Great article, but it states that China does not have any AIP boats. It has been reported on several open-souce sites that the Chinese Type 041 Yuan SSK and the Type 043 Qing class both are equipped with an advanced AIP system. As for their status, they may not be operational at the moment, but as we see with China's naval developments, they will be soon.

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There are a lot of good reasons to re-visit the diesel submarine for the US Navy; not least of which being the perceived advantages in cost savings and a smaller size that makes operation in confined and shallow waters easier.  (The Straits of Taiwan and the Persian Gulf for example.)  But it should be remembered that US Submarines also need to be an integral part of a fleet, and that requires a boat capable of keeping up.  Diesel boats are quiet, but not fast, and while they can dash at speeds up to 25 knots, they cannot do it for long.  The last US diesel boat, the Barbel class, could only hold maximum speed for just 90 minutes, making them useless for anything beyond coastal defense and consequently worthless to a super-power.  The Kilo class (Arguably the most dangerous diesel boat out there.) is even slower with a dash potential of just over 10 miles.  The creation of a new class of diesel submarine would (as far as the US navy is concerned) create a limited use boat with the same problems associated with the navy's dubious flirtation with the Knox and Perry class frigate, which were built with an eye on saving money, but, as it turned out, were no bargain; being too slow to operate effectively with a carrier task force and doomed to early retirement.  The same would happen if the US started building diesel boats... we would have a boat without a clear mission and no ability to function as the unit of a task force.   Add to that the fact that the US navy has the ability to service nuke boats already in place, and it becomes clear that there is no reason for the US navy to re-introduce the diesel.  It would make much more sense to work on further miniaturizing the nuclear reactor until one can be mounted in a smaller hull like that of the Barbel, the 214 or the Kilo.  That would create a more versatile sub, capable of operating in shallow waters, with unlimited endurance at higher speeds, making them also a useful part of a fleet.  IMHO, we should leave the diesel designs to regional powers... Super powers need nukes...

^^ Exactly right

How about magnetohydrodynamics for water flow rather than a pump?   Fluctuating magnetic coil energization makes sea water flow and has been considered as a propulsion method.  Similar to a rail gun in some ways.  We DO need to test our sonar methods but our newer high energy sonar DOES harm sea life including whales and porpoises and dolphins with their ultra sensitive sensing capabilities.  Why not test in the dead zones we have created, such as the Mississippi Delta, where all the nitrogen from fertilizers has killed off the fish and depleted the oxygen levels to the point there is little life there to begin with?   Apparently we do need quieter submarines.  Yet we are short on funding.  And waiting until we find out the hard way that our most likely near future adversary of major concern, China, has AIP and can do great harm to our ships (such as with their high speed anti-ship missiles, both cruise missile style and their ballistic missile type (D5?) that they already have) could have disastrous consequences.