M1 / IPM1 Abrams Main Battle Tank

Designed in the 1970's by the Land Systems Division of the General Dynamics Corporation in response to the U.S. Army's MBT-70 program, the first M1 rolled off the assembly line in 1978. After two years of acceptance trials, the first of these vehicles was delivered to the US Army on February 28, 1980. By 1985, evaluations of field service had prompted the first modification requests, and production shifted to the M1A1. The first M1A1's were delivered to units in August of 1985. The Army converted 368 older M1s to M1A2s. An additional 580 M1s were upgraded to A2s under a five-year contract awarded in FY1996, with a total of 998 M1 upgrades. In 1999 the Army began upgrading M1s to the M1A2 System Enhancement Program (SEP) configuration. The SEP embeds digitization capabilities inside the Abrams' electronic architecture, eliminating the requirement for electronic appliques.

The last original model of the M1 tank was retired from duty in the active Army in September 1996. HHC, 2-81 Armor of the 1st Armor Training Brigade at Fort Knox used this early model of the M1 to train National Guard and Reserve units. It was the last active duty unit to carry this model in its inventory. The Fort Knox armor unit's 10 M1s being retired from active duty were rebuilt as M1A2s. Meanwhile, the unit was to receive M1A2s as replacements.

The original M1 revolutionized the Army's combat capabilities and marked a turning point in U.S. tank development. Its most impressive feature was its special armor, a composite "sandwich" of steel and other materials capable of defeating HEAT rounds in addition to kinetic energy penetrators. The M1 was faster and more maneuverable than its predecessors in the M60 series, while offering a lower, smaller silhouette. It was constructed of flat armor sections welded together, rather than armor castings, the method used in earlier U.S tanks.

The earliest M1s were armed with the M60's 105mm rifled cannon, a British design first adopted to the final versions of the old M48 series. Subsequent M1s were upgunned with the German Rheinmetall smoothbore cannon of 120mm. Another revolutionary feature of the first M1 tanks were their turbine engines, replacing the diesels that powered the M48 and M60 series tanks. The engine change, despite a penalty in fuel consumption, resulted in much quieter operation, so much so that soldiers encountering the tank in early maneuvers dubbed it "Whispering Death."

Fielded in February 1980, the M1 General Abrams main battle tank revolutionized armored warfare. Incorporating an advanced shoot-on-the-move fire control system, a thermal imaging sight, a 1500 horsepower gas turbine engine and an advanced armor design similar to the Chobham armor developed in England, the M1 was the most lethal armored vehicle in the world. Conceived in 1971 as a replacement for the aging M60 tank, which was itself an extension of the 1050s era M 47/48 program, the M1 was going to be of a completely new design, establishing a new family of American main battle tanks.

Providing the Abrams with a true shoot on the move capability, the fire control system automatically corrects for range, turret slew (motion) rate, crosswind, and tank axial tilt (cant). In addition, the gunner manually enters ammunition or weapon type, air and ammunition temperatures, barometric pressure, and gun tube wear, while range is instantly calculated by a Nd:YAG (Neodymium doped Yttrium Aluminum Garnet) near infrared laser rangefinder. Lastly, the gunner can compensate for gun tube deformation (caused either by heat generated from firing the cannon or atmospheric changes) through the use of a muzzle reference system, which allows for a rapid realignment of the cannon and the gunner's primary sight.

The Chobham armor built into the M1 represents a veritable leap in armor technology. Composed of layers of metal, ceramics, and spaces, this new armor is far superior to RHA (Rolled Homogeneous Armor) in defeating kinetic and chemical energy weapons. To increase crew safety and survivability, all of the M1's ammunition is stored in armored compartments which are designed vent dangerous gasses and fragments away from the crew in the event of an ammunition explosion. The crew and engine compartments are equipped with an automatic fire suppression system, utilizing numerous fire detection sensors and pressurized Halon gas, which can react to and suppress a compartment fire in less than 250 ms.

To survive on the NBC (Nuclear, Biological, Chemical) battlefield the M1 is also equipped with both an over pressurization and air sterilization system which will protect the crew from these hazards and allow them to continue combat operations without having to wear protective overgarments and masks while buttoned up inside the vehicle.

Lastly, the M1 was the first land combat vehicle to utilize a gas turbine multi fuel engine, which offers a higher power to weight ratio than any other contemporary tank power plant and gives the Abrams unparalleled tactical mobility and cross country speed. The M1 retains the M68 105mm rifled cannon used on the M60 series tanks, which was originally based on the British M7 105mm cannon design, and is capable of firing both rifled and fin stabilized ammunition. In addition, the M1 is equipped with two M240 7.62mm machine guns; one mounted coaxially with the main gun and fired by gunner, and the other mounted at the loader's station. The Commanders Weapon Station (CWS) is equipped with an M2 heavy barrel Caliber .50 machine gun. The CWS can be reconfigured to fire the M240 machine gun as a substitute.) The M1 is equipped with a pair of M250 red phosphorus smoke grenade launchers and is capable of generating smoke by injecting diesel fuel into the engine exhaust.

Originally designated the XM1, the first production model was designated the M1, of which 2,374 were built between 1982 and 1985. In 1984 the M1IP (Improved Product) was introduced, which was outwardly identical to the M1, but which incorporated a number of internal automotive, electronic and armor improvements. Production of the M1IP was halted at 84 tanks in 1986, when the Lima and Detroit tank plants were reconfigured to produce the up-gunned 120mm M1A1. In 1992 a study was conducted evaluating the feasibility of upgrading the Army's fleet of M1s to M1A2 SEP (Standard Equipment Package) standard and low rate production was approved in 1994. Since then the Army agreed to convert 547 M1s to the M1A2 SEP standard.

The M1A2 System Enhancement Package Version 2 is the latest M1 variant. The most technologically advanced digital tank in US, the M1A2 SEP V2 includes improved color displays, day and night thermal sights, auxiliary power and a tank-infantry phone. It can also accommodate future technology improvements for compatibility with the U.S. Army's Future Combat Systems. In January 2008 the U.S. TACOM Lifecycle Management Command awarded General Dynamics Land Systems a contract for parts to upgrade 435 M1A1 Abrams tanks to the M1A2 Systems Enhancement Package Version Two configuration. The U.S. Army TACOM Lifecycle Management Command awarded General Dynamics Land Systems $614 million on 01 August 2008 to upgrade 235 M1A1 Abrams main battle tanks to the M1A2 Systems Enhancement Package (SEP) Version Two (V2) configuration. The order was made under the multi-year contract awarded in February 2008 which authorized the modernization of 435 M1A1 tanks that have been in the Army's inventory for more than 20 years. An additional 180 tanks remain to be upgraded through the program, which will complete the conversion of all tanks in the Army's active component to the M1A2 SEP V2 configuration.

The Army is looking at further versions, up to V4, with capabilities being considered by the Army's Training and Doctrine Command.