Technology
The main difference between conventional submarines and nuclear submarines is the power generation system. Nuclear submarines employ nuclear reactors for this task. They either generate electricity that powers electric motors connected to the propeller shaft or rely on the reactor heat to produce steam that drives steam turbines (cf. nuclear marine propulsion). Reactors used in submarines typically use highly enriched fuel (often greater than 20%) to enable them to deliver a large amount of power from a smaller reactor and operate longer between refuelings – which are difficult due to the reactor's position within the submarine's pressure hull.
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. All naval nuclear reactors currently in use are operated with diesel generators as a backup power system. These engines are able to provide emergency electrical power for reactor decay heat removal, as well as enough electric power to supply an emergency propulsion mechanism. Submarines may carry nuclear fuel for up to 30 years of operation. The only resource that limits the time underwater is the food supply for the crew and maintenance of the vessel.
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 coupled into the sea water. This leaves a "thermal wake", a plume of warm water of lower density which ascends to the sea surface and creates a "thermal scar" observable by thermal imaging systems, e.g. FLIR. Another problem is that the reactor is always running, creating steam noise, which can be heard on SONAR, and the reactor pump (used to circulate reactor coolant), also creates noise, as opposed to a conventional submarine, which can move about on incredibly silent electric motors.
Read more about this topic: Nuclear Submarine
Famous quotes containing the word technology:
“Radio put technology into storytelling and made it sick. TV killed it. Then you were locked into somebody else’s sighting of that story. You no longer had the benefit of making that picture for yourself, using your imagination. Storytelling brings back that humanness that we have lost with TV. You talk to children and they don’t hear you. They are television addicts. Mamas bring them home from the hospital and drag them up in front of the set and the great stare-out begins.”
—Jackie Torrence (b. 1944)
“If the technology cannot shoulder the entire burden of strategic change, it nevertheless can set into motion a series of dynamics that present an important challenge to imperative control and the industrial division of labor. The more blurred the distinction between what workers know and what managers know, the more fragile and pointless any traditional relationships of domination and subordination between them will become.”
—Shoshana Zuboff (b. 1951)
“Primitive peoples tried to annul death by portraying the human body—we do it by finding substitutes for the human body. Technology instead of mysticism!”
—Max Frisch (1911–1991)