Multihull aircraft carrier.

[Elheru Aran]

I hadn't thought the railgun barrel erosion thing was *that* much of an issue. Interesting. Is replacing them at sea an option, though? I could see that being one way to get around the erosion problem, especially if railgun barrels aren't as hefty as 16-inch barrels...

BTW, by 'salvo of railgun rounds' I was picturing more of a group of ships firing a few shots each, not necessarily one ship firing a buttload of shots.

[Eternal_Freedom]

Whatever the realities of railguns vs lasers as naval weapons, the point still stands that if an enemy vessels is close enough to engage the carrier directly, it's fucked anyway, so being designed a certain way won't help much.

[Simon_Jester]

I hadn't thought the railgun barrel erosion thing was *that* much of an issue. Interesting. Is replacing them at sea an option, though? I could see that being one way to get around the erosion problem, especially if railgun barrels aren't as hefty as 16-inch barrels...

They're still going to weigh many tons and require precise alignment; I wouldn't recommend it.

What it comes down to is that at the moment we are marginally able to build railguns that don't fatally erode themselves after one shot; we are nowhere close to being able to get, oh, hundreds and hundreds of shots out of the same weapon. If we were that close we'd have such guns fielded already.

BTW, by 'salvo of railgun rounds' I was picturing more of a group of ships firing a few shots each, not necessarily one ship firing a buttload of shots.

The ships considered for railgun mounts in the foreseeable future are neither small nor cheap; grouping several of them in one place to have reliable ability to engage enemy warships is problematic. Especially when one ship could launch a salvo of high speed cruise missiles and wipe out the same target.

Sure... those missiles cost umpty million dollars. But the warship they just sank could easily cost ten times that, or even a hundred times that.

Whereas having several railgun-capable ships form a surface action group involves putting several billion dollars of warship out on the line to drown the enemy in inaccurate railgun fire from well within the range of their own guided missiles and aircraft.

[Sky Captain]

Whatever the realities of railguns vs lasers as naval weapons, the point still stands that if an enemy vessels is close enough to engage the carrier directly, it's fucked anyway, so being designed a certain way won't help much.

Yeah if carrier is directly engaged by enemy surface vessels it means air wing is wiped out and escorts already sunk or out of missiles. In that situation being monohull or multihull design won't make much difference. One situation where multihull may fare better is if enemy submarine manages to get close and hit carrier with torpedo. Since each hull would have independent engines carrier may be able to remain functional if engines only in one hull are damaged.

[U.P. Cinnabar]

I hadn't thought the railgun barrel erosion thing was *that* much of an issue. Interesting. Is replacing them at sea an option, though? I could see that being one way to get around the erosion problem, especially if railgun barrels aren't as hefty as 16-inch barrels...

BTW, by 'salvo of railgun rounds' I was picturing more of a group of ships firing a few shots each, not necessarily one ship firing a buttload of shots.

Heat erosion of the electromagnetic rails remains a significant issue with railguns, and no, it will likely require a dockyard maintenance availability period to replace worn-out barrels, same as with other naval rifles.

The ships considered for railgun mounts in the foreseeable future are neither small nor cheap;

Currently, only the Zumwalt-class are being considered for conversion to railgun mounts(they are currently fitted with AGS), and possibly for any future modification of the Burkes. Nothing smaller, certainly nothing cheaper(though, given the state of the art in naval platforms, I can't see how any of them can be described as "cheap").

For now, railguns remain in the future of naval gunfire support, with the Advanced Gun System, along with improved projectiles for the current generation of 5"/54 naval rifles being very much the state of the art where that technology's concerned.

My opinion, for what it's worth, when we see railguns supplant conventional rifles as main gun armament, it will be on new construction specifically built from the keel up to take advantage of the new technology, by which point, should have matured.

Whatever the realities of railguns vs lasers as naval weapons, the point still stands that if an enemy vessels is close enough to engage the carrier directly, it's fucked anyway, so being designed a certain way won't help much.

Which goes without saying, though a railgun would have a longer range than conventional naval rifles and even the AGS, and indirect-fire capability which may help that.

It will definitely help with point-defense, by extending the ranges at which anti-ship guided missiles can currently be engaged by CIWS and Sea Sparrow systems.

[Simon_Jester]

Er... what will help with point defense? Railguns won't; did you mean lasers?

Whatever the realities of railguns vs lasers as naval weapons, the point still stands that if an enemy vessels is close enough to engage the carrier directly, it's fucked anyway, so being designed a certain way won't help much.

Yeah if carrier is directly engaged by enemy surface vessels it means air wing is wiped out and escorts already sunk or out of missiles. In that situation being monohull or multihull design won't make much difference. One situation where multihull may fare better is if enemy submarine manages to get close and hit carrier with torpedo. Since each hull would have independent engines carrier may be able to remain functional if engines only in one hull are damaged.

Modern torpedoes tend to explode under the keel and break the back of the target ship. It's not just engine damage that's the issue, it's staying afloat with a broken keel... which a multihull ship isn't going to be able to do unless it has one HELL of a lot of reserve buoyancy in the other hull.

Against historical WWII-type torpedoes, one torpedo taking out all engine power in a single hull is actually pretty rare, by contrast.

[U.P. Cinnabar]

Lasers as well, Simon. At Mach 6+, a railgun round would certainly fall under "faster than a missile." A railgun would also have the potential to out-range current anti-missile/CIWS systems(proposed 100nmi range, as opposed to the 10nmi range of the Sea Sparrow).

But, that's not the foreseeable future, even if the USN wants railguns on ships by 2025. I'm thinking at least 2035-50, before we see railguns supplanting conventional naval rifles or current missile-defense systems.

For the forseeable future, naval gunfire support will continue being provided by the AGS, the contemporaries it will doubtlessly spawn, and improved ordinance for the naval rifles currently in service, while guided missiles will remain the solution of choice for anti-surface warfare.

Missiles will also continue being the first line of anti-missile defense as well, supplemented by naval rifles, and Phalanx/Goalkeeper-type CIW systems.

[Starglider]

]Modern torpedoes tend to explode under the keel and break the back of the target ship. It's not just engine damage that's the issue, it's staying afloat with a broken keel... which a multihull ship isn't going to be able to do unless it has one HELL of a lot of reserve buoyancy in the other hull.

The problem isn't reserve bouyancy; fully compartmentalised ships generally have enough of that. The problem is that breaking the keel usually breaks the ship in half, and the remaining sections are not seaworthy. Multihull ships have a large braced superstructure above the hulls, but I don't know if it would be strong enough to keep everything together at that scale.

[Simon_Jester]

Lasers as well, Simon. At Mach 6+, a railgun round would certainly fall under "faster than a missile." A railgun would also have the potential to out-range current anti-missile/CIWS systems(proposed 100nmi range, as opposed to the 10nmi range of the Sea Sparrow).

Railgun rounds are only incrementally faster than missiles, and with foreseeable technology they do NOT lend themselves to rapid rates of fire. You'd still be hosing down the general area you expect the missile to fly through with a mass of dumb bullets. Your engagement range might be longer, your hit probability would be higher, but it wouldn't be over the horizon... and I suspect we're more like fifty years from seeing quick-firing railguns for antimissile defense, not twenty.

Modern torpedoes tend to explode under the keel and break the back of the target ship. It's not just engine damage that's the issue, it's staying afloat with a broken keel... which a multihull ship isn't going to be able to do unless it has one HELL of a lot of reserve buoyancy in the other hull.

The problem isn't reserve bouyancy; fully compartmentalised ships generally have enough of that. The problem is that breaking the keel usually breaks the ship in half, and the remaining sections are not seaworthy. Multihull ships have a large braced superstructure above the hulls, but I don't know if it would be strong enough to keep everything together at that scale.

Hm. Good point about compartmentalization; I tend to imagine a broken-keeled ship breaking in half and flooding and sinking, but that's not necessarily correct.

[Sky Captain]

Whatever the realities of railguns vs lasers as naval weapons, the point still stands that if an enemy vessels is close enough to engage the carrier directly, it's fucked anyway, so being designed a certain way won't help much.

Yeah if carrier is directly engaged by enemy surface vessels it means air wing is wiped out and escorts already sunk or out of missiles. In that situation being monohull or multihull design won't make much difference. One situation where multihull may fare better is if enemy submarine manages to get close and hit carrier with torpedo. Since each hull would have independent engines carrier may be able to remain functional if engines only in one hull are damaged.

Modern torpedoes tend to explode under the keel and break the back of the target ship. It's not just engine damage that's the issue, it's staying afloat with a broken keel... which a multihull ship isn't going to be able to do unless it has one HELL of a lot of reserve buoyancy in the other hull.

Against historical WWII-type torpedoes, one torpedo taking out all engine power in a single hull is actually pretty rare, by contrast.

Is it expected a torpedo hit would break in half an aircraft carrier too? IIRC all live fire tests have been done on destroyer sized ships. Aircraft carrier should be much more heavily built than destroyer just to stay in one piece during extreme storms.

[Elheru Aran]

A torpedo might not literally break an aircraft carrier in half... but it wouldn't do it any good, and the structural damage from a solid explosion under the keel would be significant.

You don't need a particularly "heavily built" ship to stay in one piece during a storm; they did it with wooden ships back in the day. I think your example is a bit off there.

[Sky Captain]

A torpedo might not literally break an aircraft carrier in half... but it wouldn't do it any good, and the structural damage from a solid explosion under the keel would be significant.

You don't need a particularly "heavily built" ship to stay in one piece during a storm; they did it with wooden ships back in the day. I think your example is a bit off there.

Historically wooden ships topped out at around 100 meters and that was pushing the limit. They needed a lot of steel reinforcements and leaked a lot. Wooden ship the size of aircraft carrier would fall apart in first storm. Structural loads go up much faster than size. If you increase the length and width twice mass and with it loads structure has to withstand go up 8 times.

[Simon_Jester]

Thing is, a torpedo blast is totally unlike anything else ships have to withstand.

There are indications that modern USN carriers are designed to withstand under-the-keel explosions, sort of, but it's an open question how well they'll handle it.

The fundamental point, though, is that the multihull design doesn't really do much to address these problems, because the superstructure connecting the hulls probably won't be strong enough to act as a "cast" to hold together the fundamentally broken backbone of a ship which has taken serious torpedo damage.

[TimothyC]

There are indications that modern USN carriers are designed to withstand under-the-keel explosions, sort of, but it's an open question how well they'll handle it.

To elaborate, Anything launched after the Forrestals is still NOFORN (No Foreign Nationals) for dealing with their under the water line protection (Not sure how they will handle scrapping them). That established the Kitty Hawks as one level (with Enterprise). There are indications that JFK got an upgraded system, and the first three of the Nimitz class got a further upgrade, with latter versions getting further upgrades, but this is all culled from open sources, and is somewhat gathered by looking at what isn't said vs. what is so take it with the requisite volume of salt.

[Simon_Jester]

Well, as I recall USS America was done with a SINKEX (they shot the ship with underwater explosives, presumably to see how well the torpedo defense scheme held up). However, they can only do that so many times. A few supercarriers may become museums, but not many; there are only so many museum ships the demand can support.

Also, when scrapping the Nimitzes and for that matter Enterprise, there's a radioactive waste issue to deal with, I imagine, so they would HAVE to have some special protocol for sinking.

[U.P. Cinnabar]

Well, as I recall USS America was done with a SINKEX (they shot the ship with underwater explosives, presumably to see how well the torpedo defense scheme held up). However, they can only do that so many times. A few supercarriers may become museums, but not many; there are only so many museum ships the demand can support.

Also, when scrapping the Nimitzes and for that matter Enterprise, there's a radioactive waste issue to deal with, I imagine, so they would HAVE to have some special protocol for sinking.

Nuclear-powered USN ships are taken to the Navy Yard in Bremerton, Washington(I believe)to undergo a disposal proceedure specific to nuclear-powered vessels.

Also, the America's former crew and officers lobbied unsuccessfully to turn her into a museum ship. She was the largest USN platform expended in a SINKEX to date.

[Simon_Jester]

In that case, that resolves the question of how to dispose of the nuclear carriers with classified torpedo protection schemes; they'll be scrapped at a US naval facility.

For the other two Kitty Hawks, we'll either have to sink them, make them museums, or change the policy.

[U.P. Cinnabar]

In that case, that resolves the question of how to dispose of the nuclear carriers with classified torpedo protection schemes; they'll be scrapped at a US naval facility.

For the other two Kitty Hawks, we'll either have to sink them, make them museums, or change the policy.

A group in Wilmington, NC was trying to fund the preservation of USS Kitty Hawk as a museum. She is supposed to be released from reserve this year, when the Gerald R. Ford is comissioned, so we'll know then.

The JFK is on donation hold, pending the Rhode Island Aviation Hall Of Fame's efforts to have her permanently moored at Pier 2 of Naval Station Newport as a museum.

As both are amongst the last oil-fired carriers in USN service, they're both good candidates for preservation; Kitty Hawk, more so, as she was the first and last active ship of her class.

Somehow, I doubt any potential museum guides are going to be let in on the classified torpedo protection scheme, unless the new generation of supercarriers employs something different, and the Nimitz-class are all decomissioned, in which case, it will be declassified.

If the French and British haven't figured it out already(both are building or were building new fleet carriers, while the Russians have no plans to build a second).

[U.P. Cinnabar]

More on the USN's Ship-Submarine Recycling Program, if anyone's interested.

[Sea Skimmer]

I hadn't thought the railgun barrel erosion thing was *that* much of an issue. Interesting. Is replacing them at sea an option, though? I could see that being one way to get around the erosion problem, especially if railgun barrels aren't as hefty as 16-inch barrels...

BTW, by 'salvo of railgun rounds' I was picturing more of a group of ships firing a few shots each, not necessarily one ship firing a buttload of shots.

The problem is the target will have multiple high power lasers for much less ship impact then multiple railgun mounts. In even fairly hazy weather those lasers will be able to burn up a lot of railgun rounds enough that they miss, if not always destroying them. A couple defending railgun mounts of much smaller size could also do this. That's a very likely future role in fact. Gunpowder fueled artillery is also being demonstrated right now that can shoot down incoming threats on predictable courses.

A steady barrage of shells isn't a very effective way to penetrate a defense like this, really nothing on a predictable trajectory is. Present anti ship missiles are very agile and that's only on the rise for subsonic and supersonic missiles alike. The JASSM missile for example, now also the LRASM has that big vee tail for agility, actually intended to make it more accurate against IR/optically detected targets (which only works at close distances) but now useable to evade defenses.

About 20 seconds into this video you can see how evasive the Coyote target drone can be and it also does mach 2.5
https://www.youtube.com/watch?v=lou_ka-NNTs

A couple hundred shots is now the useful barrel life of the bench testing 32 MJ railgun the uSN has. Mind you this thing is only going to fire about 110nm with a 17lb projectile. That is not exactly overwhelming capability in a ship to ship fight. A much bigger weapon could compete better, but in practical terms firing more then about 250nm will end up requiring enormously long barrels. At that point you'll need dedicated ships, and in realistic earth centered terms that's not going to make sense compared to building an aircraft carrier. Carrier aircraft even unrefueled can already reach that kind of distance easily, with refueling and long range missiles the coverage is much greater. And they do a huge number of other vital tasks. Big gun only fires shells, small ones in this context.

Better guns will be very useful, but they aren't going to overturn the balance of naval power. This is why say, China, is working to build aircraft carriers and big deck amphibious ships, which they would not if a few railgun destroyers of the near future would do so.

I suggest also that when you start to add up the amount of firepower even a WW2 heavy cruiser threw out in electrical terms it turns into an awful lot of power with any realistic efficiency.

A missile isn't too efficient on cost, but its not that expensive compared to a ship either, people are usually more concerned about the topweight implications then the actual cost of any anti surface missile installation, short perhaps of the P-700 absurdity. A VLS loaded out with decent SSMs can put a huge amount of firepower on a target in a very short time window, at a low altitude and with projectiles probably a lot more likely to ever find the target and seriously damage it.

[TimothyC]

For the other two Kitty Hawks, we'll either have to sink them, make them museums, or change the policy.

Brownsville Texas isn't foreign port for the US (no matter what the more leftist members of this board may think), and is where the Forrestals and ex-Constellation have been scrapped (She's actually being scrapped right now).

[Sea Skimmer]

US warships haven't been allowed to be broken up overseas since the late 1990s for environmental reasons. This was pretty much one of the earlier attempts to put Alang India out of action, an effort which apparently has as of 2015 nearly completely succeeded, and left everyone doing it with no jobs.

As far as classification goes the solution is just to declassify the design on paper before asking for scrap bids on the hulls. Otherwise all the US scrapyard workers would have to have security clearances anyway!

The navy has no more reason to care about this technology strongly anyway, its 1960s materials and welding developed before computers and several generations of improved hull steels. No good reason exists to openly publish it either, but handing over blueprints. USS Ford is made completely of much newer steels, and yet photos were published of her lower hull construction in a manner never done for a Nimitz.

OF course another reality is that such carriers are so large, and the aviation tankage requirements so great that you'd really have to screw up not to give them a crazy effective TDS. Its just so huge, and no matter how (realistically) powerful the enemy torpedo is cube squared rule still applies to the weakening of the blast.

[Esquire]

Could you expand on the cube-squared rule? I've always been interested in naval mathematics, but finding good information can be tricky. I'd take a book recommendation if you don't feel like a full explanation right now.

[Sea Skimmer]

That's just me being hairbrained in how I phrase something. I was merely referring to how the volume of an explosion increases so rapidly with total blast radius, subject of course to tamping effects like the shape of the actual charge and ocean depth.

Within a couple diameters of a good sized HE charge you can shatter any metal that isn't like actual battleship belt armor thick with the direct blast, and even that you can dislodge. But even a really big torpedo warhead isn't all that large caliber of an explosive. About 220% expansion is the rule of thumb for how far an explosive will actually drive solid metal liners before the explosion is no longer adding useful acceleration.

With a side torpedo hit most of the energy will naturally want to go out radially from the length of the warhead, tamped by its own shape. You can and some torpedoes do use shaped charges, but the enormous amount of liquid loading in the CVN side, made possible by it being the ships jet fuel space that won't easily explode, would really limit what that could accomplish.

If you want another use for railguns, the DARPA MAHEM project for explosive pumped EM fired shaped charges has indicated that you can actually make one which accelerates the blast of an explosion itself. Making a sort of pressure punch shaped charge that might be the ideal way for attacking something like this. But its just easier at that point to go for under the keel.

[Purple]

One thing you should consider when discussing the issue of torpedoes vs carriers is that all the major world powers during the cold war and presumably today stockpile torpedoes with atomic warheads for exactly this purpose.