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.