter of the bore) weighs in at 2,700 pounds, with an optimum range of 23.4 miles, and a muzzle velocity of 2,500 ft/second (762 m/s). This is assuming a maximum charge of six 110 pound bags of powder. Assuming the weapon hits, which is far from guaranteed, the impact delivering approximately 18.28 megajoules (nearly 13.5 million ft/lbs) of energy. Due to the fact that the shells often impacted at oblique angles, they used a blunt cap sealed to the top of the actual warhead (the pointed cap you see is just the ballistic cap. It's hollow) to allow for better penetration at non-optimum angles.
By comparison, the 'semi-armor piercing' P-700, weighing in at 15,000 pounds, and flying at a minimum of 1784 ft/s (544 m/s), and a potential maximum of 2,789 ft/s (805 m/s) is going to deliver between 76.16 megajoules (nearly 56.2 million foot pounds) of impact force to a maximum of 112.7 megajoules (over 83.1 million foot pounds). At it's WORST estimates, the P-700 has more penetrating power available to do the job, plus the advantages of being able to hit at a much closer to optimum angle, and the ability to evade CIWS batteries.
Before moving on to the issues presented with the suggested armoring, it's worth noting two things... First, the shells in question are only as fast as the missiles CIWS batteries are meant to defeat, do not evade, and fly in a predictable, easily tracked arc. Pretty much anything from SeaRAM to Phalanx can track, engage, and destroy incoming weapons of this type. The system doesn't care if it's a shell or a missile, and the effects of it's delivered ordinance will be the same.
Second, the only difference between the 'armor piercing, capped' shells, and the 'semi-armor piercing' missiles is a relatively thin cap in the shell... The missiles (if they don't already. I'm not privy to everything) can use a more efficient conical penetrator (which tends to scoop and skip off at odd angles, hence why the shells use a blunt cap) with minimal modification to the airframe. Remember... The estimates are for the current, semi-armor piercing, weapons. Just imagine what a simple modification could do.
All of this brings me to the question... 'What does Sen think it takes to stop a missile?'. The answer is, more than four inches of plate and a layer of uber-goo. The relatively puny Harpoon, in it's earliest incarnation (I've heard anecdotal recounts that the air launched SLAM-ER variant and the Block II may have twice the penetration), MIGHT be stopped by those plates, if it's only capable of penetrating under three inches... And you've got even odds at it's maximum estimates. That doesn't sound good, and it gets much worse with capital ship killers like the Granit (And it's brother the P-800 Oniks, and cousin BraMos).
So, at four inches, you've got an even chance of stopping a Harpoon, but none at all of stopping the big Russian weapons. So, that leaves a choice... Either we go to 8 inches equivalent, and reassure ourselves that these weapons couldn't POSSIBLY perform to the maximum estimates... Or we acknowledge the danger, and go with the equivalent of 11 inches.
8-11 inches RHA equivalent of armor. I call that Slab, friends.
Now, as for armor composition... Let's explore ballistic steel and non-Newtonian fluids a bit. We all know what hardened steel is, which is the same animal as 'ballistic steel', which is also known as RHA (Rolled Homogeneous Armor), so we already know how much of this we need to stop a given weapon. Two two inch plates just isn't enough, unless we're cutting corners in cost. In that case, why use expensive armor on an outer layer that wont stop the weapons to start with?
Non-Newtonian fluids, more properly known as Shear Thickening Fluid in the context we're using, are fluids that react as a solid when struck. We've all heard the hype about the 'liquid body armor' that's been in testing for some time now, but there are some misconceptions about the STF, how it's used, what it is, and what it can do, that lead to ideas like this goo sandwich armor plan. So, I'm going to digress long enough to paint the whole picture...
The liquid body armor... Is Kevlar.
Thats right, it's good old, Dupont Kevlar. Now, the STF, in this case sillica suspended in ethylene glycol, does not form a fluid layer between the Kevlar layers, but is instead an immulsion. It's dhilluted in ethanol, then the Kevlar is soaked in it before being baked to boil away the ethanol, leaving the STF bonded with the fibers. The net result is that the STF assists in absorbing the shock of an impact, by lending it's properties to the Kevlar, not allowing the fibers to stretch so much. The net result is that four layers of Kevlar perform like ten. Impressive, but on it's own, the STF is nothing more than goop.
The error in using it as a stand alone layer in solid armor is twofold. First, it's still a liquid, with a finite viscosity (it only gets so 'solid' before it can do no more), and finite surface tension that doesn't even begin to approach that of solid metal. A pool filled with this stuff wouldn't stop a missile, or even a high powered rifle round, on it's own. It probably wouldn't even slow it down much before it hits the concrete bottom and blasts goop all over. Second, the outer layer of ballistic steel has no real give. It doesn't transfer the kinetic energy of impacts very well at all, and thus won't make good use of any sort of STF as a means of spreading out the impact before the weapon in question breaks through the first two inch plate, and just plows through the gooey layer underneath.
Barring flights of fancy regarding pseudo-magical substances that have the potential viscosity of steel, that leaves STF relatively pointless as a means to armor a ship... Though you COULD use the treated Kevlar. In fact, I'd recommend it.
Now, moving on to "Chobham", which seems to have become common slang for any type of composite vehicle armor lately, allow me to shed some light on how it works, and what sort of threats it is meant to defeat. Originally, this form of armor was developed at Chobham Academy, in England, hence the common use of the name. As we all know, it's a multi-layer mishmash of composite, fabric and metal meant to armor up heavy combat vehicles, such as tanks. Primarily, Chobham is intended to defeat two threats... High velocity kinetic penetrators, and HEAT rounds, neither of which are likely to be encountered by a ship, or pose much of a threat to it.
Having already discussed why HEAT warheads aren't a threat, and having already presented that you don't need any such device to defeat this armor concept, I think it's time we got off the HEAT Horse once and for all. Nobody is going to bother with an ineffective weapon, and armoring against an idealized threat is self defeating.
As for the type of kinetic penetrators I've brought up... I'm referring to the APFSDS-LRP style rounds fired by tanks, which have very little in common with an anti ship missile. Modern anti-tank rounds are, minus the casing, powder, and sabot, darts. Approximately 2-3 cm in diameter and 50-60 centimeters long, and getting both thinner and longer as time goes on. Sure, these will fly right through most any conventional armor... And much like HEAT, not really do all that much in the aftermath without an enclosed space to bounce white hot fragments around in.
Chobham armor works in two ways to defeat these threats... It breaks, and it deforms. No joke. When faced with a HEAT round, the armor layers variously ablate, crack and break, deforming the jet within the armor via said cracks and breaks, and defeating the weapon. It's similar for a kinetic round, which being a relatively light, incredibly high velocity weapon, has a tendency to shatter, bend, or deflect when it abruptly stops. Boron carbide, or other similar materials, can defeat such weapons in this way, and often wind up cracked or broken in the process, aiding in deflecting the attack off to an odd angle within the plate. This means three things... It doesn't have very good multiple-hit capability once it's damaged, losing it's protective qualities rapidly, must be backed by traditional steel plate to work effectively, and must be replaced once damaged. It can't be repaired, welded, or plugged.
What this means in more concise terms is that the armor might stop the initial strike (assuming the two ton or heavier missile doesn't overcome it's relatively brittle hardness), but will do little against a multiple hit scenario. And it's expensive. Not a very good combination for large scale use on warships, I daresay. It's just not optimized for the threats any ship would realistically face.
Which leaves us with... Steel and Kevlar. Steel is more easily repaired, replaced, and cheaper than fancy composites, and Kevlar is an amazing material when you need to protect vital areas. This seems to be the thinking of the engineers that designed the Arleigh Burke's, actually... Which, contrary to popular belief, are actually constructed of "military grade" (read RHA) steel, with 130 tons of Kevlar internal armor. Yup... It's actually built of armor grade 'ballistic' steel, like many modern combat vehicles.
So... In order to produce an armored warship... It's actually going to have to be armored well enough to meet the threats that are actually out there. There are no cheats, no miracles... As Nemo said "Nothing is new under the sun." It's either all or nothing.
Now, as much as I have enjoyed the debate regarding armor, battleships, and ideas regarding both, I feel that it has reached it's limits, in terms of existing technology, and discussion, without wandering into the realm of conjecture and wishful thinking on both sides. On that note, I thank you all, without sarcasm, for the entertaining diversion.
