Joe Buff On The Nuke Vs. Diesel Debate

Submarine author Joe Buff has a good discussion up at military.com (a re-print of an article the originally appeared in USNI's Proceedings, whose current issue features a spotlight on submarine warfare) on the question of whether or not the U.S. should build diesel submarines. Some excerpts:

Proponents of acquiring diesel subs argue that because an SSI is smaller and requires less sea clearance than a nuclear boat, it can penetrate far closer to shore without risk of bumping its nose, dragging its tail, or breaking the surface unintentionally. In reality, however, the differences aren’t that great. The typical SSGN is only about 25 feet higher than a diesel-propelled SSI, and for the Virginia-class SSN the disparity is only some 15 feet. Moreover, the question of how much clearance is acceptable for a particular class of sub depends more on a vessel’s ship-handling and stability than on the size of the boat itself. Submariners say the key to operating safely in littoral areas with a large sub is simply to move slowly.
What is more, the ability of nuclear boats to operate closer to shore can be improved by equipping them with minisized unmanned undersea vehicles or autonomous undersea vehicles (UUVs or AUVs). They can be used as remote robot sensor probes, enabling crew members to scout ahead and combine their survey of on-the-spot conditions with satellite data on local sea characteristics.
Contentions that nuclear-powered subs are less maneuverable than diesels are similarly flawed. Virginia-class subs are equipped with a new computer-controlled autopilot and hovering system that enables them to maintain a specific depth to within one-tenth of a foot and to remain perfectly level in any but the roughest seas. Thus, they can penetrate close to shore wherever the contours of the sea floor permit. Ohio-class SSGNs -- onetime SSBNs that have been converted into SSGNs -- also are very stable. In their former incarnations, they had to be able to fire sub-launched ballistic missiles (SLBMs) over thousands of miles with pinpoint accuracy and recover quickly from each jolt to be ready for another possible launch. As the Ohio-class subs are overhauled, they receive hovering and trim systems enhancements...
...It is also a misconception that submerged, non-snorkeling SSIs can run at their top speeds for long periods. When a diesel submarine accelerates to sprint speed, it draws power from its regular batteries. Once the batteries go flat, the AIP equipment of an SSI’s propulsion system permits cruising at only a few knots. If the captain wants to use the AIP system to recharge his batteries, his speed is even more restricted for quite some time. The reality is that it limits the range of the SSI, making it easier for an enemy nuclear sub to pursue and destroy the diesel. If the pursuing nuclear boat gets into trouble, its superior mobility and its wider array of available countermeasures (and burgeoning arsenal of “stand-and-fight” weapons such as sub-launched anti-air Sidewinders and anti-torpedo torpedoes) will enable it to defend itself if necessary, withdraw to deep water and later repenetrate the littoral area at a more opportune time. While an SSI must use its fuels carefully and recharge its batteries frequently, a nuclear boat can recharge its minivehicles (its UUVs and AUVs) indefinitely.

Read the whole thing. (You can also read Joe's other essays here.) I agree with Joe that lowering ourselves to the technology level of our potential adversaries isn't a smart move, but I would add one thing. Joe says that diesel subs can be built for 3 to 5 times less that nuke boats, but I'm thinking that when you add in all the SubSafe and fancy coner gear that U.S. subs really can't do without, you'll find that an American diesel boat would come in costing more than half of what a Virginia costs. And personally, I'd rather have one SSN than two AIP diesel boats if I was in a fight -- speed is life.

Bell-ringer 1115 12 June: Jim C. wrote more about this topic back in November.