N-L-M

There are a few tricks that separate gasoline and diesel (and AFAIK supercharged and naturally aspirated) 2 stroke engines.
The problem with 2-stroke engines is that the moment the down-stroke is done, the entire cylinder has to be scavenged and filled with clean air (and fuel, for gasoline engines). And the cylinder is full of hot gas above atmospheric pressure.
So on small engines, the crankcase and piston are used as a pump, with the piston sliding also playing the role of the valves. On the up stroke air is drawn into the crankcase, on the down stroke it gets pressured and then pumped into the cylinder, ready to work.

This of course means you have a lot of air going through your crankcase and can't just spray oil on it, but mix it in with the fuel. You can also get iffy performance thanks to questionable scavenging, rich mixture (if its a diesel, the fuel is injected directly, regardless of the scavenging efficiency), and so on.
In larger 2-strokes, the overpressure problem is solved with a blower of some kind, usually an engine-powered supercharger (turbos don't work at low speed, but external blowing is also possible), which allows the crankcase to not be used for air pumping. This means it can be lubricated like a normal engine.
Additionally, with some cam-operated valves, and careful arrangement of the system, good axial scavenging can be achieved.

Linear scavenging is even more useful for cylinders with a high stroke to bore ratio; such as are found on opposed-piston engines. These are tempermental beasts, but when properly tuned put out a lot of power for their weight and volume. 

The Napier Deltic took this to a whole new level, and it worked pretty well, but was very hard to maintain.
 
With modern CFD and CAD, the precise arrangement of ports, timing, and dimensions can be found to make this work reliably and efficiently. 

You're missing 2 important points with that line.
The first is that BAE are not the OEM of the MCT-30. It's not their design to modify, that's Kongsberg's job. BAE are offering integration onto the CV90 they sell. The absence of APS integration on current-production MCT-30 does not prove it to be impossible.
The second is that the D series is not ready for mass production. At all. They say it'll integrate APS, but they don't have anything more than mockups of Iron Fist on the thing. And Iron Fist is also not production ready.
 
I want a source on the claims that the MCT-30 is too small and doesn't have enough power.

There are a few tricks that separate gasoline and diesel (and AFAIK supercharged and naturally aspirated) 2 stroke engines.
The problem with 2-stroke engines is that the moment the down-stroke is done, the entire cylinder has to be scavenged and filled with clean air (and fuel, for gasoline engines). And the cylinder is full of hot gas above atmospheric pressure.
So on small engines, the crankcase and piston are used as a pump, with the piston sliding also playing the role of the valves. On the up stroke air is drawn into the crankcase, on the down stroke it gets pressured and then pumped into the cylinder, ready to work.

This of course means you have a lot of air going through your crankcase and can't just spray oil on it, but mix it in with the fuel. You can also get iffy performance thanks to questionable scavenging, rich mixture (if its a diesel, the fuel is injected directly, regardless of the scavenging efficiency), and so on.
In larger 2-strokes, the overpressure problem is solved with a blower of some kind, usually an engine-powered supercharger (turbos don't work at low speed, but external blowing is also possible), which allows the crankcase to not be used for air pumping. This means it can be lubricated like a normal engine.
Additionally, with some cam-operated valves, and careful arrangement of the system, good axial scavenging can be achieved.

Linear scavenging is even more useful for cylinders with a high stroke to bore ratio; such as are found on opposed-piston engines. These are tempermental beasts, but when properly tuned put out a lot of power for their weight and volume. 

The Napier Deltic took this to a whole new level, and it worked pretty well, but was very hard to maintain.
 
With modern CFD and CAD, the precise arrangement of ports, timing, and dimensions can be found to make this work reliably and efficiently. 

FINAL SUBMISSION:
XM-2239 NORMAN

[ooc: this is written from a timeframe at which only a few prototypes have been built and tested, mass production awaits selection. Square brackets denote ooc comments]
Classified: top secret
for Cascadian eyes only
 
When General Foundry and Mechanics (henceforth, GF&M) received the brief from the Cascadian armored corps on the requirements for a future armored fighting direct combat vehicle, medium (henceforth, medium tank), and future armored fighting direct combat vehicle, light (light tank), focus was immediately concentrated on the larger requirement of the pair. It was quickly realized that the requirements fell significantly short of the state of the art; and that said state of the art permits the development of a vehicle not only superior to the requirements in every regard, but capable of matching the requirements of the future as well, thus ensuring the safety and freedom of Cascadia for generations to come.
Intelligence gathered from neighbouring states set the basic offensive and defensive requirements; the larger mechanized and armored forces of California to the south, and the more mobile and dynamic, but lighter, forces of Deseret to the south-east. Protection requirements for the medium tank were set by existing and projected future enemy weapons, as detailed in report (REDACTED).
Likewise, the performance characteristics of the main armament were set by the current and projected protection of vehicles in the possession of the neighbouring states, as detailed in report (REDACTED).
Upon receipt of the above reports and requirements, GF&M’s Archival Division in conjunction with the engineering divisions (Mechanical, Electric, Aeronautic, Automotive, and Ballistic) conducted a survey of the current engineering state of the art, in particular with regard to the ability to construct large complex assemblies to an exacting standard. From this survey, it was determined that the current industrial base is roughly the equivalent of that available in Tank City, Michigan, circa 1950. Likewise it was determined that the state of the art from an electronics standpoint is roughly equivalent to that available in the same time period. Theoretical knowledge available, however, significantly exceeded that level; the divisional chief engineers all have archival clearance and are well-educated on the finer details of the achievements in their respective fields all the way up to the Ultimate War. While the state of the art does not support the immediate manufacture of prewar equipment, many lessons were learned in the past through trial and error, which is estimated to have saved years and many cycles of iterative design and testing in the development of the medium tank.
Following the industrial survey, the archival division conducted another study; this one historical, examining the vehicles produced pre-war with similar industrial capabilities, as well as the evolution of design from that point to the onset of the War. Individual designs were examined based on archival evidence throughout their lifetimes, noting their technical-tactical characteristics as well as more subjective factors such as efficiency of design and manufacture, maintainability, upgradeability, crew comfort, battle efficiency and so on.
Following this survey, it was found that the pre-war Soviet tank T-55 is well within the capability of the industry to construct, and other than minor dimensioning issues more than outmatches the required specifications. While this design had many flaws, and by design was not optimized for the nature of the Cascadian environment, it was chosen as a baseline as it was evaluated to offer more potential than the other possible baselines (Centurion, M-48 Patton), mostly due to small dimensions, reputation of maintainability and reliability, and efficient layout.
From this baseline, a series of improvements were suggested by the Archival Division to the engineering divisions, to better suit the medium tank to the Cascadian environment, as well as to apply the lessons learned throughout the service lives of the vehicles studied.
The list of suggested improvements was as follows:
1.     More compact, autofrettaged gun of ~4” calibre.
2.      Crew water stowage.
3.     Increased crew working volume. Specifically, improved head space for loader.
4.     Improved gunnery optics (including the installation of a rangefinder).
5.     8-10 degrees of gun depression.
6.     APU of roughly 1-2 cylinders (2-4 HP)
7.     Basic air conditioning
8.     Spaced armor arrays
9.     Reversed turret crew (gunner and commander on right, loader on left
10.  More, better accessible, ready ammunition racks. In the bustle with blowoff panels, if possible.
11.  Improved hatches (sprung) and access.
12.  Desertised larger air intakes and filters.
13.  External coil spring suspension, with return rollers.
14.  Improved protected external stowage.
15.  2-channel gunner’s sight, with periscopic mirror head.
16.  2-axis stabilizers, with the gunner’s line of sight being stabilized independently of the main gun, with the gun following the sight, to allow accurate observation and quick firing from the short halt, as well as the use of the coaxial MG on the move. Such a system also allows the implementation of fixed-angle loading, easing the loader’s work without affecting the gunner’s observation of the target.
17.  Separated hydraulics, in the turret bustle.
18.  Commander’s MG useable under armor.
19.  Infantry telephone in rear sponson.
20.  Ammunition loading hatch near ground level.
21.  Automatic fire suppression.
22.  Over-barrel fitting for either spotlight (white light or IR) or .50 BMG.
23.  Thicker front hull for mine resistance.
24.  Roof machine gun for both loader and commander.
25.  Frontally removable gun, with separately removable barrel, for faster and simpler field maintenance of the weapon system and to allow easier modification and upgrading of the vehicle throughout its service life.
26.  Making the Commander’s cupola a hunter-killer system. This involves the use of an independently driven cupola, with independently stabilized optic, and slew-to-cue control of the turret, allowing the commander to find, range, and pass over targets to the gunner, greatly increasing the battle efficiency of the vehicle.
27.  Fitting of indirect fire equipment. As the gun on the tank is liable to be one of the larger guns available in any given setting, the ability to conduct indirect fire when possible is considered to be a great advantage.
28.  Boiling Vessel, allowing the crew to heat their food and that of any infantrymen, boosting morale and reducing fatigue.
29.  Ammunition load of roughly 40-50 rounds for the main gun, and roughly 5,000 rounds of secondary ammunition
30.  Improved suspension damping and increased wheel travel.
31.  6 wheel stations per side
32.  Volume allocation for more advanced electronics, including but not limited to image intensifiers, ballistic computers, and so on.
33.  Improved transmission, with emphasis on reverse speed.
34.  Fittings for tank riders, should doctrine require.
35.  Design for upgradeability, particularly with regard to electronics and armor technology.
36.  Drive system packaged as powerpack to allow easier repair and maintenance.
With the above list of changes, the resulting vehicle bears only a mild resemblance to the venerable T-55 upon which it is based, and yet maintains many of the classic features which made its forbearer a success.
The resulting vehicle entered iterative development and prototyping; In the basic stages of which it was found that all the desired improvements could not only be fulfilled, but even exceeded; The resulting vehicle has greatly improved protection in the frontal 40 degree arc for the hull and 60 degree arc for the turret, along with having all the main gun ammunition safely stowed in separated compartments with blow-off panels, keeping the crew safe. The greater weight of the vehicle compared to the T-55 is compensated by use of a more powerful engine of similar size, a more advanced transmission, and longer track contact along with more wheels, reducing the mean maximum pressure.
Despite HVAP being the standard AP ammo, it was decided not to optimize the gun around that ammo type, as very soon APDS and APFSDS will be available, and will completely eclipse HVAP.
The features of the vehicle are as follows:
Mobility:
1.     600HP (750HP with supercharger) V-12 diesel engine [T-55 engine, uprated to the historical KV levels, with supercharger it’s at T-72 levels]
2.     Mechanical-Hydraulic cross-drive 12 speed transmission, 6 forwards, 6 reverse, with good mountain fighting ability [Stolen off of a Pz 61]
3.     1500L diesel fuel, stowed outside crew compartment
4.     4 HP APU exhaust acts as engine compartment heater in cold weather.
5.     Small air compressor fitted to engine and compressed air tank allow starting in extreme weather without batteries, along with easy cleaning of the air filters at routine intervals.
6.     Enlarged engine bay relative to T-55, to house larger radiators and fans, improving cooling capacity in desert environments. Air is exhausted downwards behind the vehicle, M60 style, to avoid the “rooster tail” effect of the original T-55.
7.     Rotary dampers on each swing arm hub and linear dampers on first, second and last swing arms.
8.     Vertical travel of roughly 400mm up, 150mm rebound
9.     Ground clearance of 540mm
 
Survivability:
Low profile- 2.32m turret roof height, 2.66m top of commander’s sight, extremely low profile in hull-down positions.

Frontal arc - no less than 200mm LOS base steel* with air gap and another 60mm LOS spaced hard steel layer, or angles exceeding 80 degrees from normal.
Lower glacis- 30mm hard face, 500mm fuel tank, 50mm back face at 20 degrees from normal.
Sides- crew compartment armor at least 40mm LOS with 20mm high-hardness plate welded on hull, 100mm on turret, with spaced 30mm,
Non-crew compartment-40mm side armor. 20-5mm spaced skirts on hull. Sponson boxes- 30mm armor on frontal boxes, 10mm on rear boxes.
All-around armor- no less than 30mm steel for direct and air fire, 30mm front floor, 20mm rear floor.
Mounting points for explosive reactive armor are available on the external faces of the spaced armor arrays.**
All ammunition separated from the crew behind blow-out panels.
Instantaneous (WP) smoke grenade launchers- 24 ready, 24 stowed. (4+4 salvos of 6) [launchers on the turret flanks, not modelled]
Automatic IR-detection fire suppression system in crew and engine compartment.
While not fitted as standard, the crew compartment is spacious enough to allow the fitting of spall liners when the technology to make them reliable and not a fire hazard is around.
*The base steel is not homogenous; on the turret cheeks and sides, and on the hull front, it is an arrangement that can only adequately be described as “inverse Stillbrew”. The armor comprises a 50mm thick base layer, with the secondary casting bolted on with a rubber interlayer in the middle. The purpose of this arrangement is not to increase protection (although it should a bit), but rather to aid upgradeability- when better armor gets developed, it is intended that the thick steel facing plates be swapped for more weight-efficient armor. The volume needed for these arrays is already available, as the spaces of the spaced armor. The stowed equipment in those pockets will be displaced to less critical locations.
**It is intended that with the steel armor replaced by NERA arrays and the external face topped with ERA, that the total armor array will be ERA-hard armor-NERA-backing steel armor.
Such an array is reminiscent of the T-72BV turret and could quite reasonably be expected to handle tandem HEAT and moderately advanced APFSDS constructions. This drastic improvement in protection could easily be a simple part of a midlife upgrade, with the chosen construction methods.
Firepower:
A.    Weapons:
1.     Dual stabilized (sight following) 105mm L/51 autofrettaged gun with brass cases, fitted with fume extractor and thermal shroud. [basically an M68 with a slightly larger case].
Ammunition natures:
APCBC [BR-412D with slightly higher velocity]
HE
Smoke-WP [unless it really doesn’t work with horizontal stowage]
HVAP [T29E3 at lower velocity than from the gun T5E1]
 
Stowed ammo: 56 rounds, of which 16 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
2.     Upgradeable to 125mm L/45 gun, when available, intended to use combustible-body stub cases [basically slightly larger NATO 120, there’s room in the turret but the gun isn’t industrially feasible yet]
Stowed ammo: ~42-45, of which ~10 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
3.     1 coax M240
 Stowed ammo: 6,000 rounds, of which 2000 ready.
4.     1 M240 on commander’s cupola, fireable under armor.
Stowed ammo: 2400, of which 600 ready.
5.     1 M240 on skate mount [modelled as pintle] for loader.
Stowed ammo: 2000, of which 200 ready.
6.     1 M2 HMG over barrel (optional)
Stowed ammo: 1300, of which 100 ready.
B.    Optics:
1.     Dual-channel 2-axis independently stabilized gunner’s sight with extension for commander.
2.     Gunner’s secondary direct-vision telescopic sight.
3.     Commander’s fire control cupola: single-channel (selectable) main independently stabilized optic, with secondary coincidence rangefinder channel. 5 periscopes allow all-around vision, slew-to-cue feature.
4.     3 periscopes for loader improve situational awareness.
5.     Commander’s hatch with open protected position in development.
C.    FCS:
1.     Range-finding stadiametric reticles.
2.     ballistic cam computer with automatic feed in from commander’s rangefinder, automatic superelevation.
3.     Gun follows sight (with offset based on superelevation from ballistic computer)
4.     Hydraulic control- 15 deg/sec elevation, 40 deg/sec traverse (basic turret), 30 deg/sec (fully up-armored). Pump, accumulator and reservoir are separated from the crew, in the bustle, and the system is fitted with a pressure-loss automatic cutoff to prevent the hydraulic fluid spraying everywhere in case of a rupture.
5.     Commander has override handles.
For the external machine guns, spare ammunition is carried in belt boxes in the spaced armor of the turret. 12 boxes of .50 can be carried in the frontal pockets, with 100 rounds linked each; and 9 7.62 boxes in each side of the turret, with 200 rounds linked each. The commander’s cupola has a 600-round ring ammo box around the cupola [not modelled].
Crew comfort:
1.     Air conditioning. Operating armored vehicles in the desert without this feature is torture, to say the least. In the bustle, between the hydraulic unit and the ammo rack, sits a powerful air conditioning unit. Rated at 3 HP, this is enough to properly cool down the fighting compartment even with moderate air leakage. While currently no requirement for NBC exists, such an air filtration system could be merged into the aircon unit. When firing, the blower fan is directed into the fighting compartment and not the aircon radiator, to clear out the gasses.
Aircon also aids in maintaining the life of electronic components, an important feature for such an electronically-rich vehicle.
With flow reversal, the aircon unit heats the crew compartment during the winter, with none of the dangers of a fuel-powered crew heater.
2.     Drinking water. There is a tank for drinking water installed, aft of the turret. With a capacity of 240 litres, this allows the tank to operate in the desert and support infantry for extended operations without supply. Additional external stowage is of course possible. A small water container sits directly in front of the aircon vents, allowing the crew to drink at a comfortable temperature. (The main water tank sits up against the engine firewall and will likely get a bit too hot for comfort.)
3.     Boiling Vessel. Allows cooking MREs for the crew and infantry, and hot drinks during the winter.
4.     Height. All seats are adjustable and suitable to the above-average Cascadian recruit. The loader’s position is arranged in such a way that most of his duties can be performed sitting down. There is sufficient headroom and elbow space in every crew position, and using the equipment requires no contortionisms.
5.     Ammo loading hatch- allows loading ammo into the tank from ground level, and not from roof hatches, results in less tiring and quicker loading.
6.     Fume extractor on the barrel greatly reduces the flow of gas into the fighting compartment when the gun fires.

Upgradeability:
1.     Overbuilt, easily upgradeable suspension. Allows weight growth, at cost of increasing ground pressure.
2.     Armor upgradeability, as explained in armor section. Current armor is fairly inexpensive, and allows inexpensive upgrading at a later date, allowing fairly cheap buildup of forces and allows use of more mature armor when the upgrade occurs (as current reactive armor arrays developed at GF&M are fairly crude). Current armor more than outmatches current and projected enemy weapons.
3.     Powerpack dimensions, and those of engine bay, allow upgrading with bigger and better powerplants and transmissions as they come available. The engine bay is 200mm longer and 200mm taller (at the hump) than that of the T-55, to allow better cooling and more upgradeability. It is expected that upgrade powerpacks with 1000HP transversely mounted engines with automatic transmissions, as were available pre-war for the T-72, will be possible for a late-life upgrade.
4.     Spare internal volume for more vetronics.
5.     Frontally removable gun, allows easy maintenance and upgrading.
6.     Configurable ammo racks inside blowoff bunkers allows depot-level reconfiguring for different calibres.
Vents were not modelled due to lack of time.
 
Mass components:
Turret structure: 6.0 tons, includes internal subdivisions and basket
Turret spaced: 1.8 tons, includes partitions
Hull structure: 13.8 tons, includes suspension mounting points and internal subdivisions.
Hull spaced: 1.92 tons, includes sponson stowage boxes.
Suspension: 4 tons.
Tracks: 3.3 tons, based on T-72 track links.
Armament: 1.3 tons
Ammo: 1.5 tons
Fuel: 1500L, 1.23 tons.
Engine, cooling and accessories: 1.5 tons
Transmission: 2 tons
Extras: 6 tons, includes 0.5 tons electric systems, 0.5 hydraulics, 0.3 tons water, 1 ton structural components, 0.3 tons for the aircon system, 0.5 tons for fittings, 0.4 tons of crew, and a margin of 2.3 tons for things unaccounted for.
Total, loaded: 44.3 tons.

Dimensions:
Length, gun forwards: 8.7m
Length, hull: 6.3m
Width, OA: 3.3m
Width over tracks: 3.24m
Ground clearance: 540mm
Height, turret roof: 2.33m
Height, overall: 2.66m
Idler height: 0.84m (relevant for vertical step climbing)
Track contact length, zero penetration: 4.38m
Track width: 550mm
Roadwheel diameter: 686mm
 
Extra notes:
1. The gun uses brass-cased ammo as semi-combustible case tech does not seem to be ready for prime-time with 1950 tech, as evidenced by the problems with the ammunition of the US 152mm gun on the M60A2 and Sheridan in the 1960s; The combination of good rigidity needed to hold large propellant loads onto big heavy projectiles (like 105mm APCBC) and good burn characteristics would seem to be beyond current tech, and therefore extremely risky to develop.
2. As brass-cased ammunition was chosen, 105mm was the logical caliber to use, as it is the largest caliber which can still be relatively easily man-handled in the confines of a turret, when brass cased full-bore AP rounds are used. 
3. The future 125mm intended for the mid-life upgrade is intended to be stub-cased combustible, smoothbore, with APFSDS as the primary anti-armor round. It is expected that by the time the gun is ready and needed, the technology will have progressed sufficiently to allow higher pressures and reliable strong combustible case bodies. As the ammo stowage is already compartmentalized, this ammunition will pose no greater risk to the crew.
4. The tank, with its current weight, is train-deployable fully loaded. The weight margins ensure that when upgraded it will still be transportable in MLC-45, without loaded ammunition, fuel, crew, and other extras.
5. Current development of variants includes:
a. CEV (similar in concept to M728 CEV, with 155mm demolition gun/low velocity howitzer)
b. Bridgelayer (Similar in concept to M60 AVLB, with bridge designed for MLC 70-80)
c. ARV (similar in concept to M88 ARV, with a crane)
d. HAPC/HIFV (similar in concept to Achzarit with small cannon/MG turret, axial instead of transverse engine)
e. SPAA (Shilka-like turret, with twin 35mm guns, and basic air search and ranging radars; plenty of space for more advanced electronics when available)
6. The compressed air starting system connects to a pneumatic joint in the engine bay, to which air-powered tools can be attached. Current supplied tools as basic vehicle equipment include a pressure blower for cleaning air filters and the like, a pneumatic bolt-driver, a pneumatic jack, and other assorted goodies.
7. A coincidence rangefinder was chosen, as no low-risk practical alternative could be thought up. It is intended to be replaced as soon as possible with a laser rangefinder, and an additional laser rangefinder to be installed in the gunner's FCS suite. A coincidence rangefinder takes around 10-12 seconds to range effectively; with the rangefinder in a separate mount, the commander can range a target while the gunner engages a different one, allowing high-speed hunter-killer operation.
 

FINAL SUBMISSION:
XM-2239 NORMAN

[ooc: this is written from a timeframe at which only a few prototypes have been built and tested, mass production awaits selection. Square brackets denote ooc comments]
Classified: top secret
for Cascadian eyes only
 
When General Foundry and Mechanics (henceforth, GF&M) received the brief from the Cascadian armored corps on the requirements for a future armored fighting direct combat vehicle, medium (henceforth, medium tank), and future armored fighting direct combat vehicle, light (light tank), focus was immediately concentrated on the larger requirement of the pair. It was quickly realized that the requirements fell significantly short of the state of the art; and that said state of the art permits the development of a vehicle not only superior to the requirements in every regard, but capable of matching the requirements of the future as well, thus ensuring the safety and freedom of Cascadia for generations to come.
Intelligence gathered from neighbouring states set the basic offensive and defensive requirements; the larger mechanized and armored forces of California to the south, and the more mobile and dynamic, but lighter, forces of Deseret to the south-east. Protection requirements for the medium tank were set by existing and projected future enemy weapons, as detailed in report (REDACTED).
Likewise, the performance characteristics of the main armament were set by the current and projected protection of vehicles in the possession of the neighbouring states, as detailed in report (REDACTED).
Upon receipt of the above reports and requirements, GF&M’s Archival Division in conjunction with the engineering divisions (Mechanical, Electric, Aeronautic, Automotive, and Ballistic) conducted a survey of the current engineering state of the art, in particular with regard to the ability to construct large complex assemblies to an exacting standard. From this survey, it was determined that the current industrial base is roughly the equivalent of that available in Tank City, Michigan, circa 1950. Likewise it was determined that the state of the art from an electronics standpoint is roughly equivalent to that available in the same time period. Theoretical knowledge available, however, significantly exceeded that level; the divisional chief engineers all have archival clearance and are well-educated on the finer details of the achievements in their respective fields all the way up to the Ultimate War. While the state of the art does not support the immediate manufacture of prewar equipment, many lessons were learned in the past through trial and error, which is estimated to have saved years and many cycles of iterative design and testing in the development of the medium tank.
Following the industrial survey, the archival division conducted another study; this one historical, examining the vehicles produced pre-war with similar industrial capabilities, as well as the evolution of design from that point to the onset of the War. Individual designs were examined based on archival evidence throughout their lifetimes, noting their technical-tactical characteristics as well as more subjective factors such as efficiency of design and manufacture, maintainability, upgradeability, crew comfort, battle efficiency and so on.
Following this survey, it was found that the pre-war Soviet tank T-55 is well within the capability of the industry to construct, and other than minor dimensioning issues more than outmatches the required specifications. While this design had many flaws, and by design was not optimized for the nature of the Cascadian environment, it was chosen as a baseline as it was evaluated to offer more potential than the other possible baselines (Centurion, M-48 Patton), mostly due to small dimensions, reputation of maintainability and reliability, and efficient layout.
From this baseline, a series of improvements were suggested by the Archival Division to the engineering divisions, to better suit the medium tank to the Cascadian environment, as well as to apply the lessons learned throughout the service lives of the vehicles studied.
The list of suggested improvements was as follows:
1.     More compact, autofrettaged gun of ~4” calibre.
2.      Crew water stowage.
3.     Increased crew working volume. Specifically, improved head space for loader.
4.     Improved gunnery optics (including the installation of a rangefinder).
5.     8-10 degrees of gun depression.
6.     APU of roughly 1-2 cylinders (2-4 HP)
7.     Basic air conditioning
8.     Spaced armor arrays
9.     Reversed turret crew (gunner and commander on right, loader on left
10.  More, better accessible, ready ammunition racks. In the bustle with blowoff panels, if possible.
11.  Improved hatches (sprung) and access.
12.  Desertised larger air intakes and filters.
13.  External coil spring suspension, with return rollers.
14.  Improved protected external stowage.
15.  2-channel gunner’s sight, with periscopic mirror head.
16.  2-axis stabilizers, with the gunner’s line of sight being stabilized independently of the main gun, with the gun following the sight, to allow accurate observation and quick firing from the short halt, as well as the use of the coaxial MG on the move. Such a system also allows the implementation of fixed-angle loading, easing the loader’s work without affecting the gunner’s observation of the target.
17.  Separated hydraulics, in the turret bustle.
18.  Commander’s MG useable under armor.
19.  Infantry telephone in rear sponson.
20.  Ammunition loading hatch near ground level.
21.  Automatic fire suppression.
22.  Over-barrel fitting for either spotlight (white light or IR) or .50 BMG.
23.  Thicker front hull for mine resistance.
24.  Roof machine gun for both loader and commander.
25.  Frontally removable gun, with separately removable barrel, for faster and simpler field maintenance of the weapon system and to allow easier modification and upgrading of the vehicle throughout its service life.
26.  Making the Commander’s cupola a hunter-killer system. This involves the use of an independently driven cupola, with independently stabilized optic, and slew-to-cue control of the turret, allowing the commander to find, range, and pass over targets to the gunner, greatly increasing the battle efficiency of the vehicle.
27.  Fitting of indirect fire equipment. As the gun on the tank is liable to be one of the larger guns available in any given setting, the ability to conduct indirect fire when possible is considered to be a great advantage.
28.  Boiling Vessel, allowing the crew to heat their food and that of any infantrymen, boosting morale and reducing fatigue.
29.  Ammunition load of roughly 40-50 rounds for the main gun, and roughly 5,000 rounds of secondary ammunition
30.  Improved suspension damping and increased wheel travel.
31.  6 wheel stations per side
32.  Volume allocation for more advanced electronics, including but not limited to image intensifiers, ballistic computers, and so on.
33.  Improved transmission, with emphasis on reverse speed.
34.  Fittings for tank riders, should doctrine require.
35.  Design for upgradeability, particularly with regard to electronics and armor technology.
36.  Drive system packaged as powerpack to allow easier repair and maintenance.
With the above list of changes, the resulting vehicle bears only a mild resemblance to the venerable T-55 upon which it is based, and yet maintains many of the classic features which made its forbearer a success.
The resulting vehicle entered iterative development and prototyping; In the basic stages of which it was found that all the desired improvements could not only be fulfilled, but even exceeded; The resulting vehicle has greatly improved protection in the frontal 40 degree arc for the hull and 60 degree arc for the turret, along with having all the main gun ammunition safely stowed in separated compartments with blow-off panels, keeping the crew safe. The greater weight of the vehicle compared to the T-55 is compensated by use of a more powerful engine of similar size, a more advanced transmission, and longer track contact along with more wheels, reducing the mean maximum pressure.
Despite HVAP being the standard AP ammo, it was decided not to optimize the gun around that ammo type, as very soon APDS and APFSDS will be available, and will completely eclipse HVAP.
The features of the vehicle are as follows:
Mobility:
1.     600HP (750HP with supercharger) V-12 diesel engine [T-55 engine, uprated to the historical KV levels, with supercharger it’s at T-72 levels]
2.     Mechanical-Hydraulic cross-drive 12 speed transmission, 6 forwards, 6 reverse, with good mountain fighting ability [Stolen off of a Pz 61]
3.     1500L diesel fuel, stowed outside crew compartment
4.     4 HP APU exhaust acts as engine compartment heater in cold weather.
5.     Small air compressor fitted to engine and compressed air tank allow starting in extreme weather without batteries, along with easy cleaning of the air filters at routine intervals.
6.     Enlarged engine bay relative to T-55, to house larger radiators and fans, improving cooling capacity in desert environments. Air is exhausted downwards behind the vehicle, M60 style, to avoid the “rooster tail” effect of the original T-55.
7.     Rotary dampers on each swing arm hub and linear dampers on first, second and last swing arms.
8.     Vertical travel of roughly 400mm up, 150mm rebound
9.     Ground clearance of 540mm
 
Survivability:
Low profile- 2.32m turret roof height, 2.66m top of commander’s sight, extremely low profile in hull-down positions.

Frontal arc - no less than 200mm LOS base steel* with air gap and another 60mm LOS spaced hard steel layer, or angles exceeding 80 degrees from normal.
Lower glacis- 30mm hard face, 500mm fuel tank, 50mm back face at 20 degrees from normal.
Sides- crew compartment armor at least 40mm LOS with 20mm high-hardness plate welded on hull, 100mm on turret, with spaced 30mm,
Non-crew compartment-40mm side armor. 20-5mm spaced skirts on hull. Sponson boxes- 30mm armor on frontal boxes, 10mm on rear boxes.
All-around armor- no less than 30mm steel for direct and air fire, 30mm front floor, 20mm rear floor.
Mounting points for explosive reactive armor are available on the external faces of the spaced armor arrays.**
All ammunition separated from the crew behind blow-out panels.
Instantaneous (WP) smoke grenade launchers- 24 ready, 24 stowed. (4+4 salvos of 6) [launchers on the turret flanks, not modelled]
Automatic IR-detection fire suppression system in crew and engine compartment.
While not fitted as standard, the crew compartment is spacious enough to allow the fitting of spall liners when the technology to make them reliable and not a fire hazard is around.
*The base steel is not homogenous; on the turret cheeks and sides, and on the hull front, it is an arrangement that can only adequately be described as “inverse Stillbrew”. The armor comprises a 50mm thick base layer, with the secondary casting bolted on with a rubber interlayer in the middle. The purpose of this arrangement is not to increase protection (although it should a bit), but rather to aid upgradeability- when better armor gets developed, it is intended that the thick steel facing plates be swapped for more weight-efficient armor. The volume needed for these arrays is already available, as the spaces of the spaced armor. The stowed equipment in those pockets will be displaced to less critical locations.
**It is intended that with the steel armor replaced by NERA arrays and the external face topped with ERA, that the total armor array will be ERA-hard armor-NERA-backing steel armor.
Such an array is reminiscent of the T-72BV turret and could quite reasonably be expected to handle tandem HEAT and moderately advanced APFSDS constructions. This drastic improvement in protection could easily be a simple part of a midlife upgrade, with the chosen construction methods.
Firepower:
A.    Weapons:
1.     Dual stabilized (sight following) 105mm L/51 autofrettaged gun with brass cases, fitted with fume extractor and thermal shroud. [basically an M68 with a slightly larger case].
Ammunition natures:
APCBC [BR-412D with slightly higher velocity]
HE
Smoke-WP [unless it really doesn’t work with horizontal stowage]
HVAP [T29E3 at lower velocity than from the gun T5E1]
 
Stowed ammo: 56 rounds, of which 16 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
2.     Upgradeable to 125mm L/45 gun, when available, intended to use combustible-body stub cases [basically slightly larger NATO 120, there’s room in the turret but the gun isn’t industrially feasible yet]
Stowed ammo: ~42-45, of which ~10 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
3.     1 coax M240
 Stowed ammo: 6,000 rounds, of which 2000 ready.
4.     1 M240 on commander’s cupola, fireable under armor.
Stowed ammo: 2400, of which 600 ready.
5.     1 M240 on skate mount [modelled as pintle] for loader.
Stowed ammo: 2000, of which 200 ready.
6.     1 M2 HMG over barrel (optional)
Stowed ammo: 1300, of which 100 ready.
B.    Optics:
1.     Dual-channel 2-axis independently stabilized gunner’s sight with extension for commander.
2.     Gunner’s secondary direct-vision telescopic sight.
3.     Commander’s fire control cupola: single-channel (selectable) main independently stabilized optic, with secondary coincidence rangefinder channel. 5 periscopes allow all-around vision, slew-to-cue feature.
4.     3 periscopes for loader improve situational awareness.
5.     Commander’s hatch with open protected position in development.
C.    FCS:
1.     Range-finding stadiametric reticles.
2.     ballistic cam computer with automatic feed in from commander’s rangefinder, automatic superelevation.
3.     Gun follows sight (with offset based on superelevation from ballistic computer)
4.     Hydraulic control- 15 deg/sec elevation, 40 deg/sec traverse (basic turret), 30 deg/sec (fully up-armored). Pump, accumulator and reservoir are separated from the crew, in the bustle, and the system is fitted with a pressure-loss automatic cutoff to prevent the hydraulic fluid spraying everywhere in case of a rupture.
5.     Commander has override handles.
For the external machine guns, spare ammunition is carried in belt boxes in the spaced armor of the turret. 12 boxes of .50 can be carried in the frontal pockets, with 100 rounds linked each; and 9 7.62 boxes in each side of the turret, with 200 rounds linked each. The commander’s cupola has a 600-round ring ammo box around the cupola [not modelled].
Crew comfort:
1.     Air conditioning. Operating armored vehicles in the desert without this feature is torture, to say the least. In the bustle, between the hydraulic unit and the ammo rack, sits a powerful air conditioning unit. Rated at 3 HP, this is enough to properly cool down the fighting compartment even with moderate air leakage. While currently no requirement for NBC exists, such an air filtration system could be merged into the aircon unit. When firing, the blower fan is directed into the fighting compartment and not the aircon radiator, to clear out the gasses.
Aircon also aids in maintaining the life of electronic components, an important feature for such an electronically-rich vehicle.
With flow reversal, the aircon unit heats the crew compartment during the winter, with none of the dangers of a fuel-powered crew heater.
2.     Drinking water. There is a tank for drinking water installed, aft of the turret. With a capacity of 240 litres, this allows the tank to operate in the desert and support infantry for extended operations without supply. Additional external stowage is of course possible. A small water container sits directly in front of the aircon vents, allowing the crew to drink at a comfortable temperature. (The main water tank sits up against the engine firewall and will likely get a bit too hot for comfort.)
3.     Boiling Vessel. Allows cooking MREs for the crew and infantry, and hot drinks during the winter.
4.     Height. All seats are adjustable and suitable to the above-average Cascadian recruit. The loader’s position is arranged in such a way that most of his duties can be performed sitting down. There is sufficient headroom and elbow space in every crew position, and using the equipment requires no contortionisms.
5.     Ammo loading hatch- allows loading ammo into the tank from ground level, and not from roof hatches, results in less tiring and quicker loading.
6.     Fume extractor on the barrel greatly reduces the flow of gas into the fighting compartment when the gun fires.

Upgradeability:
1.     Overbuilt, easily upgradeable suspension. Allows weight growth, at cost of increasing ground pressure.
2.     Armor upgradeability, as explained in armor section. Current armor is fairly inexpensive, and allows inexpensive upgrading at a later date, allowing fairly cheap buildup of forces and allows use of more mature armor when the upgrade occurs (as current reactive armor arrays developed at GF&M are fairly crude). Current armor more than outmatches current and projected enemy weapons.
3.     Powerpack dimensions, and those of engine bay, allow upgrading with bigger and better powerplants and transmissions as they come available. The engine bay is 200mm longer and 200mm taller (at the hump) than that of the T-55, to allow better cooling and more upgradeability. It is expected that upgrade powerpacks with 1000HP transversely mounted engines with automatic transmissions, as were available pre-war for the T-72, will be possible for a late-life upgrade.
4.     Spare internal volume for more vetronics.
5.     Frontally removable gun, allows easy maintenance and upgrading.
6.     Configurable ammo racks inside blowoff bunkers allows depot-level reconfiguring for different calibres.
Vents were not modelled due to lack of time.
 
Mass components:
Turret structure: 6.0 tons, includes internal subdivisions and basket
Turret spaced: 1.8 tons, includes partitions
Hull structure: 13.8 tons, includes suspension mounting points and internal subdivisions.
Hull spaced: 1.92 tons, includes sponson stowage boxes.
Suspension: 4 tons.
Tracks: 3.3 tons, based on T-72 track links.
Armament: 1.3 tons
Ammo: 1.5 tons
Fuel: 1500L, 1.23 tons.
Engine, cooling and accessories: 1.5 tons
Transmission: 2 tons
Extras: 6 tons, includes 0.5 tons electric systems, 0.5 hydraulics, 0.3 tons water, 1 ton structural components, 0.3 tons for the aircon system, 0.5 tons for fittings, 0.4 tons of crew, and a margin of 2.3 tons for things unaccounted for.
Total, loaded: 44.3 tons.

Dimensions:
Length, gun forwards: 8.7m
Length, hull: 6.3m
Width, OA: 3.3m
Width over tracks: 3.24m
Ground clearance: 540mm
Height, turret roof: 2.33m
Height, overall: 2.66m
Idler height: 0.84m (relevant for vertical step climbing)
Track contact length, zero penetration: 4.38m
Track width: 550mm
Roadwheel diameter: 686mm
 
Extra notes:
1. The gun uses brass-cased ammo as semi-combustible case tech does not seem to be ready for prime-time with 1950 tech, as evidenced by the problems with the ammunition of the US 152mm gun on the M60A2 and Sheridan in the 1960s; The combination of good rigidity needed to hold large propellant loads onto big heavy projectiles (like 105mm APCBC) and good burn characteristics would seem to be beyond current tech, and therefore extremely risky to develop.
2. As brass-cased ammunition was chosen, 105mm was the logical caliber to use, as it is the largest caliber which can still be relatively easily man-handled in the confines of a turret, when brass cased full-bore AP rounds are used. 
3. The future 125mm intended for the mid-life upgrade is intended to be stub-cased combustible, smoothbore, with APFSDS as the primary anti-armor round. It is expected that by the time the gun is ready and needed, the technology will have progressed sufficiently to allow higher pressures and reliable strong combustible case bodies. As the ammo stowage is already compartmentalized, this ammunition will pose no greater risk to the crew.
4. The tank, with its current weight, is train-deployable fully loaded. The weight margins ensure that when upgraded it will still be transportable in MLC-45, without loaded ammunition, fuel, crew, and other extras.
5. Current development of variants includes:
a. CEV (similar in concept to M728 CEV, with 155mm demolition gun/low velocity howitzer)
b. Bridgelayer (Similar in concept to M60 AVLB, with bridge designed for MLC 70-80)
c. ARV (similar in concept to M88 ARV, with a crane)
d. HAPC/HIFV (similar in concept to Achzarit with small cannon/MG turret, axial instead of transverse engine)
e. SPAA (Shilka-like turret, with twin 35mm guns, and basic air search and ranging radars; plenty of space for more advanced electronics when available)
6. The compressed air starting system connects to a pneumatic joint in the engine bay, to which air-powered tools can be attached. Current supplied tools as basic vehicle equipment include a pressure blower for cleaning air filters and the like, a pneumatic bolt-driver, a pneumatic jack, and other assorted goodies.
7. A coincidence rangefinder was chosen, as no low-risk practical alternative could be thought up. It is intended to be replaced as soon as possible with a laser rangefinder, and an additional laser rangefinder to be installed in the gunner's FCS suite. A coincidence rangefinder takes around 10-12 seconds to range effectively; with the rangefinder in a separate mount, the commander can range a target while the gunner engages a different one, allowing high-speed hunter-killer operation.
 

FINAL SUBMISSION:
XM-2239 NORMAN

[ooc: this is written from a timeframe at which only a few prototypes have been built and tested, mass production awaits selection. Square brackets denote ooc comments]
Classified: top secret
for Cascadian eyes only
 
When General Foundry and Mechanics (henceforth, GF&M) received the brief from the Cascadian armored corps on the requirements for a future armored fighting direct combat vehicle, medium (henceforth, medium tank), and future armored fighting direct combat vehicle, light (light tank), focus was immediately concentrated on the larger requirement of the pair. It was quickly realized that the requirements fell significantly short of the state of the art; and that said state of the art permits the development of a vehicle not only superior to the requirements in every regard, but capable of matching the requirements of the future as well, thus ensuring the safety and freedom of Cascadia for generations to come.
Intelligence gathered from neighbouring states set the basic offensive and defensive requirements; the larger mechanized and armored forces of California to the south, and the more mobile and dynamic, but lighter, forces of Deseret to the south-east. Protection requirements for the medium tank were set by existing and projected future enemy weapons, as detailed in report (REDACTED).
Likewise, the performance characteristics of the main armament were set by the current and projected protection of vehicles in the possession of the neighbouring states, as detailed in report (REDACTED).
Upon receipt of the above reports and requirements, GF&M’s Archival Division in conjunction with the engineering divisions (Mechanical, Electric, Aeronautic, Automotive, and Ballistic) conducted a survey of the current engineering state of the art, in particular with regard to the ability to construct large complex assemblies to an exacting standard. From this survey, it was determined that the current industrial base is roughly the equivalent of that available in Tank City, Michigan, circa 1950. Likewise it was determined that the state of the art from an electronics standpoint is roughly equivalent to that available in the same time period. Theoretical knowledge available, however, significantly exceeded that level; the divisional chief engineers all have archival clearance and are well-educated on the finer details of the achievements in their respective fields all the way up to the Ultimate War. While the state of the art does not support the immediate manufacture of prewar equipment, many lessons were learned in the past through trial and error, which is estimated to have saved years and many cycles of iterative design and testing in the development of the medium tank.
Following the industrial survey, the archival division conducted another study; this one historical, examining the vehicles produced pre-war with similar industrial capabilities, as well as the evolution of design from that point to the onset of the War. Individual designs were examined based on archival evidence throughout their lifetimes, noting their technical-tactical characteristics as well as more subjective factors such as efficiency of design and manufacture, maintainability, upgradeability, crew comfort, battle efficiency and so on.
Following this survey, it was found that the pre-war Soviet tank T-55 is well within the capability of the industry to construct, and other than minor dimensioning issues more than outmatches the required specifications. While this design had many flaws, and by design was not optimized for the nature of the Cascadian environment, it was chosen as a baseline as it was evaluated to offer more potential than the other possible baselines (Centurion, M-48 Patton), mostly due to small dimensions, reputation of maintainability and reliability, and efficient layout.
From this baseline, a series of improvements were suggested by the Archival Division to the engineering divisions, to better suit the medium tank to the Cascadian environment, as well as to apply the lessons learned throughout the service lives of the vehicles studied.
The list of suggested improvements was as follows:
1.     More compact, autofrettaged gun of ~4” calibre.
2.      Crew water stowage.
3.     Increased crew working volume. Specifically, improved head space for loader.
4.     Improved gunnery optics (including the installation of a rangefinder).
5.     8-10 degrees of gun depression.
6.     APU of roughly 1-2 cylinders (2-4 HP)
7.     Basic air conditioning
8.     Spaced armor arrays
9.     Reversed turret crew (gunner and commander on right, loader on left
10.  More, better accessible, ready ammunition racks. In the bustle with blowoff panels, if possible.
11.  Improved hatches (sprung) and access.
12.  Desertised larger air intakes and filters.
13.  External coil spring suspension, with return rollers.
14.  Improved protected external stowage.
15.  2-channel gunner’s sight, with periscopic mirror head.
16.  2-axis stabilizers, with the gunner’s line of sight being stabilized independently of the main gun, with the gun following the sight, to allow accurate observation and quick firing from the short halt, as well as the use of the coaxial MG on the move. Such a system also allows the implementation of fixed-angle loading, easing the loader’s work without affecting the gunner’s observation of the target.
17.  Separated hydraulics, in the turret bustle.
18.  Commander’s MG useable under armor.
19.  Infantry telephone in rear sponson.
20.  Ammunition loading hatch near ground level.
21.  Automatic fire suppression.
22.  Over-barrel fitting for either spotlight (white light or IR) or .50 BMG.
23.  Thicker front hull for mine resistance.
24.  Roof machine gun for both loader and commander.
25.  Frontally removable gun, with separately removable barrel, for faster and simpler field maintenance of the weapon system and to allow easier modification and upgrading of the vehicle throughout its service life.
26.  Making the Commander’s cupola a hunter-killer system. This involves the use of an independently driven cupola, with independently stabilized optic, and slew-to-cue control of the turret, allowing the commander to find, range, and pass over targets to the gunner, greatly increasing the battle efficiency of the vehicle.
27.  Fitting of indirect fire equipment. As the gun on the tank is liable to be one of the larger guns available in any given setting, the ability to conduct indirect fire when possible is considered to be a great advantage.
28.  Boiling Vessel, allowing the crew to heat their food and that of any infantrymen, boosting morale and reducing fatigue.
29.  Ammunition load of roughly 40-50 rounds for the main gun, and roughly 5,000 rounds of secondary ammunition
30.  Improved suspension damping and increased wheel travel.
31.  6 wheel stations per side
32.  Volume allocation for more advanced electronics, including but not limited to image intensifiers, ballistic computers, and so on.
33.  Improved transmission, with emphasis on reverse speed.
34.  Fittings for tank riders, should doctrine require.
35.  Design for upgradeability, particularly with regard to electronics and armor technology.
36.  Drive system packaged as powerpack to allow easier repair and maintenance.
With the above list of changes, the resulting vehicle bears only a mild resemblance to the venerable T-55 upon which it is based, and yet maintains many of the classic features which made its forbearer a success.
The resulting vehicle entered iterative development and prototyping; In the basic stages of which it was found that all the desired improvements could not only be fulfilled, but even exceeded; The resulting vehicle has greatly improved protection in the frontal 40 degree arc for the hull and 60 degree arc for the turret, along with having all the main gun ammunition safely stowed in separated compartments with blow-off panels, keeping the crew safe. The greater weight of the vehicle compared to the T-55 is compensated by use of a more powerful engine of similar size, a more advanced transmission, and longer track contact along with more wheels, reducing the mean maximum pressure.
Despite HVAP being the standard AP ammo, it was decided not to optimize the gun around that ammo type, as very soon APDS and APFSDS will be available, and will completely eclipse HVAP.
The features of the vehicle are as follows:
Mobility:
1.     600HP (750HP with supercharger) V-12 diesel engine [T-55 engine, uprated to the historical KV levels, with supercharger it’s at T-72 levels]
2.     Mechanical-Hydraulic cross-drive 12 speed transmission, 6 forwards, 6 reverse, with good mountain fighting ability [Stolen off of a Pz 61]
3.     1500L diesel fuel, stowed outside crew compartment
4.     4 HP APU exhaust acts as engine compartment heater in cold weather.
5.     Small air compressor fitted to engine and compressed air tank allow starting in extreme weather without batteries, along with easy cleaning of the air filters at routine intervals.
6.     Enlarged engine bay relative to T-55, to house larger radiators and fans, improving cooling capacity in desert environments. Air is exhausted downwards behind the vehicle, M60 style, to avoid the “rooster tail” effect of the original T-55.
7.     Rotary dampers on each swing arm hub and linear dampers on first, second and last swing arms.
8.     Vertical travel of roughly 400mm up, 150mm rebound
9.     Ground clearance of 540mm
 
Survivability:
Low profile- 2.32m turret roof height, 2.66m top of commander’s sight, extremely low profile in hull-down positions.

Frontal arc - no less than 200mm LOS base steel* with air gap and another 60mm LOS spaced hard steel layer, or angles exceeding 80 degrees from normal.
Lower glacis- 30mm hard face, 500mm fuel tank, 50mm back face at 20 degrees from normal.
Sides- crew compartment armor at least 40mm LOS with 20mm high-hardness plate welded on hull, 100mm on turret, with spaced 30mm,
Non-crew compartment-40mm side armor. 20-5mm spaced skirts on hull. Sponson boxes- 30mm armor on frontal boxes, 10mm on rear boxes.
All-around armor- no less than 30mm steel for direct and air fire, 30mm front floor, 20mm rear floor.
Mounting points for explosive reactive armor are available on the external faces of the spaced armor arrays.**
All ammunition separated from the crew behind blow-out panels.
Instantaneous (WP) smoke grenade launchers- 24 ready, 24 stowed. (4+4 salvos of 6) [launchers on the turret flanks, not modelled]
Automatic IR-detection fire suppression system in crew and engine compartment.
While not fitted as standard, the crew compartment is spacious enough to allow the fitting of spall liners when the technology to make them reliable and not a fire hazard is around.
*The base steel is not homogenous; on the turret cheeks and sides, and on the hull front, it is an arrangement that can only adequately be described as “inverse Stillbrew”. The armor comprises a 50mm thick base layer, with the secondary casting bolted on with a rubber interlayer in the middle. The purpose of this arrangement is not to increase protection (although it should a bit), but rather to aid upgradeability- when better armor gets developed, it is intended that the thick steel facing plates be swapped for more weight-efficient armor. The volume needed for these arrays is already available, as the spaces of the spaced armor. The stowed equipment in those pockets will be displaced to less critical locations.
**It is intended that with the steel armor replaced by NERA arrays and the external face topped with ERA, that the total armor array will be ERA-hard armor-NERA-backing steel armor.
Such an array is reminiscent of the T-72BV turret and could quite reasonably be expected to handle tandem HEAT and moderately advanced APFSDS constructions. This drastic improvement in protection could easily be a simple part of a midlife upgrade, with the chosen construction methods.
Firepower:
A.    Weapons:
1.     Dual stabilized (sight following) 105mm L/51 autofrettaged gun with brass cases, fitted with fume extractor and thermal shroud. [basically an M68 with a slightly larger case].
Ammunition natures:
APCBC [BR-412D with slightly higher velocity]
HE
Smoke-WP [unless it really doesn’t work with horizontal stowage]
HVAP [T29E3 at lower velocity than from the gun T5E1]
 
Stowed ammo: 56 rounds, of which 16 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
2.     Upgradeable to 125mm L/45 gun, when available, intended to use combustible-body stub cases [basically slightly larger NATO 120, there’s room in the turret but the gun isn’t industrially feasible yet]
Stowed ammo: ~42-45, of which ~10 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
3.     1 coax M240
 Stowed ammo: 6,000 rounds, of which 2000 ready.
4.     1 M240 on commander’s cupola, fireable under armor.
Stowed ammo: 2400, of which 600 ready.
5.     1 M240 on skate mount [modelled as pintle] for loader.
Stowed ammo: 2000, of which 200 ready.
6.     1 M2 HMG over barrel (optional)
Stowed ammo: 1300, of which 100 ready.
B.    Optics:
1.     Dual-channel 2-axis independently stabilized gunner’s sight with extension for commander.
2.     Gunner’s secondary direct-vision telescopic sight.
3.     Commander’s fire control cupola: single-channel (selectable) main independently stabilized optic, with secondary coincidence rangefinder channel. 5 periscopes allow all-around vision, slew-to-cue feature.
4.     3 periscopes for loader improve situational awareness.
5.     Commander’s hatch with open protected position in development.
C.    FCS:
1.     Range-finding stadiametric reticles.
2.     ballistic cam computer with automatic feed in from commander’s rangefinder, automatic superelevation.
3.     Gun follows sight (with offset based on superelevation from ballistic computer)
4.     Hydraulic control- 15 deg/sec elevation, 40 deg/sec traverse (basic turret), 30 deg/sec (fully up-armored). Pump, accumulator and reservoir are separated from the crew, in the bustle, and the system is fitted with a pressure-loss automatic cutoff to prevent the hydraulic fluid spraying everywhere in case of a rupture.
5.     Commander has override handles.
For the external machine guns, spare ammunition is carried in belt boxes in the spaced armor of the turret. 12 boxes of .50 can be carried in the frontal pockets, with 100 rounds linked each; and 9 7.62 boxes in each side of the turret, with 200 rounds linked each. The commander’s cupola has a 600-round ring ammo box around the cupola [not modelled].
Crew comfort:
1.     Air conditioning. Operating armored vehicles in the desert without this feature is torture, to say the least. In the bustle, between the hydraulic unit and the ammo rack, sits a powerful air conditioning unit. Rated at 3 HP, this is enough to properly cool down the fighting compartment even with moderate air leakage. While currently no requirement for NBC exists, such an air filtration system could be merged into the aircon unit. When firing, the blower fan is directed into the fighting compartment and not the aircon radiator, to clear out the gasses.
Aircon also aids in maintaining the life of electronic components, an important feature for such an electronically-rich vehicle.
With flow reversal, the aircon unit heats the crew compartment during the winter, with none of the dangers of a fuel-powered crew heater.
2.     Drinking water. There is a tank for drinking water installed, aft of the turret. With a capacity of 240 litres, this allows the tank to operate in the desert and support infantry for extended operations without supply. Additional external stowage is of course possible. A small water container sits directly in front of the aircon vents, allowing the crew to drink at a comfortable temperature. (The main water tank sits up against the engine firewall and will likely get a bit too hot for comfort.)
3.     Boiling Vessel. Allows cooking MREs for the crew and infantry, and hot drinks during the winter.
4.     Height. All seats are adjustable and suitable to the above-average Cascadian recruit. The loader’s position is arranged in such a way that most of his duties can be performed sitting down. There is sufficient headroom and elbow space in every crew position, and using the equipment requires no contortionisms.
5.     Ammo loading hatch- allows loading ammo into the tank from ground level, and not from roof hatches, results in less tiring and quicker loading.
6.     Fume extractor on the barrel greatly reduces the flow of gas into the fighting compartment when the gun fires.

Upgradeability:
1.     Overbuilt, easily upgradeable suspension. Allows weight growth, at cost of increasing ground pressure.
2.     Armor upgradeability, as explained in armor section. Current armor is fairly inexpensive, and allows inexpensive upgrading at a later date, allowing fairly cheap buildup of forces and allows use of more mature armor when the upgrade occurs (as current reactive armor arrays developed at GF&M are fairly crude). Current armor more than outmatches current and projected enemy weapons.
3.     Powerpack dimensions, and those of engine bay, allow upgrading with bigger and better powerplants and transmissions as they come available. The engine bay is 200mm longer and 200mm taller (at the hump) than that of the T-55, to allow better cooling and more upgradeability. It is expected that upgrade powerpacks with 1000HP transversely mounted engines with automatic transmissions, as were available pre-war for the T-72, will be possible for a late-life upgrade.
4.     Spare internal volume for more vetronics.
5.     Frontally removable gun, allows easy maintenance and upgrading.
6.     Configurable ammo racks inside blowoff bunkers allows depot-level reconfiguring for different calibres.
Vents were not modelled due to lack of time.
 
Mass components:
Turret structure: 6.0 tons, includes internal subdivisions and basket
Turret spaced: 1.8 tons, includes partitions
Hull structure: 13.8 tons, includes suspension mounting points and internal subdivisions.
Hull spaced: 1.92 tons, includes sponson stowage boxes.
Suspension: 4 tons.
Tracks: 3.3 tons, based on T-72 track links.
Armament: 1.3 tons
Ammo: 1.5 tons
Fuel: 1500L, 1.23 tons.
Engine, cooling and accessories: 1.5 tons
Transmission: 2 tons
Extras: 6 tons, includes 0.5 tons electric systems, 0.5 hydraulics, 0.3 tons water, 1 ton structural components, 0.3 tons for the aircon system, 0.5 tons for fittings, 0.4 tons of crew, and a margin of 2.3 tons for things unaccounted for.
Total, loaded: 44.3 tons.

Dimensions:
Length, gun forwards: 8.7m
Length, hull: 6.3m
Width, OA: 3.3m
Width over tracks: 3.24m
Ground clearance: 540mm
Height, turret roof: 2.33m
Height, overall: 2.66m
Idler height: 0.84m (relevant for vertical step climbing)
Track contact length, zero penetration: 4.38m
Track width: 550mm
Roadwheel diameter: 686mm
 
Extra notes:
1. The gun uses brass-cased ammo as semi-combustible case tech does not seem to be ready for prime-time with 1950 tech, as evidenced by the problems with the ammunition of the US 152mm gun on the M60A2 and Sheridan in the 1960s; The combination of good rigidity needed to hold large propellant loads onto big heavy projectiles (like 105mm APCBC) and good burn characteristics would seem to be beyond current tech, and therefore extremely risky to develop.
2. As brass-cased ammunition was chosen, 105mm was the logical caliber to use, as it is the largest caliber which can still be relatively easily man-handled in the confines of a turret, when brass cased full-bore AP rounds are used. 
3. The future 125mm intended for the mid-life upgrade is intended to be stub-cased combustible, smoothbore, with APFSDS as the primary anti-armor round. It is expected that by the time the gun is ready and needed, the technology will have progressed sufficiently to allow higher pressures and reliable strong combustible case bodies. As the ammo stowage is already compartmentalized, this ammunition will pose no greater risk to the crew.
4. The tank, with its current weight, is train-deployable fully loaded. The weight margins ensure that when upgraded it will still be transportable in MLC-45, without loaded ammunition, fuel, crew, and other extras.
5. Current development of variants includes:
a. CEV (similar in concept to M728 CEV, with 155mm demolition gun/low velocity howitzer)
b. Bridgelayer (Similar in concept to M60 AVLB, with bridge designed for MLC 70-80)
c. ARV (similar in concept to M88 ARV, with a crane)
d. HAPC/HIFV (similar in concept to Achzarit with small cannon/MG turret, axial instead of transverse engine)
e. SPAA (Shilka-like turret, with twin 35mm guns, and basic air search and ranging radars; plenty of space for more advanced electronics when available)
6. The compressed air starting system connects to a pneumatic joint in the engine bay, to which air-powered tools can be attached. Current supplied tools as basic vehicle equipment include a pressure blower for cleaning air filters and the like, a pneumatic bolt-driver, a pneumatic jack, and other assorted goodies.
7. A coincidence rangefinder was chosen, as no low-risk practical alternative could be thought up. It is intended to be replaced as soon as possible with a laser rangefinder, and an additional laser rangefinder to be installed in the gunner's FCS suite. A coincidence rangefinder takes around 10-12 seconds to range effectively; with the rangefinder in a separate mount, the commander can range a target while the gunner engages a different one, allowing high-speed hunter-killer operation.
 

FINAL SUBMISSION:
XM-2239 NORMAN

[ooc: this is written from a timeframe at which only a few prototypes have been built and tested, mass production awaits selection. Square brackets denote ooc comments]
Classified: top secret
for Cascadian eyes only
 
When General Foundry and Mechanics (henceforth, GF&M) received the brief from the Cascadian armored corps on the requirements for a future armored fighting direct combat vehicle, medium (henceforth, medium tank), and future armored fighting direct combat vehicle, light (light tank), focus was immediately concentrated on the larger requirement of the pair. It was quickly realized that the requirements fell significantly short of the state of the art; and that said state of the art permits the development of a vehicle not only superior to the requirements in every regard, but capable of matching the requirements of the future as well, thus ensuring the safety and freedom of Cascadia for generations to come.
Intelligence gathered from neighbouring states set the basic offensive and defensive requirements; the larger mechanized and armored forces of California to the south, and the more mobile and dynamic, but lighter, forces of Deseret to the south-east. Protection requirements for the medium tank were set by existing and projected future enemy weapons, as detailed in report (REDACTED).
Likewise, the performance characteristics of the main armament were set by the current and projected protection of vehicles in the possession of the neighbouring states, as detailed in report (REDACTED).
Upon receipt of the above reports and requirements, GF&M’s Archival Division in conjunction with the engineering divisions (Mechanical, Electric, Aeronautic, Automotive, and Ballistic) conducted a survey of the current engineering state of the art, in particular with regard to the ability to construct large complex assemblies to an exacting standard. From this survey, it was determined that the current industrial base is roughly the equivalent of that available in Tank City, Michigan, circa 1950. Likewise it was determined that the state of the art from an electronics standpoint is roughly equivalent to that available in the same time period. Theoretical knowledge available, however, significantly exceeded that level; the divisional chief engineers all have archival clearance and are well-educated on the finer details of the achievements in their respective fields all the way up to the Ultimate War. While the state of the art does not support the immediate manufacture of prewar equipment, many lessons were learned in the past through trial and error, which is estimated to have saved years and many cycles of iterative design and testing in the development of the medium tank.
Following the industrial survey, the archival division conducted another study; this one historical, examining the vehicles produced pre-war with similar industrial capabilities, as well as the evolution of design from that point to the onset of the War. Individual designs were examined based on archival evidence throughout their lifetimes, noting their technical-tactical characteristics as well as more subjective factors such as efficiency of design and manufacture, maintainability, upgradeability, crew comfort, battle efficiency and so on.
Following this survey, it was found that the pre-war Soviet tank T-55 is well within the capability of the industry to construct, and other than minor dimensioning issues more than outmatches the required specifications. While this design had many flaws, and by design was not optimized for the nature of the Cascadian environment, it was chosen as a baseline as it was evaluated to offer more potential than the other possible baselines (Centurion, M-48 Patton), mostly due to small dimensions, reputation of maintainability and reliability, and efficient layout.
From this baseline, a series of improvements were suggested by the Archival Division to the engineering divisions, to better suit the medium tank to the Cascadian environment, as well as to apply the lessons learned throughout the service lives of the vehicles studied.
The list of suggested improvements was as follows:
1.     More compact, autofrettaged gun of ~4” calibre.
2.      Crew water stowage.
3.     Increased crew working volume. Specifically, improved head space for loader.
4.     Improved gunnery optics (including the installation of a rangefinder).
5.     8-10 degrees of gun depression.
6.     APU of roughly 1-2 cylinders (2-4 HP)
7.     Basic air conditioning
8.     Spaced armor arrays
9.     Reversed turret crew (gunner and commander on right, loader on left
10.  More, better accessible, ready ammunition racks. In the bustle with blowoff panels, if possible.
11.  Improved hatches (sprung) and access.
12.  Desertised larger air intakes and filters.
13.  External coil spring suspension, with return rollers.
14.  Improved protected external stowage.
15.  2-channel gunner’s sight, with periscopic mirror head.
16.  2-axis stabilizers, with the gunner’s line of sight being stabilized independently of the main gun, with the gun following the sight, to allow accurate observation and quick firing from the short halt, as well as the use of the coaxial MG on the move. Such a system also allows the implementation of fixed-angle loading, easing the loader’s work without affecting the gunner’s observation of the target.
17.  Separated hydraulics, in the turret bustle.
18.  Commander’s MG useable under armor.
19.  Infantry telephone in rear sponson.
20.  Ammunition loading hatch near ground level.
21.  Automatic fire suppression.
22.  Over-barrel fitting for either spotlight (white light or IR) or .50 BMG.
23.  Thicker front hull for mine resistance.
24.  Roof machine gun for both loader and commander.
25.  Frontally removable gun, with separately removable barrel, for faster and simpler field maintenance of the weapon system and to allow easier modification and upgrading of the vehicle throughout its service life.
26.  Making the Commander’s cupola a hunter-killer system. This involves the use of an independently driven cupola, with independently stabilized optic, and slew-to-cue control of the turret, allowing the commander to find, range, and pass over targets to the gunner, greatly increasing the battle efficiency of the vehicle.
27.  Fitting of indirect fire equipment. As the gun on the tank is liable to be one of the larger guns available in any given setting, the ability to conduct indirect fire when possible is considered to be a great advantage.
28.  Boiling Vessel, allowing the crew to heat their food and that of any infantrymen, boosting morale and reducing fatigue.
29.  Ammunition load of roughly 40-50 rounds for the main gun, and roughly 5,000 rounds of secondary ammunition
30.  Improved suspension damping and increased wheel travel.
31.  6 wheel stations per side
32.  Volume allocation for more advanced electronics, including but not limited to image intensifiers, ballistic computers, and so on.
33.  Improved transmission, with emphasis on reverse speed.
34.  Fittings for tank riders, should doctrine require.
35.  Design for upgradeability, particularly with regard to electronics and armor technology.
36.  Drive system packaged as powerpack to allow easier repair and maintenance.
With the above list of changes, the resulting vehicle bears only a mild resemblance to the venerable T-55 upon which it is based, and yet maintains many of the classic features which made its forbearer a success.
The resulting vehicle entered iterative development and prototyping; In the basic stages of which it was found that all the desired improvements could not only be fulfilled, but even exceeded; The resulting vehicle has greatly improved protection in the frontal 40 degree arc for the hull and 60 degree arc for the turret, along with having all the main gun ammunition safely stowed in separated compartments with blow-off panels, keeping the crew safe. The greater weight of the vehicle compared to the T-55 is compensated by use of a more powerful engine of similar size, a more advanced transmission, and longer track contact along with more wheels, reducing the mean maximum pressure.
Despite HVAP being the standard AP ammo, it was decided not to optimize the gun around that ammo type, as very soon APDS and APFSDS will be available, and will completely eclipse HVAP.
The features of the vehicle are as follows:
Mobility:
1.     600HP (750HP with supercharger) V-12 diesel engine [T-55 engine, uprated to the historical KV levels, with supercharger it’s at T-72 levels]
2.     Mechanical-Hydraulic cross-drive 12 speed transmission, 6 forwards, 6 reverse, with good mountain fighting ability [Stolen off of a Pz 61]
3.     1500L diesel fuel, stowed outside crew compartment
4.     4 HP APU exhaust acts as engine compartment heater in cold weather.
5.     Small air compressor fitted to engine and compressed air tank allow starting in extreme weather without batteries, along with easy cleaning of the air filters at routine intervals.
6.     Enlarged engine bay relative to T-55, to house larger radiators and fans, improving cooling capacity in desert environments. Air is exhausted downwards behind the vehicle, M60 style, to avoid the “rooster tail” effect of the original T-55.
7.     Rotary dampers on each swing arm hub and linear dampers on first, second and last swing arms.
8.     Vertical travel of roughly 400mm up, 150mm rebound
9.     Ground clearance of 540mm
 
Survivability:
Low profile- 2.32m turret roof height, 2.66m top of commander’s sight, extremely low profile in hull-down positions.

Frontal arc - no less than 200mm LOS base steel* with air gap and another 60mm LOS spaced hard steel layer, or angles exceeding 80 degrees from normal.
Lower glacis- 30mm hard face, 500mm fuel tank, 50mm back face at 20 degrees from normal.
Sides- crew compartment armor at least 40mm LOS with 20mm high-hardness plate welded on hull, 100mm on turret, with spaced 30mm,
Non-crew compartment-40mm side armor. 20-5mm spaced skirts on hull. Sponson boxes- 30mm armor on frontal boxes, 10mm on rear boxes.
All-around armor- no less than 30mm steel for direct and air fire, 30mm front floor, 20mm rear floor.
Mounting points for explosive reactive armor are available on the external faces of the spaced armor arrays.**
All ammunition separated from the crew behind blow-out panels.
Instantaneous (WP) smoke grenade launchers- 24 ready, 24 stowed. (4+4 salvos of 6) [launchers on the turret flanks, not modelled]
Automatic IR-detection fire suppression system in crew and engine compartment.
While not fitted as standard, the crew compartment is spacious enough to allow the fitting of spall liners when the technology to make them reliable and not a fire hazard is around.
*The base steel is not homogenous; on the turret cheeks and sides, and on the hull front, it is an arrangement that can only adequately be described as “inverse Stillbrew”. The armor comprises a 50mm thick base layer, with the secondary casting bolted on with a rubber interlayer in the middle. The purpose of this arrangement is not to increase protection (although it should a bit), but rather to aid upgradeability- when better armor gets developed, it is intended that the thick steel facing plates be swapped for more weight-efficient armor. The volume needed for these arrays is already available, as the spaces of the spaced armor. The stowed equipment in those pockets will be displaced to less critical locations.
**It is intended that with the steel armor replaced by NERA arrays and the external face topped with ERA, that the total armor array will be ERA-hard armor-NERA-backing steel armor.
Such an array is reminiscent of the T-72BV turret and could quite reasonably be expected to handle tandem HEAT and moderately advanced APFSDS constructions. This drastic improvement in protection could easily be a simple part of a midlife upgrade, with the chosen construction methods.
Firepower:
A.    Weapons:
1.     Dual stabilized (sight following) 105mm L/51 autofrettaged gun with brass cases, fitted with fume extractor and thermal shroud. [basically an M68 with a slightly larger case].
Ammunition natures:
APCBC [BR-412D with slightly higher velocity]
HE
Smoke-WP [unless it really doesn’t work with horizontal stowage]
HVAP [T29E3 at lower velocity than from the gun T5E1]
 
Stowed ammo: 56 rounds, of which 16 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
2.     Upgradeable to 125mm L/45 gun, when available, intended to use combustible-body stub cases [basically slightly larger NATO 120, there’s room in the turret but the gun isn’t industrially feasible yet]
Stowed ammo: ~42-45, of which ~10 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
3.     1 coax M240
 Stowed ammo: 6,000 rounds, of which 2000 ready.
4.     1 M240 on commander’s cupola, fireable under armor.
Stowed ammo: 2400, of which 600 ready.
5.     1 M240 on skate mount [modelled as pintle] for loader.
Stowed ammo: 2000, of which 200 ready.
6.     1 M2 HMG over barrel (optional)
Stowed ammo: 1300, of which 100 ready.
B.    Optics:
1.     Dual-channel 2-axis independently stabilized gunner’s sight with extension for commander.
2.     Gunner’s secondary direct-vision telescopic sight.
3.     Commander’s fire control cupola: single-channel (selectable) main independently stabilized optic, with secondary coincidence rangefinder channel. 5 periscopes allow all-around vision, slew-to-cue feature.
4.     3 periscopes for loader improve situational awareness.
5.     Commander’s hatch with open protected position in development.
C.    FCS:
1.     Range-finding stadiametric reticles.
2.     ballistic cam computer with automatic feed in from commander’s rangefinder, automatic superelevation.
3.     Gun follows sight (with offset based on superelevation from ballistic computer)
4.     Hydraulic control- 15 deg/sec elevation, 40 deg/sec traverse (basic turret), 30 deg/sec (fully up-armored). Pump, accumulator and reservoir are separated from the crew, in the bustle, and the system is fitted with a pressure-loss automatic cutoff to prevent the hydraulic fluid spraying everywhere in case of a rupture.
5.     Commander has override handles.
For the external machine guns, spare ammunition is carried in belt boxes in the spaced armor of the turret. 12 boxes of .50 can be carried in the frontal pockets, with 100 rounds linked each; and 9 7.62 boxes in each side of the turret, with 200 rounds linked each. The commander’s cupola has a 600-round ring ammo box around the cupola [not modelled].
Crew comfort:
1.     Air conditioning. Operating armored vehicles in the desert without this feature is torture, to say the least. In the bustle, between the hydraulic unit and the ammo rack, sits a powerful air conditioning unit. Rated at 3 HP, this is enough to properly cool down the fighting compartment even with moderate air leakage. While currently no requirement for NBC exists, such an air filtration system could be merged into the aircon unit. When firing, the blower fan is directed into the fighting compartment and not the aircon radiator, to clear out the gasses.
Aircon also aids in maintaining the life of electronic components, an important feature for such an electronically-rich vehicle.
With flow reversal, the aircon unit heats the crew compartment during the winter, with none of the dangers of a fuel-powered crew heater.
2.     Drinking water. There is a tank for drinking water installed, aft of the turret. With a capacity of 240 litres, this allows the tank to operate in the desert and support infantry for extended operations without supply. Additional external stowage is of course possible. A small water container sits directly in front of the aircon vents, allowing the crew to drink at a comfortable temperature. (The main water tank sits up against the engine firewall and will likely get a bit too hot for comfort.)
3.     Boiling Vessel. Allows cooking MREs for the crew and infantry, and hot drinks during the winter.
4.     Height. All seats are adjustable and suitable to the above-average Cascadian recruit. The loader’s position is arranged in such a way that most of his duties can be performed sitting down. There is sufficient headroom and elbow space in every crew position, and using the equipment requires no contortionisms.
5.     Ammo loading hatch- allows loading ammo into the tank from ground level, and not from roof hatches, results in less tiring and quicker loading.
6.     Fume extractor on the barrel greatly reduces the flow of gas into the fighting compartment when the gun fires.

Upgradeability:
1.     Overbuilt, easily upgradeable suspension. Allows weight growth, at cost of increasing ground pressure.
2.     Armor upgradeability, as explained in armor section. Current armor is fairly inexpensive, and allows inexpensive upgrading at a later date, allowing fairly cheap buildup of forces and allows use of more mature armor when the upgrade occurs (as current reactive armor arrays developed at GF&M are fairly crude). Current armor more than outmatches current and projected enemy weapons.
3.     Powerpack dimensions, and those of engine bay, allow upgrading with bigger and better powerplants and transmissions as they come available. The engine bay is 200mm longer and 200mm taller (at the hump) than that of the T-55, to allow better cooling and more upgradeability. It is expected that upgrade powerpacks with 1000HP transversely mounted engines with automatic transmissions, as were available pre-war for the T-72, will be possible for a late-life upgrade.
4.     Spare internal volume for more vetronics.
5.     Frontally removable gun, allows easy maintenance and upgrading.
6.     Configurable ammo racks inside blowoff bunkers allows depot-level reconfiguring for different calibres.
Vents were not modelled due to lack of time.
 
Mass components:
Turret structure: 6.0 tons, includes internal subdivisions and basket
Turret spaced: 1.8 tons, includes partitions
Hull structure: 13.8 tons, includes suspension mounting points and internal subdivisions.
Hull spaced: 1.92 tons, includes sponson stowage boxes.
Suspension: 4 tons.
Tracks: 3.3 tons, based on T-72 track links.
Armament: 1.3 tons
Ammo: 1.5 tons
Fuel: 1500L, 1.23 tons.
Engine, cooling and accessories: 1.5 tons
Transmission: 2 tons
Extras: 6 tons, includes 0.5 tons electric systems, 0.5 hydraulics, 0.3 tons water, 1 ton structural components, 0.3 tons for the aircon system, 0.5 tons for fittings, 0.4 tons of crew, and a margin of 2.3 tons for things unaccounted for.
Total, loaded: 44.3 tons.

Dimensions:
Length, gun forwards: 8.7m
Length, hull: 6.3m
Width, OA: 3.3m
Width over tracks: 3.24m
Ground clearance: 540mm
Height, turret roof: 2.33m
Height, overall: 2.66m
Idler height: 0.84m (relevant for vertical step climbing)
Track contact length, zero penetration: 4.38m
Track width: 550mm
Roadwheel diameter: 686mm
 
Extra notes:
1. The gun uses brass-cased ammo as semi-combustible case tech does not seem to be ready for prime-time with 1950 tech, as evidenced by the problems with the ammunition of the US 152mm gun on the M60A2 and Sheridan in the 1960s; The combination of good rigidity needed to hold large propellant loads onto big heavy projectiles (like 105mm APCBC) and good burn characteristics would seem to be beyond current tech, and therefore extremely risky to develop.
2. As brass-cased ammunition was chosen, 105mm was the logical caliber to use, as it is the largest caliber which can still be relatively easily man-handled in the confines of a turret, when brass cased full-bore AP rounds are used. 
3. The future 125mm intended for the mid-life upgrade is intended to be stub-cased combustible, smoothbore, with APFSDS as the primary anti-armor round. It is expected that by the time the gun is ready and needed, the technology will have progressed sufficiently to allow higher pressures and reliable strong combustible case bodies. As the ammo stowage is already compartmentalized, this ammunition will pose no greater risk to the crew.
4. The tank, with its current weight, is train-deployable fully loaded. The weight margins ensure that when upgraded it will still be transportable in MLC-45, without loaded ammunition, fuel, crew, and other extras.
5. Current development of variants includes:
a. CEV (similar in concept to M728 CEV, with 155mm demolition gun/low velocity howitzer)
b. Bridgelayer (Similar in concept to M60 AVLB, with bridge designed for MLC 70-80)
c. ARV (similar in concept to M88 ARV, with a crane)
d. HAPC/HIFV (similar in concept to Achzarit with small cannon/MG turret, axial instead of transverse engine)
e. SPAA (Shilka-like turret, with twin 35mm guns, and basic air search and ranging radars; plenty of space for more advanced electronics when available)
6. The compressed air starting system connects to a pneumatic joint in the engine bay, to which air-powered tools can be attached. Current supplied tools as basic vehicle equipment include a pressure blower for cleaning air filters and the like, a pneumatic bolt-driver, a pneumatic jack, and other assorted goodies.
7. A coincidence rangefinder was chosen, as no low-risk practical alternative could be thought up. It is intended to be replaced as soon as possible with a laser rangefinder, and an additional laser rangefinder to be installed in the gunner's FCS suite. A coincidence rangefinder takes around 10-12 seconds to range effectively; with the rangefinder in a separate mount, the commander can range a target while the gunner engages a different one, allowing high-speed hunter-killer operation.
 

FINAL SUBMISSION:
XM-2239 NORMAN

[ooc: this is written from a timeframe at which only a few prototypes have been built and tested, mass production awaits selection. Square brackets denote ooc comments]
Classified: top secret
for Cascadian eyes only
 
When General Foundry and Mechanics (henceforth, GF&M) received the brief from the Cascadian armored corps on the requirements for a future armored fighting direct combat vehicle, medium (henceforth, medium tank), and future armored fighting direct combat vehicle, light (light tank), focus was immediately concentrated on the larger requirement of the pair. It was quickly realized that the requirements fell significantly short of the state of the art; and that said state of the art permits the development of a vehicle not only superior to the requirements in every regard, but capable of matching the requirements of the future as well, thus ensuring the safety and freedom of Cascadia for generations to come.
Intelligence gathered from neighbouring states set the basic offensive and defensive requirements; the larger mechanized and armored forces of California to the south, and the more mobile and dynamic, but lighter, forces of Deseret to the south-east. Protection requirements for the medium tank were set by existing and projected future enemy weapons, as detailed in report (REDACTED).
Likewise, the performance characteristics of the main armament were set by the current and projected protection of vehicles in the possession of the neighbouring states, as detailed in report (REDACTED).
Upon receipt of the above reports and requirements, GF&M’s Archival Division in conjunction with the engineering divisions (Mechanical, Electric, Aeronautic, Automotive, and Ballistic) conducted a survey of the current engineering state of the art, in particular with regard to the ability to construct large complex assemblies to an exacting standard. From this survey, it was determined that the current industrial base is roughly the equivalent of that available in Tank City, Michigan, circa 1950. Likewise it was determined that the state of the art from an electronics standpoint is roughly equivalent to that available in the same time period. Theoretical knowledge available, however, significantly exceeded that level; the divisional chief engineers all have archival clearance and are well-educated on the finer details of the achievements in their respective fields all the way up to the Ultimate War. While the state of the art does not support the immediate manufacture of prewar equipment, many lessons were learned in the past through trial and error, which is estimated to have saved years and many cycles of iterative design and testing in the development of the medium tank.
Following the industrial survey, the archival division conducted another study; this one historical, examining the vehicles produced pre-war with similar industrial capabilities, as well as the evolution of design from that point to the onset of the War. Individual designs were examined based on archival evidence throughout their lifetimes, noting their technical-tactical characteristics as well as more subjective factors such as efficiency of design and manufacture, maintainability, upgradeability, crew comfort, battle efficiency and so on.
Following this survey, it was found that the pre-war Soviet tank T-55 is well within the capability of the industry to construct, and other than minor dimensioning issues more than outmatches the required specifications. While this design had many flaws, and by design was not optimized for the nature of the Cascadian environment, it was chosen as a baseline as it was evaluated to offer more potential than the other possible baselines (Centurion, M-48 Patton), mostly due to small dimensions, reputation of maintainability and reliability, and efficient layout.
From this baseline, a series of improvements were suggested by the Archival Division to the engineering divisions, to better suit the medium tank to the Cascadian environment, as well as to apply the lessons learned throughout the service lives of the vehicles studied.
The list of suggested improvements was as follows:
1.     More compact, autofrettaged gun of ~4” calibre.
2.      Crew water stowage.
3.     Increased crew working volume. Specifically, improved head space for loader.
4.     Improved gunnery optics (including the installation of a rangefinder).
5.     8-10 degrees of gun depression.
6.     APU of roughly 1-2 cylinders (2-4 HP)
7.     Basic air conditioning
8.     Spaced armor arrays
9.     Reversed turret crew (gunner and commander on right, loader on left
10.  More, better accessible, ready ammunition racks. In the bustle with blowoff panels, if possible.
11.  Improved hatches (sprung) and access.
12.  Desertised larger air intakes and filters.
13.  External coil spring suspension, with return rollers.
14.  Improved protected external stowage.
15.  2-channel gunner’s sight, with periscopic mirror head.
16.  2-axis stabilizers, with the gunner’s line of sight being stabilized independently of the main gun, with the gun following the sight, to allow accurate observation and quick firing from the short halt, as well as the use of the coaxial MG on the move. Such a system also allows the implementation of fixed-angle loading, easing the loader’s work without affecting the gunner’s observation of the target.
17.  Separated hydraulics, in the turret bustle.
18.  Commander’s MG useable under armor.
19.  Infantry telephone in rear sponson.
20.  Ammunition loading hatch near ground level.
21.  Automatic fire suppression.
22.  Over-barrel fitting for either spotlight (white light or IR) or .50 BMG.
23.  Thicker front hull for mine resistance.
24.  Roof machine gun for both loader and commander.
25.  Frontally removable gun, with separately removable barrel, for faster and simpler field maintenance of the weapon system and to allow easier modification and upgrading of the vehicle throughout its service life.
26.  Making the Commander’s cupola a hunter-killer system. This involves the use of an independently driven cupola, with independently stabilized optic, and slew-to-cue control of the turret, allowing the commander to find, range, and pass over targets to the gunner, greatly increasing the battle efficiency of the vehicle.
27.  Fitting of indirect fire equipment. As the gun on the tank is liable to be one of the larger guns available in any given setting, the ability to conduct indirect fire when possible is considered to be a great advantage.
28.  Boiling Vessel, allowing the crew to heat their food and that of any infantrymen, boosting morale and reducing fatigue.
29.  Ammunition load of roughly 40-50 rounds for the main gun, and roughly 5,000 rounds of secondary ammunition
30.  Improved suspension damping and increased wheel travel.
31.  6 wheel stations per side
32.  Volume allocation for more advanced electronics, including but not limited to image intensifiers, ballistic computers, and so on.
33.  Improved transmission, with emphasis on reverse speed.
34.  Fittings for tank riders, should doctrine require.
35.  Design for upgradeability, particularly with regard to electronics and armor technology.
36.  Drive system packaged as powerpack to allow easier repair and maintenance.
With the above list of changes, the resulting vehicle bears only a mild resemblance to the venerable T-55 upon which it is based, and yet maintains many of the classic features which made its forbearer a success.
The resulting vehicle entered iterative development and prototyping; In the basic stages of which it was found that all the desired improvements could not only be fulfilled, but even exceeded; The resulting vehicle has greatly improved protection in the frontal 40 degree arc for the hull and 60 degree arc for the turret, along with having all the main gun ammunition safely stowed in separated compartments with blow-off panels, keeping the crew safe. The greater weight of the vehicle compared to the T-55 is compensated by use of a more powerful engine of similar size, a more advanced transmission, and longer track contact along with more wheels, reducing the mean maximum pressure.
Despite HVAP being the standard AP ammo, it was decided not to optimize the gun around that ammo type, as very soon APDS and APFSDS will be available, and will completely eclipse HVAP.
The features of the vehicle are as follows:
Mobility:
1.     600HP (750HP with supercharger) V-12 diesel engine [T-55 engine, uprated to the historical KV levels, with supercharger it’s at T-72 levels]
2.     Mechanical-Hydraulic cross-drive 12 speed transmission, 6 forwards, 6 reverse, with good mountain fighting ability [Stolen off of a Pz 61]
3.     1500L diesel fuel, stowed outside crew compartment
4.     4 HP APU exhaust acts as engine compartment heater in cold weather.
5.     Small air compressor fitted to engine and compressed air tank allow starting in extreme weather without batteries, along with easy cleaning of the air filters at routine intervals.
6.     Enlarged engine bay relative to T-55, to house larger radiators and fans, improving cooling capacity in desert environments. Air is exhausted downwards behind the vehicle, M60 style, to avoid the “rooster tail” effect of the original T-55.
7.     Rotary dampers on each swing arm hub and linear dampers on first, second and last swing arms.
8.     Vertical travel of roughly 400mm up, 150mm rebound
9.     Ground clearance of 540mm
 
Survivability:
Low profile- 2.32m turret roof height, 2.66m top of commander’s sight, extremely low profile in hull-down positions.

Frontal arc - no less than 200mm LOS base steel* with air gap and another 60mm LOS spaced hard steel layer, or angles exceeding 80 degrees from normal.
Lower glacis- 30mm hard face, 500mm fuel tank, 50mm back face at 20 degrees from normal.
Sides- crew compartment armor at least 40mm LOS with 20mm high-hardness plate welded on hull, 100mm on turret, with spaced 30mm,
Non-crew compartment-40mm side armor. 20-5mm spaced skirts on hull. Sponson boxes- 30mm armor on frontal boxes, 10mm on rear boxes.
All-around armor- no less than 30mm steel for direct and air fire, 30mm front floor, 20mm rear floor.
Mounting points for explosive reactive armor are available on the external faces of the spaced armor arrays.**
All ammunition separated from the crew behind blow-out panels.
Instantaneous (WP) smoke grenade launchers- 24 ready, 24 stowed. (4+4 salvos of 6) [launchers on the turret flanks, not modelled]
Automatic IR-detection fire suppression system in crew and engine compartment.
While not fitted as standard, the crew compartment is spacious enough to allow the fitting of spall liners when the technology to make them reliable and not a fire hazard is around.
*The base steel is not homogenous; on the turret cheeks and sides, and on the hull front, it is an arrangement that can only adequately be described as “inverse Stillbrew”. The armor comprises a 50mm thick base layer, with the secondary casting bolted on with a rubber interlayer in the middle. The purpose of this arrangement is not to increase protection (although it should a bit), but rather to aid upgradeability- when better armor gets developed, it is intended that the thick steel facing plates be swapped for more weight-efficient armor. The volume needed for these arrays is already available, as the spaces of the spaced armor. The stowed equipment in those pockets will be displaced to less critical locations.
**It is intended that with the steel armor replaced by NERA arrays and the external face topped with ERA, that the total armor array will be ERA-hard armor-NERA-backing steel armor.
Such an array is reminiscent of the T-72BV turret and could quite reasonably be expected to handle tandem HEAT and moderately advanced APFSDS constructions. This drastic improvement in protection could easily be a simple part of a midlife upgrade, with the chosen construction methods.
Firepower:
A.    Weapons:
1.     Dual stabilized (sight following) 105mm L/51 autofrettaged gun with brass cases, fitted with fume extractor and thermal shroud. [basically an M68 with a slightly larger case].
Ammunition natures:
APCBC [BR-412D with slightly higher velocity]
HE
Smoke-WP [unless it really doesn’t work with horizontal stowage]
HVAP [T29E3 at lower velocity than from the gun T5E1]
 
Stowed ammo: 56 rounds, of which 16 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
2.     Upgradeable to 125mm L/45 gun, when available, intended to use combustible-body stub cases [basically slightly larger NATO 120, there’s room in the turret but the gun isn’t industrially feasible yet]
Stowed ammo: ~42-45, of which ~10 ready in bustle; the rest behind blast doors and equipped with blowoff panels in the hull.
3.     1 coax M240
 Stowed ammo: 6,000 rounds, of which 2000 ready.
4.     1 M240 on commander’s cupola, fireable under armor.
Stowed ammo: 2400, of which 600 ready.
5.     1 M240 on skate mount [modelled as pintle] for loader.
Stowed ammo: 2000, of which 200 ready.
6.     1 M2 HMG over barrel (optional)
Stowed ammo: 1300, of which 100 ready.
B.    Optics:
1.     Dual-channel 2-axis independently stabilized gunner’s sight with extension for commander.
2.     Gunner’s secondary direct-vision telescopic sight.
3.     Commander’s fire control cupola: single-channel (selectable) main independently stabilized optic, with secondary coincidence rangefinder channel. 5 periscopes allow all-around vision, slew-to-cue feature.
4.     3 periscopes for loader improve situational awareness.
5.     Commander’s hatch with open protected position in development.
C.    FCS:
1.     Range-finding stadiametric reticles.
2.     ballistic cam computer with automatic feed in from commander’s rangefinder, automatic superelevation.
3.     Gun follows sight (with offset based on superelevation from ballistic computer)
4.     Hydraulic control- 15 deg/sec elevation, 40 deg/sec traverse (basic turret), 30 deg/sec (fully up-armored). Pump, accumulator and reservoir are separated from the crew, in the bustle, and the system is fitted with a pressure-loss automatic cutoff to prevent the hydraulic fluid spraying everywhere in case of a rupture.
5.     Commander has override handles.
For the external machine guns, spare ammunition is carried in belt boxes in the spaced armor of the turret. 12 boxes of .50 can be carried in the frontal pockets, with 100 rounds linked each; and 9 7.62 boxes in each side of the turret, with 200 rounds linked each. The commander’s cupola has a 600-round ring ammo box around the cupola [not modelled].
Crew comfort:
1.     Air conditioning. Operating armored vehicles in the desert without this feature is torture, to say the least. In the bustle, between the hydraulic unit and the ammo rack, sits a powerful air conditioning unit. Rated at 3 HP, this is enough to properly cool down the fighting compartment even with moderate air leakage. While currently no requirement for NBC exists, such an air filtration system could be merged into the aircon unit. When firing, the blower fan is directed into the fighting compartment and not the aircon radiator, to clear out the gasses.
Aircon also aids in maintaining the life of electronic components, an important feature for such an electronically-rich vehicle.
With flow reversal, the aircon unit heats the crew compartment during the winter, with none of the dangers of a fuel-powered crew heater.
2.     Drinking water. There is a tank for drinking water installed, aft of the turret. With a capacity of 240 litres, this allows the tank to operate in the desert and support infantry for extended operations without supply. Additional external stowage is of course possible. A small water container sits directly in front of the aircon vents, allowing the crew to drink at a comfortable temperature. (The main water tank sits up against the engine firewall and will likely get a bit too hot for comfort.)
3.     Boiling Vessel. Allows cooking MREs for the crew and infantry, and hot drinks during the winter.
4.     Height. All seats are adjustable and suitable to the above-average Cascadian recruit. The loader’s position is arranged in such a way that most of his duties can be performed sitting down. There is sufficient headroom and elbow space in every crew position, and using the equipment requires no contortionisms.
5.     Ammo loading hatch- allows loading ammo into the tank from ground level, and not from roof hatches, results in less tiring and quicker loading.
6.     Fume extractor on the barrel greatly reduces the flow of gas into the fighting compartment when the gun fires.

Upgradeability:
1.     Overbuilt, easily upgradeable suspension. Allows weight growth, at cost of increasing ground pressure.
2.     Armor upgradeability, as explained in armor section. Current armor is fairly inexpensive, and allows inexpensive upgrading at a later date, allowing fairly cheap buildup of forces and allows use of more mature armor when the upgrade occurs (as current reactive armor arrays developed at GF&M are fairly crude). Current armor more than outmatches current and projected enemy weapons.
3.     Powerpack dimensions, and those of engine bay, allow upgrading with bigger and better powerplants and transmissions as they come available. The engine bay is 200mm longer and 200mm taller (at the hump) than that of the T-55, to allow better cooling and more upgradeability. It is expected that upgrade powerpacks with 1000HP transversely mounted engines with automatic transmissions, as were available pre-war for the T-72, will be possible for a late-life upgrade.
4.     Spare internal volume for more vetronics.
5.     Frontally removable gun, allows easy maintenance and upgrading.
6.     Configurable ammo racks inside blowoff bunkers allows depot-level reconfiguring for different calibres.
Vents were not modelled due to lack of time.
 
Mass components:
Turret structure: 6.0 tons, includes internal subdivisions and basket
Turret spaced: 1.8 tons, includes partitions
Hull structure: 13.8 tons, includes suspension mounting points and internal subdivisions.
Hull spaced: 1.92 tons, includes sponson stowage boxes.
Suspension: 4 tons.
Tracks: 3.3 tons, based on T-72 track links.
Armament: 1.3 tons
Ammo: 1.5 tons
Fuel: 1500L, 1.23 tons.
Engine, cooling and accessories: 1.5 tons
Transmission: 2 tons
Extras: 6 tons, includes 0.5 tons electric systems, 0.5 hydraulics, 0.3 tons water, 1 ton structural components, 0.3 tons for the aircon system, 0.5 tons for fittings, 0.4 tons of crew, and a margin of 2.3 tons for things unaccounted for.
Total, loaded: 44.3 tons.

Dimensions:
Length, gun forwards: 8.7m
Length, hull: 6.3m
Width, OA: 3.3m
Width over tracks: 3.24m
Ground clearance: 540mm
Height, turret roof: 2.33m
Height, overall: 2.66m
Idler height: 0.84m (relevant for vertical step climbing)
Track contact length, zero penetration: 4.38m
Track width: 550mm
Roadwheel diameter: 686mm
 
Extra notes:
1. The gun uses brass-cased ammo as semi-combustible case tech does not seem to be ready for prime-time with 1950 tech, as evidenced by the problems with the ammunition of the US 152mm gun on the M60A2 and Sheridan in the 1960s; The combination of good rigidity needed to hold large propellant loads onto big heavy projectiles (like 105mm APCBC) and good burn characteristics would seem to be beyond current tech, and therefore extremely risky to develop.
2. As brass-cased ammunition was chosen, 105mm was the logical caliber to use, as it is the largest caliber which can still be relatively easily man-handled in the confines of a turret, when brass cased full-bore AP rounds are used. 
3. The future 125mm intended for the mid-life upgrade is intended to be stub-cased combustible, smoothbore, with APFSDS as the primary anti-armor round. It is expected that by the time the gun is ready and needed, the technology will have progressed sufficiently to allow higher pressures and reliable strong combustible case bodies. As the ammo stowage is already compartmentalized, this ammunition will pose no greater risk to the crew.
4. The tank, with its current weight, is train-deployable fully loaded. The weight margins ensure that when upgraded it will still be transportable in MLC-45, without loaded ammunition, fuel, crew, and other extras.
5. Current development of variants includes:
a. CEV (similar in concept to M728 CEV, with 155mm demolition gun/low velocity howitzer)
b. Bridgelayer (Similar in concept to M60 AVLB, with bridge designed for MLC 70-80)
c. ARV (similar in concept to M88 ARV, with a crane)
d. HAPC/HIFV (similar in concept to Achzarit with small cannon/MG turret, axial instead of transverse engine)
e. SPAA (Shilka-like turret, with twin 35mm guns, and basic air search and ranging radars; plenty of space for more advanced electronics when available)
6. The compressed air starting system connects to a pneumatic joint in the engine bay, to which air-powered tools can be attached. Current supplied tools as basic vehicle equipment include a pressure blower for cleaning air filters and the like, a pneumatic bolt-driver, a pneumatic jack, and other assorted goodies.
7. A coincidence rangefinder was chosen, as no low-risk practical alternative could be thought up. It is intended to be replaced as soon as possible with a laser rangefinder, and an additional laser rangefinder to be installed in the gunner's FCS suite. A coincidence rangefinder takes around 10-12 seconds to range effectively; with the rangefinder in a separate mount, the commander can range a target while the gunner engages a different one, allowing high-speed hunter-killer operation.
 

@Collimatrix
@N-L-M
@Bronezhilet
 
Molot is secretly an agent of Kremlin
 

Potentially the best CIA document declassified to date.
 
https://www.cia.gov/library/readingroom/docs/CIA-RDP89G00720R000800040003-6.pdf

It is nice to see you being telepate and knowing exactly why Russian politicians decided to participate in Syrian war. We already discussed this with @Collimatrix in details, i am too lazy and angry to write it again, it is on our discord. Turkey is more important to Russia than Syria. Iranian influence in Syria for Russia is not doing anything against Russian politicians interests in Syria. In light of Russia allowing Turkish interests to be presented in Syria, i am not even speaking about Iran, with which our politicians want to have a good business (up to going against US sanctions)
 
   
 

PART ONE OF FIVE
 
The XM12 Donward: Cascadia's First Main Battle Tank?
 
by Cho Wilson
 
To the tank crews who served with them in the First and Second Californian Wars, and the Idaho War, it was the M15 Roach that wears the title of "first main battle tank of the Cascade Republic". These flexible tanks were the mainstay of the Cascadian Army for over 35 years, and for many of those they went unmatched in firepower and armor by the tanks of the Democratic California Republic and the Holy State of Deseret. If we were to look back, however, we'd see that another, even earlier tank contends for the title - the lesser-known M12 Donward, and its prototypes.
 
Development of the Heavy Tank, M12, Donward began in the late 2230s with a realization within the CR Army that the long post-war period of tribal pacification was coming to an end, and a new era of potential conflict between industrialized nations was now beginning. The re-formed nation of California to the South, and Deseret to the East, had begun to challenge the Cascade Republic's hold on the regions near Oregon and Idaho. Informed by this, the CR Army determined that existing M6 Light Tanks, which were designed for ease of maintenance within the context of mobile peacekeeping operations against poorly equipped barbarian forces, would be insufficient to meet the needs of the remade world. Therefore, the CR Army Ordnance released a solicitation for two new tanks which would overmatch the tanks both in service and under development by the Deseret, and especially Californian armies. The specification called for a medium weighing no more than 45 tons with at least 3 inches of armor, and a light tank weighing no more than 25 tons with at least 1 inch of armor. These requirements were released as part of a solicitation package to the Cascadian design bureaus, who began their work.
 
The M12's story begins with Bureau 39, a semi-private organization formed from the government design bureau which had been responsible for the earlier M1 Armored Car (originally the Field Kit, Truck, M1 before the restart of truck production) that was used extensively in pacification campaigns. Upon the release of the CR Army solicitation for a new tank in 2239, Bureau 39 undertook to create a tank design that would not only meet, but far exceed, the solicitation's specifications. A study of pre-war tank design, as well as a survey of Cascadian production capabilities, indicated that a vehicle far exceeding the requirements could be readily built and produced within the 45 tonne weight limit. The initial design prompt - called "Project 20" - issued internally to the Bureau called for "a tank of pre-war power and effectiveness, capable of being upgraded and used well into the 2280s and beyond" - this philosophy underpinned the Bureau's design effort from the beginning.
 
Initial analysis done in support of Project 20 looked at several successful pre-war tanks, as well as promising prototypes which nevertheless did not reach production. First design studies took their cues mainly from the Centurion, M103, and Patton, but Bureau notes indicate that the US T95 and T54 tanks played their own role in inspiration as well. Early on, an elliptical glacis plate of 4.4" thick was chosen, mated to a cast hull. Although Cascadian industry was relatively new to casting large objects from armor steel, it was determined that this would be the best and cheapest way to produce hulls with the degree of protection called for by Bureau Director Gordon White. Even so, the hull was engineered so that, in the event that casting it in one piece was not feasible, it could still be welded from plates, or cast in multiple pieces and then welded into a whole. The hull was made big enough to house the 750 horsepower air- and liquid-cooled engines then in development. The crew complement was to be four based on pre-war convention.
 

 
The XM12E1 hull cast test article, with attached wooden mockup side skirts and turret. This was an important validation article which proved the viability of casting hulls as a single piece. Note the early-style fully enclosed commander's cupola.
 
Leaning on pre-war experience, Director White instructed his designers to use the same 85-inch turret ring in all their designs. The reason for this was twofold, as White explained in his memoirs:
 
"The Bureau had multiple projects [to meet the solicitation] ongoing simultaneously. There was a lot of competition, which I felt was a good thing. It was myself, James Whittle, and Kim Wu, and we decided the way to get the best submissions was to have everybody come up with their own ideas and pick the best form them. But at the same time, we needed to standardize some things, so that we could combine the best elements of different designs. I pushed for an 85-inch turret ring, because that size lasted from 1951 until the end of the war almost 70 years later. It's really hard to beat that kind of flexibility. We also knew that eventually, there would be a need for guns as large as 140mm, and you need a bigger turret to accommodate that. So everyone was told to design around the 85-inch ring. I didn't see the need for anything smaller."
 
The weapon chosen to arm Project 20 was significantly smaller than a 140mm cannon, however. CR Army Ordnance had directed designers to arm their tanks with current-issue APCR ammunition in mind, and internal Bureau 39 studies had indicated that a new 85mm weapon along with an optimized projectile design would produce the best penetration with APCR at long ranges. This gun was commissioned with the test designation 85mm Anti-Tank Gun XM34, and twelve tubes were produced for testing and sent to the Bureau's headquarters. To house the gun, Director White had selected a three-man "needlenose" turret designed by Bureau engineer Art Janson, which used a combined mount for both the XM34 and its auxiliary XM151 20mm autocannon. A wooden mockup validated the ergonomics of the hull and turret combination, and the design was finalized with vision and fire control elements, including a fully enclosed commander's hatch with 10 vision blocks, and stereoscopic rangefinders with cast-in mounts. With the basic design wrapped up, the plans were sent to CR Army Ordnance, who elected to fund further development of the tank, beginning with a mockup and cast hull test article. During this time additional studies indicated that a more compact cupola design with an externally-mounted and remotely fired gun on an erectable mount would be both cheaper and better. Instead of 10 vision blocks, this new turret had 7 blocks and a fully rotatable top-mounted periscope. In June of 2240, four prototypes of the freshly dubbed "Medium Tank XM12E1" were commissioned, made with fully cast armor steel hulls and turrets, the new style of cupolas, and functional guns. 
 

 
One of the four XM12E1 prototypes on winter exercises in Elliot Forest, in the Oregon state of the Cascade Republic, late 2240.
 
All four test models were put into validation trials in Oregon, where they underwent cross-country, rough terrain, cold weather, and automotive endurance tests. Powered by a relatively thirsty 850 horsepower gasoline engine, the XM12E1 gave good reliability and mobility, but left something to be desired where range was concerned. The original 21-inch-wide single-pin track also had a tendency to shear, leading to its replacement during testing with newly designed double pin tracks. However, the generously-sized doubled roadwheel assemblies gave good resistance to slush, dirt, and mud, and were recommended by the testing Board. During the trials, crew accommodations were found to be very generous, as XM12E1 crews found that they not only had plenty of room to manage all of their fighting tasks, but the tank also provided space for "live-in" operations, where crews would be required to inhabit their tanks for hours or days at a time. The biggest shortcoming in crew ergonomics was that the fairly tall XM12E1s had insufficient handholds for climbing, which was solved by welding "jungle gym" bars onto the turrets of the test vehicles.
 

 
Designed for mountain combat, an XM12E1 demonstrates its ability to traverse rocky obstacles during rough terrain trials in Eastern Oregon.
 
After automotive and cross country trials were complete, the XM12E1 prototypes were returned to the factory for repair and fitment of newly produced prototype stereoscopic rangefinders, stabilizers, and other internal hardware. These tanks were then sent back to CR Army Ordnance for additional testing, including gunnery and troop trials. The results of these trials showed that the Donward was an accurate and stable gun platform with the 85mm gun, but there were some reliability issues with the vertical stabilizers and they were removed for the remainder of testing. At the same time, two sets of armor hull, turret, and skirts castings were made for protection testing against both captured Californian guns and experimental Cascadian designs then in development. Testing revealed that the XM12E1's glacis was immune to fire from the 89mm Californian gun across the frontal 30 degree arc at all distances, while the turret was immune across the 45 degree arc at all distances unless hit on the bustle at very close range (<100m). Versus the new Cascadian XM34 85mm gun, the XM12E1's turret and glacis both were immune across a 30 degree arc at all ranges, except for a very small area just above the turret ring which could be penetrated at close range. At 45 degrees, the turret was vulnerable to the 89mm gun to about 1,000 meters, but this was deemed acceptable. The hull and turret sides were vulnerable to the 89mm gun at all ranges, though this was well within specifications. The lower glacis was deemed one of the more vulnerable areas of the tank, able to be penetrated by both the 89mm and 85mm guns, as well as the smaller Californian 70mm guns at very close ranges.
 

 
An XM12E1 prototype illustrates the excellent gun depression of the type with its 85mm high velocity gun while on gunnery validation trials in Eastern Oregon. Note the "jungle gym" handholds welded to the turret.
 
 
XM12E1 Donward

GENERAL CHARACTERISTICS
Crew: 4
Length (gun forward): 9.78 m
Length (gun to rear): 8.75 m
Length (w/o gun): 7.37 m
Gun Overhang (gun forward): 1.46 m
Width (over skirts): 3.47 m
Width (without skirts): 3.35 m
Height (to roof): 2.61 m
Height (to 7.62 MG): 2.95 m
Ground Clearance: 0.61 m
Turret Ring Diameter (inside): 85 in
Weight, Curb: 43,038 kg
Weight, Gross: 45,303 kg
Power to Weight Ratio (gross): 18.8 hp/t
Ground Pressure: 11.4 PSI

PROTECTION
Hull armor:
Upper glacis - 4.4" at 28 degrees - 239mm LOS (slightly elliptical)
Lower glacis - 3" at 44.6 degrees - 108mm LOS
Side - 2" at 15 degrees, plus 1" side skirts spaced at 22-38" - 78.4mm
LOS
Turret armor:
0 degrees: 512mm at forehead, 240mm at nose, 186mm above ring
15 degrees: 502mm at forehead, 220mm at nose, 167mm above ring, 339mm sides
30 degrees: 358mm at forehead, 200mm at nose, 147mm above ring, 175mm sides
45 degrees: 262mm at forehead, 154mm at nose, 136mm above ring, 124mm sides

ARMAMENT
Primary: 85x640mmR XM34 L/50 Rifled Gun
    Traverse: Electrohydraulic and manual, 360 degrees
    Traverse Rate (max): 24 d/s, 15 seconds/360 degrees
    Elevation: Electrohydraulic and manual, +25/-10 degrees
    Elevation Rate: 15 d/s
    Firing Rate (max): 8 rounds/min
    Stabilizer: Vertical
Secondary:
    (1) 20x140mm XM151 autocannon, coaxial
    (1) 7.62mm M240 machine gun, coaxial
    (1) .50 caliber M2 machine gun, commander's hatch
    (1) 7.62mm M240 machine gun, loader's position
    Provision for (1) 9mm M95 Submachine Gun

AMMUNITION
    62 rounds 85x640mmR
    500 rounds 20x140mm
    800 rounds .50 caliber
    6,000 rounds 7.62mm (coaxial)
    1,200 rounds 7.62mm (loader)
    210 rounds 9mm
    24 smoke grenades

FIRE CONTROL AND VISION EQUIPMENT
Primary Weapon:
    Direct: Gunner's Primary Sight
        Gunner's Auxiliary Sight
        Ballistic Calculator
        Stereoscopic Rangefinder
    Indirect: Azimuth Indicator
          Elevation Quadrant
          Gunner's Quadrant
Vision Devices:
    Driver: Periscopes (3), Night Vision
    Commander: Periscope Vision Blocks (7), Rotatable         
    Periscope (1), Weapon Sight (1)
    Gunner: Gunner's Primary Sight, Gunner's Auxiliary Sight
    Loader: Periscope (1)
    
POWERPLANT
XG850 850 hp air-cooled turbocharged V12 gasoline engine, 29.4 L displacement,
cross-drive transmission

Thanks to the miracle of asset reuse, the Red Fox is more detailed than it has any right to be. The gun is a 35mm autocannon, and the cupola and optics (and hatches) stolen from the Norman.
The render may not get significantly more complex than the current state, as I lack the time.

Regarding the missile, a few notes which popped up:
>The intent is to have an MCLOS missile broadly analogous to the AT-5 Spandrel (Though with a larger missile body), easily upgradeable to SACLOS when the tech arrives without loss of capability relative to a purpose-built SACLOS like the AT-5.
>The missile is lightly spun to maintain direction throughout flight without requiring constant operator input
>I'm also intending for an MLU to replace the rocket motors and warheads
>There's space in the nose for a precursor, and the warhead sits a bit further back than is good for it with existing HEAT tech, because a 160mm HEAT warhead even at standoff greater than optimal will kill things pretty dead, and later warheads will benefit from the standoff.

Regarding the concept- light tanks are not intended to go toe-to-toe with MBTs or heavy tanks. The 35mm allows the destruction of anything short of a medium tank from the front, and mediums/MBTs at close range from the sides and rear.
The missiles are intended to allow self defense and ambush capability against the heaviest vehicles the enemy can field, as well as the destruction of fortifications and strong points, in the absence of heavy enemy armor.

Thanks to the miracle of asset reuse, the Red Fox is more detailed than it has any right to be. The gun is a 35mm autocannon, and the cupola and optics (and hatches) stolen from the Norman.
The render may not get significantly more complex than the current state, as I lack the time.

Regarding the missile, a few notes which popped up:
>The intent is to have an MCLOS missile broadly analogous to the AT-5 Spandrel (Though with a larger missile body), easily upgradeable to SACLOS when the tech arrives without loss of capability relative to a purpose-built SACLOS like the AT-5.
>The missile is lightly spun to maintain direction throughout flight without requiring constant operator input
>I'm also intending for an MLU to replace the rocket motors and warheads
>There's space in the nose for a precursor, and the warhead sits a bit further back than is good for it with existing HEAT tech, because a 160mm HEAT warhead even at standoff greater than optimal will kill things pretty dead, and later warheads will benefit from the standoff.

Regarding the concept- light tanks are not intended to go toe-to-toe with MBTs or heavy tanks. The 35mm allows the destruction of anything short of a medium tank from the front, and mediums/MBTs at close range from the sides and rear.
The missiles are intended to allow self defense and ambush capability against the heaviest vehicles the enemy can field, as well as the destruction of fortifications and strong points, in the absence of heavy enemy armor.

The tail is fixed, and the canards are monobloc control surfaces. The lines on the fins are just a result of how I defined them.
 

Secondary armament for the Red Fox light tank/scout car is in:
Yes that is a guided missile and yes I will be exhaustively justifying why I believe it to be feasible with the existing tech. The ATGM is MCLOS and easily converted to SACLOS; space will be reserved in the turret for the guidance equipment. The aerodynamic setup is reminiscent of the AT-5 Spandrel, and has been chosen to avoid the most common problem of MCLOS ATGMs as built before the war, and will also be exhaustively discussed in the final submission.
Exact dimensions are still liable to change.

Secondary armament for the Red Fox light tank/scout car is in:
Yes that is a guided missile and yes I will be exhaustively justifying why I believe it to be feasible with the existing tech. The ATGM is MCLOS and easily converted to SACLOS; space will be reserved in the turret for the guidance equipment. The aerodynamic setup is reminiscent of the AT-5 Spandrel, and has been chosen to avoid the most common problem of MCLOS ATGMs as built before the war, and will also be exhaustively discussed in the final submission.
Exact dimensions are still liable to change.

The basic form of the Red Fox is now in. Current plate thicknesses are not indicative, and the tires are just for show.

(hopefully) FINALISED ENTRY
 
XM8 “Elk”

General
 
Dimensions:
Length: 6.40m (hull) 8.00m or 9.25m (gun forward) Width: 1.90m (hull), 3.18m (total) Height: 1.15m (crew compartment), 1.30 (engine compartment), 0.75 (turret) 2.70m (total) Ground clearance: 0.47m Weight:
Light: 25t combat weight Medium: 44 t combat weight Crew: 4 (commander, gunner, loader, driver)
 
Defensive
 
Armour (light):
145mm aluminium @ 45’ (upper hull front) 70mm aluminium @ 45’ (lower hull front) 65mm aluminium (hull side forward) 25mm aluminium (hull side rear) 25mm aluminium (hull rear) 25mm aluminium (hull roof) 25mm aluminium (hull floor) 175mm aluminium @ 30’ (turret front) 65mm aluminium (turret side forward) 65mm aluminium (turret side rear) 25mm aluminium (turret rear) 200mm aluminium (mantlet) 35mm aluminium @ 80’ (turret roof forward) 25mm aluminium (turret roof rear)  
Armour (medium):
145mm RHA @ 45’ (upper hull front) 70mm RHA @ 45’ (lower hull front) 65mm RHA (hull side forward) 25mm RHA (hull side rear) 25mm RHA (hull rear) 25mm RHA (hull roof) 25mm RHA (hull floor) 175mm CHA @ 30’ (turret front) 65mm CHA (turret side forward) 65mm CHA (turret side rear) 25mm CHA (turret rear) 200mm RHA (mantlet) 35mm CHA @ 80’ (turret roof forward) 25mm CHA (turret roof rear)  
Weapons (light)
 
80mm L/55 cannon:
AP: 8.4kg @ 955m/s, ~180mm @ 500m APCR: 4.7kg @ 1280m/s, ~240mm @ 500m HE: 7.5kg @ 700m/s ME: 3.85MJ Vertical movement: -12’/+35’  
Browning M2 machinegun (turret roof)
 
M240 machinegun (coaxial)
 
Weapons (medium)
 
105mm L/52 cannon:
AP: 17kg @ 900m/s, ~200mm @ 500m APCR: 10kg @ 1230m/s, ~290mm @ 500m HE: 15.1kg @ 700m/s ME: 7.6MJ Vertical movement: -10’/+20’  
Browning M2 machinegun (turret roof)
 
M240 machinegun (coaxial)
 
Automotive
 
Engine :
Light: 18L, 450 HP (340 kW) V8 petrol engine (Ford GAA derivative) Medium: 29L, 750 HP (559 kW) V12 diesel engine (Continental AVDS-1790 derivative) Internal fuel tanks: 700l stored on either side of driver + 450l stored in rear of hull compartment on either side of turret basket. Power/weight:
Light:18 kW/t Medium: 17 kW/t Max speed:
70 km/h (road) 35 km/h (offroad) Range:
Light: 1050km (road) Medium: 450km (road)  

Description
 
The XM8 “Elk” was the result of a proactive, iterative design process, intended to provide a ‘universal’ tank optimised for fighting a defensive war against Californian forces and serving in a more mobile role in the Oregon/Idaho sector. The design is also intended to have reserve capacity for upgrades as they become available.
 
The core of the vehicle is a simple hull with a clean, sloped front and a large engine bay in the rear separated from the crew compartment by a 25mm armoured bulkhead. The armour layout emphasises frontal engagements and crew protection, with the forward side armour (covering the crew compartment) being significantly thicker than the rear side armour. The primary fuel cells are placed in the front hull to either side of the driver to improve protection against HEAT weapons and mitigate spall. secondary fuel cells are placed to the rear sides of the turret basket.
 
The XM8 is offered in two variants: a 44t ‘medium’ version and a 25t ‘light’ version. The medium version is designed to resist current-generation heavy anti-tank weapons across the hull front and turret frontal arc from any distance, with current generation medium anti-tank weapons being resisted across a 45 degree arc covering the crew compartment. The medium is expected to remain well protected against medium anti-tank weapons for the foreseeable future, and is expected to resist heavy anti-tank weapons across the hull front and turret front at ranges beyond 1000m.
 
The light version achieves its lower mass by being made entirely from aluminium and having a lighter engine, transmission and suspension package. The aluminium armour is significantly less protective than steel, but still provides approximately 85mm of LOS RHA equivalence (and around 140mm of LOS HEAT protection) across the upper hull and turret front. Having sacrificed protection, the light variant does gain significantly better flotation and strategic mobility. Use of light tank hulls and turrets fitted with medium components would also allow a 'blended' XM8 to fit up to 14 extra tonnes of extra armour and equipment without needing to upgrade the suspension or transmission elements. This crossover capability is expected to be useful if shaped charge weapon systems become predominant on the battlefield.
 
The engine bay is designed to facilitate service and repair, and has large rear doors for access to the engine and transmission. The engine and transmission, in turn, are mounted using a rail system so that they can be easily pulled. The radiators and fans are mounted in hinged doors on the hull roof, which also double as access points for service. The emphasis on ease of maintenance continues to the suspension system, which is an external torsion bar system. The vehicle has a respectable level of ground clearance.
 

 
The cast turret is roomy thanks to a large 1.9m turret ring, which is also expected to facilitate upgrade programs going forwards. The turret is six-sided, somewhat sloped, and contains generously-sized hatches for the crew. The turret is equipped with a skeletonised basket incorporating large openings for accessing ammunition storage in the hull. The commander’s hatch is equipped with multiple vision blocks to provide good visibility while buttoned up. The commander and loader also have access to rotating periscopes (based on the M10 design) for the purposes of target acquisition. These periscopes have azimuth indicators for directing the gunner. The gunner, in turn,  has access to an azimuth indicator mounted to the turret ring, periscope and telescopic sight (based on the M70 series) for target acquisition and lay-in. The periscope is selectable for 1X, 3X and 6X magnification. The sight has various reticles for the main ammunition types. A gunner’s quadrant is provided for ranged fire missions. Range finding is done using the stadiametric approach with coincidence and, eventually, laser rangefinders being envisioned as future upgrades.
 
The gun is vertically stabilized, allowing for more accurate snap shooting at low speeds and (more importantly) quicker shots after a short stop. Two and three-axis stabilisation are expected to form part of future upgrades.
 
The rear of the turret houses the radio set – a new transistor design based on the pre-war SCR-500 series. This set includes an intercom system, and is expected to be less maintenance-intensive than our existing sets. The rear hull side contains a small telephone, linked to the intercom system, to allow infantry to communicate with the crew.
 
The turret drive is electric, and manages a full rotation in around 15 seconds. The electric unit does not allow for very precise movement of the turret at present, so the gunner’s hand wheel is necessary for fine adjustment. Future hydraulic or electric drive systems are expected to overcome this issue.
 
The 80mm main gun used on the light version of the XM8 is a high-velocity piece able to penetrate any commonly-encountered armoured vehicle from the front at combat ranges using the present AP and APCR shells. The gun also sports a very good HE shell, which is fired using a lower-velocity charge. The 80mm is expected to remain viable against most light and medium vehicles for the foreseeable future using existing ammunition, with the development of APDS and APFSDS ammunition expected to allow it to take on medium tanks and some MBT analogues (our engineers have calculated a theoretical maximum performance of ~350mm RHA penetration at the muzzle using high-L/D, jacketed APFSDS). The 105mm gun used in the medium version provides the same ballistics as the famous pre-war L7/M68 guns. This weapon is capable of taking on all comers with present-generation ammunition, and like its predecessor is expected to eventually fire APFSDS ammunition capable of over 400mm of RHA penetration at combat ranges.
 
A compressed air bore evacuation system improves crew comfort and efficiency. The mantlet and recoil system is common to both guns, allowing them to be swapped at a field workshop. The rounds for the main gun are stored in wet racks in the sides (forward of the turret), central hull (behind thew driver's station) and lower turret basket, with only a few ready rounds being carried in the turret basket racks. Rack storage is for 50 rounds regardless of calibre.
 
The coaxial M240 machine gun provides a reliable level of firepower for anti-infantry work. The roof-mounted M2 heavy machine gun provides auxiliary firepower against soft-skinned vehicles, as well as giving the tank a rudimentary anti-aircraft capability.
 
Overall the XM8 offers good firepower, protection and mobility. It also offers a platform with a significant margin for further development.
 
Upgrades
 
M8A1:

The M8A1 upgrade package substantially increases the combat effectiveness of the vehicle by improving first-round hit probability. This is primarily due to the inclusion of the LRS-2 ruby laser rangefinder, TBC-3A ballistic computer and IAPO-3 telescopic sight. All of these components were developed specifically for the XM8 program, and are expected to be in their final configuration within two years of initial rollout.
 
The LRS-2 rangefinder uses a flashlamp-pumped ruby laser, twin photocell optical sensors, quartz timing circuit and the sequential event time sampling approach (with post-sampling amplification) to allow time-of-flight rangefinding using a lower timebase and bandwidth compatible with current electronics. Solid state electronic components allow the system to be fairly compact and robust. Even so the laser and sensor units still require a large, armoured external housing on the mantlet. The housing has a hinged cover on the front which can be opened and closed from inside the vehicle. The rangefinder features both a numerical readout in the gunner’s station and a data link for inputting range data into the ballistic computer. The rangefinder has a maximum operating range of 5km in clear conditions and has an average estimation error of 1%.
 
The TBC-3A replaces the radio in the bustle, which is moved next to the driver at the expense of halving the volume of the right front fuel cell. This electronic ballistic computer also benefits from the use of solid state components. The computer takes input from the gunner (including ammunition selection and manual range input) and rangefinder and uses it to compute a sight offset (horizontal and vertical) for firing. This is then entered into the IAPO-3 sight in order to apply the computed compensation (the existing gunner's telescopic sight is retained as a backup). The computer has a number of operating configurations for various shell types (including all current 85mm and 105mm ammunition), which are stored on a removable magnetic drum. Each drum can store data for up to 32 shell types, with the appropriate type being selected by a dial on the gunner’s station. The computer is also capable of accepting and factoring in wind direction/strength, temperature, humidity and barometric pressure data from an external sensor mast (presently in development under the Integrated Ambient Environment Sensor program).
 
The combination of these devices has been shown to increase first-round hit accuracy against stationary targets at a range of 1000m to almost 90%, and allows first-round hits against stationary targets at a range 2000m to be made over 40% of the time.
 
Additionally, the M8A1 upgrade package includes the addition of sloped spaced armour on the upper hull front, mantlet, turret cheeks and brow. The armour consists of thin RHA plates angled forwards 30’ from the vertical, and is intended to decap and adversely yaw AP projectiles before the main armour is encountered. This is also expected to significantly increase protection against APCR projectiles.
 
The addition of the new components and armour raises the mass of the vehicle to just under 45 tonnes, and substantially increases the unit cost of each vehicle. Nevertheless, the increased combat effectiveness which results from installing these components more than justifies this increased cost.
 
M8A2:

The M8A2 is a speculative upgrade based on known historical trends in tank development, with the presented vehicle being a mock-up. This upgrade package would replace the M8A1 add-on armour with a new composite array designed to defeat improved HEAT warheads and the APFSDS projectiles which are expected to enter the battlefield around 2255. The composite array is a classic NERA design which makes use of thin (2-5mm) steel and aluminium plates sandwiching a thicker (10-20mm) plate made of lower-density material (primarily rubber or plastic, but also glass). The thicknesses, compositions and geometries of the sandwich plates vary depending on their position in the array, but overall densities are estimated at 2.2g/cm3.
 
The total package weighs in at 4.3 tonnes, and provides a substantial increase in armour protection for the crew compartment across the frontal arc of the vehicle. When applied to a ‘blended’ aluminium hull, this results in a vehicle weighing in at just under 37 tonnes. The thick armour arrays are expected to provide around 500mm/740mm KE/HEAT resistance on the upper hull and turret front. This good frontal armour is, however offset by the aluminium hull’s weakness against threats from the side and rear. When applied to an all-steel hull, on the other hand, this results in a vehicle weighing just over 49 tonnes but capable of resisting up to 640mm/800mm KE/HEAT on the upper hull and turret front while still retaining good all-around protection as well.
 
The M8A2 is also expected to benefit from advances in automotive technology, with a projected 850HP turbodiesel engine being used as a weight-for-weight replacement for the existing 750HP unit. This would be allied with an improved transmission system to provide increased cross-country performance and lower driver workload.
 
The single-axis stabilizer is expected to be replaced with an interim two-axis system before the introduction of a fully stabilized system of the pre-war type (ie: combining a gun stabilizer, stabilized sight and barrel registration system). Both systems will be controlled from a fixed handle unit with thumb/finger switches (prototype currently in development), as this is known to provide a slight increase in accuracy by limiting the effects of gross operator movements. The turret traverse and elevation will be handled by a hydro-electric system (currently being researched) with significantly higher power and proportionality of response than the current electrical traverse system. This will, amongst other improvements, result in much faster traverse times.
 
All in all, the M8A2 upgrade package would be expected to allow the M8 design to successfully serve into 2260s and beyond.

 
135mm L/40 cannon:

HEAT-FS (early, fixed-fin): 17.2kg @ 600m/s, ~270mm RHA penetration @ all ranges HE-FS (fixed-fin): @ 27.5kg @ 600m/s AP-FS (fixed-fin): 31kg @ 750 m/s, ~190mm RHA penetration @ 500m HEAT-FS (improved, folding-fin): 29.0kg @ 600m/s, ~310mm RHA penetration @ all ranges APCR-FS (folding-fin): 20kg @ 940m/s, ~230mm RHA penetration @ 500m HEAT-FS (projected, 2nd-gen):  29.0kg @ 780m/s, ~440mm RHA penetration @ all ranges APFSDS (projected, 1st-gen):  7.75kg @ 1330m/s, ~330mm RHA penetration @ 500m Max ME: 8.8MJ Vertical movement: -7'/+20'
The final proposed upgrade to the M8 series of vehicles is the replacement of the 105mm main gun with a 135mm smoothbore gun. The gun as presently developed includes a conventional mid-barrel bore extractor and phenolic resin jacket, and fits into an enlarged version of the existing mantlet gun mount. Ammunition stowage with the 135mm gun is decreased to 35 rounds, stored in new wet racks which slot into the same areas as the existing ones.
 
Although it is currently limited to firing primitive finned projectiles (AP-FS, APCR-FS, HE-FS and HEAT-FS) at a fraction of its capacity, the development of upgraded HEAT-FS and APFSDS is expected to slowly unlock more of the potential of the weapon as time goes on, up to a maximum of around 600mm of RHA equivalence for HEAT-FS and 440mm for APFSDS . Finally, the generous bore of the gun is expected to ease development of GLATGMs as time goes on.
 
Acknowledgements
 
Jeeps (the Sherman site is freaking goldmine)
Various Sketchup users (especially Sketchy@Best, Stefan F., M L. and zdanwoj)
Whoever came up with that Tank Designer spreadsheet that Sturgeon posted

Finalised gun designs:
 
80mm L/55
AP: 8.4kg @ 955m/s, ~180mm @ 500m
APCR: 4.7kg @ 1280m/s, ~240mm @ 500m
HE: 7.5kg @ 700m/s
Max ME: 3.85MJ
Notes: Gun is a 17-pounder/20-pounder hybrid.
 
105mm L/52
AP: 17kg @ 900m/s, ~200mm @ 500m
APCR: 10kg @ 1230m/s, ~290mm @ 500m
HE: 15.1kg @ 700m/s
Max ME: 7.6MJ
Notes: Gun is a L7 with the serial numbers filed off.
 
135mm L/40
HEAT-FS: 29.0kg @ 600m/s, ~270mm @ all ranges
HE-FS: @ 27.5kg @ 600m/s
AP-FS: 17.5kg @ 950 m/s, ~180mm @ 500m
APCR-FS: 8.8kg @ 1350m/s, ~250mm @ 500m
Max ME: 8MJ
Note: gun is a bored-out 122mm D25. "Finned Sabot" refers here to a more primitive design compared to the post-war stuff.
 
General note: AP and APCR penetration values for the 80mm and 105mm were calculated using a number of DeMarre values with similar real-world guns as references. These were then averaged and rounded to the nearesr 10mm to get the final value. The 135mm AP-FS value was obtained by mocking up and calculating values using BR-471D as a reference. The APCR-FS value was obtained by mocking up the round, running the core through longrods and then sanity-checking against known APCR/APDS rounds with similar characteristics. The core is modelled as a 30x220mm tungsten rod (~2.7kg). 

If your preferred energy source isn't nuclear just get the fuck out.
 
 

The Cent has none of the fittings for ERA, so it's probably a wreck from the YKW or earlier. Both the Israelis and the Jordanians used the Cent in that war, so there would likely have been a few hulks left over in Syria.

Absolutely. The best description I've seen was by someone on this site, who described a tank as a "reverse TARDIS, much smaller on the inside". Even just an open museum or gate guard/monument, where you can climb in, gives you a useful scale. Everything inside a tank is harder, sharper and stronger than you. You are always the squishiest component, which has to squeeze out of the way of the bigger stuff in there. Proper systems integration and adequate volume allocation make the difference between sharp corner hell and a comfy (if tight) working space.

So here is what we have so far:

The suspension is supposed to get replaced at some point (with external torsion bars), and the rear hull needs reworking.
Plans to make the hull lower, shorter and thinner failed: I ended up using up all the freed space by putting in those crazy modular armour compartments and ended up haing to make the whole thing longer and taller to fit the driver's vision devices in (the poor bastard still has to enter/exit via the turret or the bottom escape hatch) once I'd lengthened the turret. The turret is currently missing the mantlet and coax.
 
The gun is a smooth-bore 120mm/L35 piece which is limited (for now) to firing modified mortar shells at lower velocities (~600 m/s) ala the 8cm PAW 600. The HEAT shell should be able to do ~240mm of penetration even with crappy WW2-era HEAT designs thanks to the lack of spin. The turret actually has 4 crew members crammed into it - one to act as a dedicated rangefinder operator. I have no idea what the elevation/depression on the gun is, but I plan to mess with the turret until it's -10/+30. The gun is massively overbuilt for what it's currently doing, and should be capable of slinging proper HEAT-FS and APFSDS whenever that comes online. The casing for the shell is about 850mm long, so there's lot's of room to play with.
 
The weight without anything in the armour compartments is about 25t, with all the suspension/transmission components rated for 45t. The armour compartments are designed to cover up to the rear of the turret ring in a 45' arc and attacks directly to the side of the crew compartment. The base armour is pretty much nothing (20mm, 500mm air gap and 10mm front plate) but will keep HMGs and early HEAT rockets out. When fully loaded up with modern NERA, however, this thing should be able to keep modern HEAT weapons and previous-gen APFSDS at bay.