Saturday, June 9, 2012

Ship Construction and Naval Armor

One of the disappointing trends in modern ship construction has been the steady decrease in armor and high strength steel in the construction of ship hulls thus rendering the ships more susceptible to damage.  This trend has culminated in the thin aluminum construction of the LCS, among other examples.  Just to put things in historical perspective, WWII ships were built to absorb a lot of damage and examples of that capability abound.  Those ships were built much tougher than today’s ships with both stronger and thicker steel used.

Let’s look at a specific example from the modern U.S. Navy – the bombing of the USS Cole.  The expert commentary related to the photos below come from GM1(EXW) David Walsh.

"Most people don't realize it, but the damage done to the USS Cole shows the stunning difference between HY-80 and High Strength Steel (HSS) which is slightly stonger than mild shipbuilding steel.  Take a look below at the horizontal weld line that runs the length of the hull about halfway between the rail and the water.  You can see where the line going all the way across practically draws the top of the hole.  The area above the weld is called a "strake" and that is one of the strengthening members for the hull made out of HY-80.  The rest of the hull below the weld line is simply made out of HSS."

HY-80 Strake Defines the Upper Bound of the Damage


"In this next photo, at the top along the weld line, you can see that the HY-80 stopped the upward expansion of the blast and damage.  The HSS literally tore away from the weld at the HY-80:"

The HSS Tore Away at the Weld


"You can see here how much of her underside was destroyed as well.  If that HY-80 strake had not been there it is likely that a chunk would have been carved out of her entire side."

Extensive Damage to the HSS Plating


Aside from the obvious weight and cost savings, I don’t really know why the Navy has gotten away from building better armored ships capable of taking damage and continuing to fight.  For multi-billion dollar ships, It certainly seems like a penny-wise and pound-foolish decision. 

On a related note, at one point, the Navy learned the lesson about the dangers and drawbacks of aluminum structures but has recently forgotten the lesson with the return to the all or mostly aluminum LCS versions.

Clearly, the Navy could build much tougher and better protected warships but has chosen to put ships and crew at greater risk.  As the Cole bombing illustrates, the price has already been paid and will continue so.  On a positive note, some documents indicate that the Navy is looking into constructing the Burke Flt III out HY-80 and HY-100 which would offer significant survivability improvements.

Thanks to GM1(EXW) David Walsh!

14 comments:

  1. I think the navy needs to figure out a high low mix.

    It wants 3+bil dollar surface vessels but will use inferior parts or skip on offensive or defensive armament if it will save them 20mil or so in the process.

    Multimission frigates, PC, or DE, MCM, etc.. at one end and the DDG's, carrier's and amphibs at the other.

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    1. You're quite right. Skimping on something as fundamental as ship survivability to save a few dollars, especially for the mainstay ship class of the fleet (the Burkes) is a poor decision by the Navy. But, this is the same Navy that opted to drop galvanic corrosion protection from the LCS design to save money and we see what happened there.

      Your other comment regarding hi-lo mix is interesting. The last time that debate took place, the result was the Perry FFG class. Some view that as an outstanding example of the benefits of hi-lo while others view it as proof of the inherent weakness of the hi-lo concept, having produced FFGs that could do a little of everything but were good at nothing (their opinion, not mine). I suspect that's one of those endless debates that will never be resolved. Personally, I strongly favor a hi-lo mix, if carefully thought out.

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    2. Hell the problem was right there in what you wrote.

      "having produced FFGs that could do a little of everything but were good at nothing"

      And so they built..........LCS good litteraly at nothing.

      The thing is that instead of trying to cram everything into 1 hull (which may or may not be the right fit for it)build 2 different ships. Each one suited for 1 mission really well and another where its just OK. Then operate them together so that their strengths and weaknesses cancel out.

      The problem is getting them cheap enough to buy and use in bulk. Accept your FF isnt a guided missile destroyer and your half way there.

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  3. I'm currently reading "Fleet Tactics and Coastal Combat" by Wayne P. Hughes Jr. who is a long-standing professor at US Naval Post-Graduate School.

    One of the points Hughes makes is that attempting to armor a modern combatant against advanced weapons (i.e. mines, ASCMs, heavyweight torps) is a losing proposition, or at least one of diminshing returns. The weapons are just far too accurate and powerful relative to the size of the vessel.

    In Hughes' view, success in modern naval combat is predicated upon concealment, detecting the enemy fleet first, and then striking with overwhelming force before he sees you. Armor is of lesser importance because any hit is going to disable a warship; even if the hit doesn't outright sink it, the ship is going to be out of the fight.

    The key (according to Hughes) is to disperse combat power among many small ships. In this way, you complicate the enemy's targeting problem, and the aggregate combat power of your fleet is less susceptible to individual hits.

    I actually think Hughes's ideas are sound, and might've served the USN well had they been implemented properly. For example - the Streetfighter concept which followed directly from his logic.

    Unfortunately, the Navy essentially bastardized Hughes' work into LCS - which has little offensive punch and is far too expensive to actually field in large numbers.

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    1. Hughes book is outstanding and thought provoking. It does, however, have some problems and limitations which render some of the conclusions debatable. The mathematical models he proposes are a great foundation for further study but are far too simplified for more than cursory analysis - which, to be fair, is all he attempts! For example, the models make little attempt to account for area air defense, whereby one ship (an Aegis ship) can protect several other ships thereby increasing their apparent abilities insofar as the model is concerned. Similarly, Cooperative Engagement Capability (CEC), point defenses, ECM, etc. are untreated in the analysis other than by lumping them into a single fudge factor. The same applies to armor. In the models, a hit on a ship is treated equally whether the hit occurs against an armored or unarmored ship.

      On page 162, he references a NSWC study about armor and other protections for ships,

      "Can modern designs be effective against cruise or theater ballistic missiles to keep a modern combatant in action? The aforementioned classified 1990 study by NSWC Carderock asserted that a great deal can be done: moreover, the toughening will come at only a modest increase in cost."

      Remember that Hughes work was focused on smaller craft, hence the Coastal Combat portion of the title, and that one should be very cautious in applying his conclusions to larger ships. When he concludes that more and smaller ships are preferred over fewer and larger ones, he is comparing small missile boats to larger corvette/frigates which are still, essentially unprotected and moderately defenselss and thus he concludes that it would be better to "break" them into small ships. That's valid. Trying to apply that conclusion to cruiser size destroyers with Aegis, CEC, point defenses, ECM, and decoys is no longer comparing apples and apples.

      Hughes conclusions also contained the implicit assumption that his desired smaller craft would be expendable, meaning that they would be cheap. Fair enough, but our current Navy seems unable to produce cheap ships!

      Your comment (and Hughes assertion) about the futility of applying armor to ships is correct for smaller vessels. You just can't get enough armor onto a Cyclone PC or Visby to prevent catastophic damage from an Exocet or similar type missile. However, it is possible to apply enough armor to a Burke, for instance, to make the exercise worthwhile. At the extreme end of that concept is the Iowa class battleship which has sufficient armor to almost render it invulnerable to anti-ship missiles of the Harpoon and Exocet type.

      Hughes also ignores things like what happens if you break a destroyer into a bunch of tiny missile boats and a group of helos shows up against you? You'll lose all the boats because they are too small to have effective AAW capability.

      Hughes work is excellent and should be accored great respect. The entire LCS program could have benefited greatly from a consideration of his writings prior to embarking on it.

      Please do not in any way take this as critical of your post. In fact, you make a good point about Hughes work as it applies (or ought to) to Streetfighter and LCS.

      Consider these comments and let me know your further thoughts on armor for larger ships.

      Good to hear from you!

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  4. I do agree that there's need to be a distinction between small (coastal) and large combatants. I don't know if Hughes was really pushing for a fleet composed completely of small combatant - hope I didn't misportray his work.

    I can agree with you on the damage-resistance of BBs, but isn't that also a factor of their size? Hughes alludes to a Navy study which showed that damage resistance is related to hull-length. I took that to mean a bigger ship occupies more area and therefore is less affected by any single hit.

    I don't yet know enough about naval armouring to know whether or not a DDG/CG could be made substantially more resistant to modern weapons. I'd think that a cruise missile striking a ship which is only 500 ft long is going to get a 'mission kill' no matter what. There is just too much vitals area to cover.

    I'm more familiar with the ASW problem - wherein the Navy has long since given up on armoring or blisters as a means to protect against torpedoes. The weapon has far outprogressed any form of constructive defense. I think we may be on the same path with regards to missiles and above water weapons.

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    PS: I appreciate the feedback and civility - and believe me I don't take offense! I've actually been looking for a book to complement/counter Hughes if you have any suggestions.

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  5. I could do a whole post on the use and effect of armor. Come to think of it, we kind of are with this discussion! All the better.

    Consider that armor has multiple benefits aside from the most obvious of trying to "stop" a bullet/missile/torpedo. Armor also provides an immediate damage mitigation effect (lessening the impact of the hit) by stopping shrapnel, blast debris, unspent fuel, and so forth from penetrating as far as it would in the absence of armor and thereby reducing secondary fires, power outages, flooding, etc. Armor also offers containment of damage. Fires and flooding are less apt to spread across armored zones.


    So, armor doesn't have to totally stop the hit to still provide valuable benefits.

    You ask whether we can usefully protect larger ships like DDGs since the weapons may be outpacing the protection.

    Well, the weapons may be outpacing currently used types of steel and armor but, as WWII demonstrated, we had armor that was capable of providing a great deal of protection against 5"/6"/8"/16" shells, 1000 lb torpedos, 500/1000 lb bombs, etc. If we chose to, we could use much stronger, thicker steel (HY-100, HY-130).


    Also, damage protection is conferred not just by armor but also by separation of key equipment so that a single blast can't take out multiple pieces of critical equipment (consider that all four faces of the Burke's Aegis arrays are on a single, small superstructure - no useful separation, at all!) and redundancy (backups) so that a single blast doesn't eliminate a capability (consider that a Burke has only one gun versus a WWII Fletcher which had five 5" guns on a smaller hull - I know, things are different but the idea is still valid), among other damage mitigation techniques.

    So, the combination of intelligent armoring, separation, and redundancy, to name a few, do, indeed, offer the potential to greatly enhance the ability of a modern ship to prevent and/or mitigate damage and continue to fight hurt, when damaged. So, my answer to you is yes!

    You mention ship size as a factor. Bigger size traditionally means more compartmentation (more resistance to flooding) and a bigger crew for damage control. Bigger size also inherently tends to offer greater separation of critical components.

    Study a drawing of a Burke, sometime, and look for key components in light of what we've discussed (separation, redundancy, armor, etc.) and see if you don't wind up thinking that we could do a lot more to toughen our ships for relatively little cost. You might even want to read/reread the naval battles of Guadalcanal and note the incredible amounts of damage those ships took while continuing to fight. Let me know what you think!

    The U.S. Navy's warship design philosophy has gravitated away from "war" ships built to stand and fight, and fight hurt, if need be, and towards thin-skinned, offensive oriented ships that are highly susceptible to one-shot mission kills. Not a good trend, in my opinion!

    As an aside, I've found very few books on naval tactics akin to Hughes. In fact, I don't know of another that deals with tactics in the missile age.

    Good discussion!

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  6. Interesting discussion. BTW, how do we send things to you ? Didn't notice any email in your web site.

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  7. Hello Retired! I intentionally limit my public exposure to the blog and comments (no email) so as to avoid having to deal with the nut cases out there. It's unfortunate but that's the state of the Internet today. Assuming that it's not ticking, what type of thing did you want to send me? There may be other ways to do it. If not, I'll provide an email. Let me know.

    Thanks for looking in!

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  8. If the damage wasn't as extensive as it was the impetus to pursue 'terrorists' wouldn't be as high. Warfare is as much political as it is strategic. The best way to run an empire on the cheap is many paper tigers. Why we wish to continually occupy foreign waters is not a benevolent one, but for globalist commerce and banking. Like general smedley butler,USMC said war is a racket.
    I'm still on topic. We need to change our posture in the world.

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  9. Anti-ship missiles are more or less universally of a semi-armor piercing design. A mildly thicker or stronger hull would provide no real increase in defense since they're specifically fused to penetrate before detonation anyway. A slightly stronger hull is largely worthless against modern 'keel beaker' type torpedoes as well, it might be of minor use against an omnidirectional mine or a charge detonated against the hull but spending the money on improved sweeping systems and training for port security would be a far better investment.

    Beyond this people need to learn history no ship of a Burke's displacement ever took a heavy torpedo to the engine room (the effective equivalent of this attack) and kept fighting, in fact many ship nearly twice her size didn't either. Atlanta is illustrative a 7,400 ton light cruiser with some armoring she sustained one torpedo hit to her own forward engine room in a surface action. All power was instantly lost aside from an emergency generators, gunnery systems disabled, and steering knocked out. The ship was combat ineffective instantly.

    She was then a victim of friendly shelling, but this was largely incidental the hits where mostly in the upper works. The torpedo was the fatal damage. Restoration of power proved impossible, the ship was left completely adrift and flooding became progressive. Unable to save the vessel she was scuttled the next morning.

    USS Houston and USS Canberra 12 and 17,000 ton heavy cruisers respectively each took a single aerial torpedo hit. These weapons had smaller warheads then surface torpedoes. Regardless each was effectively instantly and completely disabled losing motive power and requiring tow to an anchorage. Needless to say ships without any means to make way cannot 'continue fighting' even if they might nominally be able to ineffectually spray shells into the surrounding ocean.

    By the way this occurred in the same action back to back. Thus was "Cruiser Division 1" transformed into "Cripple Division 1".

    Nothing short of a full blown battleship has ever sustained heavy anti-ship weapon hits and continued to engage with some semblance of effectivenes, and many of them didn't either; Kongo took two torpedoes flooded and then exploded, Taihou was hit once filled with fumes and went up like a bomb, etc. Cruisers heavy and light, destroyers, and light carriers have all regardless of era been more or less universally disabled to the point of ineffectiveness by one torpedo, large bomb, or mine. Either via loss of speed, power, or fire control systems.

    The idea that World War II era ships of comparable displacement to modern vessels could just shrug of hundreds of pounds of HE and kept fighting is preposterous and utterly incorrect. Indeed the reason armoring went away was precisely modern weapons completely overtook it.

    The reason modern ships aren't built "stronger" is because modern weapons have rendered such efforts a fruitless waste of time. A comparatively tiny cost in upgraded warheads in threat weapons would utterly negate millions or even billions of dollars in complex passive protection systems. Though in fact even current weapons have so much overmatch built in already that you'd probably need something approaching the scale of a battleships to force much change in said weapons, and even then only really in ASMs.

    The size of modern combatants is driven by the demands of power to run modern systems and space to fit weapons and these are also what drives the real costs. Steel is comparatively speaking quite cheap, so increasing the cost of that segment of the design with more expensive alloys for highly dubious benefits to 'toughness' would in fact be the truly foolish move.

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  10. This has been a rather refreshing list of comments to read compared to the usual babble out there. My two cents boils down to the fact that armor for ships is largely outdated in conventional warfare, and vigilance against non-state actors is usually sufficient (the Cole is an excellent example of failure with the latter). No ship to my knowledge has been hit by an anti ship ballistic missile outside of an exercise. Even you-tube has footage of modern weapons being used in these exercises where torpedoes are nearly blowing ships in half. Electronic Warfare and now directed energy are the countermeasures of first class naval warfare, and are effective versus surface and air based threats. These countermeasures make armor moot since they negate the impact necessary for armor to apply. Against non-state actors, the fully automatic grenade launcher is usually more than sufficient. This leaves torpedoes and underwater mines as the greatest threats to modern navies, and there are several effective countermeasures to those so long as those threats are detected within sufficient time....

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