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M1 Abrams main battle tank


Written by Sakhal

For knowing more details about the initial development and characteristics of the M1 Abrams main battle tank, you can visit the article Chrysler M-1 main battle tank.

Background

After the cancellation of the MBT-70/XM803 program, the United States Army ellaborated a new group of specifications for what should be the main battle tank for the incoming 1980s. In January 1973 the United States Secretary of Defense approved the document for the development concept, and the 28th June 1973 contracts were awarded to the Chrysler Corporation and to the Detroit Diesel Allison Division of the General Motors Corporation for creating prototypes for a program denominated XM-1. Both companies proposed tanks weighing around 50 tonnes, supported by a torsion-bar suspension and armed with the M68 105-millimeter cannon and the Bushmaster 25-millimeter chain cannon, which was later removed from the specification. General Motors proposed a tank propelled by one or two Diesel engines, whereas Chrysler proposed the adoption of either a Diesel engine or a gas turbine, despite this latter was not liked.

However, both proposals showed that it would not be possible to achieve the desired protection levels within the initially specified weight. The engineers of the United States Army Tank Command began to work to find a solution. In March 1973 it was clear that sloped plates of laminated and spaced composite armor offered the best possibilities. Still, it would be necessary to increase the total weight of the tank. Also the original cost limit per unit would have to revised upward, from 400,000 to 500,000 dollars. The contracts for Chrysler and General Motors were awarded at 69 and 87.9 millions of dollars, respectively, which should cover the costs and profits of the development, manufacture and trials of the prototypes.

When both companies presented their projects a great surprise arose. Even if the United States Army Tank Operation Group had shown firm opposition against the gas turbine engine, the Chrysler project team had chosen this engine for their prototype. It was adduced as justification the higher power, smaller size, lesser power loss, lesser noise levels, absence of smoke and easier start up at low temperatures. It was a risky decision, but in the end the Avco Lycoming AG-1500 demonstrated to be a very good engine. Albeit it was more expensive to produce than the AVCR-1360 Diesel engine specified by General Motors, it was also less expensive to maintain, so the difference of costs between both engines would be very small if considering the expected service life of each.

In the late 1975 the two XM-1 prototypes were delivered to the Aberdeen Proving Ground, and from February to May 1976 they were submitted for trials, being both tanks able to perform in accordance with the specifications. The choice between the two prototypes was made in July, but kept secret for the time being. However, it was leaked that the Army had chosen the prototype of General Motors but that at the same time it had decided to adopt the turbine engine specified by Chrysler. Besides, It had been anticipated that in the future it would be necessary to install a more powerful cannon and this would require to redesign the turret. Because of this the final decision was delayed until November 1976. Both competitors took advantage of this opportunity and presented revised projects fitted with both engine types.

The 12th November it was announced that the offer of 196 millions of dollars presented by Chrysler had been selected against that of 232 millions presented by General Motors. This company had not been able to limit the higher installation cost of the turbine engine and therefore Chrysler's model would be put into serial production. After ten years of development and 400 millions of dollars (of 1972), the United States Army had a third-generation main battle tank. The new tank was named after General Creighton Abrams, a former chief of armored units who later became chief of the Army's High Staff.

Production

The first preseries exemplar left the factory in February 1978. The Lima Army Modification Center started in 1979 the construction of the first 110 series exemplars, being delivered the two first tanks to the Army the 28th February 1980. The initial number of series exemplars was estimated in 3312, with a cost of 4900 millions of dollars. Two years later the Detroit Tank Arsenal, close to complete the production of the M60, prepared its production lines for the M-1, while Chrysler sold its tank manufacturing division to the General Dynamics Corporation, leaving behind a business in which it had been very influential during 40 years. The order of the Army reached 7251 exemplars to be delivered before the end of the 1980s, and the production, initially of 30 exemplars per month, was increased to 60 in 1982 and reached 70 in the late 1983.

In February 1984 they were 2374 the exemplars produced of the M1 variant, followed by 894 exemplars of an improved batch completed in May 1986, when it was ordered, parallely, the M1A1 version. This one attracted attention from the Marine Corps, which ordered 221 exemplars, delivered between November 1990 and the late 1991; to these would be added another 50 exemplars, transferred in the spring of 1995 from the Army arsenals. The production of the M1, M1A1 and M1DU (version with enhanced armor based on depleted uranium) ended in September 1991, with a total amount of 7467 exemplars.

In 1992 they started to be delivered the new M1A2 which had been ordered in April 1990 and, the 18th December 1992, the Secretary of Defense authorized the first phase to upgrade 210 M1 to the A2 variant. From September 1993 to June 1996 they were installed 1500 EAPU (External Auxiliary Power Unit). In April 1994 it was consolidated the upgrade program, being started the work on 998 exemplars, which ended in September 1996; meanwhile additional funds had been raised for upgrading another 792 exemplars, to be upgraded before 2003. Parallely, from 1994 they were progressing the works in the M1A2 SEP (System Enhancement Package) variant.

The M1 Abrams constitutes the backbone of the land forces of the United States Army and Marine Corps, as well as of the armies of Egypt, Saudi Arabia and Kuwait. The prestations of this model allowed to sign a coproduction agreement with Egypt in 1988, which involved the transfer of twenty-five M1A1 from United States and the construction of 530 additional units (later extended for another 200 exemplars) in the ETP (Egyptian Tank Plant), located in the vicinity of Cairo. Saudi Arabia ordered 315 units of the M1A2 variant, to which another 150 were later added, while Kuwait ordered another 218 units.

The M1 Abrams and its competitors

After a long and costly development program it could seem a bit surprising how "conventional" the M1 Abrams was. Many suggestions had been formulated to divert from the norms accepted in the previous MBT-70/XM803 program, but they were all rejected because of being too expensive or having a limited increase in effectiveness. Consequently, there were very little innovations with exception of the engine, and neither it was the first time that a turbine engine was used in a tank. Then, why was the M1 so good?

The M1 had the same type of armor than the Challenger and the Leopard 2 and hence protection levels would be allegedly similar. The M1 was faster and more agile than the Challenger, but not better than the Leopard 2 and inferior to the AMX-56 Leclerc in this regard. Due to the characteristics of the turbine engine the M1 had a slightly better acceleration than the AMX-56, but because of its reduced final step in the transmission it was 6.5 kilometers/hour slower. Furthermore, the high temperature of the engine produced a much clearer thermal signature, a very important factor in modern armored warfare.

The height profile of the M1 was similar to that of the Challenger, being both 40 centimeters taller than the Leopard 2 and the AMX-56; this was another important factor, as tank ditches are done to cover not only the hull of the tank but the turret as well. It was said that the fire control system of the M1A2 was the best in the market but, in practice, the difference between the best and the second best fire control system was much smaller than the difference between the best and the second best gunner. There was not much choice regarding firepower, as the American, German and French tanks used similar cannons, and only the British cannon was slightly inferior, due to the different ballistic prestations of rifled and smooth bores when firing APFSDS (piercing) or HEAT (shaped charge) ammunition.

The Soviet T-80, armed with a 125-millimeter cannon/missile launcher, could not be compared in real terms with these four tanks, with exception of its firepower, which would be much greater if the tank operated according to the specifications (which was a big question mark). As it was much lighter than the tanks of the NATO, there were many reasons to believe that the protection levels were accordingly lesser, with the importance that this has regarding survivability. There were also serious doubts about the capability of the post-Soviet Russian Army - and the armies of other former Soviet clients - for maintaining their vehicles in the required levels. In any case, the former clients of the Soviet Union had never received anything better than outdated T-72 models, without possibility of reaching the levels of the M1 or any of the other tanks of the NATO, with the possible exception of the AMX-30.

This situation was well demonstrated during Operation Desert Storm, in the war for the liberation of Kuwait in 1991. Over a thousand of M1A1 entered action in the late February, moving at full speed across the desert while fighting without rest the 700 or 800 tanks deployed by the Iraqi Army, the largest part of them being T-72 and T-62, supported by numerous T-54/55. The American tanks showed a high availability rate and a great combat capability that derived from the intrinsical quality of their design. The result was really spectacular, as the M1A1 destroyed every enemy tank that they found, suffering only a handful of losses. They were so well protected that when one of them was hit by two piercing projectiles from a distance of 500 meters these could only ricochet in the armor.

Characteristics of the M1 Abrams

When the M1 Abrams made apparition it was acclaimed as the best tank in the world, built with the most effective armor in relation to its weight, equipped with the best fire control system and having the best regarding other prestations. Despite of this, shortly after its apparition the new tank seemed outdated regarding its main armament, which thanks to the early foresights could be upgraded to the 120-millimeter caliber without much effort. The M1A1, as the improved tank was called, entered service in the summer of 1985. In turn, the M1A2, which had an improved thermal imaging system for the driver and the commander, better sights and a satellite-based navigation system with GPS (Global Positioning System), entered service in 1992.

Later improvements that were known, such as the Block III program, intended to be started before the end of the 1990s, included an improved 120-millimeter cannon or one of larger caliber, any of them fitted with an automatic loader. The Block III program required as well to reallocate the engine in transversal position to gain additional space inside the hull, which could be used to carry extra ammunition or, most probably, additional fuel and an auxiliary Diesel engine to feed the electronic and tactical elements. Such layout would allow the turbine engine to operate at a lesser number of revolutions when the tank is static.

Widely modified by the results of combat actions, the last variants of the M1 incorporate notable advances in the tactical management and fire control systems, as well as in the elements which configure their armor. From the original chassis variants have been developed for the laying of bridges (Wolverine) or the neutralization of anti-tank mines (RAMTA mechanical plow).

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The basic characteristics of the M1A1 are: a crew of four, a weight of 57.154 tonnes, a length of 7.819 meters in the hull, a height of 2.438 meters and a fording capability of 1.219 meters without preparation and 1.98 meters with preparation. The M1A2 weighs about two tonnes more due to the increment of protection, albeit the dimensions of both versions are very similar. The turret and the hull are composed of composite armor plates which combine ceramics and other "classified" elements to form a wall which has enough thickness and inclination to stop without problems the effects caused by the explosion of anti-tank missiles, projectiles fired by other tanks, shrapnel expelled by artillery explosions and impacts from grenades, mines and light projectiles fired by armored cavalry vehicles.

The propulsion plant comprises a Lycoming Textron AGT 1500 gas turbine, which produces 1500 horsepower at 30000 revolutions per minute (before the 10:1 reduction gear). Connected to an Allison X-1100-3B automatic gearbox with four forward speeds and two backward speeds, it is capable of moving the tank at a maximum speed of 67 kilometers/hour and accelerate it from 0 to 32 kilometers/hour in just 6.8 seconds, which facilitates fast position changes and allows the tank to overcome 60-percent slopes and 1.066-meter tall obstacles. Its operational range reaches 465 kilometers, thanks to internal fuel tanks which can store up to 1907.6 liters, and its great mobility across rough terrains is possible thanks to an hydromechanical suspension system which includes advanced torsion bars.

The offensive vector of the M1 is the M256 120-millimeter cannon, which allows to destroy without difficulty other tanks at distances over 2.5 kilometers. The main weapon is complemented by a Browning M2HB 12.7x99-millimeter heavy machine gun and two M240 7.62x51 light machine guns. A digital fire control system, which is associated to the TIS (Thermal Imaging System) stabilized infrared sight, effectuates all the calculations related to the firing of the main weapon. A Neodimium-YAG laser rangefinder is used to measure the distance to the target, and a Kollmorgen Model 939 sight serves as auxiliary rangefinder. The main weapon, having its two axes stabilized, can be used to fire against moving targets, while the own tank is moving as well, with a high probability of successful impact and a rate of fire of three shots every fifteen seconds.

The turret of the M1 was designed in such a way that its interior presents a large space for the crew and the diverse sensors associated to the management of the vehicle; so, the three occupants can enjoy a considerable degree of comfort which affects positively their combat performance. Installed in the upper part of the turret, they are visible the vision elements associated to the surveillance and targeting systems, which allow the commander and the gunner to observe the diverse targets and manage the attacks during day and night, even against moving targets. The baskets attached to the rear part of the turret are used to transport the diverse equipment and accessories used in the different phases of combat. These elements ensure the maximum availability of the tanks and the crews which operate them.

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Interior of the turret of an M1A2 Abrams of the early generation, circa 1992.

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Main cannon: In the muzzle of the 120-millimeter cannon which arms the M1A1 there is a collimator sensor which allows to aim with greater accuracy and ensures that targets located at a distance of up to four kilometers can be hit with piercing ammunitions such as the M829 APFSDS-T, which includes a depleted uranium piercing core.

Fire control: The fire control system of the M1 is fully stabilized and allows to fight any type of targets even if the very tank and the targets are in movement. It is one of the most advanced on its genre and stands out by both its simplicity of use and high rate of availability.

Commander's cupola: Next to the commander's cupola there is a mounting which allows to aim and fire an M2 heavy machine gun, of caliber 12.7 millimeters, and which incorporates an electric motion system that allows to fire it from the interior. This weapon has a provision of 1000 cartridges that allows for a high autonomy of usage.

IFF identification: During the Gulf War the M1 tanks were provided with sideward panels that produced a certain thermal signature depending on the orientation of its sheets, which allowed the commanders of other vehicles to differentiate them from the enemies.

Logistic capacity: In the rear part of the turret there are baskets for the storage of equipment and watertight boxes for ammunition and small spare parts.

Propulsion plant: In the rear part there is a Textron Lycoming AGT gas turbine which develops 1500 horsepower and rotates at about 30000 revolutions per minute, which stands out favorably because of its notable acceleration, and negatively because of its high consumption and maintenance requirements.

Identification marks: Assiduously used during the Gulf War, these sideward identification marks allow to differentiate in a simple and effective way the own vehicles from the enemy ones.

High mobility: The wheel ensemble confers the M1 great capability for absorbing the different irregularities of the terrain, and for moving at a high speed that difficults its neutralization.

Specifications of M1A1

Price: 5 millions of dollars

Crew: 4

Armament: One M256 120-millimeter 44-caliber cannon; one 7.62-millimeter co-axial machine gun; one 7.62-millimeter machine gun in the loader's hatch; one 12.7-millimeter machine gun in the commander's cupola; six smoke launchers in each side of the turret

Ammunitions: 40 x 120-millimeter cannon; 1000 x 12.7-millimeter machine gun; 12400 x 7.62-millimeter machine gun

Armor: Chobham type

Lenght (total): 9.828 meters

Lenght (hull): 7.918 meters

Width: 3.657 meters

Height: 2.886 meters

Weight (in order of combat): 57.154 tonnes

Ground pressure: N/A

Ground clearance (center): 48 centimeters

Ground clearance (sides): 43 centimeters

Engine: Textron Lycoming gas turbine developing 1500 horsepower at 30000 revolutions per minute (before the 10:1 reduction gear)

Power/weight ratio: 26.24 horsepower/tonne

Maximum speed (in road): 66.77 kilometers/hour

Maximum speed (in countryside): N/A

Maximum operational range (in road): 465 kilometers (1907.6 liters of fuel)

Maximum surmountable trench: N/A

Maximum surmountable step: 1.244 meters

Maximum surmountable slope: 60 percent

Maximum fording (without preparation): 1.219 meter



Categories: Tanks - Cold War - 20th Century - [General] - [General]

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Website: Military History

Article submitted: 2019-02-27

Article updated: 0000-00-00


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