Competition: Tank Design 2239

[N-L-M]

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.

 

[N-L-M]

FINAL SUBMISSION:
XM-2240 RED FOX

[Fullbore autism warning]

Upon receipt of the technical requirements for the light tank competition, the design team at GF&M once more decided that the spec was extremely conservative. It was decided that a light vehicle, capable of being used in direct wars of maneuvering and in the assault against Deseret forces, as well as in a defensive ambush role against Californian forces, was more than possible.

To allow good strategic mobility, and low maintenance for long-range independent operations, a lightweight wheeled chassis was chosen, based on pre-war experiences by South African forces in Angola and Namibia. Combined with the success of pre-war French armored cars (AML, EBR, ERC, VBC, AMX-10), and the export and service success of the pre-war British vehicles (Saladin, Fox, Ferret), it is clear that wheeled vehicles have the ability to operate in rocky desert and mountainous terrain (as long as the going doesn’t get too sandy), with limited support or maintenance.

For armament, it was quickly determined that the minimum calibre gun which would remain relevant against high-end threats throughout the life of the vehicle is prohibitively large at roughly 100-110mm, forcing the tank to be bigger and heavier than it otherwise needed to be. The minimal calibre to remain relevant against light vehicles (such as light tanks, APCs, IFVs and older tanks), however, is much more reasonable: a 30-35mm autocannon. To defend against the high-end threat, a pre-war invention is resurrected: the anti-tank guided missile (ATGM).

Systems and crew comfort features were inspired by (and in some cases shared with) those in development for the Norman medium tank, saving time and development money.

Mobility:

Suspension is double wishbone on the front 2 axles, with steering; the front-most axle steers all the way, the second axle only steers roughly half.

The rear axles have Christie-style suspension, with the springs tucked away in the groove on the outside of the hull.

All axles are powered through drive systems reminiscent of that of the ERC; the engine and transmission sit in the rear of the vehicle.

Survivability:

Armor is 10mm high hardness steel facing on 60mm aluminium LOS throughout the 60 degree frontal arc for both hull and turret; for the sides, 5mm steel facing on 30mm aluminium LOS; and the rest (sides, back and belly) 30mm aluminium. The belly is V-shaped, at 10 degrees from the horizontal, to allow good performance against mines.

Smoke grenade launchers as on Norman, 24+24 for 4+4 salvoes of instantaneous smoke.

The entire vehicle has a very low profile, and is capable of firing ATGMs from turret-down positions with only the optics and box launcher exposed.

Automatic IR-detection fire suppression fitted as standard; room for spall liners is available. Mounting points for light-weight ERA when available are also integrated onto the vehicle.

Thin sheet-steel (2mm) stowage boxes over front and above wheels, around left and rear of turret, set off HE rounds at sufficient standoff to avoid having the armor cave in. [not in model]

Firepower:

A.     Armament.

1.      The main gun is, basically, a Bushmaster III, chambered in 35x230mm, with full dual-feed first-round-select semiauto/automatic fire capability, at around 200 RPM. Ammunition is belted in 2 boxes underneath the turret crew seats; 100 rounds of AP and 500 rounds are carried (50/250 ready).
Ammo types: AP, HE/HEI (APDS, APFSDS in development)

2.      1 M240 coax. The coax has a ready box with ~2500 rounds ready, with an additional 2500 stowed.

3.      1 M240 commander’s MG. Commander’s MG has 600 rounds on mount with extras stowed on the sides of the turret in unarmored boxes [not pictured]

4.      The main armament elevates from -10 to +30 degrees, and is fully stabilized in a similar manner to the Norman’s armament.

5.      The ATGM box is raisable, and carries 4 missiles; it is armored against light arms fire (10mm steel) and can elevate and depress to the full extent of the main sight. Additional missile canisters can be stowed on the sponsons (not ready to load from within)

6.      There are in fact 2 different versions of the basic MCLOS missile on offer, differing by the details of the guidance system.

B.     Optics. Same as Norman, minus loader.

C.     FCS.

1.      Same as Norman for guns. Smaller hydraulic unit needed for the much smaller and lihter turret.

2.      For missile:
Missile is controlled in current variants by gunner using a joystick. Space has been allocated for a reticle seeker feeding off of the gunner’s optics and electronics to allow SACLOS systems to be fitted. Details on missile system expanded in later section.
It is not recommended that a firing mechanism be fitted for the commander to fire the missiles in MCLOS versions.
For best accuracy it is recommended to point the launch tube directly at the target before launch.

D.     Radio.
A more powerful radio is fitted in the Red Fox, with more options. It is suggested that this radio also be fitted in command variants of the Norman.

Crew comfort: As on Norman, with smaller water tank and reduced power AC unit.

Upgradeability:

1.      Same as on Norman, minus ammo.

2.      Missile easily upgraded to SACLOS.

3.      Gun very capable of accepting newer advanced ammunition types.

4.      Main armament can be replaced with low-pressure 90mm gun (styled after the pre-war Cockerill) to create an infantry fire support platform. Estimated stowage: 30-40 rounds, HE/HEP/HEAT.

 

[I ran out of time so the modelling is woefully incomplete on the vehicle, but the general outline is available].

 

Mass of turret: 0.8 tons

Mass of hull: 2.2 tons

Engine: ~200HP diesel.  Features as on Norman (air compressor/starter, large radiators)

Estimated mass: 0.6 tons.

500L fuel, 0.4 tons.

Transmission: smaller version of that on the Norman, 4 speeds forwards, 4 reverse.

mass: probably around 2 tons (including drive shafts).

Suspension: Probably around 2 tons. (including tires)

Armament mass: probably around 2.5 tons including mantlet, ammo and ATGM box.

Mass of extras: 3 tons.

Total estimated mass: 15 tons.

Dimensions:
Length, gun forwards: 6.0m
Length, hull: 5.0m (wheel to wheel, maximum)
Width, OA: 2.75m with ATGM launcher.
Width over tracks: 2.5m
Ground clearance: 450mm to bottom of V, 580mm to top of V hull.
Height, turret roof: 1.95m
Height, overall: 2.3m to top of commander’s sight
Wheel diameter: 1.1m
Wheel hub diameter: 0.5m
Wheel width: 300mm

 

As an additional note, the secrets of multi-alkali photocathodes and cascade image intensifiers are known to the engineers of the EL-OP subsection of the Electronics Division. The Cascader Mark 1 is expected to be in field trials soon. While too large for infantry weapons, tank gunnery integration is expected to proceed rapidly.
(This refers to first-generation image intensifier equipment, intended for integration in both tanks)

Likewise, IR detectors and spin scan reticles are being developed; conscans will soon be in development as well. Their use in SACLOS systems as well as anti-air applications will be apparent soon.
(These reticle seekers will be used for automatic missile detection and aiming in SACLOS, and target detection in anti-aircraft applications)

And now, the moment you’ve all been waiting for:

MISSILE TECH EXPLAINED

As a forewarning, this is going to be fullbore autism, and I strongly recommend you read up on gyros, control theory, and missile guidance before you read the explanation.

Useful links:

http://www.shorlandsite.com/images/landroversmissileselliott.pdf
Contains useful info on the development of British first generation ATGMs. And missiles on Land Rovers, which are cute.

http://www.dtic.mil/dtic/tr/fulltext/u2/b807471.pdf
Scientific Advisory Commission report on guided and homing weapons, May, 1946.
http://www.tpub.com/neets/book15/63e.htm

Gyro basics.

https://sci-hub.tw/https://ieeexplore.ieee.org/document/1104289
Non-minimum-phase dynamic systems.

The following is based on my knowledge of control systems and missile guidance, as well as basic knowledge of human reactions and as-built 1^st gen ATGMs.

The problem is as follows: we want a missile to fly along the line of sight, to the target, despite target maneuvers and outside disturbances.
For this, we track the missile, and send commands to the missile to correct for its heading, to maintain the missile along the line of sight to the target. As long as the missile can be made to always be on the line of sight, and is moving faster than the target, a hit is guaranteed.
This is the basic premise of CLOS guidance.

To ensure aerodynamic stability and direction-keeping despite manufacturing flaws and inconsistencies, the missile is lightly spun around its axis throughout flight by its fins. These are on an adjustable base, so as part of the SACLOS upgrade the spin can be disabled.

There are a few points to address in this regard-

1.       How is the missile tracked?

2.      How are the commands given? What do they mean?

3.      How are the commands sent and how are they interpreted?

4.      How are the commands carried out?

The answers will be given for 3 systems-
a. classic MCLOS

b. classic SACLOS

c. The BGM-1A and BGM-1B missiles

let’s start.
1.A: operator tracks target and missile through sight.

1.B: Operator tracks target by centering sight on it; guidance system detects missile location relative to crosshairs through spin or later conscan reticle similar to those in early A2A missiles.

1.C. Same as traditional MCLOS

2.A. Manual Joystick, usually acceleration command to the missile, command intensity proportional to joystick deflection; force feedback.

2.B. automatic, often bang-bang, to center of crosshairs, usually acceleration.

2.C. Manual Joystick, proportional, velocity control.

3.A. From joystick take-off, through amplifier, through wires, direct to gyrostabilized commutator (in spun missile), to actuators on open loop.

3.B. From detector output, through wires, direct to gyrostabilized commutator (in spun missile), to actuators on open loop.

3.C. BGM-1A: From joystick take-off, to flight control box, Through wires, direct to gyrostabilized commutator (spun missile),  to actuators on open loop.
 BGM-1B: From joystick take-off, to flight control box, Through wires, direct to gyrostabilized commutator (spun missile), to autopilot in missile; autopilot operates actuators on closed loop with horizontal and vertical rate gyros to achieve fixed angle for given command.

4.A. TVC or rear control surfaces.

4.B. aerodynamic control surfaces, front or rear.

4.C. Front control surfaces.

 

The disadvantages of classic MCLOS are that it was difficult to use, and required great skill, as the acceleration commands combined with rear steering missiles. These missiles exhibit extremely unintuitive steering mechanics, with delayed response, and inverse response: rear steering throws the aft end of the missile in the opposite direction to point the missile towards the target, which means the whole missile moves the wrong way until sufficient wing lift can be generated to push the missile in the intended direction. This is extremely unintuitive for the user and takes a lot of practice to accurately predict; frontal control on the other hand is minimum-phase and intuitive- the missile goes where you want it to, and goes there faster for the same control authority.
Likewise, acceleration feedback is not intuitive for human beings; we are not used to it. Speed feedback is however within the abilities of humans to handle reliably, and therefore the autopilot has been chosen to perform this duty, greatly easing the use of the missile system by humans and thereby improving accuracy, within the limits of established technology.

Example of front vs. rear steering. Note the rear-steered missile going the wrong way initially. This is very confusing and leads to overcompensation in all except the well trained and highly skilled.

The differences between the flight control of the BGM-1A and BGM-1B are as follows:
The BGM-1A has a single inertia gyro, spinning on a horizontal axis normal to the missile’s axis. This gyro stabilizes the commutator to allow the proper splitting of command to the surfaces despite missile spin.

Velocity control is achieved through matching to an internal simulator in the flight control box. This receives the command, and relays it to both the missile and the internal missile flight estimator (a reduced 3-variable (local sideslip angle, turn rate, and heading) first order differential solver. The system is linked to an internal PID controller aimed at bringing the missile velocity across the line of sight to the value dictated by the command joystick input. The missile itself, in flight, is controlled on open loop, and therefore velocity errors are liable to accumulate throughout flight. With a flight time of only around 20 seconds to maximal range (4000m), however, this is not considered to be too great a risk.

This flight control box also forms the basis of the built-in missile simulator; hooked up to a driven mirror assembly with HUD-style reflector plate in the gunner’s sight, it can be used to project a dot representing the gunner’s view of the missile tracer flare onto the gunner’s sight. This can be used to practice missile firings as many times per day as is desired, to maintain high skills with minimal support and minimal live-firings of practice missiles.

The BGM-1B has an additional gyro in the missile, this one a displacement gyro with its rotation axis aligned with the missile body. The angle take-offs from the 2 gimbal frames are fed through the (larger) commutator, to allow the missile to know what its attitude is compared to that it had at launch. When firing this missile, the flight control box only controls the gain of the joystick (less sensitivity at short range as speeds across the line of sight have greater angular rates), and the missile itself contains a PID autopilot, controlling the servomechanisms by gyro feedback to maintain constant bearing displacement relative to launch. The size of the bearing displacement is linear as a function of the control input, as that results in proportional velocity control along the line of sight.
The BGM-1B is a slightly more expensive missile, but the increased accuracy thanks to reduced drift more than justifies the cost difference.
The BGM-1B, thanks to its design, retains a modicum of accuracy in case of a wire break, as it seeks to maintain a 0 bearing relative to launch in that plane. For this reason it is highly advised to point the launcher directly at static targets before launch.

Both missiles are fairly modular; the warheads are easily removeable and upgradeable, as are the rocket motors, flares, and batteries.

 

MCLOS missile tech better than was available pre-war is possible with the current industrial ability, as it involves no tech not present in the 1946 survey, and transistors improve reliability and significantly shrink the volume needed for guidance electronics. The better understanding of the control problems involved and the man-machine interface allows the design of more reliable more accurate missiles than were available pre-war.

 

TL;DR: Missiles work and better than any MCLOS missile built IRL.

 

 

Tech Specs of the missile:

Diameter: 160mm

Length: 1300mm

Length of launch tube (including launch gas generator): 1500mm

Wingspan: 550mm

Wing type: wrap-around fin, thin sheet steel with forming springs; sprung fold-out Monobloc canards. (As on AT-4 Spandrel and AT-5 Spigot)

Gyros: 1 free for commutator inertial stabilization, BGM-1B: extra displacement gyro for angle feedback control.

Gyro spin-up mechanism: Compressed air start, no sustain.

Servo actuation mechanism: Electrical servo-controlled compressed air actuators.

Velocity: ~200-250m/sec [ss.11 was 220 m/s, clearly this is a controllable speed]

Range: 4000m, wire limited.

Time to max range: 16-20 sec.

Warheads:
Antitank: Precursor 60mm HEAT, main 160mm HEAT, precision formed, crush-cone fuze, base detonated with wave shapers.

Anti-structure/ Anti-ship:
Precursor: none.
Main: 160mm blast-frag.
 

Current development of variants includes:
a. CEV (light breaching equipment, smoke screening equipment, fascines, light digging equipment)
b. ARV (winches, light crane)
c. APC/IFV (similar in concept to Alvis Saracen with small cannon/MG turret)
d. SPAA (VADS-like turret, with twin 20mm autocannon, 1 Vulcan cannon or 1 35mm revolver cannon, and basic air search and ranging radars; missile pod replaced with SAMs (Sidewinder-style) when available).
e. Fire support vehicle- 90mm low pressure main gun.

 

 

 

[A. T. Mahan]

Hey! I'm working on a medium tank design right now -- I might have to hand draft it rather than doing it up in NX since I can't find a good model to work off of and I'm not going to try to design a tank in NX from scratch with my courseload right now, but it's going to be good.

 

 Here's a very rough draft, lacking graphics because I'm going to make those tomorrow:

 

The 120mm Gun Tank T44, designed primarily by the Renton Shipbuilding and Locomotive division of Pacific Car and Foundry, is a fully-tracked armored fighting vehicle armed with a 120mm smoothbore gun. Research and exploratory investigation determined that there were a number of designs and concepts with great potential to leverage and improve the combat effect of the vehicle. The most promising hull that PACAR-RSL located was the M47 Patton -- the combination of castings and weldments of high-quality steel was well within the production capabilities of our facility, and the vehicle weight of 93000lbs would be able to be reduced sufficiently to meet the required weight limit. Noting that the vehicle weight specified in the contract (90,000lb) does not specify whether it is the unloaded or loaded weight, the Program Manager determined that it specified the unloaded weight. In any event, PACAR-RSL has several proposed variants (and has produced prototypes of them) that meet varying weight goals.

 

Structure:

The original M47’s structure is highly dated. While PACAR-RSL has substantial experience with high-quality castings of the scale required, and while PACAR produced M26 Pershing 90mm gun medium tanks in 1944 and 1945 (and retains sufficient quantities of the technical data package to resume production of mildly improved versions of those tanks if the Government would so desire), castings are not compatible with the composite armor techniques that PACAR and our subcontractors have developed based on combat-proven prewar efforts. As a shipbuilding concern, PACAR-RSL possesses substantial experience producing high-quality weldments of extremely high grade steels, and many of our welders are certified to weld armor steels. This trained and capable workforce allowed our design team to rework the monocoque (armor-as-structure) hull and turret of the M47 to suit both the HAP-1 derived armor package and to lighten the vehicle. This resulted in an allowable armor weight of nearly 10,000lb for the hull, sufficient to utilize the HAP-1 armor on a recontoured lower frontal hull.

The hull itself is constructed of welded 1.0” to 1.5” (+/- 0.05”) high strength steel plate,

The turret is of a completely new, all-welded design heavily inspired by the pre-war Abrams design, as far as general shape is concerned.

 

Protection:

 

Central to our design is the incorporation of highly advanced composite armors to reduce the threat of shaped-charge warheads. Pre-war literature indicated that these antitank munitions were most concerning for designers of the so-called first and second generation of main battle tanks, due to their light weight and relatively high penetrative ability, and Cascadian control of the only large supplies of depleted uranium and tungsten in the region result in a greatly reduced threat from long-rod fin-stabilized discarding sabot kinetic penetrators. In cooperation with the Pacific Aero Products Company of Seattle, we have spent considerable time and effort developing ceramic and other composite armor technologies, and believe that we have managed to develop an armor package similar in concept, but less protective, than the BRL-1 armor used on early model pre-war M1 Abrams tanks. Our testing has determined that the armor package we have chosen for the vehicle is substantially lighter and more protective than rolled homogeneous steel or cast steel armor, although it is bulkier and substantially more expensive.

We have been particularly focused on Carborundum (Silicon Carbide) as the ceramic used in the armor, although experiments have determined that Boron Carbide offers more protection, but is substantially more difficult to manufacture and work with. While large quantities of B4C exist at the Hanford Site in the form of neutron dampers and shielding, and control rods, they would require substantial effort to form into a usable armor material and at this time the yield rate on B4C tiles of the appropriate size is low to the point of total impracticality - at best, we have determined that current technology will produce no more than 5% of a given batch of tiles that meets QA/QC. We have therefore determined that the most weight and efficient armor scheme would be to more-or-less duplicate the HAP-1 armor construction, substituting Silicon Carbide for Boron Carbide where appropriate, and utilizing the supplies of depleted uranium available at the Hanford Site (estimated to be 2,380 tons, appropriate for approximately 750 vehicles based on current projections of 6000lb of DU per vehicle) would provide substantial kinetic protection at the cost of increased weight.

Our armor concept, admittedly very heavily inspired by that of the early M1 Abrams designs, provides significant protection for its weight, especially considering the smaller protected volume and reduced level of protection chosen. The turret faces are intended to provide protection equivalent to 20-25 inches of rolled homogeneous steel, but are some 70% lighter.

We would note that the Cascadian Government should seek to acquire access to greater supplies of uranium for use in this and other defence programs, and note that research indicates four thousand tons of dry-cask stored spent nuclear fuel each in the former Illinois, former Pennsylvania, and former South Carolina regions and between 3,000 and 4,000 tons each in California, former Alabama, Florida, New York, and Georgia regions. While most of these areas are over a thousand miles away, if Cascadia can secure access to these supplies, they represent approximately 32,500 tons of highly enriched uranium, which would be invaluable for reprocessing into depleted uranium for tank armors, or Special Materials for use in other programs. PACAR-RSL has been making inquiries through traditional trade channels as to the feasibility of cross-country transportation of these materials, but government support would aid the endeavour greatly.

It is worth mentioning that this armor design package more-or-less requires the production of a gaseous-diffusion uranium enrichment cascade and the production of weapons-grade uranium. This could be expected to produce 16.9 tons of U-235, enough for over two thousand 25-kiloton nuclear devices.

Further protection comes from the incorporation of Contact, an explosive reactive armor derived from the Soviet Kontakt-5 tiles. These require no outside initiation, being a box with two steel plates sandwiching a piece of explosive, and the 150 tiles used on the vehicle only add 1,900lb including mounting hardware while providing greatly increased protection.

 

Firepower:

Other work with the Pacific Aero Products Company focused on the development of improved ammunition designs. PACAR-RSL leveraged PAPC’s advanced aerodynamic analytical techniques to aid in the development of improved fin-stabilized smoothbore ammunition. Research on prewar technologies demonstrated a number of programs conducted by the prewar US Army that incorporated smoothbore guns, and industrial analysis has determined that a maximum chamber-pressure of 55,000psi is within current capabilities, and based on research trends in metallurgy, a chamber pressure of 75,000psi should be achievable within five years, and 100,000psi in ten years. While this will result in a lengthened gun compared to prewar designs (The M256 120mm gun was only a 44-caliber gun), a 50-caliber 120mm gun with a tube weight of not more than 2,900lb and an all-up weight of not more than 4,400lb is entirely viable.

We have developed a gun, the 120mm Gun T123E7, that produces a muzzle energy of 4,300 ft-ton with a 50lb armor-piercing capped, ballistic capped projectile (MV = 3,500ft/sec, 50lb shot M358). We estimate that this will drive a 22lb Hanfordite (U-238) penetrator at approximately 4,500ft/sec, giving the capability to defeat greater than 25” of rolled homogenous steel at 2,000 yards, and greatly simplifying the design of the ballistic computer. It uses a vertically sliding breechblock reverse-engineered at great length from surviving examples of the Watervliet Arsenal-produced M256 120mm gun. While the current metallurgy and QA/QC is not sufficient to produce breech blocks capable of the 135,000psi of M256, we believe that with advances in electronically controlled machining, it is feasible. We are planning an exploratory expedition to the Watervleit Arsenal area to gain what prewar technical data we can, particularly on the M256 and M360 guns.

T123E7 is a 52-caliber 120-mm smoothbore gun with a vertically sliding breechblock, hydropneumatic recoil mechanism, and chrome-lined bore. It fires 120x570mm fixed ammunition using a cellulose-fiber combustible cartridge case with a metal base cap, reducing the weight of the cartridge case by some 30lb compared to a brass case (107lb for brass case M358 APC-T vs ~55lb for T494 APFSDS-T). Decreased AP projectile weight due to the usage of armor-piercing fin-stabilized discarding sabot ammunition further reduces the weight of the armor-piercing projectile by nearly half, from 50lb to 26lb.

Additional projectiles, such as HEP-FS-T, HE-FRAG-FT-T and HEAT-FS-T are under development, as are training projectiles.

The gun and mount are electrically driven in train and elevation via a geared drive and proportionally controlled motors derived from a mixture of naval fire control equipment and enlarged aircraft gun turrets. This has an added benefit of easing the development of an analog two-axis gun stabilization system. The fire control system is electromechanical and analog-electronic, and consists of [x] components: the gunner’s articulated periscope, the commander’s stereoscopic rangefinder, the electrical gun drive, and the gun computer. The gun computer is a miniaturized transistorized electromechanical/analog-electronic computer that incorporates ambient temperature, range as measured from the stereoscopic rangefinder, and the average rate of traverse of the gun over the past one to three seconds to apply lead, cant correction, and superelevation, and align the gun to the sights. When the firing switch is depressed, a set of microswitches waits to close the firing circuit until the sights are properly aligned, aiding in firing on the move or from a short halt. The gunner’s articulated periscope is a combination 1x-3x unity sight and 3-20x magnified sight, with coated lenses, reticle illumination, and compatibility with infra-red image intensifying night vision equipment. The rangefinder is mounted across the width of the turret.

There is a 7.62mm M240 machine gun mounted coaxially to the main gun, with 8,000 rounds of 7.62x51mm (2,000 ready).

There is a 7.62mm M240 machine gun provided for the loader mounted in a race-ring mount around his hatch with 2,000 rounds of 7.62x51mm (200 ready)

There is a .50 M2 machine gun provided for the commander on a ring mount around the commander’s cupola with 2,000 rounds of .50 ammunition (100 ready)

Provision is made for the storage of the crew’s individual weapons and field equipment, including four 5.56mm rifles and ammunition.

 

Mobility:

T44 uses a torsion-bar suspension, with six individually sprung road-wheels per track connected to double-acting bar-in-tube springs providing substantially improved suspension travel to the original single-acting suspension.

There are two powertrains currently proposed. The first, a prewar design Continental AVDS-1790-5B is a known quantity, an extremely reliable and widely used turbosupercharged diesel V-12 producing 810 horsepower at 2,400RPM. This, in combination with the CD-875-2 four-speed automatic transmission produces a maximum speed of 35 miles an hour on road, and the improved double-acting torsion bar suspension provides an increased rough-terrain speed of approximately 12 miles per hour, compared to nine miles an hour for the Medium Tank M4. This gives the vehicle a combat range of approximately 125 miles.

The second powertrain is derived from prewar work on gas turbines. It is a simple, reliable gas turbine of 65” length and 25” diameter that, due to manufacturing limitations, only produces about 1,000 horsepower. Similar prewar designs produced approximately 1,500 horsepower in ground use and 1,800 horsepower in aviation use, but due to manufacturing limitations and for safety reasons, the turbine is limited to 1,200hp SHP emergency power for ten minutes, and 1,000 horsepower maximum. This drives a CD-1250-1 crossdrive automatic five-speed transmission, resulting in a maximum road speed of 48 miles per hour and a rough-terrain speed of 22 miles per hour, although crew comfort is a significant concern and shock absorption is an issue at such speeds. This engine, with the associated APU, gives the vehicle a combat range of approximately 150 miles, as the reduced engine dimensions allowing increased fuel capacity.

 

In summary, the T44 medium tank meets all of the required design specifications:

• It is 90,000lb unloaded

• The fenders fold up to ensure a 129” maximum width (otherwise 135” width)

• The upper frontal plate is 3” thick sloped at 80 degrees from vertical, giving an effective line of sight thickness of 17”

• The side armor is 3” thick

• The power to weight ratio is at worst 16hp/ton (loaded, 810hp engine) and at best 19.6hp/ton

• The tank has a crew of four: Driver, TC, gunner, and commander.

• The primary armament, 120mm gun T123E7, is capable of firing both antiarmor and high explosive projectiles.

[ApplesauceBandit]

Not a submission

 

Didn't go hard on making this a serious submission this time around since I've got classes to worry about right now and a lot of those classes already have me doing stuff similar to some aspects of this (mostly the number crunching).

 

Just made this mostly for practice, though it's stuff that won't show up in the final model (hotkeys, cloning objects along a path, fancy details of the meshsmooth modifier, etc.).  The model itself isn't really in a finished state.  Turret is mostly placeholders still, hull still needs some more detail passes done to it.  I want to make some minor layout tweaks as well, mostly in regards to the turret's base and roof.  If this were to be serious, I would make myself a second turret that relies less on casting and would hopefully have a smaller frontal profile.  While I would like to eventually get this finished, that all depends on how lazy I end up.

 

Spoiler

 

Eyeballing elevation puts it at -12°/+25°

 

[Sturgeon]

PART FOUR OF FIVE

 

The Airmobile Armor Corps: A Retrospective of the "Sandy" Light Tank

 

by Cho Wilson

 

Armor anytime, anywhere - that's the unofficial motto of the Airmobile Armor Corps, a critical element of the CR Army's force projection capabilities in Western Central North America since the 2240s. The centerpieces of that force projection is the AAC's airmobile light tanks, the first of which was the M13 Sandy. Armed with an 85mm gun, yet small and light enough to drop out of cargo aircraft then under development, the Sandy light tank could be used to assault enemy positions from behind their own lines as part of coordinated attacks from both airborne and conventional forces of the CR Army.

 

 

A 5th Paratroop Infantry Battalion M13A4 Sandy on operations in Monument Valley, Deseret.

 

Development of the M13 Sandy began with a request for a new light tank to replace existing M6 Light Tanks, with an emphasis on the mobile, open desert fighting expected against Deseret. Responding to the request, the state-owned Armor Development Branch conducted a study on future light tank applications in light of the concurrent development of a new medium tank to replace the M6 Light in most combat roles. The report of the study identified the possibility of fielding a reconnaissance tank that could be carried by a cargo aircraft and dropped into the battlefield fully loaded, along with crew. Such a tank would need to be made predominantly out of aluminum to be light enough to be carried aloft, but could conceivably use the same 85mm main gun as the medium tanks then under development. With the promise of this capability in mind, the ADB began work on a new airmobile light tank under the codename "Sandy".

 

To meet the requirements for an airmobile vehicle, every element of the Sandy's design was optimized for the least possible weight while still giving acceptable structural integrity and room for weapons, engines, and other equipment. A cleft turret design was chosen for its minimum size and weight while allowing acceptable gun depression. The commander and gunner were both situated in the turret in steel armored "trash cans", but aside from that armor to the rest of the turret was limited to the cast aluminum construction necessary for structural integrity. Dissimilar heights of the "trash cans" gave the commander an all around view from 7 vision blocks and a periscope, and the gunner a more limited view from an identical arrangement of vision blocks and periscopes. The commander on the left was armed with an M2 .50 caliber machine gun operable from within his cupola, and the gunner on the right was armed with a 7.62mm M240 machine gun operable within his. A weldment of 10mm aluminum plates formed the body of the hull, mated to 20mm and 35mm aluminum glacis plates. Ten roadwheels set on swing arms - two of which on each side were doubled up on a single arm -  and suspended by coil springs. To reduce weight and improve durability in rocky country, rubber band tracks were used. Given that the weight of the tank was originally not to exceed 10 tons, band tracks were not considered a major risk.

 

 

A 1st Airborne Cavalry Regiment M13A4 Sandy on operations in the Western desert in Deseret.

 

The first XM13 Sandy tanks were constructed early in 2241, and went into testing that year. At the same time, studies were being conducted on a possible "heavy" Sandy variant for more regular fighting in Idaho and Deseret. This variant would be deployed via land and participate in more sustained operations than the previous variant. To facilitate this, a new three-person elliptical turret was designed which would contain not only the same 85mm gun, but also a human loader and the same coaxial 20mm cannon planned for the medium tank projects. As well, the elliptical turret would add protection against the primary tank guns of both California and Deseret, and it would also facilitate armament upgrades beyond what was possible with the cleft turret. Prior to production, this variant was designated XM13E6, and the cleft turret versions then under construction were designated XM13E4. The elliptical turret XM13E6 was powered by a 475 hp turbocharged water-cooled V6 diesel located in the front right hull, with a hydrokinetic transmission, while the lighter and more space-limited cleft turreted XM13E4 was powered by a smaller 305 hp turbocharged water-cooled V6 diesel and the same transmission. On both models, additional survivability was provided by the addition of large double doors at the rear of the hull for evacuation of the crew.

 

 

An M13A6 Sandy on operations in Deseret.

 

Initial testing of both the XM13E4 and XM13E6 Sandy tanks went well, and after relatively minor modifications from 2243-2244, both were recommended for production as the M13A4 and M13A6, respectively. However, at that time no cargo aircraft suitable for carrying the M13A4 had yet entered production, so production of that variant was withheld for over a year until the CS Air Force's C-12 transport aircraft entered service. 42 M13A6 tanks were first put into service with the 5th Armored Reconnaissance Squadron, 303rd Cavalry Regiment in 2245, which was deployed to Arco in the Idaho territory. The first M13A4 Sandys was deployed with the 1st Airmobile Cavalry Regiment and the 5th Paratroop Infantry Battalion starting in 2247, supported by the CR Air Force 5th Air Wing, which was receiving its first C-12 transport aircraft at the same time. 

 

 

An M13A6 Sandy light tank provides fire support to CR Army troops during operations in Utah.

 

In 2249, M13A6 Sandy tanks of the 303rd Cavalry Regiment fired some of the first Cascadian shots of the Idaho War, demonstrating the mobility and firepower of type against relatively lightly armed and armored Deseret armor. Airmobile M13A4 Sandy tanks, both as part of the 1st Airmobile Cavalry Regiment and supporting infantry as part of the 5th Paratroop Infantry Battalion, successfully assaulted Deseret positions during the Idaho War. Notably, it was M13A6 Sandy tanks that held the line against Deseret Seth light tanks during the Battle of Burley in 2250. The M13A4 also served in more limited numbers during the First and Second California Wars in the airmobile role, but against heavier Californian tanks the M13A6 was seen as too vulnerable against Californian 89mm anti-tank weapons to supplement the M15 Roach medium and M12 Donward heavy tanks being employed in that theater.

 

The M13A6 Sandy was replaced in 2268 by the M26 Fire Support Vehicle, but the M13A4 served well into the 2270s with the Airmobile Armored Cavalry due to its light weight and airdroppable capability. It was finally retired in 2278, and replaced with the M40 Lightweight Expeditionary Tank.

 

 

M13A4 Sandy

 

 

GENERAL CHARACTERISTICS

Crew: 3

Length (gun forward): 5.88 m

Length (w/o gun): 5.10 m

Gun Overhang (gun forward): 0.78 m

Width: 3.22 m

Height (to top of gun): 1.42 m

Height (to commander's periscope): 2.13 m

Ground Clearance: 0.71 m

Turret Ring Diameter (inside): 85 in

Weight, Curb: 12,949 kg

Weight, Gross: 13,888 kg

Power to Weight Ratio (gross): 22.0 hp/t

Ground Pressure: 6.2 PSI

PROTECTION

Hull armor:

Upper glacis - 20mm at 5 degrees, 35mm at 35 degrees (aluminum)

Lower glacis - 35mm at 33.5 degrees (aluminum)

Side - 10mm all around (aluminum)

Turret armor

1" thick cupola walls (steel)

ARMAMENT

Primary: 85x640mmR XM38 L/50 Autoloaded Rifled Gun

    Traverse: Electrohydraulic and manual, 360 degrees

    Traverse Rate (max): 24 d/s, 15 seconds/360 degrees

    Elevation: Electrohydraulic and manual, +25/-5 degrees

    Elevation Rate: 15 d/s

    Firing Rate (max): 8 rounds/min

    Stabilizer: None

Secondary:

    (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

    34 rounds 85x640mmR
    300 rounds 20x140mm
    500 rounds .50 caliber
    2,000 rounds 7.62mm (loader)
    210 rounds 9mm
    18 smoke grenades

FIRE CONTROL AND VISION EQUIPMENT

Primary Weapon:

    Direct: Gunner's Primary Sight
        Gunner's Auxiliary Sight

    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

    
POWERPLANT

305 hp turbocharged water-cooled V6 diesel, 7 L displacement, cross-
drive hydrokinetic transmission

 

 

M13A6 Sandy

 

 

GENERAL CHARACTERISTICS

Crew: 4

Length (gun forward): 6.02 m

Length (w/o gun): 5.10 m

Gun Overhang (gun forward): 0.78 m

Width: 3.22 m

Height (to roof): 2.41 m

Height (to 7.62 MG): 2.75 m

Ground Clearance: 0.92 m

Turret Ring Diameter (inside): 85 in

Weight, Curb: 17,692 kg

Weight, Gross: 18,631 kg

Power to Weight Ratio (gross): 25.5 hp/t

Ground Pressure: 8.3 PSI

PROTECTION

Hull armor:

Upper glacis - 20mm at 5 degrees, 35mm at 35 degrees (aluminum)

Lower glacis - 35mm at 33.5 degrees (aluminum)

Side - 10mm all around (aluminum)

Turret armor

0 degree: 211mm at base to 248mm at top of gun shield, 244mm at roof

15 degrees: 209mm at base to 245mm at top of gun shield, 241mm at roof

30 degrees: 201mm at base to 238mm at top of gun shield, 234mm at roof

45 degrees: 190mm at base to 226mm at top of gun shield, 221mm at roof

60 degrees: 174mm at base to 210mm at top of gun shield, 205mm at roof

ARMAMENT

Primary: 85x640mmR XM38 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/-5 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

    34 rounds 85x640mmR
    300 rounds 20x140mm
    500 rounds .50 caliber
    3,000 rounds 7.62mm (coaxial)
    2,000 rounds 7.62mm (loader)
    210 rounds 9mm
    18 smoke grenades

FIRE CONTROL AND VISION EQUIPMENT

Primary Weapon:

    Direct: Gunner's Primary Sight
        Gunner's Auxiliary Sight

    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

475 hp turbocharged water-cooled V6 diesel, 9 L displacement, cross-
drive hydrokinetic transmission

[Sturgeon]

Some stat sheets for weapons:

 

20mm Gun XM151

20x140mm caliber autocannon. Fires a mix of APDS and HE-I against both
hard and soft targets.

APDS: 3,800 ft/s muzzle velocity, 0.221 lb projectile, 60mm RHA
penetration at 1,500 m

HE-I: 3,450 ft/s muzzle velocity, 0.265 lb projectile

 

 

85mm Gun XM34

Hand-loaded 85mm high velocity anti-tank cannon.

20lb APCBC shot at 3,000 ft/s

5.3in (135 mm) penetration at 2,000 yd on 20deg obliquity plate

165mm at 70 degrees at 100 m

159mm at 70 degrees at 500 m

152mm at 70 degrees at 1000 m

144mm at 70 degrees at 1500 m

135mm at 70 degrees at 2000 m

11.4lb APCR shot at 3,840 ft/s

9.5in (241 mm) penetration at 2,000 yd on 20deg obliquity plate

303mm at 70 degrees at 100 m

293mm at 70 degrees at 500 m

266mm at 70 degrees at 1000 m

238mm at 70 degrees at 1500 m

197mm at 70 degrees at 2000 m

 

 

85mm Gun XM38

Autoloaded self-contained 85mm high velocity anti-tank cannon.

20lb APCBC shot at 3,000 ft/s

5.3in (135 mm) penetration at 2,000 yd on 20deg obliquity plate

11.4lb APCR shot at 3,840 ft/s

9.5in (241 mm) penetration at 2,000 yd on 20deg obliquity plate

 

 

100mm Gun XM42

Hand-loaded 100mm high velocity anti-tank cannon.

35lb APCBC shot at 3,000 ft/s

250mm at 70 degrees at 100 m

240mm at 70 degrees at 500 m

209mm at 70 degrees at 1000 m

181mm at 70 degrees at 1500 m

150mm at 70 degrees at 2000 m

18.8lb APCR shot at 3,750 ft/s

286mm at 70 degrees at 100 m

273mm at 70 degrees at 500 m

252mm at 70 degrees at 1000 m

234mm at 70 degrees at 1500 m

220mm at 70 degrees at 2000 m

 

 

120mm Gun XM43

Hand-loaded 120mm high velocity anti-tank cannon.

40lb APCBC shot at 2,800 ft/s

14.5lb APCR shot at 4,200 ft/s

 

 

152mm Gun XM59

Loader-assisted or autoloaded 152mm high velocity anti-tank cannon
firing two-piece ammunition.

95lb APCBC shot at 2,953 ft/s

10.5in (267 mm) penetration at 2,000 yd on 20 deg obliquity plate

330mm at 70 degrees at 100 m

303mm at 70 degrees at 500 m

278mm at 70 degrees at 1000 m

274mm at 70 degrees at 1500 m

267mm at 70 degrees at 2000 m

7 kg (11 kg projectile) APFSDS at 5,380 ft/s

~700mm-670mm from 0-2000 m

 

 

 

 

85x640R, 100x685R (no projectile), 120x640R, 152x923R (two piece, shown together).

 

[Jeeps_Guns_Tanks]

We're still short a few of the Mutant Hooker and Synthetic blow "proposals", and there has not been one trip to a strip club!

[Toxn]

3 hours ago, Jeeps_Guns_Tanks said:

We're still short a few of the Mutant Hooker and Synthetic blow "proposals", and there has not been one trip to a strip club!

Hang on 5 minutes. I'm already working on one.

[Jeeps_Guns_Tanks]

8 minutes ago, Toxn said:

Hang on 5 minutes. I'm already working on one.

 

 

Better hurry, I hear one of your competitors is trying to cornering the market on the ThreeT Hookers, and Another all the FourTsheep!

[Toxn]

34 minutes ago, Jeeps_Guns_Tanks said:

 

 

Better hurry, I hear one of your competitors is trying to cornering the market on the ThreeT Hookers, and Another all the FourTsheep!

I'm trying to make something crazier than the M3 Lee and failing 

[Jeeps_Guns_Tanks]

17 minutes ago, Toxn said:

I'm trying to make something crazier than the M3 Lee and failing 

 

 

M3 75s on both sides!

[Toxn]

2 minutes ago, Jeeps_Guns_Tanks said:

 

 

M3 75s on both sides!

Already done - it just looks like a fat lee. I've also put skulls and spikes on, which just makes it look like a 40K chaos marines vismod.

[Jeeps_Guns_Tanks]

Just now, Toxn said:

Already done - it just looks like a fat lee. I've also put skulls and spikes on, which just makes it look like a 40K chaos marines vismod.

 

Throw a RAM turret on it. 

[Toxn]

4 minutes ago, Jeeps_Guns_Tanks said:

 

Throw a RAM turret on it. 

I have a better idea, but it will take a bit of work.

 

I'll hit it over lunch and post the results.

[Collimatrix]

Judges, @Zyklon @Jeeps_Guns_Tanks @LoooSeR , What do you say to a 48 hour extension?  I am not asking for the sake of my design, which is silly:

 

 

But because it seems like @ApplesauceBandit, @A. T. Mahan and maybe @Lord_James could use the time of the weekend to polish up their submissions.

[Jeeps_Guns_Tanks]

18 minutes ago, Collimatrix said:

Judges, @Zyklon @Jeeps_Guns_Tanks @LoooSeR , What do you say to a 48 hour extension?  I am not asking for the sake of my design, which is silly:

 

 

But because it seems like @ApplesauceBandit, @A. T. Mahan and maybe @Lord_James could use the time of the weekend to polish up their submissions.

If everyone is cool with it, its cool with me.

[Toxn]

Best oscillating turret...

[Zyklon]

1 hour ago, Collimatrix said:

Judges, @Zyklon @Jeeps_Guns_Tanks @LoooSeR , What do you say to a 48 hour extension?  I am not asking for the sake of my design, which is silly:

 

 

But because it seems like @ApplesauceBandit, @A. T. Mahan and maybe @Lord_James could use the time of the weekend to polish up their submissions.

 

I don´t really have a problem with that, and i don´t think any of the other judges has a problem with that either.

[Sturgeon]

I approve of a three-day extension, also, or even longer if necessary. It would mean I could enjoy more of my girlfriend's weekend.

[LoooSeR]

2 hours ago, Collimatrix said:

Judges, @Zyklon @Jeeps_Guns_Tanks @LoooSeR , What do you say to a 48 hour extension?  I am not asking for the sake of my design, which is silly:

/.ZE DEUTCHE PANZER STRONK./

But because it seems like @ApplesauceBandit, @A. T. Mahan and maybe @Lord_James could use the time of the weekend to polish up their submissions.

I agree.

 

1 hour ago, Jeeps_Guns_Tanks said:

If everyone is cool with it, its cool with me.

 

53 minutes ago, Zyklon said:

I don´t really have a problem with that, and i don´t think any of the other judges has a problem with that either.

 

We extending this competition until September 33rd. 

[Sturgeon]

@ApplesauceBandit, @A. T. Mahan, @Lord_James, do we think a Wednesday deadline is enough time? I'm happy to recommend extending it further.

[ApplesauceBandit]

47 minutes ago, Sturgeon said:

@ApplesauceBandit, @A. T. Mahan, @Lord_James, do we think a Wednesday deadline is enough time? I'm happy to recommend extending it further.

I'm out of town for the weekend, but that should hopefully be enough for me to at least pretty up the turret and all that.  My tank has all been made in 3ds max as well, so nothing has any actual measurements tied to it at the moment.  I suppose I could always make a rough mockup of it in solidworks to solve that, I'll look into it when I get the chance.

[Lord_James]

I haven’t worked on my design at all since I posted a week ago. 

[A. T. Mahan]

@Sturgeon having it due Wednesday would be great!

[LoooSeR]

2 hours ago, A. T. Mahan said:

@Sturgeon having it due Wednesday would be great!

We already decided to extend time limit, so you have 3 more days.