|Fig. 1: Admiral Hyman Rickover. (Source: Wikimedia Commons)|
The nuclear navy is a term coined to describe ships powered by onboard nuclear reactors known as naval reactors. The concept of incorporating nuclear energy to naval vessels revolutionized naval warfare. The broad idea was that these vessels would not need to make routine stops for fuel like their conventional counterparts, being only truly limited by crew endurance and supplies.
The United States Navy recognized the benefits of nuclear energy for propulsion and began its research in nuclear fission from 1942 to 1946, and ultimately through the Manhattan Project. From its humble beginnings it has produced many of the world's first nuclear propelled vessels, from submarines to aircraft carriers.
At the end of the Second World War, the United States sought to develop secondary uses, to the recently developed atomic bomb, primarily nuclear energy and reactors.  Captain Hyman Rickover an electrical engineer for the United States Navy was a resilient proponent for the research. He was particularly interested in nuclear reactors for the production of electricity, for vessel propulsion.  Captain Rickover eventually led the effort to pursue and manufacture the first nuclear powered/propelled (vessel) submarine, which ultimately merited him the rank of Admiral and the recognition as "The Father of The Nuclear Navy." (Fig. 1) 
|Fig. 2: The USS Nautilus. (Source: Wikimedia Commons)|
The first U.S. nuclear powered naval vessel was the submarine, the USS Nautilus (SSN-571). It was a great feat to develop and manufacture a submarine and nuclear reactor of this magnitude as only conventional submarines had been built up unto this point in time. General Dynamics in Groton, Connecticut began the shipbuilding process of the USS Nautilus in June 1952.  Both reactor and the haul of the submarine were built simultaneously, however, because magnitude of the reactor, the Navy built a secondary test reactor in the Idaho, in order to test, qualify, and validate the design. 
Both pressurized water reactors were developed by Westingtonhouse Electric Corporation and are known as Submarine Thermal Reactors (STR).  The STRs were designed to produce 13,000 horsepower turning two shafts (propellers), to a top speed of 23 knots.  The STRs were designed to function using highly enriched U-235, to maximize the amount fissile fuel in the core, helping to create a more compact reactor, and boast increased core life.  The STR reactor on the USS Nautilus was started on January 17, 1955 and propelled the USS Nautilus' maiden voyage, making history for being first "underway on nuclear power."  Fig. 2 shows the USS Nautilus on her maiden voyage and start of her trek to the Arctic.
|Fig. 3: The USS Enterprise. (Source: Wikimedia Commons)|
After the development of the USS Nautilus, research into nuclear powered surface vessel began. Building on the success of the USS Nautilus, the United States Congress authorized research, design, and construction of a nuclear powered aircraft carrier in 1954.  This ship is known today as the USS Enterprise (CVN-65). Ship construction was accomplished by the Newport News Shipbuilding Company.The USS Enterprise is the only ship of its class (Enterprise Class) and precedes Kitty-Hawk class.  The USS Enterprise was constructed to prove possibility of have a nuclear propelled surface vessel as large as a carrier class vessel. Fig. 3, shows the completed USS Enterprise, on its maiden voyage in the Atlantic Ocean.
The propulsion power for the ship is generated by eight, second-generation Westinghouse A2W nuclear reactors. As in the USS Nautilus, the A2W reactors replaced the conventional boiler from previous aircraft carrier designs.  The A2W reactors produce 280,000 horsepower, which turn four propellers, each containing five blades, to a top speed of 34 knots.  The USS Enterprise was launched in September 1960 and was commissioned on November 25, 1961.
|Fig. 4: The USS Nimitz. (Source: Wikimedia Commons)|
With the USS Enterprising being the only ship of its class and the litmus test for the possibility of a nuclear powered surface vessel and carrier, the building process of a larger carrier vessel (Nimitz Class; named after Admiral Chester W. Nimitz) went under way on June 22, 1968 in Newport News Virginia by the Newport News Shipbuilding Company, and initiated by President Ford.  The USS Nimitz (CVN-68) vessel is the lead ship of the Nimitz class. Fig. 4 shows the shear magnitude of the USS Nimitz, as it makes its way to the Persian Gulf in 1975.
The propulsion system for all ships of this class is generated by two fourth generation separated A4W Westinghouse nuclear reactors.  Westinghouse designed the A4W reactor similar to the pressurized water reactors in the USS Nautilus, which produce heat through nuclear fission.  The power from the A4W reactors is passed through four General Electric turbines, that power the four, 25-foot diameter bronze propellers. The power of the four propeller shafts produce a maximum power output of 280,000 horsepower and a top speed of over 36 knots (56 km/h).  As a result of the use of nuclear power, Nimitz class carriers have the capacity to operate continuously for over 20 years without refueling and are predicted to have a service life of over 50 years. 
|Fig. 5: The USS Ford. (Source: Wikimedia Commons)|
As the era of the Nimitz class carriers comes to a close, as many of these carriers reach their decommissioning dates, research for the next era of nuclear powered vessels has already begun. The replacement to the Nimitz class carrier is the Ford class carrier, named after President Gerald Ford. The lead and currently only ship of the Ford class is the USS Ford (CVN-78). On September 10, 2008, the United States Navy signed a $5.1 billion contract with Northrop Grumman Shipbuilding in Newport News, Virginia, to design and construct the next generation carrier. 
The propulsion system for the USS Ford and subsequently the rest of the Ford class is generated by two Bechtel Marine Propulsion Corporation A1B nuclear reactors.  The Bechtel Marine Propulsion Corporation (BMPC) designed the A1B to be smaller, more efficient, and to have three times the electrical power of the A4W reactor.  BMPC designed the reactor to have a higher core energy density, which resulted in a decrease of required maintenance, by 2/3 of the A4W reactor.  Like the Nimitz the use of nuclear power will allow the Ford class carriers to operate continuously for over 25 years without refueling and are predicted to have a service life of over 75 years. The Ford Class carriers have not yet been commissioned as they are still in the testing and qualification phases of their development. The USS Ford is scheduled to be commissioned into service May 2016. Fig. 5, shows the USS Ford as it sit in the wet dock prior to its christening and qualification testing, in November 2013. 
© Daniel Hernandez. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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