Puzzle: What type submarine will have this technology first?
The RN's most advanced nuclear fleet submarines, the T-class are equipped with pump-jet propulsion - a high-pitch, low-revolution propeller much quieter than conventional propeller designs. The U.S.N. traditionally experiments with all technologies of promise.
The Acoustic Research Detachment (ARD) on Lake Pend Oreille has been the primary testing grounds for submarine stealth technology. The Sea Jet is the first surface ship and the first manned model to be tested at the Acoustic Research Detachment, where unmanned submarine models have been tested for a half century.
And, the Navy claims this about its planned DDX destroyer,"... It will be stealthy and as difficult to detect as an attack submarine;"
Now, "The Sea Jet is the first surface ship and the first manned model to be tested at the Acoustic Research Detachment, where unmanned submarine models have been tested for a half century." (Source). Are we seeing a pattern yet?
But what else could it be? Perhaps this (hat tip to EagleSpeak): Navy adds $13M to American Superconductor warship motor contract. Even 'High-Temperature' superconductors use liquid nitrogen (-325 degrees F.) as a coolant.
What will be the refrigeration power source for superconducting propulsion? What ships have ample nuclear power plants and a supreme need for stealth? Was your guess submarines? Mine, too.