Naval Gun Accuracy

It’s discouraging to see how many people believe that modern fire control systems guarantee unerring accuracy.  I’ve seen claims that the Oto Melara 76 mm only needs three rounds per engagement against anti-ship missiles.  That’s absurd!  When the head of Oto Melara, in a live fire test, agrees to stand on a target protected by one of his guns that has only three rounds in the magazine, I’ll begin to believe the claim.
 
So many people seem to think that modern guns can’t miss.  I guess this is an example of a little bit of knowledge being a dangerous thing.  People understand just enough about computers to know that we can write a program that predicts where a round should go to impact/intercept the target and they assume that the program can’t be wrong, therefore, the shot must hit with unfailing accuracy. 
 
Reality, however, is much different.  Yes, a program can make a prediction – that’s just simple mathematics and that’s child’s play.  What the program can’t do is account for the hundreds of factors that actually affect the accuracy of a naval gun.  Let’s briefly consider some of the more obvious factors:
 
Stabilization – One of the most blatantly incorrect beliefs among naval observers is the myth of stabilization.  People forget that both the firing platform and the target are continuously pitching and rolling, among other movements.  Yes, we have stabilization (of the firing platform, not the target!) but stabilization is not even remotely perfect.  The guns are large, heavy chunks of steel and have inertia.  Just because the stabilizer computer signals the gun to move doesn’t mean it can instantaneously accomplish that movement.  There is a lag and in the world of micro-deviations (we’ll address that shortly), which is what we’re discussing, that’s a problem.  Stabilization is a gross phenomenon, not a micro phenomenon and it does not, indeed cannot, assure accuracy – it just reduces gross inaccuracy.
 
Let’s consider some other common factors that impact accuracy:
 

• Barrel Wear – wear is a constantly changing phenomenon and is not uniform along the length of the barrel
• Barrel Temperature – changes on every shot and is not uniform along the length of the barrel
• Wind – constantly changing and changing throughout the length/time of the shell’s flight profile
• Barrel Movement – the barrel is moving (pitching, rolling, and attempting to stabilize) while the round is traveling through it!
• Shell Uniformity – every round has minute (and no so minute!) differences in weight, shape, smoothness, dents, etc. and each one affects accuracy
• Friction – this is a factor of the shape of the round, density of the air, humidity, wind, etc. and, of course, there’s always friction between the barrel and the shell
• Humidity – this is constantly changing on the micro scale as the shell encounters wind currents, spray, fog, rain, etc.
• Density – the density of the air is constantly changing due to temperature, humidity, altitude, etc. causing changes in friction and speed of the projectile
• Temperature – changes with elevation, wind currents, and wave behavior causing updrafts and downdrafts
• Target Movement – the target is constantly moving in all three dimensions while the intercepting shell is being fired and traveling through the barrel and the target continues to move during the entire travel time of intercepting shell;  some of the movement is due to physical factors (wind, friction, etc.) and some is due to intentional terminal maneuvering;  when we take a radar ‘fix’ on the target, the implicit assumption is that the target will continue on its path and that’s utterly false, as we just noted

 
What program has the slightest hope of accurately modeling those factors especially since we have no means of measuring most of them other than in the grossest sense?
 
 
Deviations
 
So, we’ve now acknowledged that there are too many factors that impact accuracy for us to account for all of them and we lack the sensors to do so even if we could program them into the fire control algorithm.  But, you say, the deviations are minor.  Well, let’s examine the magnitude of the effect of the cumulative ‘minor’ deviations.
 
Projecting a straight line from the shell in the barrel, waiting to be fired, to the predicted intercept point, gives us a travel path that we think/hope will meet the target.  Any deviation will cause an angular change from the predicted travel path.  That angular deviation can be considered in degrees.  If the shell perfectly follows the predicted path, that would be 0 degrees deviation.  If the shell were to, ridiculously, take an immediate right angle turn off the predicted path, that would be a 90 degree deviation.  Realistically, the deviation will be on the order of 0-10 degrees or so.  Let’s see what impact small degrees of deviation have on the difference between the actual intercept point as compared to the predicted point.
 
For this illustrative example, let’s consider a predicted intercept point at a distance of 1 mile (5,280 feet).  We’ll use the geometry of a right triangle to calculate the deviation.  Specifically, we’ll use the formula
 
     tan(deviation angle) = opposite/adjacent
 
rearranging,
 
     opposite = tan(deviation angle) * adjacent
 
where,
 
opposite = the deviation from theoretical intercept point, in feet
adjacent = 5,280 ft  (distance to theoretical intercept point)
deviation angle = the angular deviation from the predicted intercept path, in degrees
 
Using the above formula, we get the following results for various degrees of deviation.
 
10 deg = 931 ft
5 deg = 462 ft
1 deg = 92 ft
0.5 deg = 46 ft
0.1 deg = 9 ft
 
We see then that even a miniscule 0.5 deg deviation will result in a 46 ft miss.  We have to be down around 0.1 deg or less deviation to hit our predicted intercept point close enough to be effective.  Of course, that assumes the target perfectly followed its predicted travel path and didn’t change course, altitude, or speed!
 
Wow!  That is not much allowable deviation before we have a clean miss!  From observations of video of live fire gun exercises, my estimate is that deviations of 0.5-5 degrees are normal.  That’s not encouraging.  I’m beginning to think that hitting a target with a naval gun is almost impossible.
 
Before we throw up our hands and give up trying to hit an intercept point with a naval gun, let’s recall that there are a few things that can help improve our odds.
 
Number of Shells – It’s a given that every shot we fire will have a deviation to some extent.  However, if we fire enough shells toward the predicted intercept point, one or some of them will, statistically, wind up being close enough to be effective.  This argues for smaller caliber projectiles that can be fired quickly and in large numbers.
 
Rate of Fire – This is another way of saying, number of shells, but it goes beyond that.  There’s a time lag between every shot and the greater the time lag, the fewer shells we can put into the predicted intercept point.  To illustrate, if we could fire a thousand shells in one second, we’d saturate the intercept point and compensate for the individual inaccuracies with numbers.  On the other hand, if we can only fire one shell per minute, then we can only ever have one shell in the intercept area at a time before the intercept point changes significantly and odds are it will miss due to the various factors we’ve discussed.  This argues for extremely high rates of fire.
 
Stabilization – The quicker our gun can respond to stabilization commands, the more accurate we’ll be.  This is accomplished by decreasing the inertia of the gun which is accomplished by decreasing the weight of the gun and/or increasing the power of the train/elevation motors.  This argues for smaller, lighter weight guns.
 
We see, now, why a 5” gun is very unlikely to be effective at hitting a cruise missile.  In fact, modern 5” guns have been proven to be woefully inaccurate even against slow moving (relative to a missile) Boghammer boats (the Vincennes incident).
 
Fragmentation - Yet another compensating measure is fragmentation.  If we have to have a direct hit on the target to kill it, our odds are extremely poor.  However, if we can just be in the general vicinity of the target and kill it via shrapnel (fragmentation), our odds increase.  The larger the effective fragmentation area, the better our chances.  This suggests using large shells that can disperse large quantities of shrapnel.  However, there is a limit because the fragmentation pattern takes time to spread out after the shell explodes and if too much time is taken the target has flown past before the shrapnel can spread out.  So, there’s an effective limit on how big a pattern can be effectively used but I have no idea what that limit is.
 
Guidance – Guided projectiles offer another way to improve accuracy but at a significant, literal cost.  There are companies who offer, or are developing, small guided projectiles but, as far as I know, there is no test data under remotely realistic conditions that demonstrates that they are effective.  They may or may not be.
 
 
Conclusion
 
It is clear that naval guns are inherently inaccurate.  For the case of fixed land targets, we can compensate for inaccuracy with explosiveness.  If we’re firing 16” battleship shells, accuracy is a lesser concern as the giant 50 foot craters will compensate for a lot a inaccuracy.  We can also substitute multiple salvos for accuracy knowing that statistical odds will ensure that if we fire enough rounds, some will hit the target.  Besides, it’s not as if a fixed target is going anywhere.
 
However, if we’re trying to shoot down an anti-ship missile, we need small, light, very rapid fire guns which is the concept behind 20-30 mm CIWS guns.  It’s clear that larger guns (5”, 57/76 mm) are ineffective for the anti-air role, barring dumb luck.

Burke Flt III Delivered

The Navy has taken delivery of the first Flt III Burke destroyer, USS Jack H. Lucas, DDG-125.  Photos and concept drawings show that the ship’s entire close in defense consists of a single CIWS mounted aft of the rear stack, on top of the helo hangar.  That’s it.  One CIWS.  That’s either an extraordinary faith in the long and medium range AAW missiles or an incredible display of stupidity.  I’ll let you decide which.
 
There is also an open spot forward of the superstructure which I’m guessing is reserved for a laser of some sort.

USS Lucas DDG-125

CIWS Debris Myth

Phalanx CIWS garners a lot of criticism from naval commentators for reasons that I generally find to be invalid.  Probably the number one criticism of the Phalanx CIWS is the notion that it will merely break up an attacking missile and the resulting debris will, guaranteed, continue on to hit the ship, apparently causing as much damage as the intact missile would (or maybe more?!), in the minds of critics.  In fact, among naval commentators, this concept of debris striking the ship has taken on mythic proportions.  It’s time to examine this concept and see if it’s true or not.

 

 

CIWS Purpose

 

Let’s start by recalling what the purpose of a close in weapon system is.  It is, by definition, the last, ultimate, final chance to prevent an intact, live missile from hitting, penetrating, and exploding inside the ship.  Thus, the job of the close in weapon system is to ‘inactivate’ the attacking missile so that it cannot explode in the ship. Ideally, that will be as a result of the physical destruction of the attacking missile. Less ideal, but perfectly acceptable given the alternative, is destruction of the warhead. If some scattered, slower, debris impacts the ship that's far preferable to an intact, exploding missile hitting the ship.

 

 

Debris

 

As far as missile debris hitting the ship, I know of no real world or exercise example of such an occurrence. The theoretical possibility exists but I've seen nothing to suggest it's a significant danger. In fact, there are a few documented exercise examples of CIWS re-engaging debris.

 

Even a theoretical consideration of the debris strike scenario suggests that it is unlikely. With the main body of the attacking missile hit and destroyed to the point of generating sizable debris, the physics of the scenario suggests that the debris is far more likely to have been blasted onto an altered path, upward, downward, or sideways, away from the targeted ship. The likelihood of debris coming out of an explosion and continuing on the exact same previous path is remote.  The force of the explosion almost guarantees that can’t happen since the explosion would occur in front of, or at the front of, the missile and the explosion would impel the rest of the missile debris backwards, sideways, up, or down.  The explosion, itself, therefore, acts as a shield or deflector to alter the path of any generated debris.  Consider the following conceptual drawing which illustrates how the explosion from a CIWS intercept of an attacking missile (the arrow) scatters the debris up, down, left, and right but not on the missile's original path.  Instead, the debris pieces are deflected off the path to the defending ship.

 

Conceptual CIWS Intercept

Attacking Missile is the Arrow

Ship is to the Right

Further, any debris, by definition, will be misshapen, unpowered, and no longer aerodynamic. That means that whatever path it's on it will very quickly lose speed and gravity will further alter its path downward, away from the ship.

 

In the absolute worst case of a piece somehow continuing on a path that intersects the ship, the piece will be substantially smaller (less mass) than the original attacking missile and, being unpowered, will be very much slower than the original attacking missile and will be decelerating very quickly due to friction and the drag from its non-aerodynamic shape.

 

 

Kinetic Energy

 

One of the arguments that debris myth-holders maintain is that the kinetic energy of the debris pieces will be sufficient to vaporize or severely damage/sink the ship even without a warhead.  Of course, as naval analysts and well educated products of our public school system, we know that kinetic energy is the product of two factors:  mass and speed:

 

kinetic energy = ½ * mass * velocity squared

k.e. = ½ * m * v2

 

Since debris, by definition, is smaller pieces of the original missile, the mass of any given piece will be substantially reduced compared to the original, intact missile, thereby reducing the kinetic energy of the debris.  As we noted, the speed of the debris will be hugely reduced and slowing the entire time until impact on the ship.  Thus, the velocity term (being a squared effect!) will be hugely reduced.  The result is that the kinetic energy of a debris piece will be nearly insignificant as far as inflicting significant damage.  Thus, the fears of the ship being vaporized by the kinetic energy of debris pieces are unfounded.  Let’s check that by running through a couple of examples.

 

 

Chinese C-802/YJ-83 Missile

 

Let’s consider a common anti-ship missile like the Chinese C-802/YJ-83 series.  From Wikipedia,

 

mass = 715 kg

velocity = Mach 0.9 = 684 mph = 306 m/s

 

so,

 

k.e. = 0.5 * m * v2

k.e. = 0.5 * 715 kg * (306 m/s)*(306 m/s)

k.e. = 33,474,870 (kg*m2)/s2 = 33,474,870 J

 

By comparison, a kg of TNT releases 4,184,000 J. Thus, the k.e. of the original, intact missile is equivalent to around 8 kg of TNT. To put that into context, a U.S. Navy lightweight Mk54 torpedo has a warhead weight of 44 kg (we'll assume it's TNT even though it isn't). That means the missile would have kinetic energy equal to 18% of the explosive energy of a Mk54 lightweight torpedo - not enough to even be noticed, by comparison, and certainly not a one-shot kill/vaporization due to kinetic energy alone.

 

Of course, that calculation was for an intact missile - with a full fuel load, by the way; the missile would actually have used up much of its fuel and the mass would be lower resulting in even less kinetic energy.  Now, let’s repeat the calculation for a debris fragment.

 

 

C-802 Debris

 

For sake of discussion, let’s assume a piece of debris 1/10^th of the mass of the original missile and a velocity at impact of ½ the original speed.  That gives us,

 

mass = 0.1 * 715 kg = 71 kg

velocity = 0.5 * Mach 0.9 = Mach 0.45 = 342 mph = 153 m/s

 

so,

 

k.e. = 0.5 * 71 kg * (153 m/s)*(153 m/s)

k.e. = 831,019 (kg*m2)/s2 = 831,019 J

 

By comparison, a kg of TNT releases 4,184,000 J. Thus, the k.e. of the debris piece is equivalent to around 0.2 kg (200 grams) of TNT. To put that into context, a U.S. Navy lightweight Mk54 torpedo has a warhead weight of 44 kg (we'll assume it's TNT even though it isn't). That means the missile would have kinetic energy equal to 0.4% of the explosive energy of a Mk54 lightweight torpedo - not enough to even be noticed.

 

 

BrahMos Missile Debris

Now, what about a large, supersonic missile like the BrahMos (3000 kg, Mach 3)?  Let’s check.  Without all the wordiness, and repeating the above calculations for a piece of debris 1/10^th of the original missile and a velocity at impact of ½ the original speed.  That gives us,

 

mass = 0.1 * 3000 kg = 300 kg

velocity = 0.5 * Mach 3 = Mach 1.5 = 1140 mph = 510 m/s

 

so,

 

k.e. = 0.5 * 300 kg * (510 m/s)*(510 m/s)

k.e. = 39,015,000 (kg*m2)/s2 = 39,015,000 J

 

By comparison, a kg of TNT releases 4,184,000 J. Thus, the k.e. of the debris piece is equivalent to around 9 kg of TNT. To put that into context, a U.S. Navy lightweight Mk54 torpedo has a warhead weight of 44 kg (we'll assume it's TNT even though it isn't). That means the missile would have kinetic energy equal to 21% of the explosive energy of a Mk54 lightweight torpedo - not insignificant but nowhere near enough to be a threat to the target ship.

 

 

Mini-Summary

 

These calculations tell us that debris is simply not a threat to the defending ship, at least not as regards kinetic energy of the debris piece.  Thus, the hysteria over debris from a CIWS engagement is just that: unfounded hysteria.  Fortunately, our public school education has delivered us from the land of hysteria to the realm of science and informed discussion.

 

 

Larger Caliber

 

On a related note, one of the constant calls among naval commentators is for larger caliber CIWS weapons so as to enhance lethality.  While the use of larger caliber rounds would increase lethality, it also decreases ammo inventory and firing rate.  Anyone who has watched a CIWS live fire video cannot help but be struck by the startling inaccuracy (spread) of the rounds.  The scatter is significant.  What compensates for the scatter is the high rate of fire.  Therefore, given how little it takes to destroy a warhead and alter the path of the main missile body, the gain in lethality does not justify the loss of ammo inventory and firing rate.

 

Below are screen captures taken from videos of a CIWS shooting at a small boat.  Note the spread of the splashes.  There was no information about the range or conditions of the exercise but the impression is that the range was very close and still the scatter was quite large.

Note the Scatter

 

Again, Note the Scatter

Still captures from video:  https://www.youtube.com/watch?v=Zsf38NYzo5Q

 

It’s not that CIWS is any less accurate than any other weapon – it’s not!  It’s just that hitting a moving target (even a relatively large target like a boat as opposed to the frontal aspect of a missile) from a moving platform is very difficult.  There are literally dozens/hundreds of factors that affect accuracy and most of those factors are not measurable or controllable.  Worse, those factors are dynamically interrelated meaning that the relationships between them changes as their magnitude changes.  We do the best we can to write software to predict the aim point but our best software efforts are still very poor, contrary to so many people’s belief that a simple software calculation guarantees one shot, one kill type of accuracy.

 

If we can’t hit a giant (relative to a missile’s frontal aspect) boat, how can we consider going to larger caliber rounds with less inventory and slower rate of fire?  This is also why 5” guns are simply not effective anti-air weapons despite any overblown manufacturer’s claims.

 

 

Summary

 

To sum up, the job of a close in weapon system is not to vaporize an attacking missile but to render it non-explosive and, to the extent possible, as physically degraded as possible.  If the CIWS can vaporize the attacking missile, all the better but that is not the minimum requirement. 

 

The myth of debris continuing on, striking the ship, and doing significant damage is a complete fallacy.  Debris myth-holders also lose sight of the fact that, even if the worst were to happen, it is still far preferable to be hit by small, unpowered, slow, non-explosive, pieces of debris than an intact, functioning, explosive missile.  This is symptomatic of today’s tendency to criticize as worthless any weapon that cannot do a guaranteed, 100% perfect job.  This is why critics decry armor just because it can’t totally stop every weapon ever made, while ignoring the overwhelming benefits armor bestows by containing and mitigating the extent of damage.  This kind of shortsightedness is crippling our ability to field highly useful and beneficial systems that are less than perfect.  As we say - but actually do the opposite - perfect is the enemy of good enough.  CIWS is plenty good enough.

Burke Close In Defense

Here’s a simple awareness post.  Are you aware that our main (and only!) surface combatant has almost no close in self-defense weapon fit?  It consists of a single aft mounted CIWS and … nothing else.

 

As an example, here is a photo, dated 13-Oct-2009, of the USS McCampbell (DDG-85) showing the single aft mounted CIWS and … nothing else.

USS McCampbell - Note the single CIWS aft.

 Again, here is a Jul 2016 photo showing the Spruance and Momsen with no forward CIWS.

Spruance and Momsen without forward CIWS

Lest you think there was some temporary shortage of CIWS and that the ships have since been equipped, here is a photo of USS Nitze (DDG-94) dated 12-Oct-2020 and it shows the same single CIWS configuration.

USS Nitze, DDG-94

Although exact information is hard to come by it appears that DDG-51 to DDG-84 have two CIWS and DDG-85 on have only a single CIWS.  None have RAM or SeaRAM.

Alternatively, SeaRAM appears to have been installed on four Burkes (DDG-64, DDG-71, DDG-75, DDG-78) in place of their CIWS. 

 

Here is a Feb 2021 photo of USS Carney (DDG-64) showing a SeaRAM in place of the aft CIWS mount.

USS Carney with aft SeaRAM in place of CIWS

I don’t know whether the Navy’s experiment with SeaRAM will be continued and expanded or not.  New construction ships do not appear to show any SeaRAM so I’m assuming this is a dead end trend but we’ll see.

So, what’s the problem with only a single close in weapon system?  As we’ve previously demonstrated, naval anti-air engagements are likely to start at the horizon rather than hundreds of miles out as the Navy seems to believe (see, “Detection and Engagement Range”).  That means there will only be time for a few defensive missile launches which, in turn, means that close in weapon systems will assume vital importance.  Given the likelihood of saturation attacks and the number of missile likely to get through the very brief medium range (horizon) ESSM engagement zone, large numbers of close in weapons will be needed.  A single CIWS is going to be quickly overwhelmed.

 

The more recent CIWS versions have a ready magazine of 1550 rounds and a firing rate of 4500 rds/min.  That means the CIWS has a total firing time of 20 seconds before the ammo drum is depleted.  Even if one optimistically assumes, say, 5 seconds per engagement, that’s only 4 engagements before the CIWS is rendered inoperative due to emptying the ammo drum.  Yes, the drum can be replaced but that is a manual operation and time consuming.  Any attack will be over long before reload occurs.  The arithmetic makes it painfully obvious that a ship needs several CIWS to have any chance of survival.

 

Another problem is CIWS coverage area.  As you can see, the aft CIWS covers only the aft 180 deg or so sector.  Our main surface ship doesn’t even have full 360 deg close in defensive coverage!  If a missile approaches from a forward aspect, Burkes have no close in defense whatsoever!  Our main surface warship has no close in defensive coverage for half its aspect??!

 

I wonder if the lack of CIWS installations is the result of the Navy having bet – and lost! – that fully functional AAW lasers would be available by now and that the Navy could, therefore, save money by not installing CIWS?  That’s pure speculation on my part but it certainly fits nicely with the way the Navy thinks, doesn’t it?

 

 

In any case, we need to immediately begin adding CIWS and/or SeaRAM mounts to our Burke class destroyers.  We might also begin considering new forms of close in AAW defense (see, “A New AAW”).

 

Cruise Missile Characteristics Related To Detection and Engagement Range

The US Navy is committed to an anti-air warfare path of long range intercepts using the Aegis and Standard systems.  The wisdom of this is debatable for a variety of reasons.

Long range intercepts depend on being able to detect the target at long ranges.  You can’t engage what you can’t see!  For targets that obligingly fly at high altitudes, this is a viable approach.  For targets that fly at low altitudes or are less detectable due to small size and/or stealth, this approach is not feasible.  Unfortunately, the trend in anti-ship missile (ASM) technology is towards stealth and sea-skimming altitudes.  Many missiles have options for an initial high altitude cruise phase followed by a sea-skimming attack phase.  The question is how far out from the target does the cruise phase terminate and the sea-skimming attack phase commence?  If the cruise phase terminates and converts to the low altitude attack phase beyond the effective range of defensive missiles then the ASM is, for all practical purposes, a purely sea-skimming missile.  This is what seems to be the typical case today.  Thus, it is quite likely that a defending ship will never see, or at least not have the opportunity to engage, the attacking missile until it enters the radar horizon (20 miles or so).

Another problem with the Navy’s long range intercept path is that it’s very expensive.  For example, the Standard SM-6 costs around $4M each and has a claimed range of 150-300 miles.  Launching volleys of $4M missiles quickly becomes prohibitively expensive.  Of course, the cost of a volley of $4M missiles is, arguably, a bargain if it prevents the destruction of a multi-billion dollar ship!  Still, the price tag of Standard missiles does impact the budget and the number of missiles procured. It’s not just the missiles that are expensive.  The Aegis system that enables the Standard missile costs hundreds of millions of dollars and the developmental costs for the ever-changing software are astronomical.

Before we go any further, let’s take a moment to look at some characteristics of common potential enemy anti-ship missiles as provided by readily available open source information.  Note the attack altitudes and relatively small sizes.  These missiles will be hard to detect and engagement windows will be very short.

C-801

Speed   Mach 0.75

Flight Altitude  <20 m

Attack Altitude  <20 m

Range  40 km

Length  5.8 m

C-802

Speed  Mach 0.9

Flight Altitude  7 m

Attack Altitude  5 m

Range  120 km

Length  6.4 m

Exocet

Speed  Mach 0.92

Flight Altitude  2 m

Range  72-180 km

Length  4.7 m

P-270 Moskit (SS-N-22 Sunburn)

Speed  Mach 3.0

Flight Altitude  20 m

Attack Altitude  <7 m

Range  90-240 km, depending on version and flight profile

Length  9.7 m

P-700 Granit (SS-N-19 Shipwreck)

Speed  Mach >1.6

Flight Altitude  high

Attack Altitude  <25 m

Range  625 km

Length  10.0 m

P-800 Oniks (SS-N-26 Strobile)

Speed  Mach 2.5

Flight Altitude  high

Attack Altitude  10 m

Range  370 miles

Length  8.9 m

Kh-59 MK (AS-13 Kingbolt)

Speed  Mach 0.8

Flight Altitude  7 m

Attack Altitude  ?

Range  285 km

Length  5.7 m

BrahMos

Speed  Mach 3.0

Flight Altitude  high

Attack Altitude  5 m

Range  280 miles

Length  8.4 m

Even if not designed as stealthy airframes, ASMs are small and have an inherently small radar cross section.  A small missile, in sea-skimming mode, down in the wave clutter, will not be readily detected.  First detection is likely to be inside the radar horizon.  Even the presence of an airborne radar plane will not greatly increase the detection range of an incoming sea-skimming missile. 

Also, detection and targeting are two separate issues.  An airborne radar may detect a missile further out but being able to maintain a steady lock sufficient to guide a defensive missile is another matter and likely will not be achievable until the attacking missile has gotten much closer to its target.

What is the overall point of this discussion?  It’s that I suspect that the actual targeting detection range of most ASM’s is going to be very short.  That being the case, one can’t help but ask whether the Navy’s focus on very long range Standard missiles is appropriate.  It would seem that the Evolved Sea Sparrow Missile (RIM-162 ESSM) would be a more likely and useful defensive system.  ESSM range is given as 27 nm which would seem to be an appropriate match to the expected detection range.

In fact, I have doubts that intercepts at ranges of hundreds of miles are even feasible given the cruise characteristics of enemy anti-ship missiles.  What enemy missile or aircraft is going to fly obligingly high, straight, and level for an extended period while we guide a Standard missile to it?  Ballistic anti-ship missiles do fly predictable paths and, for those, long range intercepts are both feasible and desirable – but that’s another topic.

If my conjecture is correct and the vast majority of anti-ship cruise missile engagements are going to occur at radar horizon ranges, shouldn’t the vast majority of our defensive systems also be optimized for those same ranges?  Wouldn’t it be better to emphasize ESSM defenses over Standard missiles?

Further, given engagement ranges of radar horizon and closer, shouldn’t we also greatly beef up our short range engagement capabilities such as RAM, SeaRAM, and CIWS?  Sure, debris from a successful short range intercept may still impact the ship and cause damage but it will be a lot less damage than having an intact, functioning anti-ship cruise missile hit the ship.  Consider that most Burkes have only a single CIWS for close in defense and, for a time, Burkes were built with none.  Burkes do not mount RAM/SeaRAM.  Our short range defenses are lacking, to put it mildly.

We need to do several things to beef up our medium range (out to 30 miles or so) AAW capability.

1. Install multiple RAM/SeaRAM launchers on every ship.
2. Provide at least 3 CIWS for every Burke.
3. Focus on electronic anti-missile defenses (soft kill).
4. Develop radars/sensors optimized for medium/short range use.
5. Develop methods to effectively launch and utilize high density volleys of ESSM and RAM.  This would include the ability to track the incoming target even in the presence of high clutter returns due to near miss defensive missile explosions.  Given the short engagement window, it is vital that we can continuously track and engage rather than have to wait for the radar picture to clear after a near miss.  The traditional engagement sequence of shoot-shoot-look is no longer viable.  The engagement sequence has to be shoot-shoot-shoot-keep shooting!  We also need to be able to track the incoming missile in the presence of many outgoing missiles.

The last point also suggests that Aegis is likely not the optimum AAW radar.  We don’t need bigger and longer range AMDR radars (well, we do for ballistic missile defense but, again, that’s a topic for another post); we need very high definition, very rapid response, enhanced capability medium/short range radars combined with much greater numbers of medium range ESSM and integrated fire control systems.  We need to greatly reduce our emphasis on Aegis/Standard and put far more emphasis on medium range engagement.

We also desperately need to improve our AAW electronic countermeasure (ECM) capability.  The venerable – and never all that effective, according to reports – SLQ-32 needs to be enhanced far beyond even the current SEWIP (Surface Electronic Warfare Improvement Program) block improvements.  We need massively more capable and powerful detection and active jamming/decoy systems (remember our discussion about an electronic warfare version of the Zumwalt?).

In summary, future naval AAW engagements are not going to be the long range intercepts that the Navy has designed for – they’re going to radar horizon, close range, short window, affairs that require an optimized radar fire control system capable of operating a continuous fire defensive system, backed up by extensive short range and ECM capabilities.

CIWS Support Contract

Here’s an interesting contract related to the Phalanx CIWS.

“Raytheon Co., Tucson, Arizona, is being awarded a $159,958,743 firm-fixed-price contract for MK 15 Close-In Weapon System (CIWS) upgrades and conversions, system overhauls and associated hardware.  … This contract includes options which, if exercised, would bring the cumulative value of this contract to $461,712,911.“

I’m surprised by this.  I had thought the CIWS was considered obsolete by the Navy, being superseded by the RAM/SeaRAM system.  The announcement did not specify how many systems were covered under this contract but it’s quite a bit of money, regardless, for a system that is being phased out.

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.

Counterbattery Fire

We previously discussed the conceptual origins of the LCS as presented in a Proceedings article (1).  Read the post, here.  The Proceedings article is one of the best naval writings I’ve read in recent years.  I urge you to find a copy of the magazine and read the article in its entirety.  One of the aspects of the original LCS concept that we mentioned but did not dwell on was the ability to conduct counterbattery fire.  I’d like to examine that concept in more detail.

The article listed several capabilities that a littoral vessel should have and one of them was the ability to conduct counterbattery fire.  The article had this to say about the conceptual vessel,

          “It should have some kind of counterbattery capability to respond in real time to
           a shore-based missile attack.”

The original LCS concept, as we see, was to include the ability to stand in littoral waters and fight back against shore-based attacks on ships.  The key phrase is in the quote is “… respond in real time …”.  Thus, the littoral vessel would identify an attack, backtrack its point of origin, and conduct counterbattery fire before the launch site or platform could relocate.

Think about this capability for a moment.  What is the Navy’s biggest fear (well, one of them at any rate) in conducting amphibious operations?  Why, it’s the land-launched anti-ship missile.  That’s the reason the Navy is now doctrinally refusing to close with shorelines and why the Marines are struggling to figure out how to get ashore from amphibious ships stationed 20-50 miles offshore.  What if the Navy had a ship that could stand inshore and counter land-launched missiles?  That would greatly expand the flexibility and range of options for an amphibious force or, for that matter, for any force operating near shore for whatever reason.

Of course, a counterbattery-capable ship would not prevent the initial launch of a missile but it would limit the enemy to one shot per launch site or launch platform.  It wouldn’t take long before the enemy would become very reluctant to conduct land-based anti-ship attacks if the result was a destroyed launch platform each time.  Aegis ships would, of course, deal with the missiles that did launch.  That’s what Aegis is designed to do.  The combination of an Aegis missile umbrella and a littoral ship with counterbattery capability to limit launch sites to one shot would make for a pretty effective overall shield for amphibious operations.

 

Counterbattery Fire Needed



Remember the Scud hunts during Desert Storm?  The problem was not locating the launch position;  it was getting ordnance to the position before the mobile launchers could relocate.  An effective counterbattery capability would have greatly changed the conduct of that conflict, though with the same end result.  Inordinate resources were diverted to Scud hunts from other missions with largely ineffective results.

Let’s look at counterbattery fire a bit deeper.  Although not explicitly called for in the article, a reasonable extension of the counterbattery capability would be the application of counterbattery to artillery and mortar attacks as well as anti-ship missiles.  In general terms, ships frequently operate in close proximity to land during passages (canals, straits, and various chokepoints) and other missions.  This creates a vulnerability to artillery and mortar attacks.  Picture a ship trapped in the Panama Canal and having to fight off terrorist mortar attacks.  The ability to conduct counterbattery fire on artillery and mortars would be invaluable.  Further, the ability to actually defeat incoming ballistic ordnance would be very desirable.  In fact, the basis for doing so already exists.  The Phalanx CIWS has been adapted by the Army for land use in exactly that role and is referred to as C-RAM (Counter-Rocket, Artillery, Mortar).  Adding that capability to the Navy’s CIWS would enhance a ship’s ability to operate in near-shore scenarios.

I believe that counterbattery was one of the most important, arguably the most important, of the capabilities in the original littoral ship concept.  Unfortunately, it was never pursued.  Even the aborted NLOS was not a counterbattery weapon but, rather, just a general land attack capability.

While I remain dubious about the actual need for a littoral vessel, if the Navy is determined to pursue such a ship, counterbattery fire should be one of the first requirements.  Counterbattery would also make a reasonable addition to the Zumwalt which is intended to fight moderately near-shore.

 (1) United States Naval Institute Proceedings, “Birth of the Littoral Combat Ship”, Captain Robert Powers (Ret), Sep 2012, p.42