HT9A7/2 Yvernyr Esdirise Support Battle Tank, 1st Noble Guards Cavalry Regiment the Imperial Life Guard, on training exercises in Barony Myrstirei
Designation:
Numerical Designation: HT9A7/2
Name: "Yvernyr Esdirise" - "Ridged Wyvern"
Key Data:
Crew: 3 (Commander, Gunner, Driver)
Cost: 15.3 million NSD
Dimensions:
Length: 8.1m (Hull)/
Height: 2.9m (Turret Roof)
Width: 3.8m (4.2m w/ Modular Side Armour)
Weight: 80t
Performance:
Maximum Speed: 72kph road speed (governed).
Cross country speed: 52kph
Acceleration: 0 to 32kph in 4.8 seconds
Operational Range: 504km
Armament:
Main Armament: 155mm SC12.4 30 calibre solid propellant smoothbore cannon (35 rounds, 25 in autoloader magazine)
Co-axial weapon (left): 12.7mm MG/H8A3 (1500 rounds), or other modular block compatible weapons.
Commander's weapon: 20mm Arsenal Karonin M.28 Autocannon on Remote Weapons System (powered)
Additional: 12x mounted multipurpose grenade launchers, modular systems allow for further options.
Protection:
Passive: Calumnis-3 (metal-composite matrix outer layer, NERA, composite tiles, DU alloy mesh, IRHA plates/hull, fibreglass/rubber/Spectra spall liner)
Active: Solothel Active Protection System
Crew Protection: NBC protection (main + auxiliary), pentafluoroethane crew compartment fire extinguishing, Halon 1301 + foam fuel tank extinguishing and self-sealing suite.
Electronics:
Io FCS
SAIC Combat Networking
Power:
Propulsion: MA.252/mod H2 2,200hp (1,640kW, steady state) 10 cylinder opposing piston diesel hyperbar.
Transmission: Automatic (8 forward, 3 reverse).
Suspension: Hydractive
Power/Weight: 27.5hp/tonne
Overview
During the 1960s and 70s, a highly unorthodox branch of design and a series of increasingly innovative concepts began to take over tank development on a global scale. Made manifest in earlier tanks like the M60A2 'Starship', and carried on into the 1970s in the earlier design models of the proposed MBT-70 tank, the concept of the low velocity, high calibre 'gun launcher' and its ability to engage powerful targets at long ranges led to a scramble to develop what promised to be a step forwards in gun design to its fullest possible extent. Ultimately, however, the failure of the vehicles and associated weapons systems conceptualised and even produced during this period was to mark its death-knell; from the M551 Sheridan light tank of the US Army to the AMX-30 ACRA of the French, the gun-launcher was jettisoned in favour of smaller, high velocity guns in the form of the 120mm guns then coming into service under the Germans.
In the eyes of the Anemonian design teams who were to take upon the mantle of those who had failed before them, the reluctance of most to approach the idea of the gun launcher was a matter of misinformation. The primary reasons behind the failure of such weapons systems most likely derived primarily from the inadequacy of the weapons guidance systems being used at the time, and with the intention to overturn years of misconceptions concerning the efficacy of the gun-launcher as a weapons platform and bring its formidable firepower to bear on the modern battlefield, FOAM IECpl submitted a proposal to the Ministry of War in late 2009 concerning their intent to redevelop a single HT9A7 platform towards the use of an unorthodox 155mm gun platform and a series of other modifications to optimise its potential use as a combat asset. Mindful of their then-budget surplus, the Ministry responded in the affirmative, leaving the specialist team attached to the project at FOAM to work in conjunction with several concerns around the country to realise a dream that had been left on the side of the road some forty or so years beforehand.
FOAM IECpl's initial brief called for a fully developed vehicle in mid 2011, with the main task of the development team to redesign the turret of the vehicle and its contents almost entirely in order to accommodate new weapons systems and armour layouts. The decision to employ a 155mm gun derived accordingly from cost and time-period related concerns; as far as ammunition was concerned, the use of a 155mm round would allow existing machinery to be at least modified for use with the new main battle tank, and other similar cost and time cutting procedures would follow in due course through effective utilisation of existing technology to complement the vehicle's innovative armament. With increasingly active support from several organisations beyond the administrative authority of FOAM, the project began to pick up speed and funding at previously unimaginable rates. With the Crown Army indicating possible active trials of the new vehicle upon completion, its focus shifted from simple technological development to the full blown creation of a new vehicle, and the design began to take upon a life of its own.
Meeting the mid-2011 development targets set at the beginning of the project, the HT9A7 model displayed to the Ministry of War was subject to significant attention when it became apparent that its armament gave it flexibility and capabilities beyond that envisioned at the earlier stages of the project. Utilising its large calibre gun to great effect, the HT9A7/2 was capable of providing potent support fire against a wide range of targets and though its capabilities were not such that it would be able to operate independently of other vehicles as a standalone main battle tank, further testing seemed to indicate that its ability to fire different ammunition from a different gun made it an invaluable support asset when operating alongside the existing HT9A7 Block II Main Battle Tank. For the Ministry of War, this presented a dilemma; the advantages of the HT9A7/2 were clear, but adopting it formally would require the adoption of a parallel two-tank armoured platoon to maximise the efficacy of the new main battle tank on the field of battle, something that had not been attempted since the normalisation of tank models in the 1970s with the introduction of the HT6. Pending a decision by the end of the year, the Crown Army allocated further funding to the development team to continue improving upon it, and this led to the replacement of what elements of the vehicle had been acquired from elsewhere that compromised its overall performance.
On November 15th, 2011, the Crown Army officially announced its intent to replace the traditional five tank, single model platoon structure utilised for a half century by the Anemonian military with a four-one five tank platoon structure whereupon the fifth HT9A7 in each platoon would be replaced by an HT9A7/2. This was announced alongside a routine enlargement of the Crown Army to accommodate the rise in spare HT9A7 stocks; with the leftover tanks, additional formations would be formed, leading to a further set of procurement orders for new build HT9A7s and HT9A7/2s to fill the new force structure desired by the military. It was a surprisingly audacious step for a traditionally conservative military institution, but one readily welcomed by troops and civilians nonetheless; the new build orders would be hugely beneficial at all levels of military development and production within FOAM, whose operations stretched across Anemos Major, and the addition of a highly potent support asset to the military's arsenal would allow for a far more flexible and effective force structure to face up to threats on the modern battlefield. The first HT9A7 tanks were put into action in Asakura on December 25th, not long after the official announcement; the vehicle itself had entered finalised production a good month before the procurement order had been placed, and crew familiarity was evident with what was effectively an HT9A7 derivative, allowing for rapid training and deployment of the vehicle with minimal issues. In its frontline role the modifications made on the HT9A7/2, especially in terms of armament, served to greatly enhance its effectiveness in direct support operations and the popularity of the vehicle almost immediately upon entering limited service served to greatly enhance its initially somewhat shaky reputation as a designers' vehicle, rather than a battlefield one.
The HT9A7/2 is a highly unorthodox vehicle, revelling in its deviation from the norm and reaping all the associated benefits of a successful and unexpected design. Drawing from conceptual designs and attempted development halted some forty years ago in the belief that the gun-launcher model of tank armament was untenable, the Yvernyr Esdirise marries the basic concept with vast technological improvements and a much more flexible model of doctrinal integration to create a secondary battle tank that exerts the full potential of the gun-launcher in conjunction with the HT9A7's more conventional armament. Its effectiveness on the modern battlefield lies in its ability to inflict damage in highly unorthodox manners, relying on innovative weaponry and effective doctrine to strike at enemies in hitherto unconsidered ways; built against all expectations, the vehicle born against the odds from the experimental HT9A7/2 program is highly unorthodox in its own right and and a highly effective, successful vehicle nonetheless.
Main Armament
The cornerstone of the HT9A7/2 development project, the 155mm SC12.4 30 calibre solid propellant smoothbore cannon is a technical derivative of the HT9A7's SC10.8 cannon in terms of construction technique and layout, designed along similar lines to its derivative origin for an altogether different role alongside it. A heavy gun capable of firing rounds at high pressure with little difficulty, employing hydraulic retarders, thick barrel and travel distance in lieu of the muzzle brake found on the SC10.8, the SC12.4's design is nonetheless optimised for the use of large low-pressure 'smart' rounds across a number of potential roles in direct support of the HT9A7, providing fire support in areas where the HT9A7's long-necked, high velocity rounds, highly potent when utilising APFSDS rounds in anti-tank engagements, are nonetheless incapable of providing the clout that can only be obtained through sheer size of armament.
It must be noted that, in technical terms, the SC10.8's ability and doctrinal requirement to utilise GLATGMs and BLOS KEPs makes it a gun-launcher; the distinction is made in that the HT9A7/2's gun is specialised in design for that role and that role alone, whereas the 128mm SC10.8's long barrel allows it to be employed as a conventional gun firing high pressure, high muzzle velocity APFSDS rounds and the like.
When compared to the HT9A7, the 35 round carrying capacity of the HT9A7/2 is relatively unimpressive, made possible through the utilisation of a highly angular bustle section designed for full use of available volume for ammunition storage. Nonetheless, the figure reached is relatively high for so large a round, achieved in part by the oft-overlooked size of the HT9A7 (a heavy main battle tank designed for combat in open field environments), and the HT9A7/2's doctrinal role as a support vehicle to the main platoon means that ammunition expenditure will be lower than that of the main battle tanks to which it is attached; the smaller ammunition capacity of the HT9A7/2 when put against the original vehicle does not compromise the latter's ability to operate in the field for extended periods of time if so desired, assuming effective use of available ordnance.
A 155mm solid propellant cannon with a smoothbore barrel of 30 calibres (4.65m), the relatively short barrel length of the SC12.4 is a reflection of its intended purpose; without the need to fire high pressure rounds at high initial muzzle velocities, the HT9A7/2 was able to limit the weight of its main armament by cutting it down to about two-thirds the length of the 128mm SC10.8. Like the 128mm cannon, the 155mm gun-launcher's barrel is constructed of autofrettaged steel. Responding to problems concerning the decreasing barrel life of modern smoothbore guns due to the increased performance of propellants, it utilises a barrel construction that departs from the chromium-lined steel barrels of most modern guns. With a silicon nitride (Si3N4) barrel, the SC12.4 aims to use ceramic liners to decrease the effect of propellant erosion of the barrel when compared to chromium gun barrel linings, and gives the gun either a greater service life or the ability use increasingly powerful propellants. However, as a ceramic, silicon nitride is also very brittle, and due to the inability of the material to undergo the same autofrettaging process used by steel barrels to induce pre-compression in the gun barrel, it also utilises a 35% glass reinforced polymer composite overwrap to induce the pre-compression necessary to compensate for the brittleness of silicon nitride, utilising computer modelling to determine the deposit locations and angles necessary to achieve the desired levels of strength and stiffness within the gun barrel itself. The result of this is that the SC12.4’s gun barrel, through significantly decreased erosion in comparison to chromium-lined barrels, is able to withstand propellant-induced damage for longer periods of time. The weapon’s thermal jacket is also made of 35% glass reinforced polymers, and, opting not to utilise a standard pattern bore excavator, the SC12.4 chooses instead to utilise an automatic compressed air fume extraction system at the rear end of the gun barrel to prevent oxygen depletion and other potential effects on the crew.
With the SC12.4, recoil mitigation is achieved entirely through absorptive methods, aiming to utilise highly efficient recoil control mechanisms to prevent the firing-related issues seen in early gun launchers. Advances in technology and specific advantages available to the HT9A7 have been fully exploited. The weight of the gun-barrel itself, which has been thickened in comparison to other comparable guns for both recoil purposes and longevity, is such that the recoil of the weapon is minimised at the point of firing due to the increased energy required to move the gun. A hydro-pneumatic recoil mechanism is employed the gun with a lengthened travel distance to further dissipate the recoil forces generated by the gun, giving it movement space over which to expend energy. At that point, four hydraulic retarders (a pair to each side of the weapon) are employed to cushion what recoil forces are left, minimising the final 'jolt' that hits the vehicle upon completion of the gun's rearward travelling cycle in the post-firing period. Particular importance was attached to this part of the gun's development due to the issues seen with the recoil forces generated by large gun-launchers in a number of 1970s designs, and though the protection afforded to the HT9A7/2's electronics would be considered enough to protect them from the impact of the gun's recoil, significant effort was put into reducing the recoil itself to ensure that the problems associated with large gun-launchers in the area would be eradicated altogether. Stabilisation is achieved via two independent electro-hydraulic systems with independent horizontal and vertical stabilisation (full dual-axis electro-hydraulic stabilisation), as well gyro-stabilisation, further increasing the mobile engagement capabilities of the tank.
The use of a one-piece 155mm round in the HT9A7/2's SC12.4 gun-launcher necessitated the use of an autoloader, and the highly efficient system utilised in the original tank was replicated and scaled up for compatibility with the 155mm rounds used by the new armament. In general, 25 rounds are stored in the autoloader with 10 additional rounds in storage for later use. As a number of rounds (GLATGM and MHE, potentially more, in combat use) are used in a largely interchangeable manner on the battlefield, the autoloader system used within the HT9A7 could not, by default, be a simple bustle system as used by many other main battle tanks, while the carousel system favoured by many Eastern Bloc armoured vehicles was also not a valid option due to its storage inefficiency. As such, the system utilised is a rotary belt type bustle system with a storage capacity of 25 155mm rounds (regardless of type) behind the crew. The control system uses a combination of virtual memory-stored location records of rounds and bar code designations to correctly select and prepare rounds; rather than automatically loading rounds upon firing and spent case extraction, the gunner is able to select a number of potential options; as well as being able to set the autoloader to ‘single type automatic’, which causes the autoloader to consistently select a single type of round and load it upon extracting the spent casing of a firing round without confirmation, he is also able to set up a ‘firing list’, selecting a number of rounds in firing order for the autoloader to automatically select and load, and can also utilise a manual confirmation system where he selects a desired round prior to loading, allowing the Anemonian gunner to make full use of the wide selection of rounds employed within the HT9A7/2. The average rate of fire of the autoloader-equipped cannon when on automatic loading is 10 rounds per minute, but this figure decreases when the gunner opts to utilise individual selection.
In combat situations, the Yvernyr Esdirise employs its 155mm gun-launcher in a direct support role, relying upon two main ammunition types to do this; M09/AE Multipurpose High Explosive and the M09/mod M Gun Launched Anti-Tank Missile. Though a number of other ammunition types are available, ranging from high pressure APFSDS rounds to anti-infantry canister and white-phosphorous smoke options, the use of two primary ammunition types with relative battlefield flexibility make the ammunition selection for the tank a much simpler process while maximising its combat lethality. Making full use of the 155mm gun's sheer size, both conventional field ammunition options available to the HT9A7/2 allow it to operate in a comparatively effective manner in battlefield operations in a direct support capacity against a wide range of potential targets. M09/AE utilises innovative fuzing options and FCS coordinated fire control drawing from design elements found in the HT9A7 IFDE SHORADS system to create an HEDP derivative round with a virtually endless list of targets it is capable of engaging and neutralising. M09/mod M is the cornerstone of the Esdirise's anti-tank capabilities and a vital component of its arsenal as a support tank to the wider HT9A7 platoon, a long range, high potency anti-tank guided missile with size unrivalled by most missiles short of the box launchers found on the HT9A7 capable of extending the platoon's reach beyond conventional limits, making full use of the 155mm gun's size and the comparatively long bustle and propellant content of the HT9A7 family's armaments to extend their range beyond that of conventional 150mm size range anti-tank missiles.
The M09/mod M is a GLATGM (gun-launched anti-tank guided missile) utilising a HEAT warhead and a three stage seeker system to defeat the vast majority of existing tanks at extended ranges by accomplishing highly countermeasure-proof top-kill attacks. The seeker head uses a combination of millimetre-wavelength radar, passive IR CCD sensors and a semi-active laser seeker to acquire and track the target while in flight, decreasing the effectiveness of single-purpose countermeasure units against the missile. Utilising a soft-launch system, the M09/mod M clears the barrel of the gun before engaging its flight motor, thus greatly increasing the service life of the barrel itself when used in conjunction with the GLATGM. With folding stabilisation fins used to fit as large a missile as possible into the HT9A7/2’s 155mm gun barrel, the missile’s internal seeker system tracks the acquired enemy target and rises to the appropriate trajectory before entering its terminal descent, placing itself into a high speed, top-kill position to virtually guarantee a kill; potential targets range from a wide variety of land vehicles to, potentially, landing ships and helicopters. The warhead of the missile is a tandem charge; upon striking the enemy target, the impact detonation mechanism first detonates a smaller ‘initial’ charge to activate and eliminate the ERA lining of the tank; furthermore, the ‘initial’ charge utilised by the M09/mod M takes advantage of the increased capacity of the missile by being somewhat large, giving it enough explosive force to either destroy or damage NERA/NxRA blocks on enemy tanks and thus leave them vulnerable to the larger shaped charge warhead located behind the initial charge (separated from it by a titanium diboride blast shield). The main charge is then detonated. As such, the M09/mod M not only provides the HT9A7/2 with the ability to defeat the lighter roof armour of an enemy main battle tank from nearly 20km away utilising an independent seeker mechanism that permits BLOS engagement, it also possesses the capacity to engage and eliminate ERA, NERA and NxRA protected vehicles if necessary with its top-kill engagement pattern. There is a three stage control mechanism on the M09/mod M that prevents premature detonation; the two safety mechanisms are deactivated upon firing the missile (acceleration-based detection) and entering the terminal trajectory (computer controlled), while a tertiary protective mechanism ensures that the delay between initial and main charge detonation is maintained to permit effective use of the tandem charge layout.
M09/AE MHE is a solid propellant high explosive multipurpose round derived from the M07 HEDP round employed in the HT9A7's 128mm gun, and marks a radical shift away from its predecessor in its use of technologically advanced fuzing options to achieve potency against a wide range of potential targets. The propellant utilised in the M09/AE is the same as that employed in the M07 family of rounds, a combination propellant (60% nitrocellulose, 20% nitroglycerine, 4% RDX, 15% diethylene glycol dinitrate with 1% of other content and 55 grams of igniter); the utilisation of a low level of RDX in place of the nitroglycerine used in other propellants provides the 155mm round with a higher level of more stable propellant performance while nonetheless restricting the increase so as to retain a practically sustainable barrel service life. The basic construction of the round follows that employed by most Anemonian HEDP rounds; a lengthened 'long nose' fragmenting steel casing in front of the weapon both serves to enhance the round's anti-personnel capabilities while acting as the round's standoff, maximising its anti-tank effectiveness in the process. The warhead's explosive is a combination composition utilising trace HNIW with HMX to create a nitroamine base explosive with high energy levels to maximise the pressure effect exerted by the HEAT component of the round upon impact. The liner utilised in the round is copper, with a secondary aluminium alloy lining. A smaller pressure charge of similar construction is located ahead of the main warhead with division separating the independent detonation of each to eliminate ERA/NERA based obstructions to the warhead, utilising the 'larger initial' approach taken by the /mod M to maximise the potency of the round against anti-HEAT obstacles and thus its ability to successfully engage modern vehicles and armour layouts. The dual purpose nature of the round is reflected in its construction; with its combination of a fragmenting casing and a highly potent tandem HEAT warhead, it is capable of engaging a wide variety of targets successfully. However, the fuzing options on the M09/AE takes this one step further. A number of options exist. The first is a simple impact-based fuze, which allows the round to enter its detonation cycle upon hitting its target physically. This option is generally used in vehicular engagements, where the tandem layout of the round's warhead is optimised for this approach in its engagement pattern against armour. Additionally, however, M09/AE is also capable of electronic time fuzing via a 'smart' programming system drawn from the HT9A7 IFDE's HEFAB rounds. Two primary data inputs are initially used. The fire control system of the HT9A7/2 gauges the distance between the tank and its target, as well as a number of alternate variables to judge the effects environmental phenomena will have upon the round's flight. The second is a velocity measurement device incorporated into the muzzle of the 155mm gun, which measures the velocity of each individual MHE round upon exiting the gun's muzzle. By combining these two data sources, the programming unit is capable of gauging the time taken by each round to reach their targets. Compensating for dispersal distance, the programming unit takes the firing solution generated as a result of combining the two data inputs and relays said time to the round's fuze, thus resulting in an effect similar to that of a proximity fuze at a vastly lowered price and far less lost explosive capacity. The gunner is capable of setting the distance relative to its target at which the round is to detonate, and this allows for a vastly expanded array of potential uses for the round. Detonation prior to hitting the target allows for the dispersal of high-speed fragments before impact, creating a wider impact area. This can be effective against infantry, though a more innovative doctrinal use for this fuzing method is the fragments' ability to significantly damage the weak frontal electronics of anything up to the heaviest main battle tanks, allowing the HT9A7/2 to devastate main battle tanks frontally in a highly unorthodox fashion by attacking its weaker electronics components. On the other hand, a time delay after impact can be set to maximise the round's effect against foritifed positions by giving the round time to push through fortified obstacle prior to detonation. With its sheer size, explosive flexibility and innovative fuzing options, the M09/AE is one of the most potent high explosive rounds in service today.
Other Armaments
The co-axial armament employed by the HT9A7/2 is the 12.7mm MG/H8A3 Heavy Machine Gun. The MG/H8A3 is a short-recoil operated rotating bolt machine-gun utilising forced air cooling and forward porting to evacuate heat and propellant gases. With a barrel constructed of cold hammer forged steel, the external receiver of the weapon itself is, as a relatively new weapon, constructed of 30% glass reinforced polymer (making it relatively lightweight while remaining resistant to temperature buildups and sudden shocks), and the need for a replaceable barrel is largely removed through the installation of the highly efficient air cooling system. The ammunition is fed via a disintegrating link (a scaled up version of that utilised in the MG3/MG3R1 series’ 7.7mm ammunition), and the cyclic rate of fire of the weapon is mechanically alterable via the trigger block like the MG3 series, alternating between 450 and 750 rounds per minute as desired. The weapon itself is normally operated via a trigger located on the weapon’s single-handle (as opposed to the spade trigger used by some), but one of the differences between the infantry deployed and most vehicle deployed versions of the MG/H8A3 is the fact that they are, in fact, initial electrically ignited weapons (i.e. the initial trigger pull is replaced by electric ignition) to make them compatible with the HT9A7’s co-axial block system and greatly mechanically simplify the Remote Weapon Systems in service with the Anemonian Armed Forces. In general, two types of rounds are used with the MG/H8A3 as a component of the HT9A7/2 SBT; ball ammunition, for use against ‘soft’ targets, while HEIAP is employed for use against harder targets.
Of course, like the HT9A7, the co-axial station of the HT9A7/2 is highly flexible through its use of a quick-change/replacement layout known as the Modular Block System. The weapons systems themselves are placed in modular ‘blocks’ which are installed into a co-axial weapon ‘socket’ in their entirety (hence the electrical ignition for the MG/H8A3), while the ammunition and ammunition feed can be adapted without difficulty to fit into a small storage area located near the co-axial weapon itself (while most mechanical feed components, such as the sprockets used in the M.28, are placed within the modular block itself). Theoretically speaking, this means that almost any co-axial weapon can be installed in the tank as long as it is modular-block compatible and modified to fit the appropriate specifications; foreign heavy machine-guns and other support weapons aside, larger weapons such as 50mm cannons can potentially be retrofitted to become modular block compatible, the limited ammunition capacity of such an arrangement notwithstanding.
Another significant change made in the HT9A7/2 is its use of an armoured remote weapons system housing a high-elevation 20mm automatic cannon for anti-aircraft and vehicle engagement purposes. The original conceptualisation for this uncommon armament derives primarily, again, from a similar weapons system employed on the MBT-70 tank. However its initial implementation, utilising comparatively unsophisticated technology, was almost undoubtedly a failure with the equivalent system employed then plagued by a remarkable array of mechanical failures and design flaws inhibiting the practicality of such a weapon, and the result was that tank development for a long period of time reverted back to the use of manually operated commander's weapon systems. However the 21st century has seen a remarkable series of technological advances in the area of powered electronics and the technology employed in now conventional 12.7mm range remote weapons systems allowed the designers behind the HT9A7/2 to reconsider and reconfigure older plans for a top mounted 20mm cannon and bring them into the modern day to create an effect secondary weapon for a variety of uses, its unique positioning allowing for its use not only against personnel and structural targets but rotary wing aircraft too. The high elevation turret itself is armoured for protection against return fire, and is a fully powered remote operated traversable turret system capable of rapid movement and target engagement as required of it. The primary optical suite is mounted in an armoured box above the weapons system itself. Mounted within the turret, the 20mm Arsenal Karonin M.28/m Autocannon is a 20mm L/22 automatic cannon utilising a 1hp motor located within the receiver to cycle the weapon’s action, allowing for greater control over the feeding and cycling process of the weapon to ensure greater reliability and control over its firing qualities. The 1hp motor powers a rotating sprocket system that feeds and removes the ammunition from the autocannon’s chamber, and a second sprocket layer feeding the ammunition belts into the weapon mean together with disintegrating links mean that the gunner can easily switch between the two types of ammunition he will be using on the battlefield. The barrel of the autocannon, upgraded once since its initial development, utilises bimetallic explosively bonded tantalum/4150 steel to greatly extend its barrel life beyond that of similar weapons systems, and porting along the barrel permits for gas release and redirection (though the rigid co-axial mounting makes recoil less of a problem). Another advantage of the electric control is the ability to set highly controlled firing rates for the weapon; by default, there are four firing modes used with the M.28 – Single (Semi-Automatic), Low (120rpm), High (240rpm) and Very High (400rpm) – but other rates can be programmed into the weapon if desired.
In addition to these armaments, the HT9A7/2 responds to recent developments in tank development by incorporating support for a variety of additional equipment. The gun-launched M07/mod M can also be accommodated in a number of side slung box launchers like many other similar vehicles, though this approach is only used in high intensity open field combat due to the obvious disadvantage posed by the additional bulk of the missile launchers. Furthermore, in response to recent developments in missile technology, the Arteyr Anti-Tank Missile (a 240mm (fins folded) development of the M07/mod M built with a far longer range and larger warhead) can also be fitted into larger box launchers for engagements with enemy tanks.
Armour
The armour layout employed on the HT9A7/2, deriving naturally from its initial position as a modification to the basic HT9A7 design, employs the same Calumnis-3 specification protection as that on its parent vehicle. Despite changes to the nature of the vehicle in both size and role, no reason was seen to depart from the basic principles of design employed in the HT9A7 and the result is that the new battle tank employs the same armour-first, crew-second approach to the vehicle's internals. With changes made to the turret shaping and size, the forward protection afforded to the HT9A7/2 has been increased in comparative terms to the HT9A7 Block II, with the same replacement of steel components in areas with alloys of titanium to reduce overall vehicle weight. In terms of armour modularity, the layout employed on the HT9A7/2 is visually monolithic in comparison; however, the same ability to remove and reorganise armour exists on the new tank, albeit with less flexibility than the layout seen on the HT9A7 itself in terms of turret layout. The base HT9A7/2 layout is designed for high levels of effectiveness in high intensity combat areas up to lightly urbanised environments, envisioning warfare in both open and enclosed environments in support of Crown Army tank operations in a multitude of potential battlefields.
Outer layer protection is achieved through the use of a Titanium Diboride (TiB2) based metal composite matrix with a fibreglass spall backing. This metal composite matrix, by being significantly harder than materials used in most ammunition-based applications, is capable of breaking up rounds, including penetrators, and, through the toughness of the metal composite matrix, results in the controlled distribution of kinetic energy absorbed from the round. As the controlled distribution results in the creation of a damage area only marginally larger than the size of the round from which energy has been transferred, with any spall effects absorbed by the fibreglass backing, the external protection is capable of sustaining multiple hits from anything up to the 12.7-14.5mm round range commonly utilised in modern heavy machine-guns. The resultant outer layer of armour protection is significantly lighter than the equivalent volume of RHA, and nonetheless capable of entirely stopping armour piercing small arms fire while significantly wearing down the effectiveness of high performance kinetic penetrators before they reach the armour blocks themselves.
Another component of the HT9A7’s passive protection suite is non-energetic reactive armour (NERA). In modern times, the continued utilisation of explosive reactive armour (ERA), widely used as most armoured vehicles’ first-line protection against shaped charge warheads, has been proven to be impractical and ineffective due to a number of reasons. Firstly, the explosive composition of the filler utilised in ERA results in a situation where hits against the vehicle can potentially result in collateral damage, especially in confined spaces. Due to the necessity of utilising infantry support for armoured vehicles in such environments, this means that the practicality of ERA equipped tanks is greatly decreased due to their subsequent inability to operate effectively in certain combat situations. Secondly, however, the modern development of tandem shaped charge warheads and their frequent employment in anti-tank guided missiles, where a smaller charge detonates ERA prior to the detonation of the main charge, has created a situation where the combat threats faced by the Anemonian Armed Forces are more than capable of easily defeating ERA based solutions with minimal effort through the use of a simple design aspect in their anti-tank warheads. As such, the utilisation of NERA was looked into by FOAM during the design process for the HT9A7, and eventually replaced all planned employment of ERA in the tank due to its clear advantages over its predecessor. The NERA utilised within the HT9A7 is formed out of panels consisting of a 10mm thick layer of rubber lining sandwiched between two 6mm thick plates of steel (Domex Protect 500). When a projectile hits the NERA panel, resultant outward motion by the two Domex plates increases the effective thickness of the armour in that area, providing increased protection against projectiles. Furthermore, however, the lack of an explosive element means that the NERA utilised within the HT9A7 is both capable of taking multiple hits (to some extent) and causes no resultant collateral damage, as well as being far more resistant to the effects of a tandem charge warhead; both in terms of protection and resultant damage, it is a more desirable form of protection. Cross-wise orientation of NERA panel is employed in the armour layout to ensure that the jet bulge in the first panel generated upon impact does not result in material erosion in the second, increasing the overall protectiveness of the NERA layers against shaped charge warheads in exchange for a minimal increase in volume. Overall, the result of this is that the NERA protection of the HT9A7 is both superior to that of standard ERA and parallel arrangements of NERA, giving it first-line protection against almost any shaped charge warheads thrown at it.
In terms of ceramics, the HT9A7 primarily employs nano-ceramic Titanium Diboride (TiB2). Titanium Diboride is, in terms of properties, highly similar to the titanium carbide currently frequently used in many armoured vehicles armour and armament suites; however, in many respects, it can be said to be superior. At room temperature, its hardness is almost three times that of the equivalent volume of fully hardened structural steel. Its melting point is also incredibly high, at 3225˚C, and the result is that armour blocks incorporating normal Titanium Diboride tend to be both incredibly impact resistant and capable of withstanding the high heat generation of chemical energy warheads. Chemically, it is also a relatively field-friendly material, insofar as it is more stable than tungsten carbide when in contact with iron, and less prone to oxidation at anything short of extremely high temperatures. As such, Titanium Diboride is a highly effective material when used in impact-resistant armour applications, capable of withstanding the effects of both HEAT rounds when used in conjunction with other forms of armour but, more importantly, very effective through high levels of hardness against kinetic energy rounds and penetrators. In addition, not content with stopping there, designers decided to take the high-performance characteristics of Titanium Diboride one step further through the use of modern technological developments in nanotechnology. By starting with high purity powders and running them through plasma melting and hot isostatic pressing to inhibit grain growth, the time-temperature window of densification was extended. With nanograin sizes maintained throughout, the result was the significant decline of porosity in ceramics passed through the treatment procedure, and the subsequent production of full density ceramics at the nanometer scale. Higher strength and hardness was achieved, as such, due to the resultant low-angle, high-strength grain boundaries and less dislocation within the overall structure due to the finger grain size. The resultant nano-ceramic Titanium Diboride improves upon an already superior material to create a uniquely effective and efficient ceramic for use within the HT9A7’s composites.
The three metal alloys utilised in the HT9A7 are Type 7720 Titanium-Aluminium alloy, depleted uranium based Stakalloy, and IRHA (HRc 40, HRc 48). Type 7720 Titanium-Aluminium alloy draws from the natural advantages of a titanium-based alloy (high stress resistance and toughness for its weight range, as well as corrosion and temperature resistance). In this particular case, however, the primary advantage of Type 7720 stems from its weight advantage; compared to RHA, Type 7720 is capable of providing properties close to those of ceramic materials at 38% the weight of the equivalent volume of RHA. Of course, the difficulty of machining Type 7720 makes it an impractical choice for usage across the entirety of a main line battle tank, and the result has been that the titanium alloy has not been used as the hull material for the HT9A7 out of purely practical concerns about the workability of the material.
Stakalloy is a depleted uranium based alloy used only as a mesh-based layer of armour rather than a block in itself. The high density of depleted uranium based materials means that the weight gain, despite its highly effective protective capabilities resulting from its sheer density, is prohibitive when overused, and the radiation emission, however limited, of depleted uranium makes it a material that must be approached with trepidation when utilised as a protective material. As brittle as it is dense, depleted uranium is incapable of being used effectively as a standalone material within armour; as such, it must be used within an alloy for maximisation of effectiveness. Departing from the usual uranium-titanium alloys (Staballoy) favoured in most developments of the material, the alloy used here instead is one formed of niobium and vanadium with the depleted uranium to create a more machinable material for use within the HT9A7 while retaining the high density qualities of depleted uranium (~95% of the alloy’s composition being of DU).
IRHA, or Improved Rolled Homogeneous Armour, is a metal alloy that modifies the basic chemical composition of standard RHA to create a far harder material, altering one of the base components of many modern tanks to create a more effective alternative suited to the battlefields of the 21st century. The basic chemical composition of IRHA (by weight percentage) is 93.68% iron, 0.26% carbon, 3.25% nickel, 1.45% chromium, 0.55% molybdenum, 0.4% manganese, 0.4% silicon and some impurities (<0.01% phosphorous, <0.005% sulphur). With a 1% increase in the nickel composition of the alloy and a smaller increase in a number of other elements (chromium, molybdenum and manganese), the resultant material is much harder than standard RHA whilst retaining similar levels of ductility and toughness. Weldability and machinability, of particular importance for IRHA’s hull applications, is similarly preserved at RHA levels by maintaining carbon content at ~0.26% or below. IRHA’s physical properties are further determined by the heat level at which it is tempered; HRc 40 grade IRHA, which is used for hull applications, is tempered at 529˚C, which HRc 48 grade IRHA, for applique armour, is tempered at 218˚C. The differentiation in role stems from the fact that HRc 48 grade IRHA is more effective against kinetic energy penetrators at the cost of far less resistance to fragmented munitions that HRc 40, making it more usable in applique armour (where its shortcomings are compensated for by other materials). IRHA, as such, provides the HT9A7 with all the advantages of rolled homogeneous armour but, again, goes one step further by modifying the basic chemical composition of this erstwhile material to give the HT9A7 another advantage over many contemporary armoured vehicles.
In terms of layout, the armour is separated into two parts; the armour itself, and the hull construction and interior. The armour consists of an outer layer of TiB2 based metal composite matrix over a cross-wise oriented NERA layer, another layer of the metal composite matrix, then panels of Type 7720 TiAl alloy sandwiching square tiles of HRc 48 IRHA and nano-ceramic TiB2. Beneath this is another layer of NERA, nano-ceramic TiB2 tiles structurally maintained by Type 7720 TiAl alloy, a Stakalloy mesh and a plate backing of HRc 48 IRHA. NERA layers and some armoured protection can also be found on the roof of the tank for protection against HEAT-based ATGMs. The hull itself is constructed of HRc 40 IRHA. The tank’s interior is equipped with a spall liner made of 20% glass composition fibreglass backed by Spectra and rubber; the energy is expended against the fibreglass, with any further spalling being absorbed by the backing to provide the crew with highly effective protection against internal damage.
Slat armour constructed of aluminium alloy for weight reduction is also widely used to protect the rear of the vehicle (the engine block) from damage by shaped charge warheads, but this is an additional unit sold by FOAM and not considered to be a component of Calumnis-3.