A nuclear submarine is an amazing machine. Imagine how difficult it is to design a seaworthy vessel that can travel to great depths beneath the surface, launch ballistic missiles while underwater and maintain the life functions.Diesel submaraines typically cost anywhere from one quarter to a half of nuclear subs. They are also easier to maintain, easier to sell to a public often set against nuclear power, and, can stay submersed for up to a month. However Diesel subs are suited for small shallow

sea, with straits and needs to be in the vicinity of its target. Its frequent surfacing, makes them highly vulnerable to visual, acoustic and radar detection But when rapid movements over long ocean distances are required, nuclear propulsion is the desired choice  The nuclear reactor also supplies power to the submarine's other subsystems, such as for maintenance of air quality, fresh water production by distilling salt water from the ocean, temperature regulation, etc. Submarines may carry nuclear fuel for up to 30 years of operation. The stealth weakness of nuclear submarines is the need to cool the reactor even when the submarine is not moving; about 70% of the reactor output heat is dissipated into the sea water. Another problem is that the reactor is always running, creating steam noise, which can be heard on SONAR. Does a nation invest in expensive nuclear powered subs or opt for cheaper diesel operated vessels? A nuclear Submarine force is the right option for countries with large oceans to patrol.