The United States made the first ever nuclear powered submarine on January 21, 1954: the Nautilus. This basically had unlimited range and the ability to stay underwater for longer periods of time. The reason why is because it wouldn’t have to surface and recharge its batteries. Other submarines were designed to surface and dive occasionally but, the Nautilus was primarily made to remain underwater and barely surface.These nuclear submarines are powered by a nuclear reactor which is located in the rear of the submarine.This nuclear reactor works almost like a steam engine by, heating the water into steam. First, the water is heated and then piped to the turbine, which makes the energy to power the submarine. Then the water that was heated is cooled and recirculated to the steam generator. Following up with that, the propeller of the submarine which is powered by the nuclear reactor, then propels the submarine forward. Just how everything has pros and cons, the nuclear submarine does also. Many pros include of: being highly efficient and economical, being cleaner, not having the need to constantly surface which diesel submarines do to refuel,being way stealthier/quieter, and needing to barely surface to restock its food. However, the cons include of: them being very expensive, requiring specialized equipment, needing the knowledge to both operate it and to maintain, and needing to replace the whole engine compartment when the reactor system is overhauled which is very time consuming and expensive.One reason many countries use nuclear submarines are to help them in wars/fights. Just like in the Cold War where it had three primary roles which was to: perform strategic deterrence patrols, hunt other submarines and carried out special operations. Since these nuclear submarines are so stealthy and equipped to track, they were used to hunt and if necessary,destroy enemy submarines. Also, since these nuclear submarines had incredible range and speed this made them prime candidates to transport special operations teams, such as Navy Seals teams, into and out of enemy territory. Therefore, these nuclear submarines are like an improved version of diesel submarines. They can execute on the economical side and execute on the attack/strategic side.