In a previous life, I served for two years as the Electrical Engineering Officer onboard an FFG-7 class Guided Missile Frigate (kind of a misnomer, given that the Mk13 "Single-Armed Bandit" missile launcher had been removed a year before I stepped aboard) – a position that gave me a somewhat unique view of the ship, its operations, and the Navy as a whole. One of the interesting pieces of data I acquired in those years was that, like most warships after it, the FFGs had steel hulls (for strength) and aluminium superstructures (for weight reduction), but I never really thought about the significance of that information, or the importance of the "bimetallic strip" that the Auxiliaries Officer was constantly talking about during our Engineering Department meetings (I had enough "fun" keeping a 25-year-old electrical system running when no spare parts for it had been made in 20 years).
However, now that I am older and wiser (or, at least, older), I have learned a few other interesting pieces of data – namely, that you cannot weld aluminium and steel, or at least not easily, and not with any degree of consistency. So how does one bond the hull to the superstructure? With the aforementioned bimetallic strip – take a bar/sheet of steel, and lay it on top of a bar/sheet of aluminium (or vice versa, not exactly sure), and then add a layer of explosive material on top of that. Assuming your science/math/chemistry is right, assuming you spaced everything right, and assuming your detonation velocity is right, you end up with this crazy, unified block/sheet of metal with strange "wave" formations holding the two together. Damned if I understand the full level of complexity involved, but suffice to say, it works.
But that does not solve your entire problem. In addition to not being easily welded together, steel and aluminium simply do not play well with each other – when they are touching, and when they are in the presence of an electrolyte, they create a galvanic reaction, and corrode the crap out of one another. And guess what sea water is? That is right – an electrolyte. Think "two kids in the back seat of a minivan on a long road trip", only on a molecular level… "I’m not touching you! I’m not touching you!" "MOOOOOOOM!" *cough*
Suffice to say the AUXO was mentioning the bimetallic strip frequently to give an update on its condition and scheduled replacement; after all, having the pilot house slip off the hull into the ocean would be kind of… awkward (and I have been through a few storms where that seemed like a very likely proposition).
So where am I going with this impromptu lesson on chemistry, physics, and naval architecture? Well, I learned my lesson about the dangers of galvanic corrosion from my time in the Navy. On the other hand, despite having built too many ships to count with steel hulls and aluminium superstructures, the Navy still does not seem to grasp the concept:
Independence‘s corrosion is concentrated in her water jets – basically, shipboard versions of airplane engines – where steel "impeller housings" come in contact with the surrounding aluminum structure. Electrical charges possibly originating in the ship’s combat systems apparently sparked the electrolysis.
Now, I am not even going to go into the complete and total Charlie-Foxtrot that the Littoral Combat Ship has been and will continue to be for the Navy – that is a topic for a whole ‘nother post. Or series of posts.
Instead, let us look at what happened… This particular variant of the class (there are two entirely different ships contained within the LCS "class" – figure that one out) uses the same kind of propulsion concept that jet-skis do, and apparently the casing around the actual propeller was not getting along too well with the structure holding it in place. I would put my vote on the "electrical charges" being induced from the big, spinning blade pushing lots of water around, but that is just me – I know, all too well, how grounded Navy ships are not, so they may have a point about random charges.
Oh, and in case it was not obvious, the impellers are what makes the ship move, and a warship that cannot move can only be adequately described as a "target" (though I do not know if the corrosion was necessarily bad enough to disable the Independence, but it probably eventually would be).
But the real clincher? Check this out:
Lots of things – major weapons, for one – have been left off the LCS in order to keep the price down. The list of deleted items includes something called a "Cathodic Protection System," which is designed to prevent electrolysis.
Independence will get the protection system installed at the first opportunity, and future LCS will include it from the beginning, according to Pritchett.
Cathodic protection significantly slows, if not outright stops, the corrosion inherent in all galvanic reactions – if you have ever heard of the term "sacrificial anode", this is where it came from. Some ships use electrically-charged systems, some ships use passive systems, and, due to the massive cost overruns for the class, apparently the LCS uses no system.
And now the LCS is quietly dissolving into nothing.
I wonder how much more it will cost to fix this now, than it would have been to do it right (whatever "right" means in this context) to begin with?
There are times – mostly when I hear about guys going back over for their fourth/fifth/sixth/etc. consecutive deployment to Iraq/Afghanistan – that I still feel kind of bad for doing my four years and cutting and running… but then there are times – like when I hear about the Navy having magical disappearing ships – that I am thankful I left when I did. I wish the still-serving sailors of our Navy the very best, but I know, first hand, the hurdles and stumbling blocks they are up against, and I know how… frustrating… they can be at times. And having your ship literally disintegrate around you due to a construction omission… well, that might annoy some people indeed.