Future Combat System (FCS)
The new conception of the Future Combat Systems [plural] as a distributed battlefield system of systems [in the 20-ton class] represents a rather dramatic departure from the previous concept of the Future Combat System [singular] which was focused on a 40-ton tank.
The US Army Tank-automotive and Armaments Command's future land combat system vehicle is a 40-ton concept based on evolutionary tank design and technology which pushes the two-person crew down and forward into the hull with a remote turret. The crew receives information from on-board target acquisition and hit avoidance sensors. Target acquisition sensors are the gunner's primary sight, a panoramic sight and an auxiliary sight. Hit avoidance sensors are mounted in the four corners of the turret. A high pressure, 120mm gun (XM291) is mounted on the turret.
Variable height suspension presents a lower, smaller target and makes the tank more survivable. The height can be lowered to 64 inches or raised to 79 inches. At its maximum height, the tank has a 19-inch ground clearance equal to the M1 fleet. Other survivability technologies include a hull front with 40 inches of armor that uses advanced passive with integral reactive armor for large caliber kinetic energy and chemical energy protection. The hull flanks and turret front and flanks have electromagnetic armor. The armor will be supplemented by signature management, hit avoidance and active protection. Eighty smoke grenade launchers are buried under the skin of the turret armor. Increased cross country mobility could be provided by an electric drive transmission and semi-active suspension which would enable the vehicle to obtain speeds of about 45 miles per hour. Its light weight increases strategic deployability by allowing two to three vehicles per C-5 cargo plane and increasing the number of vehicles that can be transported by ship, rail or highway.
The Future Combat System (FCS) Integrated TD (2000-06) will demonstrate the maturity of the FCS candidate's revolutionary technologies in the vehicle configuration required for operation in the Army After Next. Leap-ahead lethality in vehicles 50 percent lighter is required to employ strategic mobility throughout the AAN vision. Using the M1A2 Abrams as a baseline, it will demonstrate 50% reduced crew workload, 40% reduced GVW, 20% increase in fuel economy, and a 40% increase in cross-country speed, and leap ahead lethality. Critical issues to be addressed are the acceptance of two crew vehicle operation, leap ahead mobility, non traditional survivability (replacing ballistic protection with signature management, countermeasures, and active protection), and indefensible lethality (both direct and indirect fire).Critical issues to be addressed are the acceptance of two-crew-vehicle operation, leap-ahead mobility (60 mph cross country), nontraditional survivability (replacing ballistic protection with signature management, countermeasures, and active protection), and indefensible lethality (both direct and indirect fire). Virtual prototypes will be constructed and evaluated, and a system integration laboratory (SIL) will be implemented with laboratory hardware to validate electronics integration.
The Future Combat System will be a revolutionary system providing greater mobility while achieving an overall system weight approaching 40 tons (<50 tons desired). The FCS lethality goals include high probability of kill in extended direct fire ranges as well as long ranges (10Km+ desired) in non line-of-sight conditions. While there is a strong interest in the expected lethality and logistics benefits from an electromagnetic based armament system, the technology is continuing to overcome technical barriers and validate target defeat capability. Therefore, the FCS Armament TD will represent a less risky solution to FCS lethality goals and facilitate successful demonstration of the planned TARDEC FCS Integrated TD in the FY06 timeframe.
The gun will be a derivative of XM291 tank gun developed originally for the future Abrams upgrades in a 120mm configuration. The XM291 gun design consisted of an integral cannon, mount, and recoil mechanism that could be installed, as one integrated unit, in a combat vehicle from the front of the vehicle. Technology application to the XM291 configuration will include a composite gun tube for reduced weight and balance of the gun at the trunnion, and Electro-Thermal Ignition and pulse-forming network transitioned from the ElectroThermal-Chemical technology program being conducted by the Army Research Laboratory, providing higher velocity through controlled burning of propellant as well as very reproducible ignition cycles. The gun design will also include an integral muzzle brake to reduce recoil forces on the vehicle's lighter weight structure, smart barrel actuator to actively control the position of the muzzle at projectile exit enhancing accuracy, and a composite gun tube thermal shroud configuration significantly reducing gun tube signature by enemy radar.
The 120 mm XM291 Gun used enhancements developed by Watervliet Arsenal (WVA) and Benet Laboratories to improve gun performance. Compatibility for refit to the M1A1 or M1A2 Abrams Main Battle Tank was another design requirement. Gun enhancements include improved breech design, thermal shroud, modular recoil design, and improved firepower. The cannon can be increased in caliber, if required, to 140mm with a simple tube change.
The 120mm/140mm XM91 Autoloader was designed, fabricated, installed, and successfully tested in the Advanced TAnk Cannon (ATAC) System vehicle testing. The Autoloader automatically takes rounds from tank storage areas and loads them into the breech of the tank gun -- previously a manual operation. The Autoloader can be upgraded to support automated replenishment of the tank's ammunition from a resupply vehicle. Development has involved mechanical design and analysis, writing of control algorithms, and control system design. The project also involved extensive prototype testing, both in the laboratory and at proving grounds. An innovative feature of the Autoloader is control of projectile loading velocity by gripping the shell and adjusting (in real time) its acceleration and deceleration.
The latest tanks are already well armed with guns of 120mm or 125mm, which are capable of defeating heavy armor, and their performance can be stretched further. However, there are indications that, even at their best, these guns will not be able to defeat the kinds of armour that are being developed for future tanks. In that situation, it is necessary to resort to guns of larger calibre, and several countries have been working for some time on 140mm guns that fire APFSDS projectiles with twice the muzzle energy of those fired by the current 120mm tank guns. As part of this development, the German firm of Rheinmetall has mounted its 140mm gun in a Leopard 2 tank. The Swiss Federal Construction Works has also mounted its 140mm gun in a Leopard 2.
These experiments indicate that the retrofitting of 140mm guns in the existing tanks is possible. But it presents a number of major problems. In particular, 140mm rounds are large and heavy, which makes them difficult, if not impossible, to manhandle. As a result they require automatic loading systems, and this implies major changes to tank turrets and a reduction in the size of tank crews from four to three men.
The UK, Germany and France are working on a 140mm tank gun. While these can be fitted to tank turrets, the size of the rounds and the need for an autoloader make the practicality of this doubtful. One option may be to adopt an assault gun configuration capable of high elevation fire. A 140mm high velocity gun could be at least equal in range to a 155mm howitzer [5.5" (140mm) were the standard medium field piece of the British Army in the Second World War]. A 140mm gun on an assault gun body could be a useful weapon system both for divisional artillery and to reinforce armored or infantry attacks. The only problems with this idea at present is that the prototype 140mm gun is smoothbore, and no 140mm Guided projectiles currently exist.
The only type of automatic loading system which may readily be installed in existing tanks is one installed in the turret bustle. In consequence, the configuration of tanks rearmed with 140mm guns should resemble that already adopted for the Japanese Type 90 and the French AMX Leclerc. In fact, this configuration has actually been adopted for CATTB, the Component Advanced Technology Test Bed built recently in the US to explore the future form of tanks. Thus CATTB has a three-man crew and a bustle auto loader for its XM-291 gun, which can be fitted with either a 120mm or a 140mm barrel.
Because of the problems they pose and the absence of a threat which would urge their adoption, the development of 140mm tank guns is proceeding slowly. The problems they pose are also encouraging people to consider potential alternatives to conventional 140mm guns. One of them is liquid-propellant guns, which were seriously considered for tanks.
The second potential alternative is electromagnetic guns. Their main attraction is that they can launch projectiles at more than 3 000m/s, or twice the muzzle velocity of APFSD projectiles fired by current tank guns. The size, weight and other problems associated with electromagnetic guns do not make them a practical proposition for tanks. Nevertheless, there is a belief in the defence ministries of the US and the UK that, given further development, electromagnetic guns might become the main armament of tanks by the year 2015 or so.
The third alternative is hybrid electrothermal-chemical guns. They have been considered a more immediate proposition for tanks than electromagnetic guns because they only require part of the projectile propulsion energy to come from the electrical equipment, which can therefore be smaller. In fact, electrothermal-chemical guns were being proposed in the US five years ago as the main armament of the next version of the Ml Abrams tank. However, they are now seen to require much further development before they can be seriously considered for tanks.
The term electrothermal chemical propulsion applies to propulsion techniques (typically applied to gun propulsion, but with some potential applications to space propulsion) wherein the burning characteristics of a chemical propellant are enhanced with an electrically induced plasma. ETC fits into a group of kinetic energy weapons (KEWs) technologies aimed at enhancing lethality by increasing velocity. In order of increasing electrical power requirements, ETC falls between true EM launchers (rail guns and coil guns) and pure chemical propulsion.
In the late 1980s, there was also some interest in pure electrothermal (plasma-driven) weapons. However, these weapons have extremely high electrical power requirements. While ETC continues to be an area of interest, the functional goals of the technology have been scaled back substantially in recent years, again because of primary power considerations. Initially, researchers envisioned ETC as a way to increase muzzle energy by sustaining the design pressure over the full length of the barrel. However, current estimates indicate that this would require on the order of 10 MJ of electrical power.
The FCS ammunition demonstrated will incorporate novel penetrators and high performance propellant formulations for enhanced target defeat capability without reduced gun tube wear life or increase in vehicle vulnerability, and axial/radial thruster mechanisms to compensate for system errors increasing accuracy. It is expected that a 100%+ increase in armor penetration could be realized over the M829A2 at extended ranges with up to 70% increase in system accuracy (Ph) at 3km under stationary conditions over the M829A2/M1A2. The cartridge envelope will be determined from a number of 6.2/6.3 technology programs including the Target Destruct TD, Advanced KE Cartridge, and the feed of results to the Advanced Future Cannon Systems work package which will conduct the virtual prototyping studies of FCS Armament systems meeting the goals of FCS.
A compact autoloader mechanism will be required to facilitate expected vehicle configurations where the crew station is in the hull, separated from gun/ammunition compartment. The specific autoloader configuration will be defined in conjunction with the TARDEC FCS contractor vehicle concept activity and will leverage early 6.2 compact autoloader efforts that resulted in the demonstration of high density magazine storage capacities, improved fratricide protection, and weight savings. Sensor technology to detect and resolve loader anomalies under operating conditions will be incorporated
The fire control system will leverage commercially based open electronic architecture developed by TACOM-TARDEC and that which may be pursued for the Future Scout Cavalry System ATD program. Promising technologies such as linear and non-linear lead solution, improved ballistics, dynamic cant sensor, down-range wind sensor, auto-zero, direct "gearless" drive, smart barrel actuators, electronic image stabilization and modern digital servo control will be developed for the specific armament system characteristics. These fire control technologies will provide an additional 30% increase in system accuracy at 3km under stationary conditions but will provide over 500% increase in accuracy during moving conditions.
The combined effects of accuracy improvement in ammunition and fire control will provide an estimated increase in system accuracy of 100%+ at 3km under stationary conditions, and 500% under moving condition as compared to the current Abrams tank.
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