The article, in the link, is a history of the U.S. diesel submarine. Maybe it can be said that a diesel submarine is about as needed as a rubber beak on a woodpecker, but I believe that we should have a fleet of diesel submarines for coastal defense and other purposes. This would leave the nucs for other operations in "blue water" areas and overseas. Also, the Gulf Of Mexico is a good candidate for diesel submarine operations.
The Wikipedia article Dick V. cites contains the following: "By the early 21st century, the U.S. Navy began to argue for the possibility of procuring modern diesel-electric submarines. The first reason is cost."
Something the US Navy would never do would be to buy a Russian Project 636.3 KILO for what Viet Nam paid for each of their six 636.3 units: $350 million.
If either the Russian LADA Class - or the AMUR 1650 export version - ever pass acceptance trials, get one of those for technical exploitation (noise trials) because it is those classes our forces would be most likely to encounter in any at-sea confrontation.
One approach the Chinese could take would be to use a noisy ROMEO or other out-dated diesel platform to lure in a US nuc and then target the nuc with a torpedo fired by a very quiet KILO lurking near the ROMEO.
You called it Richard, the cost benefit ratio makes it a great idea. The only problem I see, the Diesel boat isn't sexy. With the current push to multi task platforms, selling the coastal diesel boat will be tough.
It isn't the cost to build D/E or AIP submarines. It is the cost to crew these D/E or AIP submarines in addition to the Nucs that makes this difficult.
