Here is an inside look at a U.S, Navy submarine, where deployments underwater usually run 90-days. There are three major types of submarines in the United States Navy: ballistic missile submarines, attack submarines and cruise missile submarines. All combatant submarines are nuclear-powered. Ballistic subs have a single, strategic mission: carrying nuclear submarine-launched ballistic missiles. Attack submarines have several tactical missions, including sinking ships and subs, launching cruise missiles, and gathering intelligence. Continue reading for a video and more information.