What does driving four screws mean?
Please forgive my not knowing!
The nuclear-powered carrier has two General Electric pressurised water reactors driving four turbines of 260,000hp (194MW) and four shafts (screws). There are four emergency diesels of 10,720hp (8MW).
The carrier’s two nuclear reactors give her virtually unlimited range and endurance and a top speed in excess of 30 knots. Eight steam turbine generators each produce 8,000 kilowatts of electrical power, enough to serve a small city. The ship has enough electrical generating power to supply electricity to a city of 100,000. The ships normally carrys enough food and supplies to operate for 90 days. Four distilling units enable NIMITZ-class engineers to make over 400,000 gallons of fresh water from seawater a day, for use by the propulsion plants, catapults and crew. The ship carries approximately 3 million gallons of fuel for her aircraft and escorts, and enough weapons and stores for extended operations without replenishment. These ships also have extensive repair capabilities, including a fully equipped Aircraft Intermediate Maintenance Department, a micro-miniature electronics repair shop, and numerous ship repair shops. Keeping a NIMITZ-class carrier ready at all times requires repair shops to maintain machinery and aircraft, heavy duty tailor shops to repair parachutes and other survival gear, and electronic ships that keep communication, navigation and avionics equipment in good condition. NIMITZ-class carriers boast all the amenities that would be found in any American city with a comparable population, including a post office with its own ZIP code, TV and radio stations, a newspaper, a fire department, a library, a hospital, a general store, two barbershops and much more.