Attack submarine
An attack submarine is a submarine principally designed to attack submarines and ships. They often have supplementary missions, including cruise missile launching, intelligence collection and delivery of naval special operations forces. They have the naval vessel designation code SS (Ship Submersible), or, if nuclear-propelled, SSN (Ship Submersible Nuclear), are faster and more maneuverable, but often noisier, than ballistic missile submarines.
Technical and doctrinal issues
Blue water vs. littoral warfare
While large submarines, such as the U.S. Seawolf-class, could carry more weapons and supplies than smaller ones, an advantage in independent deep water operations, they are less flexible in shallow water operations.
Propulsion
Command and control
Another major challenge is communicating with submerged submarines. In practice, attack submarine captains have considerable delegated authority. It is generally accepted that UK and US attack submarines, when trailing ballistic missile submarines, have orders allowing preemptive attack if it is believed the target is about to launch missiles.
Most radio waves do not penetrate water well, except in the Very Low Frequency or Extremely Low Frequency bands, which require extremely long antennas. Shore stations transmitting on these frequencies are immense, so a survivable approach includes putting them in special-purpose aircraft, such as the E-6 TACAMO.