In his very nice forecast on the future use of conventionally powered submarines, Commander Theide’s enthusiasm has led him into unfamiliar territory and thence to intuitive assumptions that are not correct. Straying from the subject of his expertise, he ventures comparisons between battery powered and nuclear powered submarines. He asserts, “It has often been done, but I doubt it to be feasible – and certainly unsafe – to operate even a smaller nuclear boat in confined and shallow waters, when it is probably continuously nailed to periscope depth.” Commander Theide’s non sequitur in this quotation seems to be lost on him. Indeed, large nuclear powered submarines have operated effectively and safely in shallow waters where they were “…continuously nailed to periscope depth”. Though he has acknowledged that nuclear submarines have done just this, he continues without justification, “SSKs can perform these tasks a Jot closer to shore than the SSN”. For those without experience these judgments seem intuitive. But this intuition, no matter how often repeated, is wrong.
Like others who proclaim this aphorism, Commander Theide fails to appreciate that the sizes in question have significance only in relation to the water column and bottom gradient. There relative size is what counts and there the differences are small. All submarines operate around a keel depth of fifty to sixty five feet depending upon sea state and periscope/mast extension. In shallow waters, e.g. 100 feet, the 12 foot difference in draft between a battery powered boat (KILO = 20 feet) and a big nuclear powered attack boat (VIRGINIA = 32 feet) adds little to the challenge of maintaining ordered keel depth. Having power to cope with transients by giving the planes lift is the real key to operating in shallow waters – not the hull diameter.
Similarly comparing the size of submarines to the area in which operating demonstrates the relativity that size makes. For example, at a scale of one inch to one mile, a COLLINS is 15/100 inches long, a VIRGINIA 20/l 00 inches long. On an eight by ten inch plot representing 80 square miles only close examination would detect the difference. The same ·relationship holds in the ocean – and in shallow waters.
The widely accepted assertion that a battery powered submarine with Air Independent Propulsion is stealthier than an SSN relies on instantaneous comparison. Submarines operating on a battery at low speeds are very quiet but in ASW (“Awfully Slow Warfare”‘) the real issue is noise over time. In this context the sounds generated by modern SSNs are also very low but consistently so whereas those from the battery powered submarine must on regular occasions be large.
As Commander Theide emphasizes, “…it is speed that is essential for everything”. He acknowledges that Air Independent Propulsion does not provide propulsion – these devices support only house keeping. If the AIP submarine needs to go somewhere, the battery or the engine must be used. The state of the battery is a constant concern for the skipper of a battery powered submarine; keeping it above 50% or so is the minimum in order to be ready to make such a move. Proceeding at any speed above slow for an appreciable time must be followed by a charging evolution, the give away for a submarine.
Commander Theide repeats another commonly misunderstood characteristic suggesting that conventionally powered submarines are more ” …highly maneuverable at lower speeds …” than nuclear powered submarines. Turning radii are smaller for shorter ships but this characteristic is also related to propulsion power and size of control surfaces. The large control surfaces and big propulsors on modern submarines add maneuverability not only in depth keeping but also in turning radius. However, ASW is NOT dog fighting. Maneuverability for a submarine has meaning only in terms of closing a target or opening a datum and in both cases the advantages of nuclear powered submarines are obvious.
