June 13, 2011

Diesel-Electrics vs. Nucs - round 720823084

This article touches on a question dear to my heart, because I love submarines. However, after reading it a couple of times, I have some problems with the argument being framed here. NOTE: I do not do this for a living, and this is just off the top of my head after reading the article in question.


The first problem is that there are several enormous assumptions embedded in the argument which are never acknowledged much less addressed. Here are a few of them, in my opinion.

The authors speak approvingly of the (lower) cost of AIP diesel-electrics in comparison to the current build class of U.S. SSNs. They quote a cost of $500 million/boat based on a recent sale of 212 boats from Germany to Turkey, and a procurement cost of $2 billion for the U.S. built Virginia class. There are some numbers missing here, however. First, what would the actual switchover costs be? I am assuming, myself, that the authors are proposing that U.S. industry build these AIP boats. If so, how much would it cost to produce a new design and to retool (or tool) yards to produce this new design? Are we confident that the production costs for such a boat in a U.S. yard would be comparable to the production cost in a yard which has been building similar size and technology submarines for years?

Let's look at the price. The $500 million submarine displaces approximately 1,800 tons submerged. The $2 billion submarine displaces some 7,800 tons. The cost/ton of the smaller boat is therefore approx. $277,778. The cost/ton of the larger boat is approximately $256,410. Certainly the diesel boat is cheaper per unit - but does that tell us we need diesel boats, or smaller boats? If nuclear power is that much more expensive, we would expect to see a cost/ton advantage on the diesel boat which does not emerge. Admittedly, the Type 212 is one of the high-end conventional submarines on the market, with fuel cells and AIP - but would we propose building anything less capable? Is it possible to build a smaller nuclear boat, given the similarity in cost/ton? Older nuclear submarines were certainly smaller. Would a smaller nuclear design optimized for littoral missions at the expense of blue-water (as a diesel-electric would be) really be that much more expensive?

What would the cost be of setting up and maintaining a support infrastructure for non-nuclear boats? At a minimum, this would include separate maintenance and logistics tails, along with new and different training for non-overlapping skillsets among crews. While I'm sure that in most cases submariners would be able to move between boats without difficulty, in at least a few engineering tracks the skill sets would not transfer. More importantly, if (as the authors note) the missions of these new boats are primarily in the foreign green water, would a new system of tenders and ports be required to support these boats on deployment? Most current users of diesel/AIP boats employ them within easy reach of home ports. By definition, U.S. Navy boats would not operate in this mode. While I'm certain these boats could self-deploy, what would having consumable fuel requirements do to their deployment ratio, with and without tenders?


As part of their argument for the efficacy of diesel-electrics, the authors point to two incidents in which such submarines performed well against the U.S. Navy. However, neither incident involves the mission areas for which they advocate the procurement of these boats. Penetrating CVBG defenses in the blue-water certainly would be a mission that the U.S. Navy would allocate to its blue-water SSN force. The real question that they are posing with this example then is this - are diesel-electric boats any better at this than U.S. navy SSNs would be?

There are persuasive arguments for the efficacy of the smaller AIP boat in the littorals when compared to the current SSNs of the U.S. Navy. The real question, though, is not whether diesels do that better - but whether they do it better *enough* for U.S. Navy mission profiles (long deployment distances, solo operations in harms way) to make their acquisition worthwhile? If we're mostly concerned with tracking enemy diesel-electrics, are there asymmetric means (better satellite sensors/imagery, better/more aircraft platforms) which might perform enough of that job to make this change unnecessary?

There are many questions which need to be answered besides 'whether diesel-electric boats can do specific mission types better than nuclear boats' before we can begin to understand if this is a profitable direction for the U.S.

For a clearer view of this issue, including a better operational perspective than I could muster, see here!

Posted by jbz at June 13, 2011 4:53 PM | TrackBack

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