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The Navy is investigating adding an anti-ship missile to its submarine force — bringing it inline with the majority of the world naval submarines, the director of Naval Reactors said on Wednesday.In response to a question from the audience at the 2015 Naval Submarine League Symposium, Adm. Frank Caldwell said the Navy was exploring adding the capability to the fleet.“For this audience, I’ll tell you we are considering that and we are taking some some steps to delivering that kind of capability to our submarine force and I can’t really say anymore than that,” he said.The U.S. submarine fleet did use the UGM-84A Harpoon anti-ship missile but that Harpoon variant was retired in 1997. The current primary attack submarines is the anti-ship weapon is Mk 48 heavy torpedo and is limited in its range relative to anti-ship missiles developed and deployed with foreign navies.

Source: U.S. Navy Considering Adding Anti-Ship Missiles Back to Submarine Force – USNI News

The US Navy’s submarine force used to be equipped with both the UGM-84 Harpoon medium range anti-ship missile and the Tomahawk long range ASM.

The problem with using anti-ship missiles from an attack submarine is that subs are single sensor platforms. They rely almost exclusively on the on board sonar. In the case of long range engagements, it’s almost exclusively the passive sonar used to target enemy ships.  But while the passive sonar is quite capable of detecting ships at long range, localizing and classifying targets at long range is another matter. Errors in localization and classification made targeting problematical. And so the TASM was rather quickly withdrawn from service, and in 1997, even the medium range Harpoon was retired from the sub force.

But if a sub can receive targeting information from off-board sensors, that changes the calculation. With multiple offboard sensors capable of providing the targeting information needed, reequipping the sub force with ASMs makes a great deal of sense.

The torpedo will still remain the primary anti-ship weapon of the sub force. But ASMs give the force the ability to attrit enemy forces before the sub closes to torpedo range, which, it should be noted, is roughly analogous to enemy ASW countermeasures range.