M1A1 and M1A2 Abrams Main Battle Tank

The M1A1 is an improved version of the M1 Main Battle Tank (MBT). It includes a 120mm smoothbore main gun, an NBC overpressure protection system, and an improved armor package. This tank significantly increases the capabilities of the Fleet Marine Forces across the full spectrum of conflict in the near and midterm. The M1A1 Tank, in addition to the improved armor, 120mm smoothbore gun and the NBC overpressure system, has a Deep Water Fording Kit (DWFK), a Position Location Reporting Systems (PLRS), enhanced ship tiedowns, Digital Electronic Control Unit (DECU) (which allows significant fuel savings),and Battlefield Override.

The main weapon of the M1A1 is the M256 120mm smoothbore cannon, designed by the Rheinmetall Corporation of Germany. Engagement ranges approaching 4000 meters were successfully demonstrated during Operation Desert Storm. The primary armor-defeating ammunition of this weapon is the armor-piercing, fin-stabilized, discarding sabot (APDS-FS) round. Depleted uranium has density two and a half times greater than steel and provides high penetration characteristics. Several other types of ammunition are available as well. It is reliable, deadly accurate and has a "hit/kill ratio" that equals or surpasses any main battle tank armament in the world.

As with virtually every tank every fielded by the US, the familiar .50 caliber Browning M2 Heavy Barrel machine gun - the "Ma Duce" - is located in a powered mount at the Commander's station and is equipped with a x3 magnification sight. The Loader is provided with a 7.62mm M240 machine gun, and another M240 is mounted in-line with the main gun of the tank ("coaxially"). It is in a fixed mount and is aimed with the main gun to suppress enemy ground troops.

The layout of the Abrams follows classic tank design and accommodates a crew of four: Commander, Gunner, Loader and Driver. The Commander and Gunner are seated on the right side of the turret. The Loader is seated on the left side of the turret, and the Driver is seated at the center front of the hull.

The Commander's station is equipped with six periscopes which provide all round 360 degree view. The Independent Thermal Viewer (ITV) from Texas Instruments provides him with independent, stabilized day and night vision with a 360 degree view, automatic sector scanning, automatic target cueing of the Gunner's sight with no need for verbal communication, and a complete back-up fire control system - the Commander is capable of firing the main gun independent of the Gunner.

The Gunner's Primary Sight-Line of Sight (GPS-LOS), was developed by the Electro-Optical Systems Division of Hughes Aircraft Company. The night vision Thermal Imaging System (TIS), also from Hughes, creates an image based on the differences of heat radiated by objects in the field of view. The thermal image is displayed in the eyepiece of the Gunner's sight together with the range measurement to within 10 meters of accuracy, from a Hughes laser range finder, which is integrated into all of the fire control systems. The Abrams also has an onboard digital fire control computer. Range data from the laser rangefinder is transferred directly to the fire control computer, which automatically calculates the fire control solution. The data includes 1) the lead angle measurement, 2) the bend of the gun measured by the muzzle reference system of the main armament, 3) wind velocity measurement from a wind sensor on the roof of the turret and 4) the data from a pendulum static cant sensor located at the center of the turret roof. The Gunner or Commander manually inputs the data on the ammunition type and temperature, and the barometric pressure and the weapon is prepared for engagement.

The Loader's station is located on the left side of the turret and has no special fire control equipment.

The Driver's station is located at the center front of the hull. The Driver is in a semi-reclined position when his hatch is closed, as it must be whenever the vehicle is in operation. His station is equipped with a standard array of gages and monitors reflecting the condition of vehicle fluid levels, batteries and electrical equipment. The Driver has either three observation periscopes or two periscopes on either side and a central image intensifying ("Starlight") periscope for night vision. The periscopes provide 120 degrees field of view. The Driver's night vision equipment enables the tank to maneuver at normal daytime driving speeds in darkness and in poor visibility conditions such as in the dust and smoke encountered on the battlefield.

The turret is fitted with two six-barreled M250 smoke grenade launchers, one on each side of the main gun. The standard smoke grenade contains a phosphors compound that masks thermal signature of the vehicle to the enemy. A smoke screen can also be laid by an engine operated system.

An improvement program will eventually upgrade all M1A1 tanks with steel encased depleted uranium armor, which has a density at least two-and-a-half times greater than steel. The depleted uranium armor will raise the total weight of the Abrams tank to 65 tons, but offers vastly improved protection in the bargain.

The stowage for the main armament ammunition is in armored ammunition boxes behind sliding armor doors. Armor bulkheads separate the crew compartment from the fuel tanks. The tank is equipped with an automatic Halon fire extinguishing system. This system automatically activates within 2 milliseconds of either a flash or a fire within the various compartments of the vehicle. The top panels of the tank are designed to blow outwards in the event of penetration by a HEAT projectile.

Nuclear, Biological and Chemical (NBC) warfare protection is provided by an overpressure clean-air conditioning air system, a radiological warning system, and a chemical agent detector. The crew are individually equipped with protective suits and masks.

During Operation Desert Shield/Storm, the Marine Corps borrowed 60 M1A1s (called the M1A1 Heavy Armor) from the US Army. There were also 16 Marine Corps M1A1 Tanks delivered on an accelerated schedule for employment during the operation. This total of 76 M1A1 tanks was employed by 2d Tank Battalion and elements of 4th Tank Battalion. The M1A1 tanks saw immediate action during the I Marine Expeditionary Force (IMEF) drive through the burning Kuwaiti oil fields. All loaned tanks were returned to the US Army after Desert Storm.

Due to unique Marine Corps amphibious requirements, and the need for both supportability and interoperability between the Marine Corps and the US Army, the two services agreed to jointly produce the M1A1 Main Battle Tank. The M1A1 MBT has the capability to conduct operations ashore. It is compatible with all US Navy amphibious ships and craft (to include the LCAC) and Maritime Prepositioning Ships (MPS). The USMC completed fielding of all tanks, to include active, reserve, MPS, and depot maintenance float (DMF) during FY 96.

In 1995 the 26th MEU became the first amphibiously deployed unit to carry the M1A1. This added some complication to the logistics of the unit due to the tank's weight. Topping the scales at over 68 tons the vehicle requires special care during amphibious operations. One tank can be carried at a time on an Air Cushioned Landing Craft (LCAC), two on a Landing Craft Utility (LCU), but only during fairly calm seas. For operations with the Marine Corps, tanks have been equipped with special fording systems. These modifications include extended air intake and exhaust tubes that allow the vehicles to cross rivers and shallow waters such as the surf zones that Marines operate in.

The mission of the M1A2 Abrams tank is to close with and destroy enemy forces using firepower, maneuver, and shock effect. The M1A2 is being fielded to armor battalions and cavalry squadrons of the heavy force. In lieu of new production, the Army is upgrading approximately 1,000 older M1 tanks to the M1A2 configuration. Going from the M1A1 to M1A2, the Army did several things that significantly reduced ballistic vulnerability, adding dual, redundant harnesses components, redundant data buses, distributing electrical power systems so all the power controls are not in one place.

During the Army’s current M1A2 procurement program about 1,000 older, less capable M1 series tanks will be upgraded to the M1A2 configuration and fielded to the active forces. There is currently no plan to field the M1A2 to the ARNG. The Army has procured 62 new tanks in the A2 configuration and as of early 1997 completed the conversion of 368 older M1s to M1A2s. The first three years of M1A2 Abrams upgrade tank work, between 1991-1993, delivered 267 tanks. A multi-year procurement of 600 M1A2 upgrade tanks was run at Lima [Ohio] Army tank plant from 1996 to 2001.

adds second generation forward looking infrared technology to the gunner’s and commander’s thermal sights. This sensor also will be added to older M1A2s starting in FY 2001.

Another improvement in the M1A2 is the Thermal Management System (TMS) which keeps the temperature within the crew compartment under 95 degrees and the touch temperature of electronic units under 125 degrees during extreme conditions. By reducing the temperature in the crew compartment for the crew and electronic units, this increases the operational capability for both soldiers and the vehicle. The TMS consists of an Air Handling Unit (AHU) and a Vapor Compression System Unit (VCSU) capable of providing cooling capacity for the crew and Line Repairable Units (LRUs). The AHU is mounted in the turret bustle and the VCSU is mounted forward of the Gunner's Primary Sight (GPS). The TMS uses enviromentally friendly R134a refrigerant and propylene glycol/water mixture to maintain the LRU touch temperature at less than 140 degrees Fahrenheit. The TMS is mounted in the left side of turret bussel and weighs 384 pounds.