Spotlight: M1 Abrams

The M1 Abrams main battle tank is the principal combat tank of the United States Army and the United States Marine Corps, with three main versions being deployed starting in 1980: the M1, M1A1, and M1A2. The latest versions of the M1A2 have a new armor and electronics package. It is named after General Creighton Abrams, former Army Chief of Staff and commander of the Army's 37th Armored Regiment.

The M1 Abrams replaced the M60 Patton in US service, as well as the M48A5. It would, however, serve alongside the M60A3, which had entered service just two years before (1978) the M1, for over a decade.

The first attempt to replace the aging M60 series of tanks was the abortive MBT-70, developed with Germany. The M60 Patton was itself a gradual evolution of a design starting with the WWII era M26 Pershing, with a very tall profile, and fairly average armour and weapon compared to the contemporary Soviet designs. The MBT-70 was very ambitious, like many American weapons programs of the 1960s. It had a gun launched missile system, kneeling suspension, a driver housed in the turret, and various other ideas that ultimately proved unsuccessful. Cancellation of this project paved the way for the much more successful M1 Abrams tank, which did not incorporate most of the troublesome innovations tried by the MBT-70.

The M1 Abrams was designed by Chrysler Defense (in 1979, General Dynamics Land Systems Division purchased Chrysler Defense Division) and is currently produced by General Dynamics Corporation in Lima, Ohio, and first entered US Army service in 1980. An improved version of the M1, the M1A1, was introduced in 1985. The M1A1 has the M256 120 mm smoothbore cannon developed by Rheinmetall AG of Germany for the Leopard 2, improved armor, and a WMD protection system. The M1A2 is a further improvement of the M1A1 with a commander's thermal viewer and weapon station, position navigation equipment, digital data bus and a radio interface unit.

Further upgrades include depleted uranium armor for all variants, a system overhaul that returns all A1s to like-new condition (M1A1 AIM), a digital enhancement package for the A1 (M1A1D), a commonality program to standardize parts between the US Army and the Marine Corps (M1A1HC), and an electronic upgrade for the A2 (M1A2 SEP).

During Operations Desert Shield and Desert Storm and for Bosnia, some M1A1s were modified with armor upgrades. The M1 can be equipped with mine plow and mine roller attachments if needed. The M1 chassis also serves as a basis for the Grizzly combat engineering vehicle and the M104 Wolverine heavy assault bridge.

Over 8,800 M1 and M1A1 tanks have been produced at a cost of $2,350,000-4,300,000 per unit, depending on the variant.

Armor

The Abrams is protected by Chobham armor, a type of composite armor formed by multiple layers of steel and ceramics. It may also be fitted with reactive armor if needed (as in the Urban Survival Kit). Fuel and ammunition are in armored compartments with blowout panels to protect the crew from the risk of the tank's own ammunition cooking off if the tank is damaged. Protection against spalling is provided by a Kevlar liner. Beginning in 1988, M1A1 tanks received improved armor packages that incorporated depleted uranium (DU) mesh in their armor at the front of the turret and the front of the hull. Armor reinforced in this manner offers significantly increased resistance towards all types of anti-tank weaponry, but at the expense of adding considerable weight to the tank. The first M1A1 tanks to receive this upgrade were tanks stationed in Germany, since they were the first line of defense against the Soviet Union. US tankers participating in Operation Desert Storm received an emergency program to upgrade their tanks with depleted uranium armor immediately before the onset of the campaign. M1A2 tanks uniformly incorporate depleted uranium armor, and all M1A1 tanks in active service have been upgraded to this standard as well, the armor thickness believed to be equivalent to 24 inches (610 mm) of RHA. The strength of the armor is estimated to be about the same as similar western, contemporary main battle tanks such as the Leopard 2. The M1A1/M1A2 can survive multiple hits from the most powerful tank munitions (including 120 mm depleted uranium APFSDS) and anti-tank missiles. In the Persian Gulf War, Abrams tanks survived multiple hits at relatively close ranges from Iraqi T-72's, ATGM's. M829 "Silver Bullet" APFSDS rounds from other M1A1 Abrams were unable to penetrate the front and side armor (even at close ranges) in friendly fire incidents as well as an incident in which another Abrams tried to destroy an Abrams that got stuck in mud and had to be abandoned. In addition to the Abrams' advanced armor, some Abrams, most notably M1A1's of the US Marine Corps, are equipped with a Missile Countermeasure Device that can detect and jam the guidance systems of laser-guided anti-tank guided missiles (ATGM)[1]. This device is mounted on the turret roof in front of the Loader's hatch, and can lead some people to mistake Abrams fitted with these devices for the M1A2 version, since the Commander's Independent Thermal Viewer on the latter is mounted in the same place, though the MCD is box-shaped and fixed in place as opposed to cylindrical and rotating like the CITV.

Armament

Main armament

M68A1 rifled gun

The main armament of the original model M1 was the M68A1 105 mm rifled tank gun firing a variety of HEAT, high explosive, white phosphorus (smoke), and a highly efficient and lethal anti-personnel (multiple flechette) round. This gun is a license-built version of the British Royal Ordnance L7 gun. While a reliable weapon, the 105 mm was becoming obsolete in the face of advances in armor technology and was installed as a placeholder on the M1 until the M256 120 mm smoothbore could be completed.

M256 smoothbore gun

Secondary Armament 

The Abrams has three machine guns:

1. A .50 cal. (12.7 mm) M2 machine gun in front of the commander's hatch. On the M1, M1IP and M1A1, this gun is on a powered mount and can be fired using a 3× magnification sight, known as the Commander's Weapon Station (CWS for short), while the vehicle is buttoned up. On the M1A2 & M1A2SEP, this gun is on a flex mount, the Commander having to expose himself to fire the weapon manually. With the forthcoming TUSK addon kit, an M2 or a Mk 19 grenade launcher can be mounted on the CROWS remote weapons platform (similar to the Protector M151 remote weapon station used on the Stryker family of vehicles).
2. A 7.62 mm (.30 caliber) M240C machine gun in front of the loader's hatch on a skate mount.
3. A 7.62 mm M240C machine gun in a coaxial mount. The coaxial MG is aimed and fired with the computer fire control system used for the main gun.

The turret is fitted with two six-barreled smoke grenade launchers (USMC Abrams use an eight-barreled version). These can create a thick smoke that blocks both vision and thermal imaging, and can also be armed with chaff. The engine is also equipped with a smoke generator that is triggered by the driver. The Abrams also has provisions for storing an M16 rifle or M4 carbine inside the crew compartment for when they have to leave the protection of the tank under potentially hostile conditions, plus Abrams crews frequently carry personal sidearms, often M9 Beretta pistols.

Aiming

The Abrams is equipped with a ballistic fire-control computer that uses data from a variety of sources, including the thermal or daylight gunner's primary sight (GPS), a laser rangefinder, a crosswind sensor, a pendulum static cant sensor, data on the ammunition type, ammunition temperature, and a muzzle reference sensor (MRS) that determines barrel drop due to gravity and temperature. The fire-control system uses this data to compute a firing solution for the gunner. The ballistic solution generated ensures a hit percentage greater than 95 percent at nominal ranges. Either the commander or gunner can fire the main gun. Additionally, the Commander's Independent Thermal Viewer can be used to locate targets and pass them on for the gunner to engage while the commander scans for new targets.

Mobility

The M1 Abrams is powered by a 1500 hp (1119 kW) Honeywell AGT1500 (originally made by Lycoming) gas turbine, and a 6 speed (4 forward, 2 reverse) Allison X-1100-3B Hydro-Kinetic Automatic transmission, giving it a governed top speed of 45 mph (72 km/h) on roads, 30 mph (48 km/h) cross-country. With the engine governor removed, speeds of around 60 mph (100 km/h) are possible on an improved surface; however, damage to the drive train (especially to the tracks) and an increased risk of injuries to the crew can occur at speeds above 45 mph. The tank can be fueled with diesel fuel, kerosene, any grade of MOGAS (motor gasoline), or JP-4 or JP-8 jet fuel; the U.S. Army uses JP-8 jet fuel in order to simplify logistics.

The gas turbine propulsion system has proven quite reliable in practice and combat, but its high fuel consumption is a serious logistic issue (starting up the turbine alone consumes 40 liters of fuel). The high speed, high temperature jet exhaust emitted from the rear of M1 Abrams tanks makes it difficult for the infantry to proceed shadowing the tank in urban combat. The turbine is noisy, comparable to a helicopter engine, although the noise character (pitch) is significantly different from a contemporary diesel tank engine, reducing the audible distance of the sound, thus the nickname, "whispering death". Future US tanks may return to reciprocating engines for propulsion, as 4-stroke diesel engines have proven quite successful in other modern heavy tanks, e.g. the Leopard 2, Challenger 2 and Merkava. The small size, simplicity, power-to-weight ratio, and easy removal/replacement of the turbine powerpack does, however, present significant advantages over any proposed reciprocating replacement.

The Abrams can be carried by the C-5 Galaxy and C-17 Globemaster III. The limited capacity (one combat-ready tank or two transport-ready tanks in a C-5, one combat-ready tank in a C-17) caused serious logistical problems when deploying the tanks for the First Gulf War, though there was enough time for 1,848 tanks to be transported by ship. Tanks shipped in the transport-ready configuration require depot-level maintenance to install a number of sections of armor, and need to be fueled and loaded with ammunition. Tanks shipped in the combat-ready configuration can enter combat immediately.

Combat History

 

In World War II, it took a Sherman Tank an average of 17 rounds to destroy an enemy tank 700 meters away. The Abrams, by contrast, can destroy certain enemy tanks by firing, on the move, a single round from 2,000 meters away (Crusade by Rick Atkinson, pg. 251, 1993). As the Abrams entered service in the 1980s, they would operate alongside M60A3 within the United States military, and with other NATO tanks in numerous Cold War exercises. These exercises usually took place in Western Europe, especially West Germany, but also in some other countries like South Korea. During such training, Abrams crews honed their skills for use against the men and equipment of the Soviet Union. However, by 1990 the USSR had collapsed and the Abrams would have its trial by fire in the Middle East.

Operation Desert Storm 

The Abrams remained untested in combat until the Gulf War in 1991. A total of 1,848 M1A1s were deployed to Saudi Arabia. The M1A1 was superior to Iraq's Soviet-era T-55 and T-62 tanks, as well as Iraqi assembled Russian T-72s, and locally-produced copies (Asad Babil tank). The T-72s (like most Soviet export designs) lacked night vision and then-modern range finders, though they did have some night fighting tanks with older active infrared systems or floodlights — just not the latest starlight scopes and passive infrared scopes as on the Abrams. Only 23 M1A1s were taken out of service in the Gulf and none of these losses resulted in crew deaths from Iraqi fire. Some others took minor combat damage, with little effect on their operational readiness. There were only 3 tank crew members wounded beyond doubt by enemy action.

The M1A1 was capable of making kills at ranges in excess of 4000 m. In friendly fire incidents the front armor and fore side turret armor survived direct APFSDS hits from other M1A1s. This was not the case for the side armor of the hull and the rear armor of the turret, as both areas were penetrated at least in two occasions by friendly DU ammunition during the Battle of Norfolk.

Nearly all sources claim that no Abrams tank has ever been destroyed as a result of fire from an enemy tank, but some have certainly taken some damage which required extensive repair. There is at least one account, reported in the following Gulf War's US Official Assessment (scan), of an Abrams being damaged by three kinetic energy piercing rounds. The DoD report indicates that witnesses in the field claimed it was hit by a T-72 Asad Babil. The KE rounds were unable to fully penetrate and stuck in the armor, but the damage was enough to send the tank to a maintenance depot. This is the only verified case of an M1A1 knocked out by an Iraqi MBT.

Presumably the impacts set the storage boxes on fire. The tests at the impact point indicate the sabot shells were conventional, since no radiological trace was found there.

On the night of February 26, 1991, four Abrams were disabled in a suspected friendly fire incident by Hellfire missiles fired from AH-64 Apache attack helicopters, with the result of some crew members WIA. The tanks were part of TF 1-37, attacking a large section of Tawakalna Republican Guard Division, their numbers being B-23, C-12, D-24 and C-66. However, C-12 was definitively hit and penetrated by a friendly DU shot and there is some evidence that another Iraqi T-72 may have scored a single hit on B-23, besides the alleged Hellfire strike.

Tanks D-24 and C-66 took some casualties as well. Only B-23 became a permanent loss. The DoD's damage assessments state that B-23 was the only M1 with signs of a Hellfire missile found nearby.

Also during Operation Desert Storm, three Abrams of the 24 ID were left behind the enemy lines after a swift attack on Talil airfield, south of Nasiriyah, on February 27. One of them was hit by enemy fire, the two other embedded in mud. The tanks were destroyed by US forces in order to prevent any trophy-claim by the Iraqi Army.

Iraq, 2003

Further combat was seen during 2003 when US forces invaded Iraq and deposed the Iraqi leader Saddam Hussein. The campaign saw very similar performance from the tank with no Abrams crew member being lost to hostile fire during the battle in Iraq, mainly due to unopposed air-support. The most lopsided achievement of the M1A2s was the destruction of seven T-72s Lion of Babylon tanks in a point-blank skirmish (less than 50 yards) near Mahmoudiyah, about 18 miles south of Baghdad, with no losses for the American side. However, on October 29, 2003, two soldiers were killed and a third wounded when their tank was disabled by an anti-tank mine, which may have been combined with other explosives to increase its effect. This marked the first time deaths resulted from a hostile-fire assault on the M1 tank from enemy forces. Following lessons learned in Desert Storm, the Abrams and many other US combat vehicles used in the conflict were fitted with Combat Identification Panels to reduce friendly fire incidents. These were fitted on the sides and rear of the turret, with flat panels equipped with a four-cornered 'box' image on either side of the turret front (the latter of which can be seen in the above image). In addition to the Abrams' already-formidable armament, some crews were also issued AT4 shoulder-fired anti-tank rockets under the assumption that they might have to engage heavy armor in tight urban areas where the main gun couldn't be brought to bear. Some Abrams were also fitted with a secondary stowage bin on the back of the existing bustle rack on the rear of the turret referred to as a bustle rack extension to enable the crew to carry more supplies and personal belongings.

During the major combat operations in Iraq, Abrams crew members were lost when one tank of the US Army's 3rd Infantry Division, and US Marine Corps troops, drove onto a bridge. The bridge failed, dropping the tank into the Euphrates River, where four Marines drowned.

During an early attack on Baghdad, one M1A1 was disabled by a recoiless rifle round that had penetrated the rear engine housing, and punctured a hole in the right rear fuel cell, causing fuel to leak onto the hot turbine engine. After repeated attempts to extinguish the fire, the decision was made to destroy or remove any sensitive equipment. Oil and .50 caliber rounds were scattered in the interior, the ammunition doors were opened and several thermite grenades ignited inside. Another M1 then fired a HEAT round in order to ensure the destruction of the disabled tank. The tank was completely disabled but still intact. Later, an AGM-65 Maverick was fired into the tank to finish its destruction. Ironically the tank still appeared to be intact from the exterior.

On November 27, 2004 an Abrams tank was badly damaged from the detonation of an extremely powerful improvised explosive device (IED). The IED consisted of three M109A6 155 mm shells, with a total explosive weight of 34.5 kg, that detonated next to the tank. The tank's driver received lethal injuries from shrapnel. The other three crew members were able to escape.

On December 25, 2005 another M1A2 was disabled by a roadside bomb that left the tank burning near central Baghdad. One crew member, Spc. Sergio Gudino, died in the attack.

On June 4, 2006 two out of four soldiers died in Baghdad, Iraq, when an IED detonated near their M1A2.

Some were disabled by Iraqi infantrymen in ambushes employing short-range antitank rockets, such as the Russian RPG-7, during the 2003 invasion. Frequently the rockets were fired at the tank tracks. Another was put out of action in an incident when fuel stowed in an external rack was struck by heavy machine gun rounds. This started a fire that spread to the engine.

There have also been a number of Abrams crewmen killed by sniper fire during times when they were exposed through the turret hatches of their tanks. Some of these attacks were filmed by insurgents and can be seen in the videos attributed to the so-called Juba Sniper. 

External Links

 

Abrams US Army Fact File

M1A1/A2 Abrams Main Battle Tank Information

Main Battle Tank M1A1 Abrams

M1A1 Abrams, M1A2 Abrams, M1A2 SEP Abrams

Anatomy of an M1 Abrams

howstuffworks page on the M1 Abrams, with a detailed overview of how the tank works

M-1 TUSK Tank Urban Survivability Kit

M1A1 AIM Upgrade Program

M1A2 SEP Upgrade program

The Armor Site! page on Abrams

Globalsecurity.com

Article courtesy of Wikipedia.