Monday, November 3, 2014

CIWS Assessment

Acknowledgement:  Thanks to reader Storm Shadow for suggesting this topic!

Phalanx CIWS (Close In Weapon System)  – don’t you hate it?  It’s almost worthless.  How do I know that?  Simple – cause everyone says so!   

Wait, what now? 

That doesn’t sound like a conclusion that rises to the level of ComNavOps’ standards where conclusions are supported by data and logic.  Where’s the data?  Where’s the operational history?  Where’s the logical analysis?

It sounds like we need to take a deep breath and do a logical assessment of this weapon. 

First, to refresh our memories, let’s take a quick look at the system.  CIWS was designed to provide a last ditch, close-in weapon to defend against anti-ship missiles.  The gun has no deck penetration and is self-contained (other than ship’s utilities).  It has its own radar that tracks both the target and its own munitions, adjusting the aim until the two merge.  The unit is fast moving with a wide range of elevation and traverse.  Over time, CIWS has been upgraded to include an anti-surface engagement mode with a FLIR optical sensor and stabilized gun barrels for greater hit range.

Caliber:  20 mm
Weight:  13,000 lb
Rate of Fire:  4500 rpm
Range:  2 miles
Ammo Drum:  ~1500 rounds

Let’s start our assessment with published data.  Um …  There isn’t any.  There’s glowing manufacturer’s claims but that’s not data.  The Navy conducts live fire exercises but not in any combat-meaningful way and, regardless, they don’t share the results publicly.

All right, let’s look at the operational history.  Um …  To the best of my knowledge, there isn’t any.  I’m not aware of any actual combat performance history.

So, we have no data and no history.  That’s going to make an objective assessment difficult.  That only leaves logic.  Fortunately, we have plenty of that.

Let’s start by clearly stating what the CIWS is supposed to do.  CIWS is a last ditch defense against incoming missiles.  Its purpose is to prevent an unimpeded, catastrophic hit on a ship.  No one has claimed that CIWS was intended as anything else.

With that in mind, let’s look at the operations and criticism of the unit.

The most common criticism is that the CIWS, even if it hits its target, will not prevent an incoming missile’s debris field from striking the ship with the implication being that the ship will suffer the same degree of damage.  Many critics seem to tack on a, “So, what’s the point of even having it”, conclusion.  This is a valid observation to a degree.  However, it is far from certain that the missile debris field will strike the ship and even if it does it’s highly unlikely that the entire bulk of the missile will do so.  Much of the missile will be deflected off course.  For subsonic missiles it is quite likely that none of the debris will strike.  All of us instinctively understand that if we have to choose between being on a ship about to be struck by an unimpeded, fully functioning missile or some debris from a no-longer-functioning missile, we’ll all choose the latter.  Remember, while debris may follow the ballistic path to the ship, the resulting debris will not be powered and will no longer be aerodynamic and will slow appreciably – that’s simple physics.  In addition, and quite notably, each piece of debris will be much smaller than the entire, intact missile.  Simply physics dictates that the smaller the mass, the less the kinetic impact.  A ship will be far less damaged by a hail of debris pieces than an intact, fully functioning missile.

An incoming missile that has been hit will probably lose its functionality – it will either explode on contact or lose its explosive functionality if converted to debris.  Again, all of us would prefer to be on a ship struck by inert debris rather than a fully functioning missile.

Will damage occur if the ship is struck by missile debris?  Yes.  Possibly seriously.  However, that’s still a preferred outcome compared to being struck by an unimpeded, fully functioning missile.

Closely related to the preceding criticism is the lack of range.  This gets back to the design purpose.  It’s a last ditch, CLOSE-IN weapon.  It’s not a long range Standard missile.  This criticism is absurd.

CIWS - Unfairly Criticized?

A valid criticism is the limited supply of ammo.  The drum, containing around 1500 rounds, must be manually replaced and this is a time consuming exercise, especially when missiles are approaching!  However, this is related to the non-deck-penetrating nature of the design.  You can’t have both.  If a large magazine and automated load function are desired than the unit has to penetrate the ship’s deck thereby increasing size, weight, and internal ship’s volume.  The unit was designed as a bolt-on weapon and this was a necessary design compromise.  Still, it is a potentially fatal limitation if the unit runs out of ammo while an attack is in progress.

Another common criticism is the size of the gun.  Many seem to feel that a 20 mm gun is inherently less effective than, say, a 30 mm.  Well, it depends what you’re trying to do.  While a larger projectile will hit with more force (assuming the same projectile velocity), the tradeoff is generally lower rate of fire and smaller magazines.  We’ve already identified that both a strength and weakness of CIWS is the non-penetrating nature of the unit.  A larger projectile would further reduce the number of available rounds without turning the unit into a deck-penetrating unit.  Further, I have never seen any data or study that suggests that 20 mm is insufficient for the task of shooting down missiles.  If the school of thought that bigger is better is valid then we should be conducting anti-missile gunfire with 16” BB guns!  That’s the logical conclusion.  The reality is that once you reach the effectiveness threshold, any increase in shell size is unneeded and simply makes the weapon heavier and further decreases magazine size.  So, does the 20 mm  meet the threshold requirement?  Presumably it does – I’ve seen no data to the contrary.  Thus, 20 mm imparts the advantages of more rounds, lighter weight, and a non-penetrating unit.  Until we see data indicating that 30 mm is significantly more effective, the advantages would seem to outweigh any perceived disadvantages.  Would we like a theoretical 30 mm gun that weighs the same as the 20 mm CIWS, is non-penetrating, has the same rate of fire, and accommodates the same amount of ammo?  Sure!  However, I’m not aware that such a gun exists.

A final factor is what we’ve already alluded to:  the non-penetrating, bolt-on nature of the design combined with its light weight.  It’s ideal for “sticking” on a ship wherever there’s a bit of deck room and it’s light enough to be installed on very small vessels.  It offers a cheap, easy way to add defensive capability with little impact on the ship’s operation.

So, why has the CIWS gotten such a bad reputation?  I’m not sure.  I think people have gotten into the habit of attributing almost mythical prowess to the attacking missiles and, therefore, assumed that something as old-fashioned as a gun couldn’t possibly be effective.  That may be true or it may not.  As we said, there’s no data and no history.  I note that the ancient Soviet ZSU is still one of the most lethal AAW weapons ever made and may have shot down more aircraft than all the SAMs put together.  The “wall of lead” is still brutally effective.

So, can we draw a final conclusion?  Well, there’s still one more aspect to look at and that is ship design and AAW doctrine as practiced by the US Navy.  For whatever misguided reasons, the Navy has opted to focus its AAW efforts on long range missile intercepts and, more recently and grudgingly, on medium range missiles.  What’s been largely ignored is close-in defense and electronic countermeasures (soft kill).  Let’s face it.  A single CIWS on a Burke isn’t going to offer a great deal of protection but that’s the Navy’s design and doctrinal philosophy.  The Navy apparently doesn’t view “leakers” as much of a threat.  ComNavOps, on the other hand, has examined the historical data on AAW effectiveness (and posted it!) and concluded that there will be far more leakers than the Navy believes.  Quite the opposite from the Navy, ComNavOps would see our ships armed with many more CIWS mounts.  For example, a Burke should have enough CIWS to be able to bring three units to bear on any axis of attack (four would be even better!). 

With that in mind, the conclusion is that, barring data to the contrary, I see no reason why CIWS can’t be as effective as any gun can be in a last ditch defense.  The only shortcoming is that the Navy is underarming its ships.  We need many more units on each ship.

Now, if I don’t explicitly say this, some of you are going to draw the incorrect conclusion that I’m advocating removal of RAM, SeaRAM, ESSM, and SM-x in favor of just CIWS.  Just as I favor more CIWS, I also favor more medium and short range missiles.  What I don’t favor is continued pursuit of long range AAW missiles but that’s a topic for another time.


  1. One thing I don't understand. Honest question. We've talked before about how the Mk 110 might not be sufficient against swarm attacks.

    When they war gamed swarm attacks against our ships, did Phalanx have the ability to shoot surface targets?

    Even with its small capacity, it seems like if you could put a couple of these on a Destroyer they'd do a heck of a job against small boats, in addition to their close in capability.


    1. Jim,

      CIWS can now engage small boats.


    2. I guess that's my point.

      From Wiki (Caveats abound) Phalanx surface mode was put out there in '99. It seems like this thing would saw through most small attackers. And its radar guided, unlike the Mk 110. And it has a very fast target tracking ability and a 2 mile effective range. It seems like the ideal defense against swarm attacks. The only downside I see is its low ammunition load out.

      Yet, The Navy talked about creating a whole class of ship to deal with swarm attacks (IIRC that was one of the reasons for the LCS). I'm just wondering if it was considered to add more phalanx mounts to deal with the threat.

      From the arguments I'm hearing given its (relatively) low footprint on a ship, and multi use, Phalanx seems like a good deal; and one that could do multiple things if you had more than one. I.E. if you could put one fore and one aft with some overlapping fields of fire it would help increase the chance a missile is shot down. It would also help defend the ship against the swarm attacks the Navy was so worried about.

      It seems the biggest problem in the latter situation is knowing when to let R2D2 off its leash and fire automatically.

      Phalanx may not be perfect, and won't leave a ship unscathed, but it might be a pretty useful cost effective weapons system.

    3. Well, Jim it depends with what kinds of weapons this " small boats" are equipped with , if it is a heavy MG the phalanx is right for the job.
      But if this boats have some short range missile capability ( think iranian boats with TOWs for example ). Then it is going to be difficult.

  2. As I understand it as the round diameter increases so does it's effectiveness within reason.

    A 20mm by physics it is a solid and therefore a hittile, not an easy thing to do to an incoming missile and will need sophisticated and expensive guidance.

    The larger 30 mm round may be able to be programmed to burst into lethal fragments increasing chances of hit.

    At 35/40mm it will large enough to include a proximity fuse further increasing chances of hitting the incoming missile at a range further away lessening the chance of parts hitting ship.

    I'am sure studies will have been done looking at trade offs of in weight, complexity, rate of fire and effectiveness verse cost and value judgement made. That's why different CIWS systems exist, e.g. Phalanx & Goalkeeper.

    Not sure if any CIWS will have any chance of hitting one of the supersonic anti-ship missiles.


    1. How close does a 30mm shell have to bang to cause noticeable damage to a missile?
      These aren't big explosions.

      5" proximity fused shells can kill from a distance, 1 and a bit inch, not so much. Remember a UGL is 40mm

  3. CIWS and combat, yes how could we leave the USS Starke out of a discussion on CIWS?

    Then there is the use in Iraq to defend against mortar and improvised missiles. My understanding it it was successful in this role.

    You point out that the Phalanx system was designed as a bolt on solution for existing ships.

    My understanding is this was important at the time the system was developed as it made it possible to deploy the system to the fleet of existing ships with limited cost and delays in deploying the system against what at the time was a serious threat.

    The Stark is important because the CIWS mounted on the FFG is positioned on the assumption that a missile attack is more likely to be a side on attack. Problem being when the the real life problem did arrive the attack was head on, thus the system was ineffective, but you can't blame that on the Phalanx system itself, just its placement. We will never know if it would have worked had the threat been side as expected.

    If my history is correct, this then resulted in the a forward placement of a CIWS mount on the Burke's that followed because the importance of a 360 degree engagement envelope was one of the lessons which came from that painful experience. That said you can see a number of more modern ships which still have a CIWS with limited ability to engage targets forward quadrant.

    The Phalanx as you state above has had some limited improvements over the years, but I do not think anybody would call it a high priority program.

    Thus today the stand alone gun mount says more about the needs of the fleet in the eighties than it does about now.

    Does anybody know if any actual testing was conducted to prove that RAM being a missile is a better solution then a system of distributed penetrating gun mounts, or was that just assumed? Or was it a case can we replace both the old Short ranged Sea Sparrow and CIWS with one system?

    I do not see what a 30 mm Gatling gun gets you for all the extra size, weight, complexity and cost, that 30 mm gun in the A-10 for example is a huge weapon. Small increase in range would a given, but I not aware of any tests where the 20 mm failed to kill the target, because the ammunition failed to penetrate the target. I do not know of any anti ship missiles with tank spec armor.



    1. Mark,

      You have made several factual errors about the attack on USS Stark and drawn some dodgy conclusions.

      First: USS Stark was indeed struck from the side and the MK15 CIWS could indeed have engaged the threat. At worst the ship may have required at most a 5 degree movement – and there was time for that.

      Second: In short the Stark was a completely undefended target because of multiple command failures: CIWS was not the issue.

      The CO failed to employ the MK13 missile launcher, the 76mm gun, EW, Super Rapid Blooming Offboard Chaff (SRBOC), and the MK15 CIWS was intentionally placed in a standby mode and not operationally ready to respond.

      Blaming CIWS for a series of intelligence failures, command failures, and being offline, is incredible.


  4. Well mark, i think it uses the M-61 Vulcan gun not because it was the best solution, but because it was in wide use with the us military sevices.
    And there are lighter 30 mm gatling gun designs out there, just look at the Gsh-6-30 it weights only slghtly more than the M61. If it is going to be 30 mm i does not have to be a GAU-8.
    And remeber when you engagement window is only limited to a few seconds heavier roinds do matter, and 30mm rounds have more growth potential then 20mm ones.
    Every other modern CIWS out there uses 30mm and above.

  5. Great Topic and I’m really with you on this one CNO. Phalanx seems to have picked up all this negative vibe for some reason?
    I have a few views on this one so I’ll get numbering;
    1. Phalanx is your “last ditch defence” not just because it’s your final tier, but because it is a self-contained element. It is designed to work when the rest of your ship has been mostly blow to bits \ shot up \ whatever. It’s got virtually everything it needs to do its job when all hell has ALREADY broken loose and everything else is down. This lack or reliance on anything else is critically important. And make it very different to many of the alternatives
    2. The size of the bullet is largely irrelevant in terms of taking out the target. Aerodynamically a missile or plane will tear itself apart will relatively little structural damage. The faster the missile \ plane the better this works. YES Phalanx can engage supersonic threats; it’s just the firing solution that matters. The only reason for a bigger round is that it extends range and accuracy. There are drawback to a bigger range however. The Royal Navy is in the process of changing back from Goalkeeper to a standard of (at least) 2 Phalanx on every ship.
    3. Yes it won’t STOP a supersonic missiles airframe segment from hitting your ship in all cases, but it’s not the kinetics that you’re worried about. A little while back someone invented a thing called explosives, and really this is the stuff that causes the problems. Modern explosives are designed to be fairly stable so you don’t kill yourself transporting them. And without a nice sequence of events in the missiles sensors, fuse and detonators, the thing won’t go off. I tiny Knick from a 20mm round in any of these areas and the thing becomes a hell of a lot safer!
    4. A lot was learned from the Falklands. As supporting vessels covered the assault, they pulled close to the islands to shield themselves from Exorcet lock on. But this also knobbled their ability to lock anti air missiles. In close a missile has a minimum engagement range and limited turn circle. The enemy resorted to dumb bombs and losses ensued. We countered with guns and scored hits, but too late in some cases. Phalanx has always been anti – air in general, you can always target planes and helo’s with it at extremely close range, and they wont miss! 1500 20mm rounds at that rate of fire will basically just slice a plane in half.
    5. Finally you can’t decoy a dumb bullet. Particularly with Phalanx’s new capabilities, with man in the loop, if the target is identified and firing commences no amount of flares, chaff or amusing laser dazzlers will stop that round. And as someone has mentioned they can just be used as a really really good anti surface remote weapon station if you have a need.
    So yes, Phalanx is still very very relevant.
    Or at least I think so ;)

    1. Don't underestimate the damage a few dozen gallons of blazing rocket fuel cause.
      But its less than a 300kg bomb and a few dozen gallons of rocket fuel.

      Self contained fantastically explained!
      Phalanx will keep shooting long after the ships computers crash, the main radar is blown off and the crew is leaping in to the sea to avoid the raging inferno that is sweeping through below decks.

  6. Just to throw a different thought out there.

    What about the cost differential of a shoot-shoot-look-shoot-shoot-look etc. versus having the CIWS for in close defense? If it takes 2 missiles (best case above) to destroy one inbound that is a pretty good ecnomic engagement. If you have a 4-1 ratio that is even better. Wars have been lost because of a 2:1 advantage.

    So what is the $ savings of shoot-shoot-CIWS vice 4 missiles expended?

  7. Interesting to see how the CIWS and RAM would preform agains the new super fast Coyote target drone.

  8. Comnav, assuming Current CIWS is not up to task in the last ditch defense , what weapon system would be better for intercepting incoming subsonic or supersonic antiship missiles ? using currently available and known technology ..

    the new ASM, if i recall at the terminal phase they do some kind of maneuver to throw the aim of anti missile defense..

    - is Laser weapon quick enough to kill a missile ?
    - is some kind of magnetic shielding possible ? enveloping the whole fleet for certain radius that uses polarity difference as means to deflect the missile ?
    - is the railgun concept suitable for intercepting high speed ASM ?
    - or deploy anti missile drones at the fleet's outer defense ring ?
    - using some kind of towed decoy thingy for ASM ? like the Nixie torpedo decoy..

  9. I do wonder, if a shooting war ever breaks out you would see a great increase in the number of CIWS put ships (similar to how in WWII as the war progressed more and more AA mounts were installed/retrofitted on ships).

    1. I doubt "the next war" will last long enough for anyone to build anything so complex as Phalanx.
      Bolting .50cal guns on to the side, maybe. Building radar guided weatherised cannon?
      Is there a warehouse full of the Ku band Radar or do they need to be built? FLIR? The mounts? The guns?

      The boss frequently mentions the impossibility of "ramping up" production of high end gear, but that applies equally to everyone, China builds two of its much talked about "carrier killer" ballistic missiles each year. I doubt they can flick a switch and roll out 200 per year.

      Maybe for round two, but round one will go no worse for China than the loss of its expeditionary force, the US is hardly going to invade Shanghai, or no better for China than the capture of a few islands, its hardly going to successfully invade India, Vietnam, Korea and Japan, whilst driving the US back to Hawaii.
      After that, we might see ships with a dozen CIWS.

  10. I know several ASCM were intercepted by something during the Gulf War. You should look that up because I do not have time right now.

  11. Dudes, according to open source data, no CIWS engaded during Desert storm.

  12. Guys, I saw a brief mention above to the Stark and it being hit head on and then this comment was countered. If sea skimming missiles approach from bow or stern, can the CIWS engage them without the ships turning? I would particularly appreciate an answer related to the new Chinese types.
    Secondly, Secondly, I read an article about the BrahMos which concluded that, if the missile got through the long and medium range missile shield, the game is over. Scratch one Burke because CIWS will not have time to effectively engage. Do you agree?

    1. All direct firing weapons have engagement zones that are partially occluded by the ship's superstructure and equipment. This is compensated for by either placing multiple weapons so as to cover the occluded areas (bow and stern mounting, for instance) or by maneuvering the ship to unmask the weapon. Generally, the threat axis is known and/or there is sufficient warning time to turn the ship slightly to unmask.

      Regarding BrahMos, I think what you're referring to is the supersonic debris issue which was discussed in the post.


Comments will be moderated for posts older than 7 days in order to reduce spam.