Tank Introduction
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modified: Nov 10, 2012
Modern tanks can be described as armored combat vehicles that are intended to engage the enemy head-on. A typical tank weighs several tonnes and is armed with a large caliber gun and one or more machine guns. It has caterpillar tracks and is fitted with heavy armor to protect it from enemy fire.

Design
There are three major aspects that are taken into consideration when designing a tank: firepower - capability of identifying, engaging and destroying an enemy target; mobility - ability to move on various types of terrains and be transported by several means; and protection - the ability to effectively resist identification and destruction by enemy forces. When one designs a tank, he has to compromise and find a balance between the three aspects. For example, a heavily armored tank is well protected, however the tank's heavy weight makes it less mobile.

Armament
The main weapon of a modern tank is the large-caliber gun. Most Soviet tanks have main guns with 125mm caliber. Modern guns have thermal jackets that evenly heat the barrel to prevent the effects of uneven temperature such as the bending of the barrel, and thus improving accuracy.

Tanks also have smaller armaments for defense against infantry, very close targets, and aircrafts. Soviet and Russian secondary armaments are usually 12.7mm or 7.62mm caliber machine guns.

Accuracy
Several instruments are utilized to accurately deliver a projectile to its intended target. Laser rangefinders are used on modern tanks to determine distance with a very reasonable accuracy. Gyroscopes stabilize the main gun; computers integrate wind speed, air and gun-barrel temperature, humidity and several other types of sensor to calculate the elevation and aim-point of the main gun. In addition, infrared and night vision equipments can be incorporated during the night, and in foggy or rainy environments.

Projectile
The main gun can fire various types of rounds including kinetic energy penetrators (KEP, or armour-piercing discarding sabot, APDS), high explosive squash head (HESH, also called high explosive plastic, or HEP), and high explosive anti-tank (HEAT) rounds. For greater accuracy, the projectile can be spun by a rifled-barrel gun or fin-stabilized. Many CIS-made tanks can also fire anti-tank guided missiles (ATGMs) through their gun barrel. This missile-gun capability significantly extends the combat range of the tank and includes the ability to engage low-flying airborne targets, mainly helicopters.

Performance
Tanks are powered by a diesel or turbine engine. A typical engine has a power output of around 1,000hp or more. This large power output creates distinct thermal, acoustic, and seismic signatures thus it's easy to detect a tank, especially a moving one. Modern tanks tend to use diesel engines since diesel is less flammable and cheaper than gasoline (petrol). Some modern tanks have multi-fuel engines which are able to function on diesel, gasoline and other fuels. Gas turbines have been used as auxiliary power units because they are lighter, smaller and generate less acoustic signature than diesel engines but they are less fuel efficient and generate higher thermal signature at the same time. Fuel tanks are usually placed at the rear of the tank. External fuel tanks are also used to provide more fuel.

Protection
Tanks, if not well protected, are vulnerable to several types of attacks: infantry soldiers, anti-tank ammunition, mines, and ground attack aircrafts. Most tanks have a heavily armoured glacis plate thus, the front is the most protected part of the tank, followed by the sides. The rear, belly, and roof are less protected.

A Scheme of various tank parts
by Robert Blazek under PD (Worldwide)
1.Caterpillar Tracks      2.Main gun      3.Track covers      4.Smoke dischargers
5.Anti-aircraft (AA) machine gun      6.Engine cover      7.Commander's cupola
8.Coaxial machine gun      9.Glacis plate      10.Hull machine gun

Smoke grenades serve as a passive defense mechanism by blocking the naked-eye and infrared view of the attacker. Other passive systems include laser and radio warning devices which warn if the tank has been targeted by laser or radio systems respectively. Active protection systems prevent projectiles from acquiring or destroying a target. The Soviet developed Drozd system uses a Doppler radar to detect incoming anti-tank missiles and RPGs and destroys them by firing a projectile. Explosive reactive armor works by detonating when impacted to deflect or break up the projectile. Active protection systems and explosive reactive armor can be dangerous to bystanders such as nearby friendly soldiers.

The commander is unsafe when he is riding with his head out of the turret, but ironically, this is the safest state for the tank since the commander can view the terrain with no restrictions, and he can also spot enemy operations easily.

Mobility
The mobility of a tank is separated into battlefield mobility, tactical mobility and strategic mobility. The battlefield mobility is heavily dependent on the performance of the tank engine such as speed and acceleration. Tactical mobility refers to the ability of the tank to be moved within an operation theatre. It is based on operational range, bridges the tank can cross and what vehicles can haul it. The last one, strategic mobility is the transportation from one operation theatre to another. The weight of the tank and its air portability affect strategic mobility.

Most tanks are able to ford through water with a depth of 3 to 4 feet. With the use of a snorkel, this fording depth can be increased and is known as "deep fording". All modern Soviet and Russian tanks are able to perform deep fording operations. Amphibious tanks, such as the PT-76, are able to swim through bodies of water.

Specialized tanks
Tanks can be engineered for specialized roles. These include flamethrower tanks that carry a flame gun in lieu of a main gun. There are bridge laying vehicles that allow tanks to cross rivers. Mine-clearing vehicles clear a path for other tanks through minefields. Armored recovery vehicles are used to repair or tow away battle-damaged or broken-down tanks.


References:WP