M1 Abrams


The M1 Abrams is a third-generation American main battle tank designed by Chrysler Defense. Conceived for modern armored ground warfare and now one of the heaviest tanks in service at nearly 68 short tons, it introduced several innovative features, including a multifuel turbine engine, sophisticated Chobham composite armor, a computer fire control system, separate ammunition storage in a blow-out compartment, and NBC protection for crew safety. Initial models of the M1 were armed with a licensed-produced 105 mm Royal Ordnance L7 gun, while later variants feature a licensed Rheinmetall 120 mm L/44.
The M1 Abrams was developed from the failure of the MBT-70 project to replace the obsolescent M60 Patton. There are three main operational Abrams versions, the M1, M1A1, and M1A2, with each new iteration seeing improvements in armament, protection, and electronics. Efforts to develop an M1A3 version were first publicly disclosed in 2009. Extensive improvements have been implemented to the latest M1A2C and D versions such as improved composite armor, better optics, digital systems and ammunition. The Abrams was due to be replaced by the Future Combat Systems XM1202 but due to its cancellation, the U.S. military has opted to continue maintaining and operating the M1 series for the foreseeable future by upgrading with improved optics, armor and firepower.
The M1 Abrams entered service in 1980 and currently serves as the main battle tank of the United States Army and Marine Corps. The export version is used by the armies of Egypt, Kuwait, Saudi Arabia, Australia, and Iraq. The Abrams was first used in combat in the Persian Gulf War and has seen combat in both the War in Afghanistan and Iraq War under U.S. service, while Iraqi Abrams tanks have seen action in the war against ISIL and have seen use by Saudi Arabia during the Yemeni Civil War.

History

Previous developments

Through the 1960s the US Army and German Army had collaborated on a single design that would replace both the M60 Patton and the Leopard 1. The overall goal was to have a single new design with improved firepower to handle new Soviet tanks like the T-62, while providing improved protection against the T-62's new 115 mm smoothbore gun and especially high explosive anti-tank rounds.
The resulting design, the MBT-70, incorporated new technologies across the board. A hydropneumatic suspension provided excellent cross-country ride quality and also allowed the entire tank to be raised or lowered by the driver, with the lowest position placing the top of the tank only off the ground. New 1,500 hp-class engines powered the designs which could both reach, 50% faster than the T-62. Finally, two new guns were introduced, a US 152 mm design whose primary long-range weapon was the Shillelagh missile, while the Germans introduced a new 120 mm smoothbore design.
While the design was highly capable, its weight continued to grow, as did its budget. By 1969, the unit cost stood at five times the original estimates. In August 1969 the Senate halted funding of the program until the Government Accounting Office could undertake an audit of the program.

Starting afresh

As a result of the problems with the MBT-70, the U.S. Army introduced the XM803, using some technologies from the MBT-70 but removing some of the more troublesome features. This succeeded only in producing an expensive system with capabilities similar to the M60. Congress canceled the MBT-70 in November and XM803 December 1971, and redistributed the funds to the XM1 Abrams named after General Creighton Abrams.
The Tank-automotive and Armaments Command began examining specific goals. After several rounds of input, the decision was made to offer maximum armor to defeat the "heavy threat". Heavy in this context considered the 115 mm gun of the T-62 using projected improvements of their APFSDS ammunition through the 1980s, or the new 125 mm gun of the T-64 and T-72 firing high-explosive anti-tank rounds.
To this end, a new design basis emerged in February 1973, LK 10372. It had to defeat any hit from a Soviet gun within 800 meters and 30 degrees to either side. The tank would be armed with the 105 mm M68 gun, a licensed version of the Royal Ordnance L7, along with a coaxial 20 mm version of the Bushmaster.
Examining the experiences of the Yom Kippur War that year, a number of design changes were made. The newly-created "Burlington" armor from the British Army's labs was incorporated to improve protection, especially against HEAT, and to incorporate the new armor package, the original goal of keeping weight under was abandoned. The Bushmaster was seen as superfluous and was replaced with a M240 machine gun, the US version of the FN MAG. As TACOM continued to improve the detailed design, initial samples of the armor system were sent to the Ballistics Research Laboratory for testing.
At the time, the US military's procurement system was beset with problems being caused by the desire to have the best possible design. This often resulted in the programs being canceled due to cost overruns, leaving the forces with outdated systems, as was the case with the MBT-70. There was a strong movement within the Army to get a new design within budget to prevent the MBT-70 experience from repeating itself. For the new design, the Army stated the unit cost was to be no more than $507,000 in 1972 dollars and gave the contract out to the industry. Chrysler and GM entered bids.

More changes

Through the period while the initial prototypes were being built, a debate broke out between Germany and US about the use of the 105 mm gun. The Army was planning on introducing several new types of ammunition for the 105 that would greatly improve its performance, notably, the XM-774 using depleted uranium. These rounds would give it the performance needed to defeat any Soviet tank with ease. There was some concern that depleted uranium would not be allowed in Germany, perhaps just in peacetime, so improvements to the tungsten cored M735 were also considered.
Through this same period, there was an ongoing effort to improve NATO logistics by standardizing ammunition to the maximum possible degree. The Germans were moving ahead with their 120 mm gun on the Leopard 2K, and noted that the British had also introduced a 120 mm gun of their own in keeping with their long-range combat doctrine. Although initially skeptical of the need for a 120 mm gun, at some point the issue was raised that the Soviets might introduce a tank with composite armor. In this case, the 120 would give them the performance needed to defeat such a development even without depleted uranium.
By 1977 the decision had been made to eventually move the new tank to a 120 mm gun. After head-to-head testing between the Royal Ordnance L11A5 and the Rheinmetall Rh-120, the latter was chosen. The turret designs of the two prototypes were modified to allow either gun to be fitted. Although the L11/M256 120mm gun was chosen to be the main weapon of the M1 Abrams in 1979, the improved ammunition for the gun still was not fully developed, thus delaying its fielding until 1984. The early production versions of the M1 Abrams were armed with the M68A1 for two reasons. First was due to the large number of M60 Patton tanks with the M68E1 gun still in widespread US service in the 1980s and a large on-hand stockpile of 105mm munitions. Fitting the M1 with the M68A1 gun was viewed as an economical and practical solution that allowed for commonality in ammunition among the two types of tanks. Secondly was that the M68A1 could employ the newly developed M900 APFSDS depleted uranium round that had improved penetration performance in comparison to the M774.

Prototypes

Prototypes were delivered in 1976 by Chrysler Defense and General Motors armed with the license-built M68E1 version of the 105 mm Royal Ordnance L7. They entered head-to-head testing at Aberdeen Proving Ground, along with a Leopard 2 "2K" prototype for comparison. The testing showed that the GM design was generally superior, offering better armor protection, and better fire control and turret stabilization systems. These early preproduction prototypes were provisionally armed with the M68E1 105mm main gun while a preferred 120mm gun and its ammunition were in their design and component development phase. These prototypes used a combination mount that allowed for the evaluation of both 105mm and 120mm guns.
In January 1978, a program was initiated to develop an enhanced version of the 105mm gun, the M68A1 as a possible alternate weapon for the M1 Abrams. The new XM24/L55 gun barrel was 18 inches longer in comparison to the XM24/L52 barrel used on the M60 tanks. It has a higher chamber pressure, reinforced breach and a higher muzzle velocity.
During testing, the power packs of both designs proved to have issues. The Chrysler design used a gas turbine engine from Lycoming Engines, the AGT1500, which had extensive heat recovery systems in an attempt to improve its fuel economy to something similar to a traditional internal combustion engine. This proved not to be the case; the engine consumed much more fuel than expected. The GM design used a new variable-compression Diesel design which proved to be problematic. There is no evidence that GM considered using the MTU engine of the MBT-70, which outperformed both and had been chosen for the Leopard 2K.
By the spring of 1977, the decision to choose the GM design was largely complete. In addition to offering better overall performance, there were concerns about Chrysler's engine both from a reliability and fuel consumption standpoint. The GM program was also slightly cheaper overall at $208 million compared to $221 million for Chrysler. In July 1977, Lt. Colonel George Mohrmann prepared a stack of letters informing Congress of the decision to move ahead with the GM design. All that was required was the final sign-off by the Secretary of Defense, Donald Rumsfeld.

Chrysler is chosen

On 20 July, United States Secretary of the Army Martin Hoffman and a group of generals visited Deputy Defense Secretary Bill Clements and Director of Defense Research and Engineering Malcolm Currie on their decision. They were surprised when Clements and Currie criticized their decision and demanded the turbine be selected. Donald Rumsfeld heard arguments from both in the afternoon and asked for twenty-four hours to review the issues. The Army team spent the night writing briefs and presented them to Rumsfeld the next morning, who then announced a four-month delay.
Within days, GM was asked to present a new design with a turbine engine. According to Assistant Secretary for Research and Development Ed Miller, "It became increasingly clear that the only solution which would be acceptable to Clements and Currie was the turbine... It was a political decision that was reached, and for all intents and purposes that decision gave the award to Chrysler since they were the only contractor with a gas turbine." However, the Chrysler design had the advantage that the entire power pack had room to be replaced by any number of engine designs, including a Diesel if needed.
The turbine engine does not appear to be the only reason for this decision. Chrysler was the only company that appeared to be seriously interested in tank development; the M60 had been lucrative for the company and relied on that program for much of its profit. In contrast, GM made only about 1% of its income from military sales, compared to 5% for Chrysler, and only submitted their bid after a "special plea" from the Pentagon.
On 12 November 1976, the Defense Department awarded a $20 billion development contract to Chrysler.

Production starts

Low initial rate production of the vehicle was approved on 7 May 1979. In February 1982, General Dynamics Land Systems Division purchased Chrysler Defense, after Chrysler built over 1,000 M1s. The M1 Abrams was the first vehicle to adopt Chobham armor.
A total of 3,273 M1 Abrams tanks were produced during 1979–1985 and first entered U.S. Army service in 1980. Production at the government-owned, GDLS-operated Lima Army Tank Plant in Lima, Ohio, was joined by vehicles built at the Detroit Arsenal Tank Plant in Warren, Michigan from 1982 to 1996. The U.S. Army Laboratory Command, under the supervision of the United States Army Research Laboratory, was also heavily involved with designing the tank with M1A1 armor resistant shells, M829A2 armor-penetrating rounds, and improved weapon range. The M1 was armed with the license-built M68A1 version of the 105 mm Royal Ordnance L7 gun. The tank featured the first of its kind Chobham armor. The M1 Abrams was the first to use this advanced armor. It consisted of an arrangement of metal plates, ceramic blocks and open space. An improved model called the M1IP was produced briefly in 1984 and contained small upgrades. The M1IP models were used in the Canadian Army Trophy NATO tank gunnery competition in 1985 and 1987.
used computerized tools during the development of the M1, which led to the development of BRL-CAD. Here, a Vector General 3D graphics terminal displays a model of the M1.
About 5,000 M1A1 Abrams tanks were produced from 1986–92 and featured the M256 smoothbore cannon developed by Rheinmetall AG of Germany for the Leopard 2, improved armor, consisting of depleted uranium and other classified materials, and a CBRN protection system. Production of M1 and M1A1 tanks totaled some 9,000 tanks at a cost of approximately $4.3 million per unit. By 1999, costs for the tank were upwards of a vehicle.
In 1990, Project on Government Oversight in a report criticized the M1's high costs and low fuel efficiency in comparison with other tanks of similar power and effectiveness such as the Leopard 2. The report was based on data from U.S. Army sources and the Congressional record.
As the Abrams entered service in the 1980s, they operated alongside M60A3 within the U.S. military, and with other NATO tanks in various Cold War exercises which usually took place in Western Europe, especially West Germany. The exercises were aimed at countering Soviet forces. However, by January 1991, the Berlin Wall had fallen and the Abrams was deployed in the Middle East.
Adaptations before the Persian Gulf War gave the vehicle better firepower and NBC protection.

Gulf War

The Abrams remained untested in combat until the Persian Gulf War in 1991, during Operation Desert Storm. A total of 1,848 M1A1s were deployed to Saudi Arabia to participate in the liberation of Kuwait. The M1A1 was superior to Iraq's Soviet-era T-55 and T-62 tanks, as well as T-72 versions imported from the Soviet Union and Poland. Polish officials state no license-produced T-72 tanks were finished prior to the Iraqi Taji tank plant being destroyed in 1991. The T-72s, like most Soviet export designs, lacked night vision systems and then-modern rangefinders, though they did have some night-fighting tanks with older active infrared systems or floodlights. A total of 23 M1A1s were damaged or destroyed during the war. Of the nine Abrams tanks destroyed, seven were destroyed by friendly fire, and two were purposely destroyed to prevent capture after being damaged. Some others took minor combat damage, with little effect on their operational readiness. Very few M1 tanks were hit by enemy fire and none were destroyed as a direct result of enemy fire, none of which resulted in any fatalities.
The M1A1 could kill other tanks at ranges in excess of. This range was crucial in combat against previous generation tanks of Soviet design in Desert Storm, as the effective range of the main gun in the Soviet/Iraqi tanks was less than. This meant Abrams tanks could hit Iraqi tanks before the enemy got in range—a decisive advantage in this kind of combat. In friendly fire incidents, the front armor and fore side turret armor survived direct armor-piercing fin-stabilized discarding-sabot 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 on at least two occasions by unintentional strikes by depleted uranium ammunition during the Battle of Norfolk.
During Operations Operation Desert Shield and Desert Storm some M1IP and M1A1s were modified locally in theater by modification work orders with additional rolled homogenous armor plating welded on the turret front. The M1 can be equipped with mine plow and mine roller attachments.
Lessons from the war improved the tank's weapons sights and fire control unit.

Upgrades

The M1A2 was a further improvement of the M1A1 with a commander's independent thermal viewer, weapon station, position navigation equipment, and a full set of controls and displays linked by a digital data bus. These upgrades also provided the M1A2 with an improved fire control system. The M1A2 System Enhancement Package added digital maps, Force XXI Battle Command Brigade and Below Linux communications system capabilities for commanders, and an improved cooling system to compensate for heat generated by the additional computer systems. The M1A2 SEP also serves as the basis for the M104 Wolverine heavy assault bridge. The M1A2 SEPv2 added Common Remotely Operated Weapon Station support, color displays, better interfaces, a new operating system, better front and side armor, and an upgraded transmission for better durability. Further upgrades included depleted uranium armor for all variants, a system overhaul that returns all A1s to like-new condition, a digital enhancement package for the A1, and a commonality program to standardize parts between the U.S. Army and the Marine Corps. The development for the improved M1A3 variant has been known since 2009.

Iraq War

Further combat was seen during 2003 when U.S. forces invaded Iraq and deposed Ba'athist Iraqi leader Saddam Hussein in the Iraq War's Operation Iraqi Freedom. During the invasion, at least nine Abrams tanks were put out of action by fire from rocket propelled grenades. By March 2005, approximately 80 Abrams tanks were forced out of action by enemy attacks; 63 tanks were restored, while 17 were damaged beyond repair with 3 of them at the beginning of 2003. From August 2005 to April 2008, at least 20 tanks of this type were destroyed.
One achievement of the M1A1s was the destruction of seven T-72s in a point-blank skirmish near Mahmoudiyah, about south of Baghdad, with no U.S. losses. This was in the face of inadequately trained Iraqi tank crews, most of whom had not fired live ammunition in the previous year due to the sanctions then in operation and made no hits at point-blank range. In addition to the Abrams's heavy armament, some crews were also issued M136 AT4 shoulder-fired anti-tank weapons under the assumption that they might have to engage heavy armor in tight urban areas where the main gun could not be brought to bear.
Following lessons learned in Desert Storm, the Abrams and many other U.S. 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. Some Abrams tanks were also fitted with a secondary storage bin on the back of the existing bustle rack on the rear of the turret to enable the crew to carry more supplies and personal belongings.
Several Abrams tanks that were irrecoverable due to loss of mobility or other circumstances were destroyed by friendly forces, usually by other Abrams tanks, to prevent their capture. Some Abrams tanks were disabled by Iraqi infantrymen in ambushes during the invasion. Some troops employed short-range anti-tank rockets and fired at the tracks, rear and top. Other tanks were put out of action by engine fires when flammable fuel stored externally in turret racks was hit by small arms fire and spilled into the engine compartment. By December 2006 more than 530 Abrams tanks had been shipped back to the U.S. for repair.
Vulnerabilities exposed during urban combat in the 2003 invasion of Iraq were addressed with the Tank Urban Survival Kit modifications, including armor upgrades and a gun shield, issued to some M1 Abrams tanks. It added protection in the rear and side of the tank to improve fighting ability in urban environments.
In May 2008, it was reported that a U.S. M1 tank had also been damaged in Iraq by insurgent fire of a Soviet-made RPG-29 "Vampir", which uses a tandem-charge high explosive anti-tank warhead to penetrate explosive reactive armor as well as composite armor behind it. The U.S. considered the RPG-29 threat to U.S. armor high and refused to allow the newly formed Iraqi Army to buy it, fearing that it would fall into the insurgents' hands.

Iraqi Army service

Between 2010 and 2012 the U.S. supplied 140 refurbished M1A1 Abrams tanks to Iraq. In mid-2014, they saw action when the Islamic State of Iraq and the Levant launched the June 2014 Northern Iraq offensive. During three months, about one-third of the Iraqi Army's M1 tanks had been damaged or destroyed by ISIL and some were captured by opposing forces. By December 2014, the Iraqi Army only had about 40 operational Abrams left. That month, the U.S. Department of State approved the sale of another 175 Abrams to Iraq.
Iranian-backed Iraqi Shiite Kata'ib Hezbollah reported to operate M1 Abrams, and released publicity showing the tanks being transported by trucks to take part in the battle of Mosul. It is not known whether the tanks were captured from ISIS, seized from Iraq's military, or handed over.
One Iraqi-operated Abrams has been nicknamed "The Beast" after it became the lone working tank when taking back the town of Hit in April 2016, destroying enemy fighting positions and IED emplacements.
In October 2017, Abrams were used by the Iraqi security forces and the Popular Mobilization Forces in assaults against the Kurdistan Regional Government Peshmerga in the town of Altun Kupri. It was claimed by Kurdish commanders that at least one Abrams was destroyed by the Peshmerga.

War in Afghanistan

Tanks may have limited utility in Afghanistan due to the mountainous terrain, although Canada and Denmark have deployed Leopard 1 and 2 MBTs that have been specially modified to operate in the relatively flat and arid conditions of southwestern Afghanistan. In late 2010, at the request of Regional Command Southwest, the U.S. Marine Corps deployed a small detachment of 14 M1A1 Abrams tanks from Delta Company, 1st Tank Battalion, 1st Marine Division, to southern Afghanistan in support of operations in Helmand and Kandahar provinces.

2015 Yemen Civil War

After the start of the Saudi Arabian intervention in Yemen during the 2015 Yemeni Civil War, Saudi Arabian M1A2 MBTs were deployed near the Saudi Arabian/Yemeni border. In August 2016, the U.S. approved a deal to sell up to 153 more Abrams tanks to Saudi Arabia, including 20 "battle damage replacements", suggesting that some Saudi Arabian Abrams had been destroyed or severely damaged in combat in Yemen.

Production

Production shutdown

The U.S. Army planned to end production at the Lima Army Tank Plant from 2013 to 2016 in an effort to save over $1 billion; it would be restarted in 2017 to upgrade existing tanks. General Dynamics Land Systems, which operates the factory, opposed the move, arguing that suspension of operations would increase long-term costs and reduce flexibility. Specifically, GDLS estimated that closing the plant would cost $380 million and restarting production would cost $1.3 billion.
By August 2013, Congress had allocated $181 million for buying parts and upgrading Abrams systems to mitigate industrial base risks and sustain development and production capability. Congress and General Dynamics were criticized for redirecting money to keep production lines open and accused of "forcing the Army to buy tanks it didn't need." General Dynamics asserted that a four-year shutdown would cost $1.1–1.6 billion to reopen the line, depending on the length of the shutdown, whether machinery would be kept operating, and whether the plant's components would be completely removed. They contended that the move was to upgrade Army National Guard units to expand a "pure fleet" and maintain production of identified "irreplaceable" subcomponents; a prolonged shutdown could cause their makers to lose their ability to produce them and foreign tank sales were not guaranteed to keep production lines open. There is still risk of production gaps even with production extended through 2015; with funds awarded before recapitalization is needed, budgetary pressures may push planned new upgrades for the Abrams from 2017 to 2019. In December 2014, Congress again allocated $120 million, against the wishes of the Army, for Abrams upgrades including improving gas mileage by integrating an auxiliary power unit to decrease idle time fuel consumption and upgrading the tank's sights and sensors.

Future plans

The tracked M8 Armored Gun System was conceived as a possible supplement for the Abrams in U.S. service for low-intensity conflict in the early 1990s. Prototypes were made but the program was canceled. The eight-wheeled M1128 Mobile Gun System was designed to supplement the Abrams in U.S. service for low-intensity conflicts. It has been introduced into service and serves with Stryker brigades.
The U.S. Army's Future Combat Systems XM1202 Mounted Combat System was to replace the Abrams in U.S. service and was in development when funding for the program was cut from the DoD's budget.
Engineering Change Proposal 1 is a two-part upgrade process. ECP1A adds space, weight, and power improvements and active protection against improvised explosive devices. Nine ECP1A prototypes have been produced as of October 2014. ECP1B, which will begin development in 2015, may include sensor upgrades and the convergence of several tank round capabilities into a multi-purpose round.
The M1A2 SEP TUSK Abrams and a modernized M1 Abrams were included in the Ground Combat Vehicle Analysis of Alternatives. Vehicles included in the AOA were determined to be inferior to the planned GCV. The U.S. Army Vice Chief of Staff Gen. Peter Chiarelli commended the M1 Abrams program and recommended a similar approach for the GCV program. The Ground Combat Vehicle family of vehicles was the planned successor to the M1 as well as many other U.S. Army vehicles. However, the Army anticipates that the remaining M1A1 fleet will remain in U.S. service until at least 2021, and the M1A2 to beyond 2050.
The M1A3 Abrams was in the early design period with the U.S. Army in 2009. At that time, the service was seeking a lighter tank version with the same protection as current versions. It aimed to build prototypes by 2014 and begin fielding the first combat-ready M1A3s by 2017. In March 2017, it was reported that the new version, the M1A2 SEP v4, is to begin testing in 2021.
Additionally an all new version for the U.S. Army has been in planning and development for several years.

Design

Countermeasures

Camouflage

Earlier U.S. military vehicles, used from World War I through the Vietnam War, used a scheme of "olive drab", often with large white stars. Prototypes, early production M1 and M1-IP models switched to a flat forest green paint scheme. The large white insignia stars have also transitioned to much smaller black markings. Some units painted their M1s with the older Mobility Equipment Research and Design Command 4-color paint scheme but the turn-in requirements for these tanks required repainting them to overall forest green. Therefore, even though a large number of the base model M1s were camouflaged in the field, few or none exist today.
M1A1s came from the factory with the NATO three color camouflage Black/Med-Green/Dark-Brown Chemical Agent Resistant Coating paint jobs. Today M1A1s are given the NATO three color paint job during rebuilds. M1s and M1A1s deployed to Operation Desert Storm were hastily painted desert tan. Some, but not all, of these tanks were re-painted to their "authorized" paint scheme. M1A2s built for Middle Eastern countries were painted in desert tan. Replacement parts are painted olive green, which can sometimes lead to vehicles with a patchwork of green and desert tan parts.
Australian M1A1s were desert tan when delivered but have undergone a transition to the Australian Army vehicle standard 'Disruptive Pattern Camouflage'; a scheme that consists of black, olive drab, and brown.
The U.S. Army can equip its Abrams tanks with the Saab Barracuda camouflage system, which provides concealment against visual, infrared, thermal infrared, and broad-band radar detection.

Concealment

The turret is fitted with two six-barreled M250 smoke grenade launchers, with one on each side. When deployed, the grenades airburst, creating a thick smoke that blocks both visual and thermal imaging. The engine is also equipped with a smoke generator that is triggered by the driver. When activated, fuel is sprayed into the hot turbine exhaust, creating the thick smoke. However, due to the change from diesel as a primary fuel to the use of JP-8, this system is disabled on most Abrams tanks today because of a slightly elevated risk of fire damage to the engine compartment.

Armor

In July 1973, representatives from Chrysler and General Motors traveled to the United Kingdom, and were escorted by personnel from the Ballistic Research Laboratory and XM1 Project Manager Major General Robert J. Baer to witness the progress of British developed Chobham armor. They observed the manufacturing processes required for the production of Chobham armor, which was an arrangement of metal plates, ceramic blocks and open space; and saw a proposed design for a new British vehicle utilizing it. HEAT and sabot rounds enter the beginning layers of armor but are unable to penetrate the crew compartment. Ceramics have the ability to absorb a great deal of heat, and can blunt physical blows by cracking and deflecting the force. The remaining hot gasses and metal shrapnel spread out or settle in empty air pockets. Both contractors reevaluated their proposed armor configurations based upon the newly obtained data. This led to major changes in the General Motors XM1. The most prominent of which is the turret front changing from vertical to sloped armor. The Chrysler XM1 on the other hand retained its basic shape although a number of changes were made. The Ballistic Research Laboratory had to develop new armor combinations in order to accommodate the changes made by the contractors.
Similar to most other main battle tanks, the M1 Abrams feature composite armor only on the frontal aspect of the hull. However, the Abrams' turret features composite armoring across both the front and the sides. In addition, the side skirts of the frontal half of the hull are also made of composite, providing superior ballistic protection against chemical energy munitions such as HEAT rounds. The composition of the Abrams' composite armor consists of sandwiched plates of non-explosive reactive armor between conventional steel plates. The NERA plates feature elasticity, allowing them to flex and distort upon perforation, disrupting the penetrating jets of shaped charges and providing more material and space for a kinetic round to pass through, thus providing increased protection compared to conventional steel armor of similar weight.
For the base model M1 Abrams, Steven J. Zaloga gives a frontal armor estimate of 350 mm vs armor-piercing fin-stabilized discarding-sabot and 700 mm vs high-explosive anti-tank warhead in M1 Abrams Main Battle Tank 1982–1992. In M1 Abrams vs T-72 Ural, he uses Soviet estimates of 470 mm vs APFSDS and 650 mm vs HEAT for the base model Abrams. He also gives the Soviet estimates for the M1A1, 600 mm vs APFSDS, and 700 mm vs HEAT.
Armor protection was improved by implementing a new special armor incorporating depleted uranium and other undisclosed materials and layouts. This was introduced into the M1A1 production starting October 1988. This new armor increased effective armor particularly against kinetic energy rounds but at the expense of adding considerable weight to the tank, as depleted uranium is 1.7 times more dense than lead. The first M1A1 tanks to receive this upgrade were tanks stationed in Germany. US-based tank battalions 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. This variant was designated as the M1A1HA. The M1A1 AIM, M1A2 SEP and all subsequent Abrams models feature depleted uranium in both the hull and turret armor. Each Abrams variant after the M1A1 have been equipped with depleted uranium armor of different generations. The M1A1HA uses 1st generation armor, while the M1A2 and M1A1HC use 2nd generation depleted uranium. The M1A2 SEP variants have been equipped with third generation depleted uranium armor combined with a graphite coating. The M1A2C also features increased physical line-of-sight turret armor.
For the M1A1HA, Zaloga gives a frontal armor estimate of 600 mm vs APFSDS and 1300 mm vs HEAT in M1 Abrams Main Battle Tank 1982–1992, nearly double the original protection of the Abrams. In M1 Abrams vs T-72 Ural, he uses different estimates of 600 mm vs APFSDS and 700 mm vs HEAT for the front hull and 800 mm vs APFSDS and 1300 mm vs HEAT for the front of the turret. The protection of M1A2 SEP is a frontal turret armor estimate of 940–960 mm vs APFSDS and 1,320–1,620 vs HEAT, glacis estimate of 560–590 mm vs APFSDS and 510–1,050 vs HEAT, and lower front hull estimate of 580–650 mm vs APFSDS and 800–970 vs HEAT
In 1998, a program was begun to incorporate improved turret side armor into the M1A2. This was intended to offer better protection against rocket-propelled grenades more modern than the baseline RPG-7. These kits were installed on about 325 older M1A2 tanks in 2001-2009 and it was also included in upgraded tanks.
The Abrams may also be fitted with explosive reactive armor over the track skirts if needed and slat armor over the rear of the tank and rear fuel cells to protect against ATGMs. Protection against spalling is provided by a kevlar liner.

Damage control

The tank has a halon firefighting system to automatically extinguish fires in the crew compartment. The engine compartment has a firefighting system that is engaged by pulling a T-handle located on the left side of the hull. The Halon gas can be dangerous to the crew. However, the toxicity of Halon 1301 gas at 7% concentration is much less than the combustion products produced by fire in the crew compartment, and CO2 dump would be lethal to the crew. The crew compartment also contains small hand-held fire extinguishers. Fuel and ammunition are stored 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—the main gun's ammunition is stored in the rear section of the turret, with blast doors that open under power by sliding sideways only to remove a round for firing, then automatically close. Doctrine mandates that the ammunition door must be closed before arming the main gun.

Tank Urban Survival Kit

The Tank Urban Survival Kit is a series of improvements to the M1 Abrams intended to improve fighting ability in urban environments. Historically, urban and other close battlefields have been poor places for tanks to fight. A tank's front armor is much stronger than that on the sides, top, or rear. In an urban environment, attacks can come from any direction, and attackers can get close enough to reliably hit weak points in the tank's armor or gain sufficient elevation to hit the top armor.
Armor upgrades include reactive armor on the sides of the tank and slat armor on the rear to protect against rocket-propelled grenades and other shaped charge warheads. A Transparent Armor Gun Shield and a thermal sight system are added to the loader's top-mounted M240B 7.62 mm machine gun, and a Kongsberg Gruppen Remote Weapon Turret carrying a 12.7 mm caliber machine gun is in place of the tank commander's original 12.7 mm caliber machine gun mount, wherein the commander had to expose himself to fire the weapon manually. An exterior telephone allows supporting infantry to communicate with the tank commander.
The TUSK system is a field-installable kit that allows tanks to be upgraded without needing to be recalled to a maintenance depot. While the reactive armor may not be needed in most situations, like those present in maneuver warfare, items like the rear slat armor, loader's gun shield, infantry phone, and Kongsberg Remote Weapons Station for the 12.7 mm caliber machine gun will be added to the entire M1A2 fleet over time.
On 29 August 2006, General Dynamics Land Systems received a U.S. Army order for 505 Tank Urban Survivability Kits for Abrams main battle tanks supporting operations in Iraq, under a US$45 million contract. Deliveries were expected to be completed by April 2009. Under a separate order, the U.S. Army awarded General Dynamics Armament and Technical Products US$30 million to produce reactive armor kits to equip M1A2s. The reactive tiles for the M1 will be locally produced at GDATP's Burlington Technology Center. Tiles will be produced at the company's reactive armor facility in Stone County Operations, McHenry, Mississippi. On 8 December 2006, the U.S. Army added Counter Improvised Explosive Device enhancements to the M1A1 and M1A2 TUSK, awarding GDLS $11.3 million contract, part of the $59 million package mentioned above. In December, GDLS also received an order, amounting to around 40% of a US$48 million order, for loader's thermal weapon sights being part of the TUSK system improvements for the M1A1 and M1A2 Abrams Tanks.

Active Protection System (APS)

In addition to the armor, some USMC Abrams tanks are equipped with a Softkill Active protection system, the AN/VLQ-6 Missile Countermeasure Device that can impede the function of guidance systems of some semi-active control line-of-sight wire- and radio guided anti-tank missiles and infrared homing missiles. The MCD works by emitting a massive, condensed infrared signal to confuse the infrared homing seeker of an anti-tank guided missile. However, the drawback to the system is that the ATGM is not destroyed, it is merely directed away from its intended target, leaving the missile to detonate elsewhere. This device is mounted on the turret roof in front of the loader's hatch, and can lead some people to mistake Abrams tanks 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.
In 2016, the U.S. Army and Marine Corps began testing out the Israeli Trophy active protection system to protect their Abrams tanks from modern RPG and ATGM threats by either jamming or firing small rounds to deflect incoming projectiles. The Army plans to field a brigade of over 80 tanks equipped with Trophy to Europe in 2020. It is planned for up to 261 Abrams to be upgraded with the system, enough for four brigades. In June 2018, the Army awarded Leonardo DRS, U.S. partner to Trophy's designer Rafael, a $193 million contract to deliver the system in support of M1 Abrams "immediate operational requirements." U.S. Army M1A2 SEP V2 Abrams tanks deployed to Germany in July 2020 fitted with Trophy systems.

Armament

Primary

M68A1 rifled gun
The main armament of the original model M1 and M1IP was the M68A1 105 mm rifled tank gun firing a variety of armor-piercing fin-stabilized discarding sabot, high explosive anti-tank, high explosive, white phosphorus rounds and an anti-personnel round. This gun used a license-made tube of the British Royal Ordnance L7 gun together with the vertical sliding breech block and other parts of the U.S. T254E2 prototype gun. However, it proved to be inadequate; a cannon with lethality beyond the range was needed to combat newer armor technologies. To attain that lethality, the projectile diameter needed to be increased. The tank was able to carry 55 105 mm rounds, with 44 stored in the turret blow-out compartment and the rest in hull stowage.
M256 smoothbore gun
The main armament of the M1A1 and M1A2 is the M256A1 120 mm smoothbore gun, designed by Rheinmetall AG of Germany, manufactured under license in the U.S. by Watervliet Arsenal, New York. The M256A1 is a variant of the Rheinmetall 120 mm L/44 gun carried on the German Leopard 2 on all variants up to the Leopard 2A5. Leopard 2A6 replaced the L/44 barrel with a longer L/55. Due to the increased calibre, only 40 or 42 rounds are able to be stored depending on if the tank is an A1 or A2 model.
The M256A1 fires a variety of rounds. The primary APFSDS round of the Abrams is the depleted uranium M829 round, of which four variants have been designed. M829A1, known as the "Silver Bullet", saw widespread service in the Gulf War, where it proved itself against Iraqi armor such as the T-72. The M829A2 APFSDS round was developed specifically as an immediate solution to address the improved protection of a Russian T-72, T-80U or T-90 main battle tank equipped with Kontakt-5 explosive reactive armor as previous rounds were found to be incapable of defeating such armor. Later, the M829A3 round was introduced to improve its effectiveness against next generation ERA equipped tanks, through usage of a multi-material penetrator and increased penetrator diameter that can resist the shear effect of K-5 type ERA. As a counter to that, the Russian army introduced Relikt, the most modern Russian ERA, which is claimed to be twice as effective as Kontakt-5. Development of the M829 series is continuing with the M829A4 currently entering production, featuring advanced technology such as data-link capability. The Abrams also fires high-explosive anti-tank warhead shaped charge rounds such as the M830, the latest version of which incorporates a sophisticated multi-mode electronic sensing fuse and more fragmentation that allows it to be used effectively against armored vehicles, personnel, and low-flying aircraft. The Abrams uses a manual loader. The fourth tank crew member on the Abrams also provides additional support for maintenance, observation post/listening post operations, and other tasks.
The new M1028 120 mm anti-personnel canister cartridge was brought into service early for use in the aftermath of the 2003 invasion of Iraq. It contains 1,098 tungsten balls that spread from the muzzle to produce a shotgun effect lethal out to. The tungsten balls can be used to clear enemy dismounts, break up hasty ambush sites in urban areas, clear defiles, stop infantry attacks and counter-attacks and support friendly infantry assaults by providing covering fire. The canister round is also a highly effective breaching round and can level cinder block walls and knock man-sized holes in reinforced concrete walls for infantry raids at distances up to. Also in use is the M908 obstacle-reduction round. It is designed to destroy obstacles and barriers. The round is a modified M830A1 with the front fuse replaced by a steel nose to penetrate into the obstacle before detonation.
The U.S. Army Research Laboratory conducted a thermal analysis of the M256 from 2002 to 2003 to evaluate the potential of using a hybrid barrel system that would allow for multiple weapon systems such as the XM1111 Mid- Range munition, airburst rounds, or XM 1147. The test concluded that mesh density impacts accuracy of the M256 and specific densities would be needed for each weapon system.
The Army is developing a new round to replace the M830/M830A1, M1028, and M908. Called the Advanced Multi-Purpose round, it will have point detonation, delay, and airburst modes through an ammunition data-link and a multi-mode, programmable fuse in a single munition. Having one round that does the job of four would simplify logistics and be able to be used on a variety of targets. The AMP is to be effective against bunkers, infantry, light armor, and obstacles out to 500 meters, and will be able to breach reinforced concrete walls and defeat ATGM teams from 500 to 2,000 meters. Orbital ATK was awarded a contract to begin the first phase of development for the AMP XM1147 High Explosive Multi-Purpose with Tracer cartridge in October 2015.
In addition to these, the XM1111 was also in development. The XM1111 was a guided munition using a dual-mode seeker that combined imaging-infrared and semi-active laser guidance. The MRM-CE was selected over the competing MRM-KE, which used a rocket-assisted kinetic energy penetrator. The CE variant was chosen due to its better effects against secondary targets, providing a more versatile weapon. The Army hoped to achieve IOC with the XM1111 by 2013. However, the Mid-Range Munition was cancelled in 2009 along with Future Combat Systems.

Secondary

The Abrams tank has three machine guns, with an optional fourth:
  1. A.50 cal. M2HB machine gun in front of the commander's hatch. On the M1 and M1A1, this gun is mounted on the Commander's Weapons Station. This allows the weapon to be aimed and fired from within the tank. The later M1A2 variant had a 'flex' mount that required the tank commander to expose his or her upper torso in order to fire the weapon. In urban environments in Iraq, this was found to be unsafe. With the Common Remote Operated Weapons System add-on kit, an M2A1.50 Caliber Machine gun, M240, or M249 SAW can be mounted on a CROWS remote weapons platform. Current variants of the Tank Urban Survival Kit on the M1A2 have forgone this, instead adding transparent gun shields to the commander's weapon station. The upgrade variant called the M1A1 Abrams Integrated Management equips the.50 caliber gun with a thermal sight for accurate night and other low-visibility shooting.
  2. A 7.62 mm M240 machine gun in front of the loader's hatch on a skate mount. Some of these were fitted with gun shields during the Iraq War, as well as night-vision scopes for low-visibility engagements and firing.
  3. A second 7.62 mm M240 machine gun in a coaxial mount to the right of the main gun. The coaxial MG is aimed and fired with the same computerized firing control system used for the main gun.
  4. A second coaxial.50 cal. M2HB machine gun can be mounted directly above the main gun in a remote weapons platform as part of the TUSK upgrade kit.

    Aiming

The Abrams is equipped with a ballistic fire-control computer that uses user and system-supplied data from a variety of sources to compute, display, and incorporate the three components of a ballistic solution—lead angle, ammunition type, and range to the target—to accurately fire the main gun. These three components are determined using a laser rangefinder, crosswind sensor, a pendulum static cant sensor, data concerning performance and flight characteristics of each specific type of round, tank-specific boresight alignment data, ammunition temperature, air temperature, barometric pressure, a muzzle reference system that determines and compensates for barrel drop at the muzzle due to gravitational pull and barrel heating due to firing or sunlight, and target speed determined by tracking rate tachometers in the Gunner's or Commander's Controls Handles. All of these factors are computed into a ballistic solution and updated 30 times per second. The updated solution is displayed in the Gunner's or Tank Commander's field of view in the form of a reticle in both day and Thermal modes. The ballistic computer manipulates the turret and a complex arrangement of mirrors so that all one has to do is keep the reticle on the target and fire to achieve a hit. Proper lead and gun tube elevation are applied to the turret by the computer, greatly simplifying the job of the gunner.
in January 2005. Hand signals enable the gunner to train the main gun onto a boresighting target.
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 on the M1A2 can be used to locate targets and pass them on for the gunner to engage while the commander scans for new targets. In the event of a malfunction or damage to the primary sight system, the main and coaxial weapons can be manually aimed using a telescopic scope boresighted to the main gun known as the Gunner's Auxiliary Sight. The GAS has two interchangeable reticles; one for High-explosive anti-tank warhead and MPAT rounds and one for APFSDS and STAFF ammunition. Turret traverse and main gun elevation can be accomplished with manual handles and cranks in the event of a Fire Control System or Hydraulic System failure. The commander's M2HB.50 caliber machine gun on the M1 and M1A1 is aimed by a 3× magnification sight incorporated into the Commander's Weapon Station, while the M1A2 uses either the machine gun's own iron sights, or a remote aiming system such as the CROWS system when used as part of the TUSK. The loader's M240 machine gun is aimed either with the built-in iron sights or with a thermal scope mounted on the machine gun.
In late 2017, the 400 USMC M1A1 Abrams will be upgraded with better and longer-range sights on the Abrams integrated display and targeting system replacing the black-and-white camera view with a color one and adding day/night thermal sights, simplified handling with a single set of controls, and a slew to cue button that repositions the turret with a single command. Preliminary testing showed the upgrades reduced target engagement time from six seconds to three by allowing the commander and gunner to work more closely and collaborate better on target acquisition.

Mobility

Tactical

The M1 Abrams's powertrain consists of a Honeywell AGT 1500 multifuel gas turbine capable of at 3,000 rpm and at 1,000 rpm, and a six-speed Allison X-1100-3B Hydro-Kinetic automatic transmission, giving it a governed top speed of on paved roads, and cross-country. With the engine governor removed, speeds of around are possible on an improved surface; however, damage to the drivetrain and an increased risk of injuries to the crew can occur at speeds above. The tank was built around this engine and it is multifuel–capable, including diesel, kerosene, any grade of motor gasoline, and jet fuel. For logistical reasons, JP-8 is the U.S. military's universal fuel powering both aircraft and vehicle fleets. On the other hand, Australian M1A1 AIM SA burn diesel fuel, since the use of JP-8 is less common in the Australian Army.
The gas turbine propulsion system has proven quite reliable in practice and combat, but its high fuel consumption is a serious logistic issue. The engine burns more than per mile when traveling cross-country and per hour when idle. The high speed, high temperature jet blast emitted from the rear of M1 Abrams tanks makes it hazardous for infantry to take cover or follow behind the tank in urban combat. The turbine is very quiet when compared to diesel engines of similar power output and produces a significantly different sound from a contemporary diesel tank engine, reducing the audible distance of the sound, thus earning the Abrams the nickname "whispering death" during its first Reforger exercise.
vehicle
Honeywell was developing another gas turbine engine with General Electric for the XM2001 Crusader program that was to be a replacement for the Abrams's AGT-1500 engine. The new LV100-5 engine was lighter and smaller with rapid acceleration, quieter running, and no visible exhaust. It also featured a 33% reduction in fuel consumption and near drop-in replacement. The Abrams-Crusader Common Engine Program was shelved when the Crusader program was canceled, however Phase 2 of Army's PROSE program called for further development of the LV100-5 and replacement of the current AGT-1500 engine.
General Dynamics has been working on a drop-in diesel engine to replace the gas turbine engine. It is smaller than the turbine, 14% cheaper to operate per mile, and has a four-fan cooling system that is to greatly reduce the tank's heat signature. General Dynamics is offering the Tognum America/12V883 diesel engine with new Diehl 570P3 tracks. The engine represents advancements in diesel engine design since the Abrams was first designed, including a common rail fuel injector system where fuel is pressurized and atomized in the cylinder rather than mechanically sprayed. It also has greater torque, an altered nuclear, biological, and chemical protection system that operates independently of the engine, uses less fuel while idle, is quieter, and gives off significantly less heat and pollutants. Incorporating the diesel engine into the Abrams would decrease the operating cost of an armored brigade combat team by 14 percent per mile, increase its operating range from 205 miles to 300+ miles, and use half the amount of fuel on a combat day than the turbine engine. The tracks are a version of the Leopard 2's tracks with different rubber pads and a larger center guide. The improved engine and tracks are not part of an Army upgrade program, but may be included in a near-term engineering change proposal phase.
Using a high power density Wankel rotary engine modified to use diesel and military grade jet fuel, the Army's TARDEC developed a Auxiliary Power Unit designed to fit into the M1 Abrams, replacing an existing battery pack that weighs about. The new APU will also be more fuel efficient than the tank's main engine. Testing of the first APUs began in 2009.
extension.
Although the M1 tank is not designed to carry riders easily, provisions exist for the Abrams to transport troops in tank desant with the turret stabilization device switched off. A battle equipped infantry squad may ride on the rear of the tank, behind the turret. The soldiers can use ropes and equipment straps to provide handholds and snap links to secure themselves. If and when enemy contact is made, the tank conceals itself allowing the infantry to dismount.

Strategic

Strategic mobility is the ability of the tanks of an armed force to arrive in a timely, cost effective, and synchronized fashion. The Abrams can be carried by a C-5 Galaxy or a C-17 Globemaster III. The limited capacity caused serious logistical problems when deploying the tanks for the first Persian Gulf War, though there was enough time for 1,848 tanks to be transported by ship.
Marines transport their Marine Air Ground Task Force -attached Abrams tanks by combat ship. A Wasp-class Landing Helicopter Dock typically carries a platoon of 4 to 5 tanks attached to the deployed Marine Expeditionary Unit, which are then amphibiously transported to shore by Landing Craft Air Cushion at 1 combat-ready tank per landing craft.
The Abrams is also transportable by truck, namely the Oshkosh M1070 and M1000 Heavy Equipment Transporter System. The HETS can operate on highways, secondary roads, and cross-country. It accommodates the four tank crew members.
The first instance of the Abrams being airlifted directly into a battlefield occurred in October 1993. Following the Battle of Mogadishu, 18 M1 tanks were airlifted by C-5 aircraft to Somalia from Hunter Army Airfield, Georgia.

Variants and upgrades

Operators

Citations