Monday, September 22, 2008

How Submarines Work

Submarines are incredible pieces of technology. Not so long ago, a naval force worked entirely above the water; with the addition of the s­ubmarine to the standard naval arsenal, the world below the surface became a battleground as well.

Submarine Image Gallery

French nuclear submarine, Le Terrible
MYCHELE DANIAU/AFP/Getty Images
The French submarine Le Terrible is inaugurated on March 21, 2008, in Cherbourg, France. Le Terrible was developed entirely through computer-assisted design and will begin service in 2010. See more submarine pictures.


The adaptations and inventions that allow sailors to not only fight a battle, but also live for months or even years underwater are some of the most brilliant developments in military history.

In this , we will see how a submarine dives and surfaces in the water, how life support is maintained, how the submarine gets its power, how a submarine finds its way in the deep ocean and how submarines might be rescued.

Diving and Surfacing


Photo courtesy U.S. Navy

­ A submarine or a ship can float because the weight of water that it displaces is equal to the­ weight of the ship. This displacement of water creates an upward force called the buoyant force and acts opposite to gravity, which would pull the ship down. Unlike a ship, a submarine can control its buoyancy, thus allowing it to sink and surface at will.

To control its buoyancy, the submarine has ballast tanks and auxiliary, or trim tanks, that can be alternately filled with water or air (see animation below). When the submarine is on the surface, the ballast tanks are filled with air and the submarine's overall density is less than that of the surrounding water. As the submarine dives, the ballast tanks are flooded with water and the air in the ballast tanks is vented from the submarine until its overall density is greater than the surrounding water and the submarine begins to sink (negative buoyancy). A supply of compressed air is maintained aboard the submarine in air flasks for life support and for use with the ballast tanks. In addition, the submarine has movable sets of short "wings" called hydroplanes on the stern (back) that help to control the angle of the dive. The hydroplanes are angled so that water moves over the stern, which forces the stern upward; therefore, the submarine is angled downward.


Buoyancy in a submarine. Click on the Surface and Submerge
buttons to watch buoyancy in action.


To keep the submarine level at any set depth, the submarine maintains a balance of air and water in the trim tanks so that its overall density is equal to the surrounding water (neutral buoyancy). When the submarine reaches its cruising depth, the hydroplanes are leveled so that the submarine travels level through the water. Water is also forced between the bow and stern trim tanks to keep the sub level. The submarine can steer in the water by using the tail rudder to turn starboard (right) or port (left) and the hydroplanes to control the fore-aft angle of the submarine. In addition, some submarines are equipped with a retractable secondary propulsion motor that can swivel 360 degrees.

When the submarine surfaces, compressed air flows from the air flasks into the ballast tanks and the water is forced out of the submarine until its overall density is less than the surrounding water (positive buoyancy) and the submarine rises. The hydroplanes are angled so that water moves up over the stern, which forces the stern downward; therefore, the submarine is angled upward. In an emergency, the ballast tanks can be filled quickly with high-pressure air to take the submarine to the surface very rapidly.

Life Support

There are three main problems of life support in the closed environment of submarine:
  • Maintaining the air quality
  • Maintaining a fresh water supply
  • Maintaining temperature

Maintaining the Air Quality
The air we breathe is made up of significant quantities of four gases:

  • Nitrogen (78 percent)
  • Oxygen (21 percent)
  • Argon (0.94 percent)
  • Carbon dioxide (0.04 percent)
When we breathe in air, our bodies consume its oxygen and convert it to carbon dioxide. Exhaled air contains about 4.5 percent carbon dioxide. Our bodies do not do anything with nitrogen or argon. A submarine is a sealed container that contains people and a limited supply of air. There are three things that must happen in order to keep air in a submarine breathable:

  • Oxygen has to be replenished as it is consumed. If the percentage of oxygen in the air falls too low, a person suffocates.
  • Carbon dioxide must be removed from the air. As the concentration of carbon dioxide rises, it becomes a toxin.
  • The moisture that we exhale in our breath must be removed.

Oxygen is supplied either from pressurized tanks, an oxygen generator (which can form oxygen from the electrolysis of water) or some sort of "oxygen canister" that releases oxygen by a very hot chemical reaction. (You may remember these canisters because of their problems on the MIR space station -- see this page for details). Oxygen is either released continuously by a computerized system that senses the percentage of oxygen in the air, or it is released in batches periodically through the day.

Carbon dioxide can be removed from the air chemically using soda lime (sodium hydroxide and calcium hydroxide) in devices called scrubbers. The carbon dioxide is trapped in the soda lime by a chemical reaction and removed from the air. Other similar reactions can accomplish the same goal.

The moisture can be removed by a dehumidifier or by chemicals. This prevents it from condensing on the walls and equipment inside the ship.

In addition, other gases such as carbon monoxide or hydrogen, which are generated by equipment and cigarette smoke, can be removed by burners. Finally, filters are used to remove particulates, dirt and dust from the air.

Maintaining a Fresh Water Supply
Most submarines have a distillation apparatus that can take in seawater and produce fresh water. The distillation plant heats the seawater to water vapor, which removes the salts, and then cools the water vapor into a collecting tank of fresh water. The distillation plant on some submarines can produce 10,000 to 40,000 gallons (38,000 - 150,000 liters) of fresh water per day. This water is used mainly for cooling electronic equipment (such as computers and navigation equipment) and for supporting the crew (for example, drinking, cooking and personal hygiene).

Maintaining Temperature
The temperature of the ocean surrounding the submarine is typically 39 degrees Fahrenheit (4 degrees Celsius). The metal of the submarine conducts internal heat to the surrounding water. So, submarines must be electrically heated to maintain a comfortable temperature for the crew. The electrical power for the heaters comes from the nuclear reactor, diesel engine, or batteries (emergency).

Power Supply

­ Nuclear submarines use nuclear reactors, steam turbines and reduction ge­aring to drive the main propeller shaft, which provides the forward and reverse thrust in the water (an electric motor drives the same shaft when docking or in an emergency).

Submarines also need electric power to operate the equipment on board. To supply this power, submarines are equipped with diesel engines that burn fuel and/or nuclear reactors that use nuclear fission. Submarines also have batteries to supply electrical power. Electrical equipment is often run off the batteries and power from the diesel engine or nuclear reactor is used to charge the batteries. In cases of emergency, the batteries may be the only source of electrical power to run the submarine.

A diesel submarine is a very good example of a hybrid vehicle. Most diesel subs have two or more diesel engines. The diesel engines can run propellers or they can run generators that recharge a very large battery bank. Or they can work in combination, one engine driving a propeller and the other driving a generator. The sub must surface (or cruise just below the surface using a snorkel) to run the diesel engines. Once the batteries are fully charged, the sub can head underwater. The batteries power electric motors driving the propellers. Battery operation is the only way a diesel sub can actually submerge. The limits of battery technology severely constrain the amount of time a diesel sub can stay underwater.

Because of these limitations of batteries, it was recognized that nuclear power in a submarine provided a huge benefit. Nuclear generators need no oxygen, so a nuclear sub can stay underwater for weeks at a time. Also, because nuclear fuel lasts much longer than diesel fuel (years), a nuclear submarine does not have to come to the surface or to a port to refuel and can stay at sea longer.

Nuclear subs and aircraft carriers are powered by nuclear reactors that are nearly identical to the reactors used in commercial power plants. The reactor produces heat to generate steam to drive a steam turbine. The turbine in a ship directly drives the propellers, as well as electrical generators. The two major differences between commercial reactors and reactors in nuclear ships are:

  • The reactor in a nuclear ship is smaller.

  • The reactor in a nuclear ship uses highly enriched fuel to allow it to deliver a large amount of energy from a smaller reactor.

Navigation

­ Light does not penetrate very far into the ocean, so submarines must nav­igate through the water virtually blind. However, submarines are equipped with navigational charts and sophisticated navigational equipment. When on the surface, a sophisticated global positioning system (GPS) accurately determines latitude and longitude, but this system cannot work when the submarine is submerged. Underwater, the submarine uses inertial guidance systems (electric, mechanical) that keep track of the ship's motion from a fixed starting point by using gyroscopes. The inertial guidance systems are accurate to 150 hours of operation and must be realigned by other surface-dependent navigational systems (GPS, radio, radar, satellite). With these systems onboard, a submarine can be accurately navigated and be within a hundred feet of its intended course.


Photo courtesy U.S. Department of Defense
Sonar station onboard the USS La Jolla nuclear-powered attack submarine


To locate a target, a submarine uses active and passive SONAR (sound navigation and ranging). Active sonar emits pulses of sound waves that travel through the water, reflect off the target and return to the ship. By knowing the speed of sound in water and the time for the sound wave to travel to the target and back, the computers can quickly calculate distance between the submarine and the target. Whales, dolphins and bats use the same technique for locating prey (echolocation). Passive sonar involves listening to sounds generated by the target. Sonar systems can also be used to realign inertial navigation systems by identifying known ocean floor features .

Rescue

­­ W­hen a submarine goes down because of a collision with something (such as another vessel, canyon wall or mine) or an onboard explosion, the crew will radio a distress call or launch a buoy that will transmit a distress call and the submarine's location. Depending upon the circumstances of the disaster, the nuclear reactors will shut down and the submarine may be on battery power alone.

If this is the case, then the crew of the submarine have four primary dangers facing them: ­

  • Flooding of the submarine must be contained and minimized.
  • Oxygen use must be minimized so that the available oxygen supply can hold out long enough for possible rescue attempts.
  • Carbon dioxide levels will rise and could produce dangerous, toxic effects.
  • If the batteries run out, then the heating systems will fail and the temperature of the submarine will fall.

­ Rescue attempts from the surface must occur quickly, usually within 48 hours of the accident. Attempts will typically involve trying to get some type of rescue vehicle down to remove the crew, or to attach some type of device to raise the submarine from the sea floor. Rescue vehicles include mini-submarines called Deep-Submergence Rescue Vehicles (DSRV) and diving bells.


Photo courtesy U.S. Department of Defense
DSRV secured to the deck of a submarine

The DSRV can travel independently to the downed submarine, latch onto the submarine over a hatch (escape trunk), create an airtight seal so that the hatch can be opened, and load up to 24 crew members. A diving bell is typically lowered from a support ship down to the submarine, where a similar operation occurs.

To raise the submarine, typically after the crew has been extracted, pontoons may be placed around the submarine and inflated to float it to the surface. Important factors in the success of a rescue operation include the depth of the downed submarine, the terrain of the sea floor, the currents in the vicinity of the downed submarine, the angle of the submarine, and the sea and weather conditions at the surface.

Posted by at

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)

Air Craft Carrier


An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a sea-going airbase. Aircraft carriers thus allow a naval force to project air power great distances without having to depend on local bases for staging aircraft operations. They have evolved from wooden vessels used to deploy a balloon into nuclear powered warships that carry dozens of fixed and rotary wing aircraft.
Balloon carriers were the first ships to deploy manned aircraft, used during the 19th and early 20th century, mainly for observation purposes. The 1903 advent of fixed wing airplanes was followed in 1910 by the first flight of such an aircraft from the deck of a US Navy cruiser. Seaplanes and seaplane tender support ships, such as HMS Engadine, followed. The development of flat top vessels produced the first large fleet ships. This evolution was well underway by the mid 1920s, resulting in ships such as the HMS Hermes, Hōshō, and the Lexington class aircraft carriers.
World War II saw the first large scale use and further refinement of the aircraft carrier, spawning several types. Escort aircraft carriers, such as USS Barnes, were built only during World War II. Although some were purpose built, most were converted from merchant ships, and were a stop-gap measure in order to provide air support for convoys and amphibious invasions. Light aircraft carriers, such as USS Independence represented a larger, more "militarized" version of the escort carrier concept. Although the light carriers usually carried the same size air groups as escort carriers, they had the advantage of higher speed as they had been converted from cruisers under construction rather than civilian merchant ships.
Wartime emergencies also saw the creation or conversion of other, unconventional aircraft carriers. CAM ships, like the SS Michael E, were cargo carrying merchant ships which could launch but not retrieve fighter aircraft from a catapult. These vessels were an emergency measure during World War II as were Merchant aircraft carriers (MACs), such as Mv Empire MacAlpine, another emergency measure which saw cargo-carrying merchant ships equipped with flight decks. Battlecarriers were created by the Imperial JapaneseNavy to partially compensate for the loss of carrier strength at Midway.
Two of them were made from Ise class battleships during late 1943. The aft turrets were removed and replaced with a hangar, deck and catapult. The heavy cruiser Mogami concurrently received a similar conversion. This "half and half" design was an unsuccessful compromise, being neither one thing nor the other. Submarine aircraft carriers, such as the French Surcouf, or the Japaneseclass I-400 submarines, which were capable of carrying 3 Aichi M6A Seiran aircraft, were first built in the 1920s, but were generally unsuccessful at war. Modern navies that operate such ships treat aircraft carriers as the capital ship of the fleet, a role previously played by the battleship. The change, part of the growth of air power as a significant part of warfare, took place during World War II. This change was driven by the superior range, flexibility and effectiveness of carrier-launched aircraft.
Following the war, the scope of carrier operations continued to increase in size and importance. Supercarriers, typically displacing 75,000 tonnes or greater, have become the pinnacle of carrier development. Most are powered by nuclear reactors and form the core of a fleet designed to operate far from home. Amphibious assault ships, such as USS Tarawa or HMS Ocean, serve the purpose of carrying and landing Marines and operate a large contingent of helicopters for that purpose. Also known as "commando carriers" or "helicopter carriers", they have a secondary capability to operate VSTOL aircraft.
Lacking the firepower of other warships, carriers by themselves are considered vulnerable to attack by other ships, aircraft, submarines or missiles and therefore travel as part of a carrier battle group (CVBG) for their protection. Unlike other types of capital ships in the 20th century, aircraft carrier designs since World War II have been effectively unlimited by any consideration save budgetary, and the ships have increased in size to handle the larger aircraft: The large, modern Nimitz class of United States Navy carriers has a displacement nearly four times that of the World War II-era USS Enterprise yet its complement of aircraft is roughly the same, a consequence of the steadily increasing size of military aircraft over the years.

Air Craft Carrier-Architecture

Air Craft Carrier-Architecture

SUB MARINE

A submarine is a watercraft that can operate independently underwater, as distinct from a submersible that has only limited underwater capability. The term submarine most commonly refers to large manned autonomous vessels, however historically or more casually, submarine can also refer to medium sized or smaller vessels, (midget submarines, wet subs), Remotely Operated Vehicles or robots. The word submarine was originally an adjective meaning "under the sea", and so consequently other uses such as "submarine engineering" or "submarine cable" may not actually refer to submarines at all. Submarine was shortened from the term "submarine boat".
Submarines are referred to as "boats" for historical reasons because vessels deployed from a ship are referred to as boats. The first submarines were launched in such a manner. The English term U-Boat for a German submarine comes from the German word for submarine, U-Boot, itself an abbreviation for Unterseeboot ("undersea boat").
Although experimental submarines had been built before, submarine design took off during the 19th century. Submarines were first widely used in World War I, and feature in many large navies. Military usage ranges from attacking enemy ships or submarines, aircraft carrier protection, blockade running, ballistic missile submarines as part of a nuclear strike force, reconnaissance and covert insertion of special forces. Civilian uses for submarines include marine science, salvage, exploration and facility inspection/maintenance. Submarines can also be specialised to a function such as search and rescue, or undersea cable repair. Submarines are also used in tourism and for academic research.
Submarines have one of the largest ranges in capabilities of any vessel, ranging from small autonomous or one- or two-man vessels operating for a few hours, to vessels which can remain submerged for 6 months such as the Russian Typhoon class. Submarines can work at greater depths than are survivable or practical for human divers. Modern deep diving submarines are derived from the bathyscaphe, which in turn was an evolution of the diving bell.
Most large submarines comprise a cylindrical body with conical ends and a vertical structure, usually located amidships, which houses communications and sensing devices as well as periscopes. In modern submarines this structure is the "sail" in American usage ("fin" in European usage). A "conning tower" was a feature of earlier designs: a separate pressure hull above the main body of the boat that allowed the use of shorter periscopes. There is a propeller (or pump jet) at the rear and various hydrodynamic control fins as well as ballast tanks. Smaller, deep diving and specialty submarines may deviate significantly from this traditional layout.

SUB MARINE

SUB MARINE

SUB MARINE1

SUB MARINE1

SUB MARINE II

SUB MARINE II

Sailing Ships

Sailing ship is now used to refer to any large, wind-powered, vessel. In technical terms, a ship was a sailing vessel with a specific rig of at least three masts, square rigged on all of them, making the sailing adjective redundant. In popular usage ship became associated with all large sailing vessels and when steam power came along the adjective became necessary.
specification:
There are many different types of sailing ship, but they all have certain basic things in common. Every sailing ship has a hull, rigging and at least one mast to hold up the sails that use the wind to power the ship. The crew who sail a ship are called sailors or hands. They take turns to take the watch, the active managers of the ship and her performance for a period.
Watches are traditionally four hours long. Some sailing ships use traditional ship's bells to tell the time and regulate the watch system, with the bell being rung once for every half hour into the watch and rung eight times at watch end (a four-hour watch).
Ocean journeys by sailing ship can take many months, and a common hazard is becoming becalmed because of lack of wind, or being blown off course by severe storms or winds that do not allow progress in the desired direction. A severe storm could lead to shipwreck, and the loss of all hands.
Sailing ships can only carry a certain quantity of supplies in their hold, so they have to plan long voyages carefully to include many stops to take on provisions and, in the days before watermakers, fresh water.

SAILING SHIPS

SAILING SHIPS

Sailing Ships

Sailing Ships

FRIGATE CLASS SHIPS



Basically a frigate [frĭg'-ĭt] is a warship. The term has been used for warships of many sizes and roles over the past few centuries.
In the 18th century, the term referred to ships which were as long as a ship-of-the-line and were square-rigged on all three masts (full rigged), but were faster and with lighter armament, used for patrolling and escort. In the 19th century, the armoured frigate was a type of ironclad warship and for a time was the most powerful type of vessel afloat.
In modern navies, frigates are used to protect other warships and merchant-marine ships, especially as anti-submarine warfare(ASW) combatants for amphibious expeditionary forces, underway replenishment groups, and merchant convoys. But ship classes dubbed "frigates" have also more closely resembled corvettes, destroyers, cruisers and even battleships.

INS GOTHAVARI

INS GOTHAVARI

INS GOTHAVARI

TYPE 16 GODAVARI CLASS:

Vessel Type:
Guided Missile Frigate.
Names & Pennant Numbers with commission dates:
Godavari F20 (10 December 1983) INS Ganga F22 (30 December 1985)INS Gomati F21(16 April 1988)
Structure:
The Type 16 Class frigates are a modification of the original Leander Class design with an indigenous content of 72% and a larger hull.
Displacement:
3600 tons standard.............3850 tons full load.
Dimensions:
Length - 126.4 metres.................Beam - 14.5 metres.................Draught - 4.5 metres.
Main Machinery:
Two turbines with 30,000 hp motors, two 550 psi boilers and two shafts.
Maximum Speed: 27 knots.
Maximum Range: 4500 miles at 12 knots.
Complement:
313 (incl. 40 Officers & 13 Aircrew).
Radar:
Air; One Signaal radar at D-band frequency (range - 145n miles; 264 km).........Air/Surface; One MR-310U Angara (NATO: Head Net-C) radar at E-band frequency (range - 70n miles; 128 km)..........Navigation/Helo Ctrl; Two Signaal ZW06 or Don Kay radars at I-band frequency..........Fire Control; Refer to 'Weapons' sub-section.
Sonar: The Bharat APSOH; hull mounted and provides active panoramic search & attack with medium frequency. The vessels also have a Fathoms Oceanic VDS (Variable Depth Sonar) and Type 162M sonar, which provides bottom classification with high frequency. INS Ganga has a Thomson Sintra DSBV 62; passive towed array sonar with very low frequency.
Weapons:
Four P-20M (SS-N-2D Styx) AShMs, fitted in single-tube launchers, with active radar (Mod 1) or infra-red (Mod 2) homing to 45n miles; 83 km at 0.9 Mach. Becomes a sea skimmer at the end of run. Has a 513 kg warhead.
INS Ganga and INS Gomati have been refitted with the Israeli Barak SAM system, with fire control provided by an EL/M-2221 STG radar.
The latter vessel was first sighted with the Barak in December 2002 and the system was reportedly operational by March 2003. It is probable that INS Godavari also has the Barak system, but that is yet to be confirmed through official channels. Prior to the fitment of the Barak system, these vessels had a single vertical launcher with the OSA-M (SA-N-4) SAM with SAR homing to 8n miles; 15 km at Mach 2.5, with a service ceiling of 3048 meters and a 50 kg warhead. A total of 20 OSA-M missiles were carried on board and they had a limited SSM capability. Fire control was provided by a single MPZ-310 (NATO: Pop Group) radar at F/H/I-band frequency, which has since been removed from the vessels that feature the Barak system.
Two 57mm (twin) guns at 90º elevation, 120 rds/min to 4.4n miles; 8 km, for use against ship- and shore-based targets. Fire control is provided by a single MR-103 (NATO: Muff Cob) radar at G/H-band frequency. In the CIWS role, the vessels are fitted with four AK-230 30mm gunmounts with 85º elevation and 500 rounds/min to 2.7n miles; 5 km with fire control provided by two MR-123 (NATO: Drum Tilt) radars at H/I-band frequency.
Features six 324mm ILAS 3 (2 triple) torpedo tubes, which fire the Whitehead A244S anti-submarine torpedo which has active/passive homing to 3.8n miles; 7 km at 33 knots with a 34 kg shaped charged warhead. INS Godavari has tube modifications for the Indian NST 58 version of A244S.
Weapons Control:
MR 301 MFCS and MR 103 GFCS.
Combat Data System: Selenia IPN-10 action data automation and a Immarsat communications (JRC) system.
Helicopters:
Two Sea King Mk.42B or a combination of one Sea King Mk.42B and one HAL Chetak. Usually one helicopter is carried with more than one air crew. French Samahé helicopter landing equipment is fitted. The Naval ALH can also be embarked.
Countermeasures:
Selenia INS-3 (Bharat Ajanta and Elettronica TQN-2) intercept and jammer is used for ESM/ECM purposes. Two chaff/flares are used as decoys. Will have the 'Super Barricade' decoys in due course. Also has a Graesby G738 towed torpedo decoy.