Californium 2250: FINAL JUDGMENT

[Collimatrix]

Restricted: for Operating Thetan Eyes Only

 

By order of Her Gracious and Serene Majesty Queen Diane Feinstein the VIII

 

The Dianetic People’s Republic of California

 

Anno Domini 2256

 

SUBJ: New tank contract awards

 

OK, praise be to Hubbard the last prophet and Tom Cruise, his true successor and all that shit that the upper party members will want to see in an official document.  You want to know Hubbard's honest truth?  This entire heavy tank development program has been one big conga line of fuckups since day one.  There's a reason that we're still out there tanking with DF-1s, and that reason is the current government of the DPRC.  Their insane commitment to Scientology has made a mockery of every attempt to maintain a stable and sensible war economy.  Until the ruling regime is liquidated and replaced with a government based on the scientific principles of Euphoric Atheism, the disasters will only compound.

The military tribunal for tank procurement has selected Hakika si Kundi la Dudes Nyeupe (HKDN) design bureau's Object 426 "Stumpy" as the basis for the DPRC's next main battle tank.  In order to facilitate crew competence and speed the de-bugging phase on the way to IOC, the first several dozen vehicles will be sent to a special test unit.  This test unit will be kept separated from the rest of the DPRC military's logistical system and chain of command.  In order to prevent sabotage of the program by the circulation of false reports, the entire test unit and its activities will be kept secret, even from the members of the civilian government.  In order to prevent any theft of the technical secrets of the vehicles, the test unit will be given the authority to shut down all communications and transport networks in the DPRC at its sole discretion.
 

Congratulations, @Toxn

[Sturgeon]

Comrade @Collimatrix has been liquidated for his insults to the glorious Dianetic People's Republic of California.

[Collimatrix]

Detailed judge's remarks incoming

[Sturgeon]

Sturgeon's remarks:

 

So, this competition was a mixed bag in terms of the administrative side of it. The initial solicitation was probably a bit too technically demanding for most people who would be otherwise interested, and then once we did get submissions that were complete the judges had a difficult time coordinating with each other to create a decision. Also, in many cases the specifications were too complex to be easily evaluated by some of the judges, and therefore the decision was sort of "parted" out with different aspects being determined by different judges. This did not have a major effect on the competition, as it turned out there were only two complete entries and all judges' preferences lined up the same way. Team Mahan/Moo/OSC/CK and Toxn's submissions were very close, but Toxn's submission was slightly more refined and also fit with the spirit of the initial solicitation a little better. I should emphasize that all judges agreed both entries were very close. The minor flaws of Team M/M/O/CK's submission with regard to armor layout and crew accessibility didn't necessarily represent intrinsic problems with the design, but we felt were more the result of the team falling into pit traps that were unintentional side effects of the very complex initial solicitation.

 

Both complete submissions were very impressive and both should be commended. In particular, the team submission was a massive improvement over their previous entry into the Cascadian competition. Overall, we agreed Toxn's was slightly better, but we are really pleased with the effort that went into both submissions. Additionally, we were happy with the degree to which other people participated, even if their submissions did not get finished. We feel that many people were discouraged from finishing due to how technically demanding the initial solicitation was.

I think this contest showed that our process for running these events needs a little work. The forum leadership is discussing how to improve competitions for the future, make them more accessible and fun.
 

[Collimatrix]

Judges' remarks:

 

Unfinished Designs:

 

Spoiler

Kal:  I like the "Gillette NERA" armor array.  This sort of array would be very good for a frontal turret array because it would increase in effectiveness faster than LOS thickness when the tank is in a hull-down position.

I am not so sure about the idea of mini Obus-G projectiles.  At the very least, they would be expensive to mass-produce.  However, the idea of a coaxial autocannon as a way to suppress ATGM teams has merit.  Per the competition description, all the ATGM threats are some sort of line-of-sight command guidance, or they are potentially beam-riding.  This means that the missile requires a live operator to guide the missile, and that from the tank's point of view this operator is more or less directly behind the missile.  So, shooting in the direction of incoming missiles has a decent chance of suppressing or killing ATGM crews, at least within the range of the autocannon.

 

I have some doubts about the ability of the main armament to depress, given that there is an autocannon on top of it taking up space near the ceiling.  I also have grave misgivings about the steering mechanism.  It sounds like clutch-and-brake, which has been used before on vehicles of this weight class, but it really isn't a good idea.

 

Lord_James:  Interesting, asymmetric hull design.  The idea of using spaced armor as a radiator ventilator was very interesting, and showed attention to details of armoring a front-engine design that often go overlooked, even in real-world designs.  I am curious what the reinforcement thickening at the back of the hull was for.  It sounds like he was intending to arm the tank with an absolutely gargantuan gun, and this was forcing some interesting design considerations.

 

Xoon:  I really liked this design, overall!  The overall crew visibility looks excellent, and the frontal armor looks very robust.  The design of the suspension and transmission was very detailed, which makes sense because an S-tank like design will need an unusual suspension and transmission in order to aim the main armament.

 

The concept of an all-hydraulic tank is interesting, and the note that power tools can be run off of the main engine is clearly a nod to maintainability.  The idea of using hydraulic accumulators in order to dampen out spikes in the drivetrain is also interesting, and it would also lead to shorter times when performing berm drills.  Since the tank needs to aim the entire hull to bring the weapon to bear, which will inevitably be somewhat slower than aiming a turret, any reduction in engagement times is welcome.

FCS sounds broadly similar to the S-tank.

 

The idea of a rigidly-mounted 200mm high-velocity cannon is probably a really, really bad one.  But it is hilarious.

Main survivability concerns would be all the high-pressure hydraulic and hot radiator fluid lines running inside the hull.  Thick armor and the well-shaped, domed belly plate would mitigate these concerns somewhat.

 

Object 138:

 

Spoiler

In general, this tank was a mix of some features the judges really liked, and some they really, really disliked.  There were a number of minor problems that could likely be ameliorated during a prototype development program, as well as a number of issues that the judges felt would require extensive re-design.

 

Tank Interior Automotive and Systems Layout: 

 

The judges had the most complaints about the internal layout of the vehicle. 

 

The autoloader design is questionable in several ways.  The access to the autoloader is not ideal.  The autoloader can be filled either through the driver's position with the shorter rounds, but necessarily needs to be reloaded through the fighting compartment to re-fill the longer rounds.  From the inside of the fighting compartment there is no aperture that the crew can access the autoloader from except the aperture behind the spanning tray, since the spall shield gets in the way from all other positions.  Therefore, the autoloader will need to be laboriously reloaded one round at a time by passing the rounds to the fighting compartment, or driver's position for the shorter rounds, advancing the autoloader one position, and putting the ammunition into the slot in the magazine.  This is no different, in terms of time and labor, than the procedure for loading up a T-72, but the notion that this arrangement would allow for particularly fast re-armament of the vehicle, as claimed in the final submission, is clearly incorrect.

 

The judges are dubious about the autoloader design being capable of handling both two piece and unitary ammunition.  It is not clear how the autoloader does this from the pictures shown.  An autoloader that can handle both types of ammunition is surely possible, but it would require special considerations in the design of the rammer, raiser, and other parts that are never elaborated upon.

 

The judges are generally unconvinced by the design of the powertrain.  The two main problems are the radiator design and the transmission design.  The specific power of the engine is believable; basically identical to the historical AVDS-1790, but the engine is a water-cooled design rather than an air-cooled one.  The judges felt that the overall package size of the engine was slightly optimistic, however.

The vehicle is described as having a T-55 style cooling system, which, given the dimensions of the engine bay was seen as somewhat optimistic.  The system is rejecting a lot more heat than the cooling system of the T-55, due both to the larger engine and the more complex transmission, and it is squeezed into the very margins of an already cramped engine bay.  More worrying is the degree to which the overhang of the turret bustle would interfere with the airflow into this cooling system.

 

The judges are utterly unconvinced that a "CD-1750 crossdrive-type eight-speed manual gearbox, mounted in VPK-3B powerpack, able to handle much greater power" would be able to fit in the space allocated.  Let's unpack that description a bit.  The Allison Crossdrive transmissions, first developed for the US post-WWII heavy tank program, would go on to faithfully propel every tank from the M46 to the M60, as well as the Israeli Sho't Kal, which is more or less an M60 that's wearing a Centurion's skin.  The Crossdrive is a fairly bulky transmission, compared to the simpler Soviet tank transmission, but it does economize on space by using a small number of propulsive gear ratios, which it can get away with thanks to a hydraulic torque converter, and by the fact that it uses planetary gearsets, which is very compact relative to the power they can handle.

 

The cross-sections of the Object 138 that the judges were shown when they asked for clarification show a very compact, essentially cylindrical package reminiscent of the transmission design of the T-72.  The transmission of the T-72 consists of two planetary "half transmissions" which are just about the smallest practical way to power an armored fighting vehicle in that weight class, with the trade-off being that they limit the tank's maneuverability.

The judges find it plausible that a transmission that combines the mechanical properties and design advantages of the Allison-style crossdrive could be combined with a cylindrical form factor.  But certainly not as described.  If the vehicle has eight speeds, then it is not economizing on gear count (and wear) by using a hydraulic torque converter.  And exactly what is meant by a "manual gearbox" is unclear, but generally speaking this phrase means that the vehicle uses a layshaft-style gearbox rather than a planetary gearbox (but this is just a convention; there are planetary gearsets that are manually adjusted and layshaft gearsets that are automatically adjusted).  So... if it doesn't have a torque converter and it doesn't use planetary gears, how exactly is this transmission similar to an Allison crossdrive?  The only thing the judges could think of that this could mean is that the vehicle uses a triple-differential steering system, the same as the Allison.

There are a number of historical tanks which have used layshaft gearboxes with no hydraulic components and triple differential steering.  The Tiger and Churchill both come to mind.  Given the size of the transmission that those tanks had, and that they were transmitting much less horsepower, the size and power of the transmission of the Object 138 seems wildly unrealistic to the judges.

 

The judges were not pleased with the decision to place the additional ammunition within the protected volume of the hull, next to the driver.

 

The rearmost road wheel swing arm is too close to the drive sprocket, and will hit it if it articulates within the specified range of motion.

 

The judges have doubts about powerpack swaps.  Even with the turret at the 4/8 o'clock position, it looks like a tight squeeze.

 

Ground pressure is slightly above threshold.

 

Crew Amenities:

 

This is a mixed bag.  Much like the early models of T-64, the design of the autoloader does not permit the driver to enter the fighting compartment.  This problem cannot be fixed without a complete re-design of the autoloader and its spall protection.  Furthermore, the driver's hatch is utterly unusable when the turret is pointing even somewhat forward because of the enormous overhang of the armor package over the hatch.  By the looks of it, the turret will need to be at least at the 4/8 o'clock position in order for the driver to get in and out.  While the People's Auditory Forces do appreciate ensuring that only the most staunchly patriotic soldiers will become drivers, by giving they/them no means to escape upwards when the turret is forwards, by giving they/them no way to escape into the fighting compartment whatsoever, and surrounding them with combustible ammunition, they also feel that increasing the mortality rate of the driver so much relative to the rest of the crew violates the principles of absolute equality of outcome that the DPRC stands for.  Sometimes rapid egress from a tank is necessary, e.g. when the tank is on fire.  Auditing teams found the relative lack of means of escape for the drivers to be borderline idolatrous; nobody should be forced to have that much faith in the armor protecting them.  The only protection they should instill that much faith in is the eternal word of L. Ron Hubbard.  On the other hand, locking the drivers in the tank during combat is certainly an effective means of preventing desertions through cowardice.

 

The design of the coaxial machine gun is puzzling.  It is described as a 7.62 PKT; so far so good.  But it is described as feeding from left to right and using a disintegrating link belt.  Normal PK machine guns feed from right to left from a non-disintegrating belt.  Fine; we'll suppose it's some sort of post-apocalyptic copy of a PK, and the engineers have made a few small tweaks.  That is certainly possible and reasonable.

But why place a gun that feeds left to right on the right side of the main armament?  This is almost the least convenient possible way to do things while still technically working.  The fact that the coax breech is on the right side of the gun tube means that the commander must be responsible for reloading the weapon.  But it also means that the ammunition belt feed starts on the side of the receiver of the machine gun opposite from the commander.  This, combined with the very forward position of the trunnions means that reloading the coaxial weapon is ergonomically difficult for the commander.  Furthermore, why is it the commander's job at all?  The commander is the overall decision-maker in the tank, and distracting xir with such non-command related busywork is detrimental to the commander's overall situational awareness.

Placing the coaxial machine gun on the commander's side of the gun tube would have made some sense if the other side of the gun tube were taken up with an articulated, backup gunsight.  But the detailed description of the fire control system makes it clear that there is no backup gun sight!

 

The lack of a backup gun sight is a serious oversight itself, but compounded with some other flaws of the FCS design, it becomes downright alarming.  The main armament has excellent depression, but the optical rangefinder, due to being a copy of the design from the T-64/T-72, cannot depress as far as the gun itself can.  Due to ballistic drop of the rounds, the rangefinder needs to be able to depress at least a few degrees more than the gun tube can in order to range targets for the gun to service at max depression.  This flaw was particularly puzzling to the judges.  If the team had simply copied the rangefinder design from the M48/M103/M60, this would be a complete non-issue and the rangefinder would work better due to longer base length.  Due to their location far aft of the lengthy armor packages, and without great elevation, the gunner's primary sight and the commander's sight both have limited depression angles, although not quite as badly as the rangefinder.

 

 

This cross-section clearly shows that the arc of the gun breech during elevation and depression intersects with the location of the arms of the commander and gunner.  While the judges were impressed by the design team's commitment to fighting ableism by finding roles suitable for amputees in the People Auditory Forces armored corps, it is suggested that making scores of new amputees is perhaps not the best way of accomplishing this goal.  In any case, if it does turn out to be the best way of accomplishing this goal, there are more expeditious ways of producing amputees readily available to the PAF.

 

On the debit side of things, the fire control system is absolutely excellent aside from the field of view issues mentioned earlier.  The idea of having a quasi-HUD to improve crew situational awareness is an excellent one, and actually an amenity that many 21st century historical vehicles largely lacked.  The gun-follows-sight digital fire control system is described in admirable detail and sounds excellent and effective.  The communications system was surprisingly well-described, and included good and useful features.  The inclusion of fire extinguishers and a boiling vessel is also thoughtful and propitious.

 

Firepower:

The firepower of the vehicle is generally excellent.  The gigantic, smoothbore 125mm gun is more than adequately lethal, and should have ample growth room if future trends in tank ammunition recapitulate those of the pre-war past.  No two ways about it, that is an extremely killy main gun. The pressure limits might be exceeded a bit with the full-caliber AP if no allowances are made in terms of propellant mass and grain design, but even if the pressures are dialed back a bit to maintain the piezometric limit, it should reasonably meet spec. 

 

The judges had some concerns that the main armament might be badly out of balance, especially with the mantlet, and require a large equilibrator.  This unbalance would also complicate the stabilization, but not to an intractable degree.  The judges were somewhat skeptical of the claims that the remote weapons station could be fully stabilized on the move.  It clearly elevates around an axis near the rear of the weapon, which would create an enormous moment of inertia and unbalance.  The judges were likewise skeptical of the gun-launched ramjet round.  The description did include performance charts, but none of the figures necessary to sanity-check the same like fuel fractions.  The judges are very skeptical about the use of SACLOS guidance on this weapon.  SACLOS guidance works well on subsonic ATGMs.  This weapon is moving an order of magnitude faster.  However, even without the ramjet round, the gun is quite satisfactorily killy.

 

Armor Layout:

The armor layout provides generous protection arcs measured on the horizontal.  Protection against elevated threats is less impressive.  The armor arrays are in general arranged in a very "brute force" way, and provide poor mass efficiency for the protected volume.  Preliminary estimates (based on approximate area and areal density of the arrays) by the judges suggest that the mass estimates provided by the team do not converge near the mass claimed for the vehicle, nor to a realistic vehicle armor mass fraction.

 

The design of the turret side arrays is puzzling.  The radio sounds bitching, but why was so much mass used to ensure it is protected?  The layout of the ERA is simply sloppy.  Why does it only cover the center of the turret roof?  Why is the ERA on the skirts vertically arranged when it is clearly designed to deal with threats originating along its long axis?  Why were the various optical instruments allowed to create so many holes in the ERA coverage?  Why do the extremely wide mud guards not have ERA on them?  Why is the hull so dependent on ERA for meeting reference threats?

 

On the plus side, the APS system described seems reasonable and effective.

 

 

Object 426:

 

Spoiler

In general, this tank was felt to be the more technically conservative design overall, but it featured some strange ideas that the judges weren't entirely sure they understood the rationale behind.  The problems the judges foresaw with this vehicle seemed largely to be soluble during a prototype development program.  Where the armor is thick it is outstanding.

 

Tank Interior Automotive and Systems Layout: 

 

The judges are entirely unclear what the advantage of placing the engine in the front but the drive sprockets in the rear is.  Even stranger, the radiators are in the rear!  This is convenient for the transmission, but it also means that there are hot coolant lines running through the hull of the vehicle.  On that subject, the idea of using the radiators as swing-out escape doors is patently insane.  The crew would need to crawl over the transmission, which is only about 90% efficient on the best of days and thus very hot, and then shove the also very hot radiators out of the way.  The judges are dubious that even with generous amounts of asbestos that this could be made to work.  But if the tank has cooled down, the swing-out radiators would be very handy service access doors.  So they are very useful, just probably not for the stated purpose.

Presumably the transaxle from the engine to the transmission runs along the left side of the vehicle, or possibly down the middle of the belly fuel tank so it doesn't get in the way.  The fact that the engine and transmission must be removed separately is a downside.

Fire control system overall seems reasonable, however, the judges have doubts about a radar rangefinder on a tank.  They've been tried, and have generally not worked well due to clutter.  The dish is fairly large, however, so perhaps the beam is narrow enough to avoid the worst of these problems.  The optional stereo rangefinder appears very doubtful.  Because it is at the back of the turret, it cannot depress very far before its view is occluded, and therefore is not useful when the tank is hull-down.  This is a secondary concern, since the tank appears to be primarily missile-armed and the stereo rangefinder is optional equipment.

 

The judges are not sure quite what is meant by the road wheel travel figures.  Either the road wheel travel is typical of an M48/M60 type tank, or it's actually slightly better than a Leo 1.  If it's the latter, then what's actually holding the tank back is the T-72 style transmission, since the vehicle has excellent specific power.  The T-72 style transmission is very compact (which is clear from his internal schematic), but does not give the best maneuverability.  Incidentally, if it is a T-72 style transmission it cannot also have a synchromesh, as T-72 style transmissions are entirely planetary.  We suspect that Toxn calculated the MMP incorrectly, and through no fault of his own.  One of the equations for MMP floating around on the internet is wrong and will give half of the actual value thanks to a missing coefficient.  If his vehicle's ground pressure were actually 114 kN/m² then it would have lower MMP than an M113!  The (more realistic) figure of 228 is still close to threshold.

 

The specific power of the engines is extremely conservative.  They have slightly more displacement than the reference AVDS-1790, but produce just over two thirds the power.  The DPRC will have no difficulty furnishing such motors.

 

The stowage of all the gun and missile ammo either in protected ammo racks or in exterior bins (at least in 85mm variant) is excellent practice.

 

Crew Amenities:

 

Crew comfort and ergonomics seems like a mixed bag, but mostly good.  The driver's position is well forward of the turret, so it appears that the driver can get in and out unless the bustle or gun tube is directly over them.  The driver also appears to have excellent access to the turret basket, since there is no ammunition on the turret basket floor or anything else in xir way.  It is unclear why the gunner's primary sight is directly in front of the commander's cupola.  Despite having a fuel tank and possibly driveshaft running under it, the turret interior is reasonably roomy.

 

Firepower:

 

Firepower seems reasonable assuming that the tank can be configured for the likely enemy beforehand.  The performance for the full-caliber 85mm AP round seems... optimistic.  It is somehow penetrating about 70mm more at 2km than the KwK 43 with only about 10% more projectile kinetic energy at the muzzle.  But perhaps with the ultra-hard steels and better shell aerodynamics unavailable to the Germans, this is possible.  The 85mm gun is just barely adequate to destroy the Norman with existing armor arrays.  With anything more advanced, the 145mm low-pressure gun will doubtless be required.  The tandem warhead 145mm round sounds extremely impressive.  The fact that such an upgrade is already planned is good future-proofing.  However, it seems that the revised ammo stowage for the 145mm version compromises the otherwise excellent safe and isolated ammunition stowage layout of the 85mm variant.  Furthermore, the low muzzle velocity, coupled with the somewhat dubious rangefinder installations would probably not lead to the quickest time-to-hit.

Both NUB and LUB ATGMs are capable of knocking out the Norman and then some with its existing armor packages.  However, the LUB is completely insane, and it does not seem likely that a mass-practical up-armor package could be developed that could stop its fantastic 1650mm tandem-charge penetration.  This weapon would also be useful for destroying large bunkers at a safe range, as the behind-armor effects of such a gigantic shaped charge would be considerable.  The judges are a little dubious about the resolution of a spin-scan based radar reticule tracker.  The IR unit, however, seems perfectly in line with what one would reasonably expect.  Judging by the graphics, it is significantly overbuilt.

 

Armor Layout:

The armor protection seems decent, but it is held back by a sentimental desire to protect the crew.  Hits to the left side of the hull from the frontal quarter seem very likely to disable the engine, as it it does not appear that there is a side armor array protecting the engine the way there is protecting the driver.  Ammunition is almost entirely isolated, at least in 85mm variant, and entirely in the turret.  The side skirt with the massive space seems like a good idea, however, it appears to be a monolithic piece of steel, and this would seriously hamper any sort of track repair and maintenance.  The turret ring seems a little exposed.

 

The roof armor protection is notably very good, and the turret roof will stop Cascadian ATGMs at two degrees over what the solicitors thought was a very optimistic angle.  The turret protection against plunging fire HEAT threats is very good, and should give this vehicle the edge in MOUT and counter-insurgency operations.  The hull protection against KE is noteworthy; the thickest parts of the hull can shrug off 105mm KE threats from ninety degrees off axis!  That's a greater protected arc than the turret enjoys!  PAF tactical theorists have been kept busy arguing about theoretical "hull up" fighting positions, which might possibly involve floating hills that could take advantage of this unusual armor layout.

 

A preliminary areal density analysis did suggest that this design converges to a weight close to what the design team predicted as well as to a realistic (but high!) armor mass fraction.

 

 

 

Bonus panel of the judges politely discussing the finer points of armored fighting vehicle powertrain design:

 

[Lord_James]

23 hours ago, Collimatrix said:

Judges' remarks:

 

Unfinished Designs:

 

  Hide contents

 

Lord_James:  Interesting, asymmetric hull design.  The idea of using spaced armor as a radiator ventilator was very interesting, and showed attention to details of armoring a front-engine design that often go overlooked, even in real-world designs.  I am curious what the reinforcement thickening at the back of the hull was for.  It sounds like he was intending to arm the tank with an absolutely gargantuan gun, and this was forcing some interesting design considerations.

 

 

Yeah, the 6” naval gun was causing me some problems, especially when trying to comfortably fit crew in the turret (I actually had no problems with ammo storage, with my hull being so tall; like 56 such shells in 2 ammo racks, at last calculation); would probably make the turret unmanned / low profile if I were to redo this. 

 

I was in the middle of making a 140mm gun, with a breach and trunnion similar to the M256, and basic ammo when my Calculus 2 summer class started; I planned on having all the major design work and arrangements set up, so I could just refine it with my spare time, but life seems to have had other plans. 

 

I agree, air intakes and exhausts are a big deal on front mounted engines, and the first thing I thought of to protect them was to use a slatted, spaced armor array at a high angle. I also calculated that any hits along the frontal arc, up to 10* elevation, would also have to pass through one of the special armor blocks around the intake to penetrate. The hardest part was actually exhaust because I refused to have it close to the intake, and was unsatisfied with having to run it through the floor. 

 

Thanks for the feedback, will try to do better next time  

 

 

 

I definitely like Xoon’s design, too (and it would have gotten my vote, if I were a judge). I have a strange allure towards exotic / unique vehicle designs, like the ELKE and it’s elevating gun, or Object 490. 

[Toxn]

On ‎9‎/‎7‎/‎2019 at 3:18 AM, Collimatrix said:

Restricted: for Operating Thetan Eyes Only

 

By order of Her Gracious and Serene Majesty Queen Diane Feinstein the VIII

 

The Dianetic People’s Republic of California

 

Anno Domini 2256

 

SUBJ: New tank contract awards

 

OK, praise be to Hubbard the last prophet and Tom Cruise, his true successor and all that shit that the upper party members will want to see in an official document.  You want to know Hubbard's honest truth?  This entire heavy tank development program has been one big conga line of fuckups since day one.  There's a reason that we're still out there tanking with DF-1s, and that reason is the current government of the DPRC.  Their insane commitment to Scientology has made a mockery of every attempt to maintain a stable and sensible war economy.  Until the ruling regime is liquidated and replaced with a government based on the scientific principles of Euphoric Atheism, the disasters will only compound.

The military tribunal for tank procurement has selected Hakika si Kundi la Dudes Nyeupe (HKDN) design bureau's Object 426 "Stumpy" as the basis for the DPRC's next main battle tank.  In order to facilitate crew competence and speed the de-bugging phase on the way to IOC, the first several dozen vehicles will be sent to a special test unit.  This test unit will be kept separated from the rest of the DPRC military's logistical system and chain of command.  In order to prevent sabotage of the program by the circulation of false reports, the entire test unit and its activities will be kept secret, even from the members of the civilian government.  In order to prevent any theft of the technical secrets of the vehicles, the test unit will be given the authority to shut down all communications and transport networks in the DPRC at its sole discretion.
 

Congratulations, @Toxn

So I'm late to this party, but thank you to the judges for selecting me.

I think this was the most technically challenging competition we've had so far, so I'm glad my design was able to solve at least some of the issues presented. 

 

Edit: I also wanted to say thank you to the organisers (especially @N-L-M) who helped make this possible. There's at least as much work going on in the background as gets put into making the submissions themselves, and so I'm very grateful to the folk who slogged through on this so that I could have fun designing imaginary tanks.

[Toxn]

On ‎9‎/‎7‎/‎2019 at 4:00 PM, Collimatrix said:

Object 426:

 

  Hide contents

In general, this tank was felt to be the more technically conservative design overall, but it featured some strange ideas that the judges weren't entirely sure they understood the rationale behind. 

 

Some of the rationale was honestly just to avoid making a beefed-up T-72 (which is more or less what one of my preliminary submissions ended up being). Most of the rest of the design decisions (for instance - the front engine setup) were dictated by the need to provide enough armour to cover the reference threats while not going into unrealistic mass fraction territory. I ended up spending an inordinate amount of time optimising armour arrays and trying to come up with novel ways to avoid having to spend more weight on armour. In the end, my tank had dimensions comparable to a (shorter, wider)T-72, while still weighing significantly more - a medium tank with the mass of a heavy tank!

 

The problems the judges foresaw with this vehicle seemed largely to be soluble during a prototype development program.  Where the armor is thick it is outstanding.

 

Tank Interior Automotive and Systems Layout: 

 

The judges are entirely unclear what the advantage of placing the engine in the front but the drive sprockets in the rear is. 

 

The idea was that your engines could act as armour while still allowing you to drive away if one got taken out. Putting the transmission in front would mean that any hits there would invariably stop the vehicle dead. Perhaps not the best trade-off, but I thought the idea was interesting.

 

Even stranger, the radiators are in the rear!  This is convenient for the transmission, but it also means that there are hot coolant lines running through the hull of the vehicle.  On that subject, the idea of using the radiators as swing-out escape doors is patently insane.  The crew would need to crawl over the transmission, which is only about 90% efficient on the best of days and thus very hot, and then shove the also very hot radiators out of the way.  The judges are dubious that even with generous amounts of asbestos that this could be made to work.  But if the tank has cooled down, the swing-out radiators would be very handy service access doors.  So they are very useful, just probably not for the stated purpose.

 

Yeah, I flat-out didn't think that one through too well.

Presumably the transaxle from the engine to the transmission runs along the left side of the vehicle, or possibly down the middle of the belly fuel tank so it doesn't get in the way.  The fact that the engine and transmission must be removed separately is a downside.

 

The transaxle and radiator pipes are supposed to run through an armoured tunnel on the hull floor between two fuel tanks.

Fire control system overall seems reasonable, however, the judges have doubts about a radar rangefinder on a tank.  They've been tried, and have generally not worked well due to clutter.  The dish is fairly large, however, so perhaps the beam is narrow enough to avoid the worst of these problems. 

 

In theory the dish size and design (which is based on the information for the SCR-584 plus some assumptions about the smaller dish size) should allow you to accurately rangefind a 2.5m target out to 2-odd kilometres. In reality you'd be lucky to find anything out in the open like that, so it's probably going to be a feature for selling the idea to certain supreme leaders rather than a useful addition to the tank's capabilities.

 

The optional stereo rangefinder appears very doubtful.  Because it is at the back of the turret, it cannot depress very far before its view is occluded, and therefore is not useful when the tank is hull-down.  This is a secondary concern, since the tank appears to be primarily missile-armed and the stereo rangefinder is optional equipment.

 

The poor commander also has to turn around to use it.

 

The judges are not sure quite what is meant by the road wheel travel figures.  Either the road wheel travel is typical of an M48/M60 type tank, or it's actually slightly better than a Leo 1. 

 

The road wheel travel was taken from information about the T-72, a lot of which is unfortunately inaccurate.

 

If it's the latter, then what's actually holding the tank back is the T-72 style transmission, since the vehicle has excellent specific power.  The T-72 style transmission is very compact (which is clear from his internal schematic), but does not give the best maneuverability.  Incidentally, if it is a T-72 style transmission it cannot also have a synchromesh, as T-72 style transmissions are entirely planetary. 

 

This is also a result of inaccurate information, sadly. Some sources list the T-72 as having synchromesh, and I'm not knowledgeable enough about transmissions to spot the error.

 

We suspect that Toxn calculated the MMP incorrectly, and through no fault of his own.  One of the equations for MMP floating around on the internet is wrong and will give half of the actual value thanks to a missing coefficient.  If his vehicle's ground pressure were actually 114 kN/m² then it would have lower MMP than an M113!  The (more realistic) figure of 228 is still close to threshold.

 

The specific power of the engines is extremely conservative.  They have slightly more displacement than the reference AVDS-1790, but produce just over two thirds the power.  The DPRC will have no difficulty furnishing such motors.

 

The stowage of all the gun and missile ammo either in protected ammo racks or in exterior bins (at least in 85mm variant) is excellent practice.

 

Crew Amenities:

 

Crew comfort and ergonomics seems like a mixed bag, but mostly good.  The driver's position is well forward of the turret, so it appears that the driver can get in and out unless the bustle or gun tube is directly over them.  The driver also appears to have excellent access to the turret basket, since there is no ammunition on the turret basket floor or anything else in xir way.  It is unclear why the gunner's primary sight is directly in front of the commander's cupola. 

 

I'll have to check my notes, but the gunner's primary sight is the front-most one while the one just in front of the cupola is the commander's. The commander is sitting more or less with his knees up the gunner's ass, so the housing for the commander's sight ends up as the headrest for the gunner. Both sights are supposed to be stabilized in one plane iirc.

 

Despite having a fuel tank and possibly driveshaft running under it, the turret interior is reasonably roomy.

 

Firepower:

 

Firepower seems reasonable assuming that the tank can be configured for the likely enemy beforehand.  The performance for the full-caliber 85mm AP round seems... optimistic.  It is somehow penetrating about 70mm more at 2km than the KwK 43 with only about 10% more projectile kinetic energy at the muzzle. 

 

Some of this is probably an artefact of the spreadsheet I was using to work up gun designs. I changed over to pressure- rather than energy-based calculations for bullet velocity, and ran the gun as hot as possible given the 1960's Soviet barrel pressure limits provided (510MPa). The propellant energy density is taken from that of the cartridge for 2A46. The penetration was calculated using the best possible shell reference (ie: the highest-performing shell I could find with roughly the same calibre and a similar muzzle velocity) scaled using DeMarre.

 

But perhaps with the ultra-hard steels and better shell aerodynamics unavailable to the Germans, this is possible.  The 85mm gun is just barely adequate to destroy the Norman with existing armor arrays.  With anything more advanced, the 145mm low-pressure gun will doubtless be required.  The tandem warhead 145mm round sounds extremely impressive.  The fact that such an upgrade is already planned is good future-proofing.  However, it seems that the revised ammo stowage for the 145mm version compromises the otherwise excellent safe and isolated ammunition stowage layout of the 85mm variant.  Furthermore, the low muzzle velocity, coupled with the somewhat dubious rangefinder installations would probably not lead to the quickest time-to-hit.

Both NUB and LUB ATGMs are capable of knocking out the Norman and then some with its existing armor packages.  However, the LUB is completely insane, and it does not seem likely that a mass-practical up-armor package could be developed that could stop its fantastic 1650mm tandem-charge penetration. 

 

The missiles ended up being my favourite part of the whole competition. I modelled them on OpenRocket using commercial hobby-grade motors and mass-appropriate internal components, with the maximum possible range being a ballistic flight path at a 30' launch angle from the horizontal. The LUB was designed so that even with rather iffy guidance from the conical-scan radar or IR head you could be sure to knock out a Norman. I'm not even sure if it needs a HEAT warhead, to be honest.

 

This weapon would also be useful for destroying large bunkers at a safe range, as the behind-armor effects of such a gigantic shaped charge would be considerable.  The judges are a little dubious about the resolution of a spin-scan based radar reticule tracker.  The IR unit, however, seems perfectly in line with what one would reasonably expect.  Judging by the graphics, it is significantly overbuilt.

 

The accuracy of the con-scan radar system got a bit of work put into it, but should be fairly good given my understanding of the technology. I made the IR unit chunkier than it needed to be purely for aesthetic reasons (it could realistically be the size and shape of a sidewinder seeker head, as that's what it was based on). The main advantage of the radar set for missile guidance is that there need not be a trailing wire. Which means that it could conceivably be modified into a miniature 1960s-ERA SAM system for AA duty. The IR unit is a lot more conventional and should provide accuracy on par with first-gen SACLOS ATGMs.

 

Armor Layout:

The armor protection seems decent, but it is held back by a sentimental desire to protect the crew.  Hits to the left side of the hull from the frontal quarter seem very likely to disable the engine, as it it does not appear that there is a side armor array protecting the engine the way there is protecting the driver.  Ammunition is almost entirely isolated, at least in 85mm variant, and entirely in the turret.  The side skirt with the massive space seems like a good idea, however, it appears to be a monolithic piece of steel, and this would seriously hamper any sort of track repair and maintenance.  The turret ring seems a little exposed.

 

The roof armor protection is notably very good, and the turret roof will stop Cascadian ATGMs at two degrees over what the solicitors thought was a very optimistic angle.  The turret protection against plunging fire HEAT threats is very good, and should give this vehicle the edge in MOUT and counter-insurgency operations.  The hull protection against KE is noteworthy; the thickest parts of the hull can shrug off 105mm KE threats from ninety degrees off axis! 

 

This is more of a side-effect of having to deal with the 250mm/750mm tandem HEAT warhead from the side and on the roof. I've mentioned it before, but dealing with HEAT threats turned out to be the biggest challenge of this competition - the only place where I even needed to consider KE protection as separate from protection against HEAT weapons was against the 120mm Norman KE, which resulted in the hull front and turret front having more HHS than I would otherwise have liked. I think the entire competition would have been different if the reference threats had ditched the 360/960mm HEAT reference threat, used the 250/750mm threat in it's place, and otherwise kept everything else the same. This would have lead to a lot more viable 'heavy tank' designs given the relatively greater freedom from the tyranny of protected volumes and plausible armour mass fractions.

 

The other single factor that probably caused the most grief was the requirement to use 40mm of RHA for all structural components. The ability to shave weight by, for instance, making the hull roof, sides and floor out of 25mm RHA (beefed up in spots to survive reference threats) would probably have taken tonnes off mass off the tank in the end. I did actually try to game a previous submission in this manner using the saving provided by 80mm Aluminium, which ended up saving something like 5mt from a 70mt design, but had the unfortunate side effect of fucking the internal volume up.

 

That's a greater protected arc than the turret enjoys!  PAF tactical theorists have been kept busy arguing about theoretical "hull up" fighting positions, which might possibly involve floating hills that could take advantage of this unusual armor layout.

 

A preliminary areal density analysis did suggest that this design converges to a weight close to what the design team predicted as well as to a realistic (but high!) armor mass fraction.

 

 

[N-L-M]

On 9/19/2019 at 12:10 PM, Toxn said:

dealing with HEAT threats turned out to be the biggest challenge of this competition - the only place where I even needed to consider KE protection as separate from protection against HEAT weapons was against the 120mm Norman KE, which resulted in the hull front and turret front having more HHS than I would otherwise have liked. I think the entire competition would have been different if the reference threats had ditched the 360/960mm HEAT reference threat, used the 250/750mm threat in it's place, and otherwise kept everything else the same. This would have lead to a lot more viable 'heavy tank' designs given the relatively greater freedom from the tyranny of protected volumes and plausible armour mass fractions.

So, regarding this-
You seem to have hit on a problem which I was mildly aware of while setting up the requirements, and which I didn't want to change by making the KE threat worse.

The design space did in fact offer at least 2 core methods for dealing with annoyingly high armor mass requirements:

1. BIIIIIIG tanks.

The weight limit of 120 tons allows a lot of fairly silly yet still well armored tanks. Bigger is better thanks to the volume of the engine bay scaling with the cube of a linear scaling whereas the armor weight needed only scales with the square, as thickness remains constant. Making a vehicle at less than half the maximal weight of course you ran into some issues.

2. ERA

Against HEAT, the main defeat mechanism is the multiplicative effect of the reactive armors. ERA gives you the same multiplicative effect as NERA at approximately half the weight and 3/4 of the volume. This effectively means that at the same weight of armor you can get double the coverage at the cost of being made of explodium, with no other additional cost. You could of course layer explosive and non explosive armor to get, for example, a front array that will only stop the 60/160 and 125mm KE with the ERA in place, but which will still stop the 2"/4" and 105mm KE bare.
The main defeat mechanism of light N/ERA against KE is LOS feeding and not multiplicative, and therefore when using it the KE threat does pop up as a thing to annoy you.

From my math, you can get a good frontal NERA array at an equivalent areal density to around 350mm steel including a 30mm backing plate. Using ERA, you can get that down to approx 250mm, While the NERA one does indeed require a careful volume conscious design, the ERA one practically lets you go wild.
 

In effect, the armor requirements could be met by a design similar to the M1 Abrams with TUSK II, at approx 85 tons, or a design similar to the T-72B3 mod 2016 or Oplot-M (depending on how explodey you want to be) at approx 45-55 tons.

By deciding to make a truly reasonable weight of tank, with no explosive armor integrated into the main arrays, with a human loader, and with moderately under-rated engines (32L engines should be pushing out north of 900HP each per the spec), you sort of ended up designing yourself into an unintended corner.

 

All in all, the Objects 426 and 138 both used ERA as an afterthought at best, which is a bit strange considering just how good it's given to be. Survivability is much better with double coverage of single-hit armor (per given area), at least for a fairly small number of hits, and I expected this to be exploited quite a bit more than it ended up being.

[Toxn]

Fair enough. I think the idea of getting multi-hit survivability might have lead to a reliance on NERA and its associated issues.

 

For my part: I actually did look into going with a 120 tonne vehicle (and designed a ridiculous 200mm high-powered gun for it) before discovering that the width requirement was going to result in interesting (read: difficult) design decisions all on its own. With APFSDS axed mid-way through the competition and decreasing returns on penetration as conventional shells scale up, I ended up settling on a 120-140mm main gun, built a tank around it, and optimised that design into Lil Bouy. Which then ended up having an obscene armour mass fraction, prompting a deep redesign that popped out as the final submission.

 

I think you could make a case that this demonstrates one of the pit-falls of a rapid, iterative approach to design (which is how I design things): that you can get stuck on local maxima.