|1. Can AIP systems be replenished while underway (i.e. recharge fuel cell, re-fill LOX) or only in-port/tender.
2. Can a Sterling cycle system be used with outside air - can a Gottland recharge it's batteries (not make passage) with snorkel air?
3. If yes to #2, wouldn't a Gottland snorkeling at very low speeds under electric power, recharging it's batteries be damn near as silent as using the AIP under-water? Couldn't the snorkel be radar-transparent/absorbent?
You can see where this is going. Once in its patrol/operational zone if a SSK can snorkel with relatively silent AIP systems instead of diesel then the challenge of maintaining stealth while on station is greatly reduced.
One final thought: Couldn't a SSK be replenished at sea by a Liberty-class LCS and it's SeaHawks? Doesn't take very many sling-loads to get fresh food and supplies to a crew of 30.