Competition: Tank Design 2239

[Toxn]

I think we're almost there:

40t version

 

25t version

[Sturgeon]

I'm pretty impressed by that, @Toxn.

 

Small suggestion: Give the turret an undercut and/or some additional curvature, and move it up a bit. If you have a pop-up-swing-out driver's hatch, should save you some hull volume.

[N-L-M]

This design keeps evolving in a familiar direction...

I like the reversed 4th swing arm, very nice detail.

[Toxn]

1 hour ago, Sturgeon said:

I'm pretty impressed by that, @Toxn.

 

Small suggestion: Give the turret an undercut and/or some additional curvature, and move it up a bit. If you have a pop-up-swing-out driver's hatch, should save you some hull volume.

I'm probably going to curve it a bit more if I decide to go for a cast-only version of the turret (the current one can be either welded or cast) but I think that options for undercuts will be limited.

It's only going to save something like 25cm anyway, so I'm not too worried.

 

Edit: rounding the turret and making a small undercut saved 10cm. It looks prettier, though.

[Toxn]

@LostCosmonaut Quick formalities question:

 

Should I edit my original post to finalise it, or make a new post and mark it as finalised? 

[Toxn]

8 hours ago, N-L-M said:

This design keeps evolving in a familiar direction...

I like the reversed 4th swing arm, very nice detail.

Thanks. I think it gives the vehicle a nice look as well.

[LostCosmonaut]

46 minutes ago, Toxn said:

@LostCosmonaut Quick formalities question:

 

Should I edit my original post to finalise it, or make a new post and mark it as finalised? 

 

Whichever one is easier for you is fine. I'd like it if you left your old designs up somewhere, though (been interesting to see the evolution of the concepts).

[Toxn]

4 minutes ago, LostCosmonaut said:

 

Whichever one is easier for you is fine. I'd like it if you left your old designs up somewhere, though (been interesting to see the evolution of the concepts).

New post it is.

[Toxn]

(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

[Sturgeon]

M15E8 Roach advanced MBT:

 

 

Closing in on the time when I'll be posting finalized writeups. I have, I think, six tanks to submit.

[Toxn]

16 minutes ago, Sturgeon said:

M15E8 Roach advanced MBT:

 

 

Closing in on the time when I'll be posting finalized writeups. I have, I think, six tanks to submit.

Talk about hedging your bets 

[Sturgeon]

XM12E1 Donward - 85mm gun

 

XM12E2 Donward - 100mm gun

 

XM12E3 Donward - 120mm gun

 

XM12E4 Donward - 152mm gun

 

XM13E4 Sandy - 85mm gun and cleft turret

XM13E6 Sandy - 85mm gun and elliptical turret

 

XM15E2 Roach - 100mm gun and no addon armor or stereo RF

 

XM15E4 Roach - 100mm gun and spaced armor array on turret, side skirts

 

XM15E5 Roach - 100mm gun and [classified] armor array on turret and hull, side skirts

 

XM15E7 Roach - 152mm gun and [classified] armor array on turret and hull, side skirts

 

XM15E8 Roach - 152mm gun and new [classified] turret, [classified] armor array on hull, side skirts

 

-for my own reference

[N-L-M]

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.

[N-L-M]

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

[Sturgeon]

10 hours ago, N-L-M said:

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.

 

I think Lost said something like X-4 type missiles were feasible, so presumably MCLOS is on the table. The question is just how much it would suck to have to manually guide a missile from your scout car against MBTs. And I mean, SS.11 missiles were plonked on just about everything, so.

[N-L-M]

30 minutes ago, Sturgeon said:

SS.11 missiles were plonked on just about everything, so.

SS.11 was indeed an inspiration. And it even has a SACLOS upgrade (Harpon) and a few other details I intend to borrow. But it too suffered from the major flaw in the control layout of first-gen ATGMs, which is why I haven't copied its aerodynamics.

Also friendly reminder that Azon, Fritz-X, Razon, and other WW2 guided bombs were also MCLOS. As previously stated, I will be exhaustively justifying the ability to build this system.

[Sturgeon]

Just now, N-L-M said:

SS.11 was indeed an inspiration. And it even has a SACLOS upgrade (Harpon) and a few other details I intend to borrow. But it too suffered from the major flaw in the control layout of first-gen ATGMs, which is why I haven't copied its aerodynamics.

Also friendly reminder that Azon, Fritz-X, Razon, and other WW2 guided bombs were also MCLOS. As previously stated, I will be exhaustively justifying the ability to build this system.

 

Like I said, I think MCLOS is OK as per the terms of the OP.

[Toxn]

I must confess that I almost went with a missile-related pet idea of mine* as well. But then I figured that I'd had enough visits from the good idea fairy for one competition.

 

 

 

* A land torpedo, basically. No guidance, it's just designed to fly very fast and in a straight line. Which eases the control requirements to stuff that was available in the 40s, and turns aiming into putting the sight on target and pulling the trigger.

[Toxn]

1 hour ago, N-L-M said:

SS.11 was indeed an inspiration. And it even has a SACLOS upgrade (Harpon) and a few other details I intend to borrow. But it too suffered from the major flaw in the control layout of first-gen ATGMs, which is why I haven't copied its aerodynamics.

Also friendly reminder that Azon, Fritz-X, Razon, and other WW2 guided bombs were also MCLOS. As previously stated, I will be exhaustively justifying the ability to build this system.

I'm looking forward to it.

[Collimatrix]

16 hours ago, N-L-M said:

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.

 

Those are some really small fins relative to historical MCLOS!

 

 

Also, you need this shirt.

[Toxn]

16 hours ago, N-L-M said:

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.

Looking at the picture again: are those control surfaces on the fins?

 

Because from what I understand about early atgms (which isn't all that much tbh) most of them went with vectoring the thrust instead because of control jitter/proportional response issues. SS-11 and AT-3 did this, for instance.

[Toxn]

10 minutes ago, Collimatrix said:

 

Those are some really small fins relative to historical MCLOS!

 

 

Also, you need this shirt.

That shirt was way too clever for me.

[N-L-M]

1 minute ago, Toxn said:

Looking at the picture again: are those control surfaces on the fins?

 

Because from what I understand about early atgms (which isn't all that much tbh) most of them went with vectoring the thrust instead because of control jitter/proportional response issues. SS-11 and AT-3 did this, for instance.

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.

 

[Toxn]

1 minute ago, N-L-M said:

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.

 

You going for proportional control?

[N-L-M]

PID per Ziegler-Nichols from operator command to servo command, servos on open loop.
Where, of course, the full deflection of the operator's joystick would translate to full deflection of control surfaces at launch, decreasing with flight time to allow better accuracy.
Space in the turret has been cleared for the SACLOS conscan device, when such a thing will be ready.
Also, there's a damned good reason I'm not going with TVC.