Ship Magazine Size
Let’s suppose we’re contemplating a new warship design. Raise your hand. How many VLS cells should the ship have? 70? 100? 125? 150? More than 150? Be honest, now, how many of you said 150 or more? I’m betting it was most of you.
From WWII on, and probably before, how many ships have exhausted their magazines during a naval battle? Very few, bordering on none.
For example, the Guadalcanal naval battles were short affairs, typically lasting minutes and the participating ships sank or retired from battle with relatively little expenditure of their magazine inventories.
The final ship to ship battle that sank the Bismarck
The final battleship to battleship engagement at Surigao Strait
And so on. There may be an example somewhere in history of a ship emptying its magazines but the general conclusion is that naval battles are short and vicious and magazine size is rarely, if ever, a factor.
The situation for land attack is, of course, different. In many amphibious assaults, the battleships and cruisers fired the majority of their magazine inventories spread over days of bombardment but that was a planned event with an orderly schedule for resupply already in hand.
Okay, so how does any of this apply to modern naval battles and warship design?
Well, the most likely naval battle will be an anti-air (AAW) defense against an enemy’s anti-ship cruise missiles. We’ve previously noted that the engagement will most likely start at the radar horizon which we’ll call 20 miles. We further noted that the realistic engagement window would be on the order of 30 seconds. That’s time for a single shoot-shoot-look sequence. So, let’s simplify this and say that a single Burke is attacked by 15 anti-ship missiles. Using a single shoot-shoot-look engagement sequence, we’d need two ESSMs per incoming missile for a total defensive missile requirement of 30 ESSMs. ESSMs are quad-packed so 30 missiles translates to 7.5 VLS cells.
Note that 15 simultaneous attacking missiles is a major engagement and defending against it required 7.5 VLS cells. Suppose a third (say 30) of the Burke’s VLS cells are loaded with ESSMs (120 ESSMs, total). That means the ship can conduct 4 major engagements of the nature described.
We’ve also previously noted that, historically, naval engagements consist of a single battle after which the force returns to base to refuel and rearm. Naval forces simply don’t stand and engage in multiple battles. Yes, there can be multiple attacks per battle and, with that in mind, we’ve just noted that a Burke could engage in 4 such major attacks.
Now, let’s take a moment to consider the reality of a future naval battle. A carrier group, for example, will consist of 3-4 carriers and 20+ Aegis escorts (seriously, you’re not going to expose 3-4 carriers with anything less than 20+ escorts, are you?). Some quick math reveals that 20 escorts, each with 30 ESSM quad-packed VLS cells, totals 2,400 ESSM missiles. A major attack against a carrier group might consist of, say, 60 anti-ship missiles. If not detected until the 20 mile mark, that would require 120 defensive ESSMs. Thus, the group could engage in 20 such major attacks before running out of ESSMs.
We see, then, that the need for AAW defensive VLS cells – the AAW magazine - is small; on the order of 30 cells per ship, if even that. Throw in some cells for longer range Standards, say, 30, and you have a fully equipped and capable AAW escort ship whose magazine, meaning VLS cells, doesn’t need to be much more than around 60. That will have a significant impact on ship size and resulting cost.
Pure AAW escort ships wouldn’t need helos/flight decks/hangars which would cut 130 ft or so from the ship length. You can see that we could build top of the line, pure AAW escorts that would be half the size of a Burke and with 2/3 the number of VLS cells at, one would reasonably hope, half to a third of the cost.
However, this post isn’t about specialized AAW escort ships. The post is about magazine size (VLS capacity). We can see that the trend towards more and more VLS cells is misguided. The odds of ever needing more than a third of the magazine capacity are poor. We’re overbuilding our ships and when they sink, they’ll take most of their magazine with them, unexpended, just as their WWII forebears did. While a WWII ship taking shells costing hundreds to thousands of dollars each is grudgingly acceptable, a modern ship taking, say, 90 cells worth of missiles that cost $1M-$3M each represents a loss of up to $300M dollars. Worse, our current inventories of most missiles numbers around a few thousand, at most. Thus, losing 90 unexpended missiles represents a significant hit to our inventory. This is exactly the same argument that highlights one of the disadvantages of the arsenal ship.
We need to start doing some serious combat simulations and planning and start basing our ship designs on the realities of combat rather than just unthinkingly trying to cram as much as we can into every ship.
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