M1 Abrams tank

M1 Abrams main battle tanks are only true tank type in the United States Army. They have gone through several upgrades, and were first used in combat in the Gulf War.

In some respects, these make no compromises with the traditional three tradeoffs in tank design: protection, weapons, and speed. Not in the classic list, but also extensive, are electronic sensors and communictions. Obviously, nothing can be optimized in all ways, and they are expensive and heavy.

Features of the M1A1 modernization program include increased armor protection; suspension improvements; and a nuclear, biological and chemical (NBC) protection system that increases survivability in a contaminated environment. The M1A1D modification consists of an M1A1 with integrated appliqué computer and a far-target-designation capability.

Protection

Their frontal armor appears to withstand direct hits from any tank gun and most antitank missiles in the world, although their thinner top and side armor has been punctured, usually with minimal damage. Complementing the armor is an automatic fire extinguishing system, a "blowout" ammunition compartment so that an explosion there does not go into the crew compartment, and other features.

Weapons

All versions that have gone into combat have a 120mm smoothbore main gun. It originally was limited to two types of ammunition, the armor-piercing, fin-stabilized, discarding-sabot (APFSDS) round used against tanks or other heavily armored target, and a shaped-charge high explosive anti-tank used against more lightly armored targets, and, originally, against all other targets.

The ammunition limitation was not inherent to the gun, but to its original ballistic fire control computer, which only could store information on two types of shell. A updated computer has more storage, so the gun can also fire blast-fragmentation, anti-personnel, and concrete penetrating. The limitation now tends to be in the number of shells for which the tank has storage.

Additional weapons include 7.62mm machine guns, with one mounted coaxially with the main gun, so pointing the turret points the machine gun. There is a .50 caliber machine gun currently fired by standing in an open tank hatch.

Protection

The main armor is a derivative of the British Chobham armor, which is a "sandwich" of several materials, each optimized against a certain type of armor-piercing weapon, and mutually reinforcing. The exact composition is classified, but is generally believed to contain steel armor plate, hard ceramic, dense depleted uranium, and possibly some fiber-resin composite materials.

Electronics=

• Independent thermal viewers for commander and gunner
• position navigation equipment,
• distributed data and power architecture
• embedded diagnostic system and improved fire control systems.
• MIL bus
• software commonality with C3I systems

Propulsion

The tank's top speed is limited by an engine speed limiter, not by the engine, a 1,500 hp turbine.