Monday, June 13, 2011

Gulliver? More like Dulliver! Exciting expert guest-post analysis of, uh, submarine stuff

Gulliver here: As some readers may know from past allusions, my brother is an active-duty line officer in the U.S. Navy. He's just as wonky and opinionated as I am, but less obnoxious; most importantly, he's almost certainly possessed of more useful technical knowledge than I. It frequently happens that I read something about shipbuilding or maritime security or China's naval buildup and write him to say "man, I can tell this is wrong, but I don't know enough to really say why, so fill in the substantive rationale for my pre-formed analysis, please." He finally took me up on one of my repeated invitations to write something for us, and I hope he'll continue to do so from time to time in the future. I've edited him slightly (which will surely infuriate him) and added a few bracketed comments to de-wonk just a little bit, provide context, and make it more suited to a general audience.

Has China built a new stealth special operations submarine?

A few weeks ago, Galrahn at Information Dissemination published some recent pictures of a new PLAN submarine. It’s clearly the same boat launched at Wuhan Shipyard in September, somewhat hilariously postulated here to be a “Chinese stealth submarine.” I’d like to address a few of Galrahn’s hypotheses.

The thing I have the least trouble agreeing with his initial reaction: that it’s reminiscent of a GOLF SSB. The long sail is the strongest clue for me that it is, in fact, a GOLF SSB replacement – most likely intended as a one-off submarine-launched ballistic missile (SLBM) test platform. There’s simply no reason for a sail to be that big unless you’ve put something inside it. [To clarify, what he means here is that it's plausible that the sail is so big because it covers ballistic-missile tubes.] The sole purpose of the sail is as a fairwater to cover the access trunk to the bridge hatch, the masts and antennas, and any other installed equipment. The American LOS ANGELES SSN sail contains an access trunk, 5 masts and two periscopes. It’s just big enough to cover these things. 

Galrahn speculates that the larger sail could be a storage area for “special operations equipment,” but there’s no reason this equipment couldn’t be stored inside the pressure hull. Either the equipment there would be exposed to the sea or the whole sail would have to be hardened to withstand submergence pressure. I’m not sure what the point would be, especially if the vessel's hull was purpose-built for specops and not simply an older design modified to that end. The sail would have to be opened while at sea, probably while submerged, to access whatever equipment was stored there. This introduces new complications. If the purpose is to stow equipment protected from the elements, then the opening would need to be above the water line when you open it – so you can’t do it submerged and covert. If it’s open to the sea, what are you putting in there?  Rubber boats? A little teeny self-propelled spec ops delivery vehicle?  This is how U.S. boats carry their spec ops equipment. The large sail hatch to which he refers is just what it looks like: an access hatch. It’s in the free-flood area of the sail and is used for personnel and equipment to access the masts and antennas that are housed inside. ["Free-flood" means that water fills this portion of the sail when the submarine goes to depth -- it is not protected from seawater.] The whole “special operations SSK” idea just doesn’t make sense.

As for the suggestion that it could be intended as a mobile DF-21 [anti-ship ballistic-missile] platform, I initially reacted with skepticism. Surely the missile’s too big, right? Nope – the DF-21 turns out simply to be a land-based version of the submarine-launched JL-1 SLBM, so it's small enough to be taken to sea. But what would be the point? Well, extending the range of the “access denied” area for U.S. forces seems like a pretty good goal, if a little gratuitous. The point of anti-access weapons is to keep opponents away from your stuff – most importantly, to keep an aircraft carrier out of its aircraft’s effective combat radius from Taiwan.  Keeping American carriers out of the western Philippine Sea is one thing; parking a sea-mobile DF-21 east of Taiwan and pushing the carriers further east seems to be a wasteful expenditure of resources. Another important aspect of anti-access weapons generally and the DF-21 specifically is that the Chinese are going to want us to know that it’s there. They’d much rather we just stay out because of the prospect of a carrier getting shot than that they actually have to shoot at a carrier and then we stay out, wouldn’t you think? SLBMs as an assured second-strike ICBM capability: great idea. SLBMs as a hidden anti-access weapon make less sense to me.

It’s not really plausible that this could be initially intended for JL-2 tests and then to carry a seaborne DF-21: the sizes of the missiles are too different. The JL-2 is 2m in diameter and 13m long, while the JL-1 is just 1.4m/10.7m. Based on the size – it’s significantly larger than the YUAN SSK also visible in this picture – it seems likely to me that it’s designed for the bigger missile and will be a SLBM test ship.

Unrelated note: There’s been some recent fuss about the Chinese aircraft carrier and whether it’s a big deal or not. I hope to address this debate in an upcoming post. Teaser: it’s not a big deal, but it’s not the Chinese naval capability that matters to us.

Gulliver again: Personally, I think it's my responsibility to assure you that all of the speculation above is nonsense. The hatch in question is really a bay door for the sophisticated caterpillar propulsion device, a fact that was revealed through consultations with a subject matter expert during hours of imagery analysis, shown here.

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