The WWII Atlanta/Juneau classes of anti-aircraft (AA) cruisers were a fascinating development. In the initial design discussions, the ships were intended as flotilla leaders but they were quickly optimized for the anti-aircraft role as war established the primacy of aircraft. Based on additional combat experience, the initial Atlanta class was further optimized as the follow on Juneau class.
USS Juneau, CL-119 |
Typical later war weapon fits are listed in the table below.
|
5”/38 dual |
40 mm quad |
40 mm dual |
20 mm dual |
20 mm single |
Atlanta Class |
6 (12 barrels) |
|
8 (16 barrels) |
|
16 (16 barrels) |
Juneau Class |
6 (12 barrels) |
6 (24 barrels) |
4 (8 barrels) |
8 (16 barrels) |
|
Atlanta class had 30 gun mounts with a total of 44 gun barrels of various types.
Juneau class had 24 gun mounts with a total of 60 gun barrels of various types.
The Atlanta/Juneau classes were extremely efficient and effective anti-aircraft platforms, for the time. Battleships, of course, had far larger anti-aircraft weapon fits but they were extremely expensive and we only had a handful of those ships. The AA cruisers offered a cheaper, yet still effective, supplement to the battleships.
The anti-aircraft cruisers had what was, for the time period, a complete fit of long range (5”), medium range (40 mm), and close in (20 mm) weapons providing total coverage and, most importantly, they had large numbers of each.
USS Spokane, CL-120 |
Atlanta/Juneau and Burke Comparison
Weapon Distribution – In comparison to the Atlanta/Juneau weapon densities noted above, a modern Burke has just three defensive mounts (2x VLS clusters, 1x CIWS). Admittedly, a direct comparison of ‘mounts’ is meaningless but it does offer an impression of the density of weapon mounts on a WWII warship versus today’s barely armed ships. The number of mounts is meaningful. A single hit on one of the Burke’s two VLS clusters would eliminate 1/3 or 2/3 of the ship’s total weapons, depending on whether the forward or aft cluster was hit, and just two hits could eliminate the ship’s entire weaponry. This is unconscionable in a warship design.
More importantly, the WWII ships had a balanced and heavy distribution of long, medium, and short range defensive weapons. Contrast this to Burkes which have good fits of long (Standard) and medium (ESSM) range weapons but almost no short range (CIWS) weapons – a shocking deficiency for an anti-aircraft ship.
Armor – The Atlanta/Juneau classes had armor appropriate for their size with nearly 4” side armor and 1-3/4” deck and turret armor.
As in the larger cruisers, the belt armor was split into a wide band over machinery spaces with narrower underwater sections fore and aft over magazines. The inner bottom extended up the side to the (flat) protective deck. Magazines would be separated from the ship’s side by fuel oil aft and by a wiring passage or cofferdam forward.[1, p.233]
In contrast, the Burke class has only scattered Kevlar spall liner protection. There may be some armor surrounding the below deck VLS space, presumably intended not as protective armor but to direct VLS explosions upward rather than inward. I’ve been unable to verify this.
The obvious observation is that the WWII ships were built to stand and fight and were intended to be able to fight hurt, stay in the fight, and remain effective for as long as possible. Burkes are bordering on one-hit mission kills, if not outright sinkings, and have little hope of staying in a fight and fighting hurt. In fact, the experience of the Port Royal Aegis cruiser grounding strongly suggests that the radar array and VLS alignments are so delicate that a single low intensity vibration (explosion shock … or gentle grounding) is enough to render the equipment unusable. See, “Port Royal Grounding Lessons”.
Survivability – As noted, both the presence of significant armor and the weapons density offered a much greater chance of ship survival than the Burke’s nearly non-existent armor and only three weapon mounts. The sheer number of weapon mounts, fire control directors, and local backups on the WWII cruisers guaranteed that the ship could continue fighting effectively even after absorbing multiple hits. In contrast, a single hit on either of the Burke’s VLS clusters will likely render the entire cluster unusable resulting in the instantaneous loss of 1/3 or 2/3 of the ship’s weapons, depending on whether the forward or aft cluster was hit.
On a related note, testing the effects of a typical anti-ship cruise missile on a VLS cluster is one of the many realistic tests the Navy desperately needs to conduct to get a handle on the true combat-worthiness of today’s ship designs.
Conceptual Design – The AA cruisers were the epitome of a focused, single function ship. They were intended to shoot down aircraft and that was all. As the war progressed, extraneous equipment such as depth charges, sonar, and torpedo tubes were generally removed and replaced with additional guns. In comparison, the Burkes are the epitome of do-everything design with the attendant corollaries of do nothing well and cost a lot. In a sense, the Burkes are the epitome of a failed and flawed, unfocused design philosophy.
Conceptual Anti-Aircraft Ship
Let’s take the lessons of the Atlanta/Juneau anti-aircraft cruiser and apply them to a modern, conceptual anti-aircraft ship design and see what we get.
First, what is the job of an anti-aircraft ship? This is not a trick question. The answer is simple … it’s anti-air warfare! It’s not anti-submarine. It’s not land attack or deep strike. It’s not helo operations. It’s not amphibious attack or logistics or harbor tug. It’s anti-air warfare. Pure and simple. One function. Do it and do it exquisitely well. Be optimized for it.
With that single function focus firmly in mind, here’s the weapons and sensors such a ship would have:
- 4x 16-VLS clusters (disperse the risk) with 32 quad packed ESSM (128 total ESSM) plus 32 Standard
- 6x SeaRAM
- 8x CIWS
- 4” side and 2” deck armor[2]
- 2x main fire control radars (TRS-4D or similar)
- 4x backup fire control radars (SPQ-8B or similar)
- Electro-optical back up fire control systems
This conceptual design provides long, medium, and short range anti-air weapons and offers the ability to stand and fight, even when hurt. It emphatically addresses the flaw (well, one of the flaws) in the Burke class which is the near total lack of close in defensive weapons.
There would be no flight deck and hangar as AAW does not require aviation capability. On the Burke, for example, aviation facilities comprise a solid third of the ship’s length (!) and represent significant size, weight, and cost.
There would also be no hull mounted sonar, stern towed array sonar, or ASW function. Eliminating those functions further reduces the size, weight, and cost of the ship.
Being physically smaller, the ship can’t help but be stealthier and some judicious shaping and repackaging (à la Visby) could make it even more stealthy which would make it more survivable and effective in its role. You see how easy ship design should be? All you have to do is pick a primary function, stick with it (and only it !), and the rest is easy. But, I digress …
So, our conceptual anti-aircraft ship will be 2/3 the length of a Burke, have more weapons, and cost a third less! What’s not to like?
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[1]Friedman, Norman, “U.S. Cruisers, An Illustrated Design History”, Naval Institute Press, Annapolis, Maryland, 1984
[2]Armor recommendation is for whatever a modern equivalent to WWII armor thicknesses would be.