All in all, there is no question that AIP-equipped boats pose a threat, under some conditions, to the large nuclear attack submarines that many great navies have come to rely on. However, this does not necessarily mean that the best response for the U.S. Navy is to invest in these conventional subs. They cannot do many of the tasks that the navy requires of its submarine force, and in coming years technology may eclipse many of the advantages that they bring.
Over the past decade, air-independent propulsion (AIP) for submarines has spread rapidly around the world.
The technology, which allows conventionally powered submarines to operate without access to outside air, has the potential the shift the balance away from the big nuclear attack submarines (SSNs) that have dominated undersea warfare since the 1950s, and back towards small conventional boats. In global terms, this might again make submarines the great strategic equalizer; small, cheap weapons that can destroy the expensive warships of the world’s most powerful navies.
Does this mean that the United States should invest in these kinds of boats? Probably not.
Invention:
Several navies experimented with AIP during the twentieth century. The earliest work began in World War II in the German and Soviet navies, although none of the experiments produced operationally suitable boats. After the war Britain, the United States and the Soviet Union took advantage of German research to produce their own experimental boats, but nuclear propulsion seemed to offer a more fruitful direction for submarine development.