Friday, April 12, 2013

Armor For Dummies

OK, it’s happened.  You’ve committed the unpardonable sin of disagreeing with ComNavOps and for that you will be shot with a .50 cal bullet.  ComNavOps is not without compassion, though.  You will be given the option of standing behind a wall of ½” armor plate when the shot is fired.  Every one of you, without exception, will opt to stand behind the ½” armor wall.  Why?  Because even those of you who have been arguing against armor and claiming it does no good, understand in your gut what your brain has failed to grasp:  that armor is better than no armor.  Will the ½” armor save you from the wrath of ComNavOps and a 0.50 cal round?  Maybe not – but it offers a better chance than no armor.  And that, right there, is the value of armor - it offers a better chance to survive hits than not having armor. 

The preceeding hypothetical example should be sufficient to resolve the armor question, however, this is the Armor for Dummies (I mean this only as a light-hearted take on the whole XXXX for Dummies book series;  it’s not an insult) lesson so I will now spell it out for everyone.

Armor is meant to mitigate (lesson the effects of) damage.  While it would be nice if the armor out and out stopped whatever the incoming weapon is, absolute stoppage is not the only purpose.  Simply reducing the amount of damage from a hit is worth the cost and weight of the armor.  If that 20 ft hole in the ship can be reduced to 10 ft that’s a “win”.  If the spray of shrapnel from a hit can be confined to one compartment rather than several, that’s a win.

One of the main arguments against armor and the one most often cited by the armor-is-pointless crowd is that a given thickness of armor can’t totally and completely stop a given weapon.  For instance, recent commentators have stated that ½” armor can’t even stop a 0.50 cal round so what’s the point of having armor.  Let’s look at this concept a bit closer.  I don’t know if ½” armor will or won’t stop a 0.50 cal but let’s accept that it won’t for sake of discussion.  Let’s stipulate that ½” armor will not stop a 0.50 cal round fired at optimum range and right angles to the armor.  OK, but what about a round that hits the armor at a 45 deg angle?  I’m betting that it will stop it and the round will ricochet off.  In combat, rounds will be impacting at all angles.  Wouldn’t it be nice if we could stop some portion of those rounds rather than having every round tear through the ship?  Well sure that would be nice but what if the round does impact under perfect conditions and penetrates the armor?  Think about that for a moment.  What would happen if we had no armor?  The round would not only pass through the skin of the ship but through multiple compartments, equipment, electronics, and people until it eventually ran out of kinetic energy and stopped in something.  In short, it would do a great deal of damage beyond the initial penetration.  So, what happens if the round passes through our notional ½” armor?  Well, the amount of kinetic energy expended by the round in passing through the armor will be such that the round will have little left for further penetration deeper into the ship – damage will be greatly limited compared to not having armor.

He's No Dummy!

Speaking more generally, now, what if the torpedo that no modern armor can stop explodes a bit further away than optimum?  What if the incoming missile that laughs at armor is exploded by a CIWS and the debris strikes the ship?  What if a 5” shell doesn’t actually hit the ship but, rather, a near-miss occurs?  What if a proximity-fused anti-radar missile explodes nearby and sends out a hail of shrapnel?  In each of these cases, armor would greatly mitigate the resulting damage.

Remember, in combat a ship is far more likely to encounter near-misses, shrapnel, and off-angle hits than perfect hits.  The ability to shrug off, or greatly mitigate, the sub-optimal hits is what armor grants.  Will perfect hits by weapons whose explosive power exceeds the armor’s resistance cause damage?  Of course!  Even then, the damage will be less with armor than without.

There seems to be a belief that armor is totally incapable of stopping modern weapons and that’s completely false.  It’s simply a question of thickness (I’m simplifying a bit, here) versus the specific weapon.  I recall reading about tests the Navy conducted many years ago in which they launched missiles (Harpoons or Tomahawks – I can’t recall which) at battleship plate armor (I don’t recall the thickness) and all the missiles did was ruin the paint.  Armor will stop weapons if the thickness is sufficient.

That brings us to the other main objection that is commonly voiced:  armor is too heavy to carry enough to make a difference.  Well, we’ve just discussed how any amount of armor is better than none.  Setting that aside, there’s a school of thought that seems to believe that modern ships just can’t carry the weight of armor.  Nonsense!  WWII Fletcher class destroyers carried ½” – ¾” armor on a 376 ft hull of 2500 tons.  If a Fletcher can carry that, surely a 500 ft, 10,000 ton Burke class destroyer can carry at least the same.

A recent comment suggested that adding ½” to 1.5” of armor would add 180 tons to 540 tons (I have not verified those numbers) to a Burke and that that additional weight was unacceptable.  Bilgewater!  If designed in from the start, that amount of armor would have no deleterious effect on the ship’s performance, as WWII ship design proved, and would greatly enhance damage resistance.  We’re risking multi-billion dollar ships for want of an inch or two of armor.  Steel is cheap.  Armor is steel.  Therefore, armor is cheap.

We examine a lot of issues that are debatable.  This isn’t one of them.


  1. You make a very compelling argument.

    But I'm not sure on your numbers, oh wait, nope, its mine that were wrong.

    A Type 45 destroyer is 152m long, 7m tall and we could argue it has two sides.
    Thats 152*7*2 = 2128 square meters.
    3cm thick armour would require 63 cubic metres, at a weight of 7800kg per cubic metre, gives us 497t of additional weight on an 8000t destroyer, a 6% increase, which seems reasonable.
    5cm would add 800kg

    Its an interesting piece.
    Although 50mm of armour isnt actually that much. The Sherman had 75mm of armour.
    I guess thats what led to "all or nothing" armouring in the first place.

    1. TrT, remember that, in practice, ship armor is not uniformly applied. Various thicknesses are applied around various areas depending on the perceived vulnerability and importance of the area. The WWII Fletcher, while having 3/4" in general, had areas that were "only" 1/2" and other areas that were 1" or more. The gun mounts had 1"-2" because the designers recognized that it was pointless to build a ship whose weapons were too easily damaged or destroyed. Today's Burkes have 5" gun mounts that have no armor - only a fiberglass weather covering. How long will those guns survive in combat? I know, the 5" gun is not the main weapon of a modern destroyer. What is the main offensive weapon of a modern destroyer? Is it the Harpoons mounted in totally unprotected quad racks out in the open on the deck? Yeah, I guess it is. My point is that we are no longer designing ships to fight and take damage and keep fighting.

    2. A bit late, but a bit smart...

      A DDG-51's main weapons aren't the Harpoons, or 5 incher, but the Mk41 VLS. You've got enough missile types in there that, if every one of those types was a BLT, you would have a bacon sandwich feast.

      Technology has obviated armor. Necessarily, given how many ships that have relied on armor have gone down under high explosive delivered by airplanes. Remember the Ostfriesland?

      Now, in a normal Block 1 Burke, you've got 90 cells. Load them all with ESSM's, that's 360 missiles. Read that sentence again, I suggest. Three Hundred and Sixty Missiles, capable of turning Migs and boghammers into burning wrecks.

      Now, you think we'll be going up against China. So far, we've built 62 Arleigh Burkes, DDG-51 to DDG-112, all with varying capabilities divided up in two flights of destroyers. They have two-TWO- Sovremenny's with old Sunburn missiles, I believe. We still have around a dozen Ticos, and enough carriers to turn their nation into not a parking lot, but maybe a shopping mall that's seen a zombie apocalypse.

      Can our ships take the same amount of damage as a WW2 DD? The USS Callaghan went down after a single kamikaze. Sure, a kamikaze may not be the same as a sea skimming, supersonic guided missile, but our ability to destroy the latter and former has increased. Against a pair of modern DDG's with Cooperative Engagement Capability, SM-3's, and even SM-6's, what chance does a DF-21 have in an ECM'ed environment?

      And should a modern warship be able to take damage and keep fighting? What kind of threats are we facing? A ASBM, like the DF-21? A Granit missile from a Sovremenny? A torpedo from a Kilo diesel sub? An Iranian Boghammer? While it may take months to repair damage, it took a long time to repair damage to warships in World War Two also. Only a few notable exceptions occurred in that war, and any war that takes place today is going to be a lot shorter.

      And if you are going to shoot me with a .50-cal, I want a gun of my own. A XM25.

    3. Anon, are you interested in a discussion or just looking to unload on me? I suspect the latter. If you'd like to have a discussion, let me know and we can do so in a polite fashion. Otherwise, you're welcome to your opinions and you might be happier finding and reading a blog that's more in agreement with your ideas.

    4. writing a novel ( attempting anyways) I came across this issue. I have solved it...using literary lic, but wanting to remain real at the same time.

      people seem to fail to grasp the complexities now posed in warfare and that the nice open lets use ESSM's, SM3's or SM6's is simple NOT always an option.

      how does a Burke class DDG engage multi high speed targets that POP UP among other vessels in a littoral environment?

      how does a burke Class DDG swap rounds with land based arty or RPG's or ATGM's when its close to the shore in a shore bombardment / support role.

      the answer is they cannot effectively do it, they have no secondary support armament, lack sufficient guns for sustained support and 7.62mm rounds will most likely penetrate the ship. who wants a ship that can be disabled by squad level weapons.

    5. I'm not quite sure what your point is? Try again?

    6. Why are you asking us those questions?

  2. As I said, my numbers were wrong, when I objected, I was doubling the weight of ships, damned maths :)

    5cm thick armor would add roughly 10% to the weight of a ship and would render it immune to small arms, and provide pretty fantastic protection against anything but a direct hit from a ship killer.
    To me it seems a pretty fair trade.

    Although, phalanx weighs only 6tons, but costs a lot more than steel to maintain.

  3. The biggest problem for modern ships that I see is that you can't armour what are both the most useful and the most vulnerable things - the sensor suite and fire control systems.

    On any ship, they have to be completely exposed to work (you can't stick 1.5" of steel in front of or around a radar). Subject them to some gunfire or even a near-miss/debris from a missile intercepted by the CIWS and you're looking at damage building pretty quick, even if the ship's hull integrity is unaffected.

    Without those sensors, the effective utility of even an Arleigh Burke in a combat situation is nil. It's a mission kill if you can't get the contents of the VLS or the 5 inch magazine to where you need them.

    1. Shockwave

      You are right of course, and its a point I have made here before, even light damage to the main radar will devastate the combat effectiveness of a ship.

      But, guns can be aimed by eye, or should be able to, Harpoon has an autonomous terminal guidance system, so in theory at least, could be fired blind and pick up the target on its own.

      On a slightly more technical level, a ship with an out of action radar could be given ranges and bearings over the radio by an active ship, and on an even more technical level, could receive a full radar dataset over datalink.

      Is emptying your magazines blind in the general direction of the missile that knocked you out worth 500t of steel? Maybe.
      And thats a worst case scenario.

      Cant believe I forgot this!!!
      Glamorgan, through a mix of skill and blind luck, managed to direct an Exocet against its most heavily armoured portion. This prevented the missile penetrating inside the ship, it instead detonated on deck.
      It took a couple of hours to put out the fires and get the ship under control, but her sister ship sheffield was hit by the same type of missile, the fire main was cracked, and the ship burnt out.

    2. But that does, of course, rely on the ship in question having Harpoons mounted (many Arleigh Burkes don't right now) or, failing that, having the target within visual range.

      As for setting up datalinks and target sharing...well, I've got no idea how hard that would be as something to do completely on the fly, likely with damaged communications and possibly in an ECM heavy environment. Wouldn't want to be something I had to rely on, at any rate.

    3. ShockwaveLover, you are correct that sensors and electronics are the Achilles Heel of modern warships. Tomahawk is strictly a land attack weapon and its targeting comes from off-board sources exclusively (in the form of co-ordinates) so that's not much of an issue. Harpoon targeting can come from a variety of sources such as other ships, helos, planes, or own ship sensors so that's a bit of an issue. The real weakness is in the Burke/Tico main mission which is AAW. While targeting can be obtained via data-link the missiles depend on target illumination from the SPG-62's (3 on Burkes, 4 on Ticos). The illuminators are exposed and unprotected. On the plus side, they're relatively small and have some chance of being repaired. Separation and redundancy are needed to protect the mission capability. Unfortunately, the illuminators tend to be clustered in pairs. A hit on one probably damages two. They should be spread out more. More recently, Co-operative Engagement Capability (CEC) allows the shooter to launch AAW missiles under the control of another platform, if there's another one around.

    4. ShockwaveLover, you mention the fact that many newer construction Burkes don't have Harpoons. You are correct, of course. My understanding from discussions with Navy ordnance people is that it's a question of inventory. The Harpoons have a shelf life and we're reaching the end unless systematic upgrades are performed. The inventory is shrinking and the usable ones are being saved for higher priority mission areas like China and N. Korea. Burkes in those areas are saiing with full (8) Harpoons. In the event of war, the inventory would be disbursed as needed. Remember, the Mk141 launcher is just a bolt on rack. The Burkes that don't have Harpoons are prepped for them.

      The Navy is developing new anti-ship missiles, LRASM for example, so, in typical Navy fashion, upgrades and maintenance to extend the life of the existing Harpoons will not be funded. If the new missiles develop as planned, that will probably be OK. However, history has taught us repeatedly that that won't happen and we'll probably face an even more severe shortfall of anti-ship missiles before new ones become available. I'm sure this is also why a vertical launch capable Harpoon has not been funded.

    5. In the event of war I imagine they would be disbursed, but that would likely provide little comfort to the poor sap caught sailing back to port or to rendezvous with a supply ship for that purpose.

      Supplying missiles only to units in high-risk areas is statistically sound - they're more likely to have to use them there. But odds are not certainties, and by doing so the Navy is accepting the risk that whoever wants to attack one of their major capital ships isn't going to play nicely and hit the most-prepared ones.

    6. So you'd rather lose the ship and crew rather than just the sensors & coms? While the Admirals may not see much difference between a kill & a mission kill, I imagine the crews care.

  4. So how about a nuclear powered heavily armored Heavy cruiser for Land attack and Surface threats?

    And with spaced armor below to deal with mines and torpedo's.

    1. It's all about priorities. There's nothing wrong with your concept but the Navy believes that the carrier and Tomahawk armed escorts are sufficient for land and surface attack. Of course, this ignores the reality of dwindling numbers of carriers and shriking air wings.

  5. The other possibility for "no armour", though this is more European design, is the possible larger radar signature of the plating. There has been a drive to lower RCS in a tactic similar to an infantryman vs tanks. They can't really shoot what they can't see or lock on to, so it is possible that the side benefits of no armour/low RCS is expected to outweigh any armour resistance gains. After all, low RCS also means your ECM works better, your enemy has to get closer to lock on, and your decoys all look nicer than your ship as a target.

    This might also imply an expectation of a missile heavy environment, not a gun/cannon heavy one.

    1. Daniel, how does plating increase RCS? Ships are completely plated anyway. Armor is simply thicker plating in places.

  6. So why doesn't the Navy armor its ships any longer? They're not dummies.

    1. "They're not dummies." ???

      JI, you're clearly new to this blog, so welcome! If you go back through the posts you'll see that the Navy is, indeed, all too often, dummies. For example, the LCS was not the result of intelligence.

    2. Gotcha', Commander. I guess any large organization, no matter how great the individual members, can really work against both itself and common sense. Your blog is great, by the way.

    3. JI, thanks for the kind words. You're absolutely correct that an organization can have good people and yet still function illogically. This is not unique to the Navy, by the way. Industry is rife with the same problems. We focus on the Navy because what they do is so important (and this is a Navy blog!). All of the Navy's problems stem from the fixation on new construction. If you haven't read it yet, go back and read the 5-July-2012 post, Altar of New Construction. I've identified the problem but I confess that I'm baffled as to why the myopic focus on new construction even to the detriment of the rest of the Navy's capabilities and responsibilities. Presumably intelligent individuals are doing something very illogical. Thanks for stopping by!

  7. OK it seem that no one else is going to do this, so I have to do this.

    I) While 1/2 inch RHA can stop some 50 cal ammo, armor peicing rounds will go right through.

    II) The Burke class destroyer do have armor, just not steel armor. They carry about 130 tons of Kevlar armor protecting their most inportant spaces, inculding the AEGIS system, CIC, and possible other.

    There is also a strong steel box around the missile launchers, but I not sure if it is made from armor plate or is just to confine a blow out.

    III) Steel armor does nothing, or less than nothing to protect against modern torpedoes and mines. The extra wieght of the steel armor actual help them breaks the ship kells. If by chance the torpedo dose hit a ship side, then maybe a thin armoe plate might prevent fragment from damaging system, but when was the last time torpedo did that?"

    IV) The Fletcher class only had armor arround its machinery space and firecontrol unit. And the later was reduce to save wieght for more 40mm guns just like today.

    V) Steel may be cheap, but RHA is not so cheap, and requires special handling when mounting to a ship. That one of the reason the USN when to Kevlar (along with weight.)

    Now this is not to say steel armor is useless, I think it might be useful as armor protecting decks mounted at the water line, to protect the hull from missile fragment. There it could be more flexible enought to keep from breaking the ships keel.

    1. Glof,

      I)The post doesn't claim that armor stops everything but does explain the immense loss of kinetic energy upon penetration and the resulting mitigation in damage.

      II)I'm aware that Burkes have anti-shrapnel Kevlar armor around key areas. That's good, as far as it goes. What they don't have is any armor dedicated to keeping the ship itself afloat: no waterline armor, no sub-waterline armor for torpedo or mine protection, no deck or superstructure armor to prevent or mitigate general damage beyond the Kevlar protections.

      III)I'm not suggesting that armor must only take the form of thick plates of steel. Void spaces, layered armor, composites, and even reactive armor could all be used along with whatever else makes sense. If there's an arrangement that makes more sense for torpedo protection, for instance, that's fine.

      IV)The Fletchers were built with 1/2-3/4" steel plate as their hull skin. I'm generically referring to that as armor. In addition, they had areas with additional armor. When I discuss armor, I'm partly referring to simply the thickness and hardness of the skin of the ship. I don't have my numbers in front of me but WWII ships were built with HY100 or so steel whereas we now build with something like HY35 or so. Even without increasing thickness, we could build with much stronger steel.

      V)I'm not aware that RHA is used anymore in shipbuilding. Whether it should be is a question I can't answer. Whatever the cost, the cost of a sunk ship is much greater. Some things are worth their cost and armor is one of them.

  8. Commander: What mischief can I commit to re-open the Iowa class debate. Yes, they're museum ship but they are still afloat and armored like nothing else at sea.

  9. Regards the battle of the Bismark Sea, this data is useful to me.
    As the U.S.A.A.F. skip bombers used 4 to 8 .50 Brownings per plane, they, with the 20mm cannon of the RAAF Beaufighters, rattled the AA fire of the escorting destroyers of the IJN, and allowed 75% of the troop convoy to be sunk with skip bombing. That method requires getting 'up close and personal' with the target, so AA suppression is vital. This article help me see a bit more of that was involved that day in WW2.

  10. Don't forget that statistically the most effective anti ship weapon in WW2 was the 50 cal.

    The vast majority of naval ships had little or no armour ( destroyers etc) and fighters could just plug em full of holes till they sank.

    Another point is that armoured ships weren't armoured all over. Vital machinery and magazines would be within the armoured citadel whereas much of the rest of the ship would merely be structural steel.

    Some modern advances such as IEP, usually a single open plan command and control room plus bridge and machinery and weapons automation could allow a modern day citadel to be relatively small. For instance sealing the engines into the hull below the waterline is traditional, but not necessary with IEP. You could have the diesels in ISOs within a citadel which merely channel electric power to the motors, and also allow easy access and very rapid engine changes or maintenance. Also worth noting that a marine diesel, provided it is redundant, represents quite a chunk of armour in and of itself.

    Sadly the 'ships have to be light' meme with its ignorance of hydrodynamics and inability to distinguish between topweight and bottom weight which actually provides stability seems to have taken hold in this internet age. Also the difference between armour piercing, kinetic energy and explosive force. Kamikazes represented far higher forces than most of the dreaded anti ship missiles, never mind large calibre AP.

    I rather suspect that if someone magicked up a WW2 light cruiser and gave it to the USMC they'd stop wittering on about 100nm amphibious raids, ergms and ( most) a2ad threats and get on with the job of closing to gun range and delivering overwhelming firepower.

  11. just imagine a modern BB design with exceptional AAW capabilities :D 400mm sloped belt armour and a dozen CIWS Phalanx and SeaRAM for defence (Sooo many VLS cells on a 260m long ship hehehe) :D *Drools*

    1. I like it. That would make for a proper modern escort for carriers and the like.

  12. As stated, armor is very useful for stopping splinters from hits tearing up adjacent compartments. WW2 experience with armor was to use 60lb (1.5") armor as upper deck armor to fuse armor piercing bombs and shells. It also mounted on the IOWA hulls because the main armor belt was inside the ship. It would be a great start to make sure that all transverse bulkheads be 60lb armor to contain damage to a single compartment. An armor deck above the waterline, perhaps 2" as in cruisers, thick, would help hold a ship together in the advent of a torpedo breaking the keel. It wont always work, but why not give our ships the extra chance? 4" of hull armor, 8' above and below the waterline, certainly protects against the idiots with motor boats. Most importantly, armor is cheap other than adding extra weight. The ships are too important to NOT have armor. Wayne Smith

    1. I agree. The mystery to me is why we moved away from armor given the lessons of WWII.