How Stuff Works: How aircraft carriers work
By Marshall Brain
http://www.JewishWorldReview.com | (MCT) With tensions rising around the world, America's military is constantly in the news. One of the most important parts of that military power is the aircraft carrier. A carrier is the largest machine in the arsenal, and it has an incredible ability. With an aircraft carrier, the United States can bring a complete, miniaturized military airfield to any part of the world in just a week or two.
The most impressive part of an aircraft carrier is its sheer size. At more than 1,000 feet long and 20 stories high, an aircraft carrier is like a mini city. It comes complete with at least 5,000 crew members to keep everything running.
Such a massive ship would need an incredible amount of fuel if it were using normal engines. Instead, U.S. aircraft carriers use nuclear reactors. Once the two reactors are installed, a carrier contains enough nuclear fuel to run for more than a decade. The reactors create steam, which drives a set of steam turbines. Each of the carrier's four massive propellers (21 feet in diameter) has its own turbine, and together the turbines create something on the order of 280,000 horsepower. The turbines also drive electric generators to provide all of the ship's power.
An aircraft carrier needs a lot of electricity. There is a huge air conditioning system to keep people and equipment cool. There's a desalination plant that processes half a million gallons of water a day. And there is a massive refrigeration system. There is enough food on board to feed 6,000 people for 70 days.
The whole point of all this technology is to create a floating airport. The flight deck covers about 4.5 acres. Beneath it is a massive hangar that can hold up to 100 airplanes. This hangar is 110 feet wide and almost 700 feet long - about 2 acres of covered space where planes can be stowed and repaired. To move the planes from the hangar to the flight deck there are four gigantic elevators. An elevator can lift about 150,000 pounds at a time.
Although an aircraft carrier is huge, it is tiny compared to a normal airport. Runways can be thousands of feet long on land. At sea there's just a few hundred feet to take off and land. An aircraft carrier gets around this problem using special technology.
When a plane needs to lift off, the technology takes the form of a steam-powered catapult. An airplane lines up and a crew member attaches its front wheel to the catapult shaft. The pilot guns the engines for maximum thrust, and then a crew member known as the "shooter" fires the catapult. A 45,000-pound plane goes from 0 to 165 miles per hour in the space of 300 feet. The whole process takes about 2 seconds, and the plane is in the air. It is possible to launch one plane every 25 seconds if needed.
When it is time to land, the technology takes the form of a tail hook on the airplane and four arresting cables stretched across the deck. The pilot's goal is to drop the plane so the hook snags a cable. Once snagged, the cable will reel out and bring the plane to a stop in about 300 feet. If the pilot misses the cables, the goal is to gun the engines, get back in the air and try again.
All these airplanes take a lot of fuel. There's more than 3 million gallons on board an aircraft carrier. But, like the crew's food, it's a limited amount. For this reason, an aircraft carrier never goes out alone. It always travels with a flotilla of other ships collectively known as a carrier battle group. The battle group includes resupply ships as well as guided missile cruisers, two destroyers, two submarines and a frigate to protect against enemy submarines. Together these ships collectively protect the aircraft carrier and each other against ships, missiles, airplanes and torpedoes.
U.S. aircraft carriers are so impressive that other nations are building up their own fleets. Britain is in the process of building several new carriers that will come on line around 2017. Russia plans to have 12 battle groups. China and India are setting up fleets as well. In 10 years, there will be dozens of aircraft carriers roaming the seas. It will be a completely different world.
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© 2007, How Stuff Works Inc. Distributed by McClatchy-Tribune Information Services.