WesWorld

I'm watching a debate of sorts in another forum so will ask you all this: In a straight-up gunfight*, which ship would you prefer to be on:

-An Iowa class battleship, with modern sensors/comms

-A Zumwalt type destroyer with four (not two) Advanced Gun Systems



*These ships are alone and unescorted. They have no missiles aboard. There is no aerial or submarine threat. Just the two ships and the guns they have aboard.

Are they both in range of the other? The Zumwalt's guns have a significantly longer range (and accuracy at that range) than the Iowa's 16"/L50s.

Let me address this mathematically.

Navwep's entry on the AGS says the gun is capable of delivering 10 RPM, with a projectile weight of 225lbs / 102kg. The Iowa's 16"/L50, by contrast, can deliver ~1-2 RPM with a projectile weight of 1,900lbs / 862kg for the HC ammo. Let's presume, for the sake of fairness, 1.5 rounds per minute for the Iowa's guns.

Working out from there, the hypothetical Zumwalt has four guns and the Iowa has nine. This means that every minute, Iowa can deliver (9 x 1.5 x 1900) = 34,200lbs worth of projectiles, while the Zumwalt delivers (4 x 10 x 225) = 9,000lbs of fire.

As for accuracy, I'm unfamiliar with what the Iowa's guns would currently be rated at, but in the WWII era, 5% accuracy was generally presumed to be decent shooting. With more modern fire control and sensors, let's boost it to 10% accuracy. Let's presume that the Zumwalt's guns, with their guided and modern ammunition, can achieve 50% accuracy.

This means that the Iowa can score 1.35 hits per minute (1.5rpm x 9 guns x 10% accuracy) for a total delivered broadside weight of 2565lbs per minute, while the Zumwalt can score 20 hits per minute (10rpm x 4 guns x 50% accuracy) with a total delivered broadside weight of 4500lbs per minute. Of course, accuracy rates can be fiddled with, up or down, and my guesstimates might not be entirely accurate.

The 155mm projectile might not pierce the Iowa's armour suite, but not every inch of the Iowa is armoured; with that many hits falling on her, she risks a soft-kill as electronics or other systems are damaged. But as the bigger and better-armoured ship, Iowa can shrug off many of those hits. Not so the unarmoured Zumwalt, with a third the displacement; she will be taking some serious body-blows once a minute or so.

...if she's in range of the Iowa.

That's what it boils down to, for me. If the Zumwalt's advantaged by choosing the range, she's going to seriously damage or at least mission-kill the Iowa. If she's close enough for the Iowa to fire back, each ship is going to get very, very badly hurt regardless of who wins.

I think there are a few more parameters to consider.

Zumwalt's guns will not be able to sink thee IOWA because her protected buoyancy will keep her floating, and most likely going. There is no chance Zumwalt can penetrate to Iowa's magazins to cause her go boom. It is also highly unlikely Zumwalt's guns can take out Iowa's main guns except barrels are hit directly.

So Zumwalt can only hope for a mission kill - which is unlikely to achieve if not all rangefinders are taken out. Even then, Iowa may use her guns under local control.

In return, every single hit from Iowa's guns has the potential to be lethal immediately by penetrating into a magazin. Then, it's not Iowa alone that can get mission killed. A 16/50 can easily penetrate into and take out Zumwalt's command center. Deck buckling that blocks a gun is more likely to happen on Zumwalt than on Iowa.

Your equation also does not take care of target area. Zumwalt's modern electronic equipment eats up more percentage of available room than does Iowa's systems.

The Iowa also has 5" guns that may add to her volume of fire if the Zumwalt is close enough. Btw, which ship is faster for a sustained period of time and can choose range? What does a chase situation to volume of gunfire and percentage of hits?

At the given rate of fire - how long will Zumwalt be able to keep up fire against Iowa? What does this do to the total volume of fire brought into target area?

In the end my bet is on the Iowa, clearly. Bigger ship, protected buoyancy, potential for single hit kill and, IMHO, less likely to get mission killed.

Quoted

Originally posted by HoOmAn
I think there are a few more parameters to consider.

Zumwalt's guns will not be able to sink thee IOWA because her protected buoyancy will keep her floating, and most likely going. There is no chance Zumwalt can penetrate to Iowa's magazins to cause her go boom. It is also highly unlikely Zumwalt's guns can take out Iowa's main guns except barrels are hit directly.

So Zumwalt can only hope for a mission kill - which is unlikely to achieve if not all rangefinders are taken out. Even then, Iowa may use her guns under local control.

I'm unfamiliar with the shell performance of the AGS - I suspect that's not released to the public. So while Iowa's armour was proof against 155mm shells when designed, I'm... hesitant to say that she's proof against AGS. I'm shying away from making any absolute statements when my knowledge of AGS is rather limited.

Quoted

Originally posted by HoOmAn
Your equation also does not take care of target area. Zumwalt's modern electronic equipment eats up more percentage of available room than does Iowa's systems.

Nor do my equations account for the fact that the Iowa is significantly larger and thus easier to hit.

Quoted

Originally posted by HoOmAn
The Iowa also has 5" guns that may add to her volume of fire if the Zumwalt is close enough.

That again requires data on the range of the engagement, which tilts the playing field sharply in favor of one side or the other.

Quoted

Originally posted by HoOmAn
At the given rate of fire - how long will Zumwalt be able to keep up fire against Iowa? What does this do to the total volume of fire brought into target area?

Well, according to the info I've seen, the AGS seems to carry about 300-335 rounds per gun, so at max rate of fire, she's out of ammo in thirty minutes. Iowa carries fewer shells (~130 rounds per gun) but they'll last longer, 86 minutes at 1.5rpm.

Quoted

Originally posted by HoOmAn
In the end my bet is on the Iowa, clearly. Bigger ship, protected buoyancy, potential for single hit kill and, IMHO, less likely to get mission killed.

I agree, but not without reservations.

Quoted

Originally posted by Brockpaine

Quoted

Originally posted by HoOmAn
Your equation also does not take care of target area. Zumwalt's modern electronic equipment eats up more percentage of available room than does Iowa's systems.

Nor do my equations account for the fact that the Iowa is significantly larger and thus easier to hit.

Well, how do you get to your 50% hit percentage? You said it is a rough guess but if you calculate it on improved targeting, this should include target size.

Btw, it would be interesting to see if the target area on either Zumwalt or Iowa is larger. Also, is the target area more packed on Zumwalt (smaller hull etc.)?

I read on internet that only 100 out of 650 shells aboard a Zumwalt will be Long Range Land Attack Projectile (LRLAP) with 100+km range and these special projectiles consist of a 11kg shell only, the rest is rocket engine etc. I doubt an Iowa has to fear a 11kg HE shell at all.

Anyway, I doubt the Zumwalt can really stand up against a true BB.

Quoted

Originally posted by HoOmAn
Well, how do you get to your 50% hit percentage? You said it is a rough guess but if you calculate it on improved targeting, this should include target size.

Wikipedia says the gun has a 50m circular error probable, but I missed that figure was for the guided munitions only.

(Frankly, I feel 50% is probably rather high, but at the same time, I pegged Iowa's guns at 10% accuracy, which I feel is probably on the high end of the scale as well.)

I think the most telling point is Iowa's protected vitals, Zumwalt will take serious if not fatal damage on the first hit. It would take a seriously flukey uber-Hood hit to do the same to Iowa. the odds for that are too great to even consider IMO.

Interesting question.

Looking at the AGS entry in wiki, it only lists a high explosive shell...this can at best mission kill. There is also a Navweaps link.

The Long range land attack rocket projectile though is either GPS or INS guided. It flies to where it is told to go. I'm not sure how that works when the target is moving. According to Navweaps, the loadout is to be 70 of these.

Basically, *IF* the LRLA munition can be targeted to hit a moving target, rather than a grid coordinate....the Zumwalt could beat on a Iowa and hope to set it on fire. With it's stealth hull, better radar and similar speed, it seems likely able to engage the Iowa without the latter even knowing where it is, much less being able to close to gun range.

But with 70 rounds, that's only 7 minutes of fire. A 50m CEP means the Iowa fills the middle of the bubble, but there is 32ft to each side that would be misses even if "on". And 70*50%*25lb charge = 875lbs HE. Probably not enough.

Now let's say this is indeed a mandatory gunfight,

so now the Zumwalt is stuck with the Ballistic Long range projectile with a range of 24nm (according to wiki), vs the Iowa's 20nm. That's where the 30kt speed vs. 33kt isn't enough. The Iowa can close the range.

Ok, let's say worse case - Iowa has to charge and engage with just the forward guns, due to either fires, stealth, jamming, or whatever, she has to default to mechanistic WWII level fire control and manages 2% TH chance.

Well, if I'm remembering how to calculate probabilities correctly (statistics *was* >20 years ago), that gives a cumulative 11% chance to hit with the first 6 rounds.
Somewhere in the 7th volley, a little under 5 minutes in the chance of a hit is up to 50%. It doesn't hit 90% until a little over 15minutes in.

In 5 minutes, the Zumwalt can land..5x2x10 = 100....wait, it's running for distance so 5x1x10 x accuracy. Say 50% = 25 rounds. None of which are likely to slow the Iowa. Speed degradagtion from a holy bow or ventilated stacks, fires, there are potential effects.

But the odds would seem to be that the Zumwalt won't land enough little hits to kill before the Iowa lands one. Considering the effects of Graf Spee's 11" hit on HMS Exter, I think that first HC shell landing and spraying splinters about will severely alter Zumwalt's universe. Before that shell, survival or victory are possible, after that shell...it's a matter of time.

So in a "gunfight" scenario, I'll take Iowa

To add to all this, two thoughts piqued my "Crazy-Awesome" sense.

1) Assume, somehow, both ships shoot off their ammunition without a decisive blow.

Which ship would better survive a ramming by the other? (Gonna guess Iowa would have a sizable edge here, too).

2) Zumwalt is going to be another AEGIS ship, and the premise says no missiles....but what about trying to intercept the 16"/50s with SM-2s? (Walter and I know of an anime that has a Japanese AEGIS 'can intercept Yamato's shells)

As to the general question, given that ranges are achieved, I'd think the Iowa could take out a Zumwalt just with the secondaries. Most of that's just in the Iowa being ridiculously over the Zumwalt's weight class.

A more interesting question would be, say, a Des Moines or Worchester with modern fire control, I think.

My 28 centavos

I originally thought that the AGS was the railgun system which could potentially pierce Iowa's armor via kinetic energy alone. But since that's not the case I give Iowa the win here even if missiles are allowed, remember the Iowa's carried both Tomahawks and Harpoons and a CIWS.

Gotta say Des Moines would be a much more interesting matchup.

Slightly off topic. Tom Clancy had Iowa carrying laser guided rounds and a helo to spot for it. Where advanced 16" rounds ever considered for the Iowas? In that case it turns into a Warspite at Narvik scenario...

If Missouri can destroy a alien invasion then I think it'll win hands down!

I'm guessing though that the AP of modern 155mm rounds is probably much better than the kind of shells Iowa was designed to withstand. Who fires first is going to be key, the longer-range AGS is going to make some serious damage on the upperworks, blasting the directors and radar systems, and causing probably some deck penetration too. The secondary 5in twins might get knocked out too and perhaps even damage to the rudder gear is possible. Saything that if the range closes to Iowa's favour then those 16in shells are going to tear up the tincan Zumwalt, although its possible a few might even pass right through hull before exploding. Modern damage control might keep her afloat longer than we think but fire is the main killer to modern ships, look at Sheffield and Belknap. Once fire takes hold things will get messy. Although if Iowa gets in close enough to use her 5in too then its game-over.

Just a thought, what kind of modern SSM would be close in kinetic and blast effects of a 16in shell? I know a few years back over at Warship Discussion there was a debate if Iowa's belt could withstand SS-N-22 type missiles.

Quoted

Originally posted by Desertfox
Slightly off topic. Tom Clancy had Iowa carrying laser guided rounds and a helo to spot for it. Where advanced 16" rounds ever considered for the Iowas? In that case it turns into a Warspite at Narvik scenario...

11" and 13" sabot rounds were investigated, but never actually produced.

http://navweaps.com/Weapons/WNUS_16-50_mk7_pics.htm Last pic on the page.

Quoted

HE-ER Mark 148 (Planned)
13 in (33 cm) extended-range (ER), sub-caliber projectile with sabot. ET-fuzed with a payload of submunitions. Experiments with this projectile were conducted during the 1980s, but development was cancelled in FY91 when the battleships were decommissioned. Projectile weight without the sabot was about 1,100 lbs. (500 kg) and range was to be in excess of 70,000 yards (64,000 m) at a muzzle velocity of 3,600 fps (1,097 mps).

HE-ER Mark ? (Planned)
Another sub-caliber projectile with sabot, this one 11 inches (28 cm) in diameter. This project was also cancelled about FY91. A sketch with additional information for this round is on the additional pictures page.

Way back when the Iowas were reactivated, I did read they were looking at laser-homing rounds for them. At the time, the US Army had an 8" round "copperhead" as I recall, that homed on a laser spot. I presume a similar tech was envisioned for the 16" rounds.

There were a number of various ideas of producing advanced shells for them - the sabot rounds Shin Ra linked to, the laser homing, and rocket assisted.

Sabot rounds were actually tested way back when and did have good range. Navweaps says 1960s, I could swear the archival document* I read was late 1940s they shot a saboted round in the South Pacific.


*my college was a govt depository, and so had old documents accessable in the library. I read the battleship ones.