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:
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.
- 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
adjacent = 5,280 ft (distance to theoretical intercept point)
deviation angle = the angular deviation from the predicted intercept path, in degrees
5 deg = 462 ft
1 deg = 92 ft
0.5 deg = 46 ft
0.1 deg = 9 ft
A simple software update could have an anti-ship missile begin flying a corkscrew pattern after if locks onto a target. This makes lasers useless and gun hits lucky.
ReplyDeleteWouldn't that diminish the missile's own accuracy, likely preventing it from hitting the ship?
Delete"Wouldn't that diminish the missile's own accuracy,"
DeleteNot in the least. Most (all?) modern missiles have terminal evasive maneuvers programmed in.
Another thing to think about is the combined kinetic energy. A relatively slow Zero acting as a Kamikaze was hard to shoot down with a 20 mm gun and the 5" guns were relatively effective once they got the radar fuses in the shells.
ReplyDeleteBut even small impacts can fatally damage faster missiles with more rigid/unforgiving structures.
So the relative advantage of a 5" shell drops a lot as kinetic energy increases, anyway.
I've been thinking about a similar situation where the radars on our destroyers and cruisers are really designed to deal with fast anti-ship missiles that dive from high altitudes like the "Kitchen." The range of the radar is basically the distance where you can detect the missile and launch an SM-2 and have it meet the enemy near the SM-2 max range. Which was important because of the enemy missile speed and SM-2's semi-active homing requires spacing between the interceptors. Time is of the essence with a big pack of missiles.
But today most missiles fly at low altitude below the radar horizon. And all our missiles have or are soon getting active seekers. So a 400 km range radar isn't doing much for you. And I tend to agree with your previous point that ballistic missile defense should be a specialized ship, not on regular destroyers or cruisers. If you halve the radar range then the equipment power/size decreases 16x. That gives you all sorts of options for better handling battle damage, buying more ships, etc.
You're assuming unguided projectiles. The current Strales system uses the DART command guided projectile capable of up to a 40G maneuvers.
ReplyDeleteRandall Rapp
I assume you read this portion of the post?
Delete"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."
Do you know of a single, semi-realistic test involving DART?
DeleteAs far as it' publicaly known there was only one test against subsonic targets, tghere should even be a video around, but that's it and the cost of the Dart ammunition is unknown but it's considered very high, so there is no way to know how many such rounds will be embarked aboard each ship.
Delete"As far as it' publicaly known there was only one test"
DeleteApparently, yet another example of unfounded manufacturer's claims. The vast bulk of history states unequivocally that those claims are substantially incorrect.
Missles aside, for the moment, let's concentrate on why we can't hit a boghammer.
ReplyDeleteThe M1A2 shoots on the move; and very effectively too. That platform seems to accommodate all of COMNAVOPS accuracy factors and has done so for years.
Anyone know how the fire control system for the 5-inch compares?
"The M1A2 shoots on the move; and very effectively too."
DeleteThere are some significant differences. While the tank shoots on the move, it is still a much more stable ride than on a ship. While the ground may rise and dip, it is still a rock solid foundation and the rises and dips are generally fairly small. I'm pretty sure a tank's accuracy would drop drastically if it was pitching AND rolling over several foot waves. Similarly, a tank's target is generally stationary or moving slowly over fairly level, stable ground. If a tank was traveling at high speed over radically rising and falling ground at a target that was also traveling at high speed over radically rising and falling ground, I'm sure the accuracy would drop drastically.
Also, a tank is generally shooting at shorter ranges than a 5" naval gun.
And so on. Lots of differences.
All your comments are valid. Here's a video game explanation of the M1 FCS:
Deletehttps://www.youtube.com/watch?v=s0U80mdfqyk
Gives you some idea of targeting considerations. I've found lots of videos showing the 5-inch firing but nothing on FCS. Yet. I dimly remember 5-inch has a electro-optical setup but don't recall lasers or any other leverage. Inclines me to believe 5-inch guns are 'all eyeball' but I confess I don't know for sure. I hope that's not the case-
"Also, a tank is generally shooting at shorter ranges than a 5" naval gun."
ReplyDeleteThat reality is compounded by the comparative muzzle velocities.
The 5" 54 caliber gun has a muzzle velocity (per wiki) of 760 m/s.
The OTO Melara 76 mm has a muzzle velocity of 915 m/s, which sounds pretty good in comparision.
Until you look at the L44,120 mm cannon from Rheinmetall that is used on the Abrams tank, which has a muzzle velocity of 1650 m/s.
And the L55 that is used on the newest Leopard 2 has a muzzle velocity of 1750 m/s.
Lutefisk
"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."
ReplyDeleteThough not perfect in every instance, proximity fuses are meant to time the warhead detonates so that the target passes through the fragmentation field.
If I understand correctly, one reason 5-inch guns worked as air defense systems in World War Two is a large ship had so many of them. (This is not a suggestion to build a modern warship with a large number of 5-inch guns for the air defense mission.)
ReplyDeleteBlack Shoes and Blue Water by Malcolm Muir, Jr., says the Navy had high hopes for the Worcester and Roanoke light cruisers, which had new 6-inch guns that could be elevated 78 degrees and throw a 100-pount shell up to 51,200 feet in the air. There was discussion of retrofitting existing light cruises and completing the battleship Kentucky with these guns. However, the new 6-inch guns never worked reliably. There also was talk of using the Des Moines-class cruisers' advanced 8-inch guns for air defense. But the book quotes a Navy officer as saying these guns could be elevated 41 degrees, which meant when the threat was within range you couldn't train the guns on the threat anymore. The book also discusses a 3"/70 gun that begun development when anti-aircraft missiles were years away. The 3/70 fell behind schedule which resulted in new ships getting the older 3/50 guns. The book also says the Mk 45 5-inch gun, with its 65 degrees of elevation and maximum 20 rounds per minute of fire was not really intended for air defense but instead naval surface fire support.
After some discussion with CNO I dropped my ideas of updating 5-inch guns to make them more effective against speedboat swarms. I do wonder if there is some value in developing a laser-guided 5-inch shell. This would not be for air defense, but to improve hit probability in the event of a surprise encounter with an enemy warship. (This blog has stated such is a real possibility if everyone starts using passive sensors to avoid detection.)
If the Oto Melara 76 mm DART ammunition actually works, it still might be better used against boats and small warships than missiles. Does anyone really know for sure? It might work against slow airborne threats like helicopters and cheap drones but other weapons may be a better choice in most situations.
One point that's clear from your equation but isn't mentioned explicitly is that the horizontal error at the target is directly proportional to the length of the "adjacent" side. So if the target is 20 nm away (the maximum effective range of our 5 inch naval guns, per Wikipedia) instead of 1 nm, the error at target will be 20 times larger than in your example !
ReplyDeleteThis is probably one more reason why the notion of 1000 mile range guns (with the exception of guided -- and very expensive -- projectiles) is fanciful.
DeleteThe only purpose of "thousand mile gun" projects is pork.
DeleteAt that range, you simply use missiles.
Sure, you can build a "self-propelled super-long-range projectile" or whatnot, but that's just the same thing with a different name, and at the same price.
"Sure, you can build a "self-propelled super-long-range projectile" or whatnot, but that's just the same thing with a different name, and at the same price."
DeleteActually, it might even be more expensive, since a missile launched from a gun must be MUCH more robust than a missile launched the normal way, since it has to survive the intense initial forces of the gun.
"the error at target will be 20 times larger"
DeleteCorrect. Error increases with distance. I chose one mile as representative of attempting to engage a cruise missile under 'close' circumstances (the best case, in terms of least error).
Error is not proportional to distance. Ask any long range shooter and they will explain to you that drift grows really quickly past a certain point: once your ballistic curve has more curve than straight, error becomes exponential so double the range results in 4 times the spread
Delete"I dropped my ideas of updating 5-inch guns to make them more effective against speedboat swarms."
ReplyDeleteI think the 5" gun would be very effective against boat swarms.
But it would be through the use of cluster munitions like DPICM.
The 5" gun can fire about 20 rounds a minute, that could fire a spread that could put a lot of bomblets in the vicinity of a speedboat.
Lutefisk
For what it's worth, the Navy does have a Mark 172 HE-ICM Cargo Round designed for this purpose.
Deletehttp://www.navweaps.com/Weapons/WNUS_5-62_mk45.php
Information is available three-quarters of the way down that page.
DeleteThanks for the link!!!
DeleteLutefisk
@Phil
DeleteI would be interested in the possible effects of these against the sensors and radars of a surface combatant.
A few of these as the first rounds striking a ship might cripple it's ability to fight effectively.
Lutefisk
"I think the 5" gun would be very effective against boat swarms.
DeleteBut it would be through the use of cluster munitions like DPICM."
Have you seen how tiny those sub-munitions are? I have grave doubts that they'd be effective relative to the dwell time issue. I think it would take many, many hits to visibly disable a boat (especially one with a bit of Kevlar shielding) and, if I'm correct, there's the dwell time issue.
"A few of these as the first rounds striking a ship might cripple it's ability to fight effectively."
DeleteAgain, those are extremely tiny sub-munitions and I'm dubious about their ability to inflict significant damage. As I understand it, they're intended mainly for anti-personnel. They would make very tiny holes in equipment. Do we know of any tests against ship-type targets?
The ending of chapter one of On the Gunline by David Bruhn and Richard Matthews describes an A-7 Corsair using the Rockeye cluster bomb with good results against North Vietnamese fast attack boats. But one of these bombs may have been much more massive than a 5-inch shell.
DeleteI used to be inspired by the Otobreda 127/64 mm gun that can fire up to 32 rounds per minute and the Russian AK-130 that fires 80 rounds per minute. I wanted a new 5-inch gun that could fire a t least 32 rounds per minute and put two of them in a turret. I figured this would be a good weapon against speedboat swarms. However, I don't know how well these guns work. Have they ever been used in combat. The Russian gun uses liquid cooling to compensate for the high rate of fire, but how well does it work? I started to think the Mk 45's 16 to 20 rounds per minute isn't bad, and if we develop a new 5-inch gun the goal should be not to increase the rate of fire but to reduce crew fatigue and improve reliability (though the Mk 45 is supposed to be much more reliable than the Mk 42 it was designed to replace).
https://en.wikipedia.org/wiki/Otobreda_127/64
https://en.wikipedia.org/wiki/AK-130
If we developed an armored turret housing two Mk 45 guns the total rate of fire would be 32-40 rounds per minute. Naval surface fire support (NSFS) missions could be accomplished more quickly, and our ships would have an advantage over enemy warships in a surprise encounter. Get those guns on target fast while other crew are preparing an anti-ship missile launch. Lutefisk, in a previous discussion you said launch a torpedo, too--yes indeed! Bring back 21-inch torpedoes.
My favorite anti-swarm weapon is Carlton Meyer's proposed NAVROC.
https://www.g2mil.com/NAVROC.htm
Possibly, the best anti-speedboat weapon in service is the radar-guided Hellfire. It is considered more effective than comptetitors.
https://defense-update.com/20150731_longbow.htm
These posts say the Hellfire is better than nothing but not good.
https://navy-matters.blogspot.com/search/label/Hellfire%20Missile
Would the ESSM or SeaRAM work well against speedboats? Is the Naval Strike Missile good at tracking speedboats (though a bunch of NSM launchers would add a lot of weight to the ship). Are there any good off-the-shelf solutions?
" I wanted a new 5-inch gun"
DeleteDo you thoroughly grasp the dwell time issue? It's paramount as you discuss anti-swarm weapons.
"Do you thoroughly grasp the dwell time issue?"
DeleteI acknowledged that even with an increased rate of fire, a 5-inch gun might not work as well for countering swarms as I hoped. I hope a 76 mm gun with guided munitions would work well for this mission, but I don't really know.
As I understand it, dwell time is the time a weapon system needs to disable or destroy a single target. A 5-inch gun, with its slow rate of fire and a ship's stability issues described in this post, is marginal for countering swarm missions.
Delete"dwell time is the time a weapon system needs to disable or destroy a single target"
DeleteNO!!!! Dwell time is the time needed to visually VERIFY a target has been destroyed. Consider a very likely scenario: a small boat is hit by a fragmentation shell and the crew is instantly killed. It's no longer a threat but you (the firing/defending platform) don't know that because the boat would continue on course and speed. To all appearances, it would be fully functional and still a threat so you'd have to fire another shell(s) and continue doing so until you were absolutely sure it was no longer a threat. Your first shot may well have eliminated the threat but you have to stay on target until you're sure it's destroyed (the boat comes to a stop and/or sinks). That's dwell time.
The problem with dwell time is that while you're firing at the (already dead?) target, the rest of the swarm is getting closer.
The only way to deal with dwell time is to use a weapon that leaves no doubt about having eliminated the threat such as a missile that explodes and, literally, removes the threat from existence.
Small caliber rounds (likely frag) just don't provide the visual evidence of destruction necessary to be sure of the kill and allow you to move on to the next target.
Frag rounds are nearly useless in a swarm scenario. You need a large, no-doubt-it's-dead explosion. A 5" HE round would work nicely but, as we demonstrated in the post, a hit is nearly impossible. A fire-and-forget missile such as Hellfire is a good option.
Do you understand, now, the implications of dwell time and how it impacts weapon selection?
"I think it would take many, many hits to visibly disable a boat (especially one with a bit of Kevlar shielding)."
DeleteIt's a good question, and I don't have a ready answer. I haven't been able to find any information about the Mark 2 Submunition which is used in the 5" cargo shell.
DPICM, for comparison, has multiple types of ordinance.
The two that make sense in this application are the fragmentation and the shaped charge.
The fragmentation is an anti-personnel munition that throws fragments like a grenade.
The shaped charge munition has a HEAT style charge that penetrates a tank through the thin top armor.
Are those enough to obviously kill a speedboat? I don't know.
I would think one of the limitations is the water. A submunition would have to directly hit the boat or else it's explosion would presumably be significantly absorbed by the water.
Maybe it could be timed to airburst a few feet above the surface, thereby increasing the amount of hot shrapnel criss-crossing in the boat's vicinity?
I could see the 5" guns being the first of a layered defense; 5" cluster munitions raining down in the path of the speedboats miles out, then Hellfire missiles, and finally CIWS. (That is one of my considerations of why I'd like Goalkeepers fore and aft on my ships. Those 30mm HE rounds should have a substantial effect on unarmored targets).
Lutefisk
"... those are extremely tiny sub-munitions and I'm dubious about their ability to inflict significant damage."
DeleteA serious question that I don't have an answer for; How much damage is needed to significantly impair a radar of other sensor?
Would explosive cluster munitions be the right choice?
Would they do enough damage to knock out a radar?
Would a 'beehive' type of round be better? Especially one that replaces the anti-personnel 'nails' with a smaller number of heavier 'bolts' hurtling down on the superstructure at high speed?
Is an airbursting HE shell better than either of those?
The key is how much damage a radar can sustain and still function effectively, and that I don't know.
Lutefisk
"Dwell time is the time needed to visually VERIFY a target has been destroyed.... Do you understand, now, the implications of dwell time and how it impacts weapon selection?"
DeleteI think so. To be specific, I'm recognizing the importance of confirming a threat is eliminated. I once saw footage of a Sherman tank losing a fight to a German tank (I can't remember the type). One of the Americans who got out was missing part of a leg. A Pershing tank then stalked the German tank, knocked it out, and then the Pershing crew fired several more shots until it caught afire. Accompanying text said it was learned the hard way that when you hit a German tank, you had to keep hitting it until it burst into flames. Whether or not this is directly analogous to a speedboat, it made an impression. Actually, it is directly analogous if the speedboat has a suicide crew or the threat is a kamikaze sea drone.
"Are those enough to obviously kill a speedboat?"
DeleteNot in a tactically useful time frame.
A frag munition will just put a bunch of tiny holes in the boat. Even if they penetrate a gas line or kill the crew, the boat will continue on for some time. Shredding the engine might produce a fairly rapid deceleration but the odds on that are not great unless the burst is directly above the engine.
A shaped charge would just punch a couple inch hole in the bottom of the boat and the boat would continue on for quite some time before it eventually took on enough water to slow and sink it.
"much damage a radar can sustain and still function effectively,"
DeleteInterestingly, the old style, lattice works, rotating radars (SPS-49, for example) would be largely immune to frag type munitions since they're mostly open space! We saw exactly this phenomenon in Operation Praying Mantis when the US ship's 5" guns were unable to inflict significant damage on oil platforms due to their open, lattice structure.
"if the speedboat has a suicide crew or the threat is a kamikaze sea drone."
DeleteIt's also relevant for swarm boats that have rockets and small missiles. You can't stop just because you think you got one hit. They may still be able to fire their weapons. You have to continue firing until you can be 100% sure they can't continue. Meanwhile, the other boats keep getting closer and closer.
Interestingly, a WWII Fletcher was much better equipped to deal with swarms than any ship today.
"Those 30mm HE rounds should have a substantial effect on unarmored targets)."
DeleteWould they? Are you sure? Or, would they simply punch straight through a very thin and weakly built wood or fiberglass boat without even exploding? We saw this phenomenon frequently in WWII where heavy caliber shells would punch straight through a small ship and not do any real damage. It's possible that a 30 cal round might be TOO much for a tiny little speedboat. I don't know the sensitivity of the fuze mechanism. Would it explode on contact with a paper thin speedboat? I truly don't know.
"Interestingly, a WWII Fletcher was much better equipped to deal with swarms than any ship today."
DeleteI've been a fan of the Fletcher class for some years, after learning how much firepower was packed in a relatively small ship.
"I don't know the sensitivity of the fuze mechanism. Would it explode on contact with a paper thin speedboat?"
DeleteHow sensitive can a fuse setting be for a round that is leaving the barrel at over 1000 m/s?
Of course, the primary purpose of the Goalkeeper would be to hit incoming missiles and any use against speedboats would be secondary.
But I would think that the lightest fuse sensitivity possible would be desirable in both applications; against the speed boat you want to be sure the round explodes on contact, and against the missile you would want the round to explode immediately on first contact to make sure that the combined oppositely moving speeds of the round and the missile don't carry the round past the missile before it explodes.
Lutefisk
An unorthodox solution might be the 20mm starshell developed for small ships by the Brits in WW2. As designed, constant slow traversing firing would provide a constant stream of illumination. It also turned out to be an incendiary weapon against enemy small craft. The burning starshell would penetrate a light hull, fragment, and set anything burnable inside afire.
Delete"Would it explode on contact with a paper thin speedboat? I truly don't know."
DeleteThere's video on youtube of a Russian BMPT doing a live fire demonstration of its 30mm HEI rounds against a schoolbus. The thin body of the bus is sufficient to set off the impact fuses in the rounds, triggering detonation.
(Hopefully in answer to Anonymous). The 20 mm starshell (no parachute like bigger shells) was not designed with a detonator. It started to burn with impressive candlepower (probably magnesium) at a short distance after firing. It would be burning when penetrating the hull of a target.
DeleteI always thought they should investigate fast-burn beehive/fragmentation rocket pods for modern missile defence.
ReplyDeleteIf you put enough metal fragments in front of the incoming missile you should get at least a stability kill given the relative speeds. Unguided in flight would be best to keep costs down.
"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."
ReplyDeleteOP, you've argued before that 16" guns can be a credible missile defense weapon, despite the disadvantages of large guns being exacerbated by 16" rifles. Have you changed your mind on the matter?
If a 57mm gun firing 220 rpm or a 3" gun firing 120 rpm is insufficient, I logically can't see how a 16" gun firing 2 rpm can be a viable missile defense weapon.
You are never going to hit a missile with a standard old-fashioned 16-inch shell, that's just retarded.
DeleteNow if something like a modern Type-3 shell (fragmentation) might at least be worth trying.
Still sounds very tricky since missiles are faster than WWII prop planes, but I'd like to see a realistic test.
"OP, you've argued before that 16" guns can be a credible missile defense weapon, despite the disadvantages of large guns being exacerbated by 16" rifles. Have you changed your mind on the matter?"
DeleteOne of CNO's stories addressed this. He proposed a broadside of 16 inch rounds fired in the general direction of incoming sea skimming missiles, which would have a new type of fragmentation shell that would fill the space between the incoming missiles and the battleships with fragments.
" I logically can't see how a 16" gun firing 2 rpm can be a viable missile defense weapon."
DeleteIt's potentially viable because it's not 2 rpm. It's 9 rounds SIMULTANEOUSLY and each round consists of 2,000 pounds of shrapnel. That's 18,000 lbs of shrapnel in one concentrated area (by the time the second round arrived, the target area would have moved as the target moves). A 57/76 mm gun can put ONE round into a given target area and, assuming a frag round, would generate perhaps one pound of shrapnel.
"You are never going to hit a missile with a standard old-fashioned 16-inch shell"
DeleteNo one has claimed that. The suggestion was that a 16" fragmentation round, fired in salvos of nine rounds, could be effective.
I remembered the WWII "splash barrage" - firing heavy shells into the sea, some way in front of torpedo-bombers, hoping to get them with the big columns of water this throws up. No use at all today: blinds your radar for way too long.
DeleteI believe the Japanese used their main 18" battleship guns as (ineffectual) air defense against American bombers. I seem to remember a fragment of an account that end on, they looked as big as rain barrels.
DeleteYou forgot about time. Arguably the most important dimension to this problem. What you have described is largely a `statics` problem.
ReplyDeleteBut we are talking about moving ships. they have 4 dimensional co-ordinates x,y,z and t (time).
The shell is very much 4 dimensional as its moving very very fast !
Its a fairly difficult problem to get the x,y and z to match, as you have discussed above, but the real trick is the get the x,y and z to match at the same time.
If they both pass through the same x,y and z but at different time we classically call this a "Miss". Rather like if the both existed at the same time but at totally different x, y or z!
The shell slows down and not in nice proportional way, even if it left the barrel at the same speed as the last one, which it didn`t.
And here is the twist we need to "guess" at when the shell will travel to for a given given time, in order guess at where the target might be at that time. Once we get a matching time we back engineer a theoretical XYZ which is invariable a bit of totally thin air with nothing in it at the moment.
Then and only then do we start with all the above malarky. or trying to get the gun to point at said thin air and fire.
To be honest its a miracle we ever hit anything at any range.
Enjoy
Beno
Nope. Didn't forget time. The post examined the case of a single shot. Each succeeding shot is a new, different, single shot aimed at a new location (the 'time' element you refer to).
DeleteThe true impact of 'time' - meaning, the movement and subsequent relocation of the intercept spot - is that it means that only a SINGLE shell can ever attempt an intercept at a given location unless you have insanely fast rates of fire, such as a CIWS with thousands of rounds per minute - and that's why we have CIWS-type systems!
" is that it means that only a SINGLE shell can ever attempt an intercept at a given location"
DeleteYes absolutely. And the intercept point is highly speculative. As velocity and accelerations are the first and second differentials of time. and wont remain constant its all a massive estimate straight off.
(See Heisenburg, you either know where something is at an instant or what its doing, not both. Anyway lets not get tooooo technical.)
This next bit I LOVE.
"only a SINGLE shell can ever attempt an intercept at a given location unless you have insanely fast rates of fire"
If the time between shot differs AT ALL the intercept point changes (unless you take a different path, see simultaneous artillery barrages)
So you would need an infinitely fast rate of fire. I.e. they all come out at once.
I mean you yanks have done some wonderful technical things but arranging for matter to co-exist simultaneously at the same point in time and space, takes the biscuit!
That really IS one hell of a rate of fire!
(Hehehehehe, just joshing with you obvs)
Beno
"If the time between shot differs AT ALL the intercept point changes"
DeleteOf course. I'm simplifying for general comprehension.
The reality, however, is that you CAN get multiple rounds in the EFFECTIVE area simultaneously with a high rate of fire. Bear in mind that frag rounds have a SPHERICAL area of effect and with a high enough rate of fire you CAN get multiple rounds to the same EFFECTIVE location. Setting accuracy issues aside, that's a simple matter of rate of fire relative to the speed of the target.
So, from an EFFECTIVE point of view, we CAN get multiple rounds to co-exist - or at least their spherical areas of effect to overlap which is the same thing.
Heisenberg was an idiot!
I know you were having fun with me and that's fine. It does, however, illustrate one of the great challenges of blogging. The audience's backgrounds are wide and varied. The challenge is to present material with sufficient detail to get the point across but without going into so much detail that you lose the majority who don't have highly technical backgrounds. That means you simplify but, inevitably, some know-it-all will jump in to 'correct' the matter.
DeleteNow I'm having fun with you! :)
;)
ReplyDeleteAnd then there's the human element. A pal of mine was a gunnery officer in the Falklands War. He was ordered to disoblige some Argentinian troops outside Port Stanley. He was muddle-headed with flu, mucked up his calculations, and hit the Cathedral.
ReplyDeleteI'm wondering why smaller caliber rotary guns with extreme rate of fire aren't used in the CIWS role to complement standard 20-30 mm systems like the Phalanx.
ReplyDeleteThe BMG .5in (12.7mm) heavy machine gun round for example, could arguably be made into a 2x6 barrel CIWS that weights the same or less than a Phalanx but
has twice the rate of fire or more and with a much larger magazine. Or a 10 mm caliber with three rotating cannons firing 15000 rounds per minute etc. etc.
With the inaccuracy of naval gunfire, we want to create a wall of lead as our last defence against missiles and it's better to hit the target with a couple of smaller rounds than to miss with all the larger ones.
Such smaller caliber guns whith high rate of fire would also be useful againts ever more present drones.
Since we're likely to be saddled with just a single gun mount for the foreseeable future, maybe this is the time to suggest a return to a twin mount at least? A double ender design is obviously more appropriate for redundancy, but since the helo facilities have taken over aft completely.....
ReplyDeleteThe Italian 40mm DARDO is a twin mount.
Deletehttps://en.wikipedia.org/wiki/DARDO
40mm allows twice the range and airburst munitions with a proximity fuze, unlike the 20mm fired by CWIS,
I was thinking about the 5in gun, but that Ital unit does sound intriguing
DeleteThe DARDO is very interesting! It's like a modern follow-up to the 40 mm antiaircraft guns of World War Two. And it might be more effective against speedboats than the 25 mm and 30 mm chain guns the US Navy uses.
Delete