Fuel celled powered SSK units will have big strategic advantage. It'll be likely that old style DIESEL ELECTRIC SSK will be/could be replaced by the FUEL CELL units. Instead of the polluting, smelly diesel engines which needs air intake and prevents the SSK for operating under water for long periods of time, now the SSK can use the
FUEL CELL stack and supplies of liquid HYDROGEN, OXYGEN instead. Using AUTOMATION, ROBOTICS, small crew size from 21 to 30 personnel is required, allowing the SSK to remain submerged for MUCH LONGER PERIODS - powering life support system and adding comfort.
The same UAV, cruise missiles, torpedoes, deep dive submersibles is possible!
Pretty standard operation - NATURAL GAS conversion into HYDROGEN <liquidified>
with standard liquid air production for OXYGEN. This will be used in the POWER PLANTS of NEXT GENERATION SSK's.
The development of such equipment is now seeing FUEL CELLS to be used in URBAN CENTRES all over the world to improve energy efficiency, mostly in the DISTRICT UTILITIES units of several MW of major buildings. Hot water, Chilled water, Electricity - Imagine the benefits and cost reduction in the CITY or in the SSK.