[TLAM Strike]

Originally Posted by bottomcrawler

Yes, that's what I said - they would need to be in an array in fairly large numbers. So?

If we imagine each RTG as a regular battery (technically a "cell", but let's ignore that), then we simply connect them in series and parallel as needed, and as many as needed, to get the power required to drive the propeller and move the sub at 2-3 kts.

And who knows? Perhaps it's possible to use a different design, more efficient in terms of specific power and specific volume, if the application is submarine propulsive power instead of power generation for a interplanetary spacecraft.

No power is power. It doesn't matter if its on a submarine or a space probe. All that might be needed is a converter to change power to the same voltage as the sub's electric motors utilize. However there is another downside of an RTG that I just realized, RTGs are designed for a low continuous drain of power while submarine batteries are designed for rapid power surges. In most any contingency a submarine's battery would probably be sufficient, if held down by an aircraft it could bottom or hover until its forced to RTB, in the case of a surface ship the sub has the advantage in weapons range (discounting embarked helos or ASROCS), but the sub still has the option of waiting for the surface ship to leave.

An RTG could drive a sub at one knot at about the same noise level at batteries indefinitely. But whats the point of running at 1 knot forever? The sub is not going to get anywhere nor can it pursue a target, batteries can probably keep a sub going until its safe to snort. If open ocean SSKs (like the Tango) were still being built then maybe having half the batteries replaced by RTGs for long duration creeping could be useful. But in today's littoral environment any submarine encounter is going to be fleeting so the option of months traveling at a few knots isn't necessary and a loss of power isn't likely to result in plunging below crush depth just bottoming and in such a situation emergency lighting is already provided by borosilicate-tritium glow lights, O2 by Oxygen generating candles, and CO2 scrubbing by Lithium Hydroxide canisters.