The utility of nuclear attack submarines

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I'm on record being no great fan of sea power as we know it, and befitting this background I'll take a contra view on nuclear attack submarines:

Nuclear attack submarines (SSN) are among the most expensive warships due to their size, their nuclear reactor and the market forms (only one or two suppliers per country that feel safe in the knowledge that the government wants to sustain them as strategic industry). A Virginia-Class SSN costs more than USD 2.5 billion, that's about as much as six more stealthy Type 214 submarines with air-independent propulsion.

The submarine fans and branches pretend that submarines are good for much, but their qualities are really mostly in killing other nuclear-powered submarines or surface ships other than really good ASW ships.
Special forces delivery and recovery is an extremely rare activity (the last notable examples were beach reconnaissance ahead of amphibious landings by divers in 1944/45).
The submarines' numbers are quite insufficient for playing much of a role in air crew rescue at sea (an important submarine task in the Pacific War).
What little reconnaissance and espionage such submarines do usually serves mostly themselves (recording sound profiles of warships, for example).
Land attack with cruise missiles launched from a submarine is almost expensive way to hit such targets because such encapsulated submarine launched missiles cost roughly twice as much as air-launched or (surface) shipborne cruise missiles.

Thus I'll pretend here that nuclear attack submarines are almost all about destroying ships, for their other capabilities matter little in wartime.

USS California SSN-781

The ability to destroy ships is not an exclusive one; air power can actually engage surface targets better with missiles (such as a combination of anti-radar and anti-ship missile attack, followed-up with heavy laser-guided bombs to sink a damaged ship), and it can do so over a very large maritime area and quickly. A submarine needs to be fairly close tot eh target unless it launches missiles at a distant target based on third party target data.

The submarines' exclusive capabilities are thus all about

1. hitting ships or submarines with heavyweight torpedoes
2. strikes in areas denied to friendly naval and air power (including under ice)
3. only underwater ASW unit capable of cruising at high speed

Torpedo strikes are very, very difficult to judge. We know for certain that a single torpedo hit has a devastating effect on mid-sized warships if not all kinds of warships (see test on a small frigate type here).
On the other hand, modern guided torpedoes were never used in combat to good effect. The British sunk a WW2 vintage cruiser in the Falklands War with a SSN, but it used WW2 vintage torpedoes for this. The Argentinians used a then-modern non-nuclear submarine with guided torpedoes, but technical malfunctions kept it from hitting anything (and it possibly attacked false contacts anyway).

Heavyweight torpedoes might be total duds against 1980's and newer warships due to their countermeasures; the public wouldn't know, and even the navies may be limited to knowing how well their own countermeasures and countermeasures of friendly navies work against their own torpedoes.

Strikes in areas denied to other friendly forces is a hot topic for "underdog" navies, as these often times cannot do much else than defensive minelaying and submarine patrols without suffering from excessive attrition rates. This isn't what the SSN operators are really paying much attention to, though. Instead, SSN are supposed to engage hostile naval forces (and especially SSBN) where other assets can't, even though said other assets can cover huge maritime areas.*

This leads to a very high level question: Should SSBN (submarines with missiles to attack land targets  with thermonuclear warheads) be attacked in wartime, or even only be threatened in peacetime?

The intuitive answer is to wish for the ability to knock out the potentially hostile SSBN in order to eliminate a terrible threat. A single SSBN is typically powerful enough to ruin an entire country. A single Delta IV SSBN may unleash the power of 64 or more 100 kt TNTeq-rated thermonuclear warheads, eliminating dozens of inner cities. That's like all the deaths of the First World War caused in thirty minutes and focused on one country.

A less intuitive answer serves navy bureaucracy interests much less: You cannot reliably eliminate all such SSBNs. That's the main part of their sales pitch, after all.
Detected attempts to gain that ability will provoke countermeasures. The worst of this is that to threaten what's known as "second (nuclear) strike ability" (the ability to attack with nukes after your country was attacked with nukes) may provoke the hostile political leadership into considering or even actually ordering a preventive first strike.

This really, really bad case scenario didn't happen during the Cold War, of course. Yet how could one possibly claim that the maintained ability to engage SSBNs with SSNs was of any use throughout the Cold War? There's no way how this serves to prevent rather than provoke nuclear war, and evidently nuclear attack submarines never destroyed SSBNs for real.

I am convinced that SSBNs should under no circumstances be threatened, so their political leadership never feels that its second strike capability is in question.

There is one more exclusive ability of nuclear-powered submarines; they can cruise at the same speed as surface convoys and are thus the only submerged units that can help the ASW effort of convoys. The SSN needs to be at considerable depth to do so, for otherwise the combination of required speed and depth (water pressure) may lead to treacherous (loud) supercavitation at the screw. Noise is generally an issue with this method of escorting; a threat submarine may sit idle in the water of move very slow and very silently on battery power only, while the SSN (with equal technology SSN are louder than conventional submarines) needs to maintain a quite high speed of 15 or more knots for most of the time. The escorting SSN is inherently disadvantaged against a threat SSI. Furthermore, the SSN's odds of actually detect a threat are marginal, especially considering the effective range of modern torpedoes and submarine-launched anti-ship missiles (20 and more nautical miles). Their range leads to a very long circumference around the convoy at which pickets would be needed to reliably detect threat submarines before they can attack the convoy. There's hardly ever more than two SSN even with a carrier battlegroup.
A SSN may literally pass by a hostile SSI at a nautical mile distance of less without detecting it. So I conclude that this "SSN as ASW escort" concept (which was really only applied with USN carrier battlegroups as far as I know) is terribly cost-inefficient.

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So what was or is the utility of SSNs?

They did, do and could do a myriad of things that could have been done cheaper with other naval (and especially air power) assets. That's about it. It's very little utility compared to the extreme expenses.

A modern non-nuclear submarine (SSI) is already a very expensive unit. The usually much bigger SSNs have always been extremely expensive. Extremely expensive units require a clear and preferably obvious raison d'être. SSNs don't have it.

S O

defence_and_freedom@gmx.de

*: Which begs the question; what is it worth to have a handful of submarines this far from friendly bases that friendly, midair-refuelled strike aircraft cannot engage them with a reasonable mission profile?Why care about targets that far away at all?

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