Recently, Japan mobilized its navy - not for a drill, but to hunt for a nuclear submarine in Japanese waters. Officials in Tokyo say the sub was Chinese. Officials in Beijing say only that they're investigating. Officials everywhere else say both nations played a dangerous game, because nuclear subs are nothing to fool around with.
DIVE! DIVE! INSIDE A NUCLEAR SUBMARINE
By Christopher Call, http://www.knowledgenews.net/ November 15, 2004
Nuclear-powered subs are, literally, dangerously advanced. Just tour America's current underwater workhorse - the Los Angeles-class attack submarine - and see.
All modern subs have the same sleek, torpedo-like hull - designed to reduce drag as the sub moves through the water. Gone are the gun emplacements, deck rails, and other accessories of the World War II era. Today, even the rivets and seams have been minimized. The final product is a hydrodynamic form that maximizes speed and efficiency better than any other combat vessel in the world.
Beneath the sleek, slippery shape is a metallic frame that must withstand the immense pressures that subs endure while submerged. The hull of a Los Angeles-class sub is pretty much a tube of thick, high-tech, low-carbon steel. This enables it to dive up to 1,500 feet (about 450 meters) before reaching the perilous “crush depth.” Acoustic tile cladding covers the hull's steel like a skin, dampening the sound of the sub as it moves through the water.
Nestled in the rear of a Los Angeles-class sub is the S6G, a full-fledged nuclear reactor. Nuclear reactors are a major improvement over the old diesel engines used in subs before 1955. They're certainly more powerful - the S6G produces 26 megawatts, enough to power 18,000 homes. And unlike diesel engines, the S6G can run while the sub is submerged, negating the need for batteries. In fact, the sub can power itself for an estimated 10 years before refueling and can cruise submerged for months.
This nuclear power flows into twin turbines that produce 35,000 horsepower. The turbines, which sit on a sound-dampening rafting system to minimize noise, turn a single shaft-driven propeller, also designed to operate as quietly as possible. Although their actual top speed is classified, Los Angeles-class subs are believed to be capable of 32 knots (almost 37 mph or 60 km/h) while submerged.
Of course, the problem with using a nuclear reactor is the possibility of a nuclear explosion or meltdown as the result of error, malfunction, or combat damage. There is also concern that reactors on sunken subs could slowly leak radioactive material into the water. Several nuclear submarines, Russian and American, lie at the bottom of the ocean. Those sites are tested frequently, and although results indicate little or no radioactive release, the environmental threat remains.
A Los Angeles-class sub comes equipped with four torpedo tubes capable of firing up to 26 launched weapons. The typical complement consists of 14 torpedoes, 8 Tomahawk cruise missiles, and 4 Harpoon missiles. The standard torpedo, the MK-48, is self-guided, with the remarkable ability to reattack if it misses its target. The 650-pound (300 kg) warhead can sink virtually any vessel within five miles (8 km).
The sub's Tomahawk cruise missiles can strike 1,000 miles (1,600 km) away, delivering a 1,000-pound (450 kg) warhead with startling accuracy. And Harpoon anti-ship missiles can strike and sink surface ships within 70 miles (110 km). All told, attack subs contain as many pounds of high explosives as they do pounds of crew.
Ballistic missile submarines, or “boomers,” carry something far more ominous: up to two dozen medium or long-range ballistic missiles, each with a powerful nuclear warhead. Their chilling mission: to deliver first-strike or rapid-response blows to strategic targets around the world by launching from concealed locations at sea.
Submarines have no windows. Like deep-sea life, they cruise through the ocean depths completely blind. Instead, submarines use their ears to navigate - they use sonar. Sonar, or “sound navigation ranging,” is both passive (listening to the sounds things make underwater) and active (bouncing sound waves off underwater objects to detect their distance, size, and shape).
Inside the bow of a Los Angeles-class sub are 1,000 passive-sensor hydrophones that can hear sounds from miles away. Underneath this array is a transducer that emits the pings needed for active sonar. The sonar array is housed in a glass-reinforced plastic bow - rather than the steel surrounding the rest of the sub - so that sound waves can penetrate. The array is backed by a baffling system that eliminates sounds coming from the sub itself. The sub can also tow sonar arrays at a distance, extending its “ear.”
Backing up the ship's sonar system is a collection of powerful computers that swiftly analyze incoming signals. These computers eliminate background noise and isolate specific sound types to classify the source of a sound, as well as its distance, bearing, and speed.
The tower that projects up off the hull of a sub is commonly called the “sail” or “conning tower.” It holds much of the sub's surface communication and sensory apparatus, including a pair of periscopes that allow it to view the surface while still submerged. The primary periscope on a Los Angeles-class sub comes equipped with a telescopic lens, still and video cameras, and infrared vision, as well as a radar-dampening coating to prevent detection. The second periscope, used when attacking ships, is smaller and harder to detect visually.
In addition to the periscopes, several retractable antennae provide the sub with a global positioning system, radio reception and transmission, and navigation radar. There is also a snorkel mast that allows the sub to operate an auxiliary diesel engine and replenish its air, although today's subs can actually make their own air by splitting water molecules into oxygen and hydrogen gas.
With all this technology at his command, a skipper at the “con” - directly below the sail - controls one of the most formidable weapons on Earth. Yet advances still remain. In fact, Los Angeles-class subs face a new competitor that is faster, quieter, and even more heavily armed.
That competitor is the U.S. Navy's newest attack sub: the Virginia-class, designed to eventually replace the 51 Los Angeles-class subs now in service.
Want to learn more? Take a virtual tour of a Los Angeles-class sub at http://www.pbs.org/wgbh/nova/subsecrets/spriconhi.htm.
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