Tank

: This article is about armoured fighting vehicles. For other meanings, see Tank (disambiguation).

Design

The three traditional factors determining a tank's effectiveness are its firepower, mobility and protection. The psychological effect of a tank's imposing battlefield presence on enemy soldiers is called shock action.

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Firepower is the ability of a tank to defeat a target. This includes the maximum distance at which targets can be engaged, the ability to engage moving targets, the speed with which multiple targets can be destroyed, the capability to defeat armoured vehicles or entrenched infantry, and the ability to continue fighting after damage has been sustained

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Mobility is the speed and agility of driving cross-country, the types of terrain that can be covered, the size of obstacles, trenches, and water that can be crossed, the ability to cross small bridges, and the distance that can be covered before refuelling is required. "Strategic mobility" also includes the ability to travel at high speed on roads, and the ability to be carried on rail or truck transport. Traditionally AFV mobility is measured by the following metrics:

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• engine power
• engine torque
• power-to-weight ratio
• road speed
• off-road speed (a somewhat nebulous figure given the possible variation)
• road range
• off-road range
• weight (bridge classification)
• ground pressure
• width of trench crossed
• vertical step climbed
• angle of slope that can be climbed
• angle of side slope that can be negotiated
• ground clearance
• unprepared fording depth
• prepared fording depth (if different)

Protection is the amount of armour, the type(s), how it is arranged (e.g., whether it is sloping or not), and which areas are given more protection (e.g., the turret and tracks) and which receive less (e.g., the rear of the chassis). It also includes low profile, low noise and thermal signature, active countermeasures, and other methods of avoiding enemy fire.

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Tank design is traditionally considered to be a compromise between these three factors?it is not possible to maximise all three. For example, increasing protection by adding armour will increase weight and therefore decrease manoeuvrability; increasing firepower by using a larger gun will decrease both manoeuvrability and protection (due to decreased armour at the front of the turret).

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How the compromise is achieved is influenced by a combination of factors, including military strategies, budget, geography, political will, and, in these modern times, the requirement to sell the tank to other countries.

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Examples of how different countries are influenced in their decisions are as follows:

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• Britain has historically always opted for better firepower and increased protection at the expense of some manoeuvrability. Britain has always maintained a small, highly trained professional army, and so tank crew survivability is important. Similarly, as limited resources may be available, the crew needs to be able to maintain their tanks in the field, and, with a succession of secondary sites available, are able to keep fighting if the primary site is out of action.
• The USA has an extremely large army with sophisticated weaponry and enormous resources. As their tanks will rarely be away from support and repair units, less emphasis is placed on the crew's ability to maintain the tank themselves or to continue fighting it once damage has been sustained.
• Germany's tanks were completely outmaneuvered on the Russian front during WWII by the T-34, which was a major factor in their defeat. Also they lost more of their overly complex Tiger and Panther tanks due to mechanical breakdowns than enemy action. As a result, their tanks have since been incredibly manoeuvrable, with the resulting decrease particularly in protection. All demonstrations of post war German tanks focus on this ability. Enhanced reliability and lower maintenance requirements were also important design goals.
• Israel is a small, but relatively rich, nation, with limited man-power and surrounded by neighbours sworn to destroy it. Its primary concern is therefore crew-survivability, and to this end it is the only nation to have produced a modern tank with the engine placed at the front (to increase protection for the crew behind).

See also Tank classification for a overview of tank designs

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