Nimitz-Class Carriers: Twin A4W Reactors, Steam Catapults and the RCOH

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All 10 Nimitz-class aircraft carriers were built at Newport News Shipbuilding in Virginia between the late 1960s and 2006. Each stretches over 1,000 feet, weighs roughly 100,000 tons, moves at more than 35 miles per hour and runs about 25 years before refueling. Starting with the USS Theodore Roosevelt, the yard moved to modular construction, prefitting wiring, ventilation and plumbing into steel blocks, with a single bow section weighing over 1.5 million pounds. Where the USS Enterprise needed eight reactors, the Nimitz class uses two A4W pressurized water reactors. A primary loop kept under pressure carries heat to a separate secondary loop that flashes into steam, driving four turbines that produce 260,000 shaft horsepower and turn four 66,000-pound bronze propellers. The freed space raised aviation fuel capacity by 90 percent and ordnance capacity by 50 percent over older supercarriers, a lesson from supply limits in the Vietnam War.

Reactor steam also feeds the catapults, which push a 60,000-pound jet from zero to 165 miles per hour in about two seconds, while a deck angled nine degrees lets pilots land at full throttle and go around after a missed wire. An air wing of up to 64 aircraft includes F-18 Super Hornets, F-35Cs, EA-18G Growlers and E-2D Hawkeyes, and crews are coded by jersey color because shouting is useless on deck. The carrier's own defenses, the Sea Sparrow and the Phalanx CIWS, are a last resort behind an Aegis-equipped strike group. Halfway through a 50-year life, each ship spends about four years and $2.6 billion in a refueling and complex overhaul, and decommissioning the Nimitz is projected to cost $750 to $900 million as the Gerald R. Ford class takes over.

• The island and elevators sit on the starboard side, so crews pump fluids between voids below the waterline to keep the deck level.
• Steel doors that divide the hangar bay into fire zones trace back to World War II kamikaze attacks.
• A 1981 EA-6B Prowler crash on the Nimitz killed 14, and a 2008 fire on the George Washington caused $70 million in damage.
• The Navy pulled a torpedo defense system from five carriers a few years after installing it because it was unreliable.
• The Abraham Lincoln aided survivors of the 2004 Indian Ocean tsunami, and the Harry S. Truman supported relief after Hurricane Katrina.