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Fiction Done Right: Designing your own MBT (1991-1999)


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Hi there!

I'm a new user, and found this forum by way of a video on the so-called "reformers". The video also included a screencap of a thread in this forum about some guy called "Black Tails Defense" or something, in which the strangest tank was shown- something with a 145 millimeter... howitzer

 

The... sheer tomfoolery of putting a long-barrel world war one era howitzer with eighty rounds of ammunition in a forty-ton vehicle somehow designed to also float... I personally enjoy entertaining the concept of designing fictional tanks for fictional universes. However, I'm critically aware of how limited my knowledge on this subject is. 

 

Honestly, I was more really concerned with the external appearance of the tank to look as "realistic" as possible- no shot traps, no funny "turrets" like on whatever that Scorpion-thingy from HALO was, as well as worrying about details like how to make sure the tank doesn't break down mid-combat and the placement of critical systems like Optics, but I'd also like to know what kind of systems should you use (e.g. Turbine or Diesel, Horstmann or Torsion bar, etc etc) 

 

There's a little thing that I'm doing where I draw up tanks et cetera within the confines of Mid-Late 80s-90s - early 2000s doctrine, and I'd like to ask you, what makes a real tank tick for tanks of this era? How should you go about designing a tank? I'm aware of the fact that one should always design inside-up (critical components such as engine, gun, et cetera up), but what are some of the caveats and nuances inevitably intertwined into it? How should one go about the design process for designing a tank?

 

What's a rough list of features you want to have, and others that you can sacrifice for any given role of a tank? I'm aware that this is like asking, "what should I put on a plane", but let's assume that it's for a tank stuck in, say, the Mid-late nineties, around the Gulf War - Kosovo period.

 

Also, in addition to this, some common questions that I'd also like settled are;

- Diesel, Turbine, or Petrol? Where/When/How should these engines be implemented?
- Rifle or Smoothbore? This debate goes on forever and I'd like some sort of concrete answer. As far as I know, the only forces that use rifled guns use them either out of necessity or reliance on a certain specific type of round.
- Why in god's name would you ever put a 145 millimeter howitzer on a tank?

- Caliber: Is there an upper limit? Is it really worth going above 120mm/maybe 130mm at a stretch when combat won't even happen above the ranges that these guns are effective due to the distances that you can see with optics? At range, Artillery and Missiles have traditionally been more efficient.

- Whither the Autoloader, or Nay? I've seen the Chieftain's video on it, but I personally would like your opinions on it.

- Barrel loaded ATGMs- are they really all that they're cracked up to be? Why/why not?

 

I'd like to strickly restrict this to Main Battle Tanks, as I'd rather ask about Infantry Fighting Vehicles later, in another thread.

 

In short, how the 1990s Tank?

 

Sincerely yours,

 

Aussie_Mantis

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2 hours ago, Aussie_Mantis said:

Hi there!

I'm a new user, and found this forum by way of a video on the so-called "reformers". The video also included a screencap of a thread in this forum about some guy called "Black Tails Defense" or something, in which the strangest tank was shown- something with a 145 millimeter... howitzer

 

The... sheer tomfoolery of putting a long-barrel world war one era howitzer with eighty rounds of ammunition in a forty-ton vehicle somehow designed to also float... I personally enjoy entertaining the concept of designing fictional tanks for fictional universes. However, I'm critically aware of how limited my knowledge on this subject is. 

 

Honestly, I was more really concerned with the external appearance of the tank to look as "realistic" as possible- no shot traps, no funny "turrets" like on whatever that Scorpion-thingy from HALO was, as well as worrying about details like how to make sure the tank doesn't break down mid-combat and the placement of critical systems like Optics, but I'd also like to know what kind of systems should you use (e.g. Turbine or Diesel, Horstmann or Torsion bar, etc etc) 

 

There's a little thing that I'm doing where I draw up tanks et cetera within the confines of Mid-Late 80s-90s - early 2000s doctrine, and I'd like to ask you, what makes a real tank tick for tanks of this era? How should you go about designing a tank? I'm aware of the fact that one should always design inside-up (critical components such as engine, gun, et cetera up), but what are some of the caveats and nuances inevitably intertwined into it? How should one go about the design process for designing a tank?

 

What's a rough list of features you want to have, and others that you can sacrifice for any given role of a tank? I'm aware that this is like asking, "what should I put on a plane", but let's assume that it's for a tank stuck in, say, the Mid-late nineties, around the Gulf War - Kosovo period.

 

Also, in addition to this, some common questions that I'd also like settled are;

- Diesel, Turbine, or Petrol? Where/When/How should these engines be implemented?
- Rifle or Smoothbore? This debate goes on forever and I'd like some sort of concrete answer. As far as I know, the only forces that use rifled guns use them either out of necessity or reliance on a certain specific type of round.
- Why in god's name would you ever put a 145 millimeter howitzer on a tank?

- Caliber: Is there an upper limit? Is it really worth going above 120mm/maybe 130mm at a stretch when combat won't even happen above the ranges that these guns are effective due to the distances that you can see with optics? At range, Artillery and Missiles have traditionally been more efficient.

- Whither the Autoloader, or Nay? I've seen the Chieftain's video on it, but I personally would like your opinions on it.

- Barrel loaded ATGMs- are they really all that they're cracked up to be? Why/why not?

 

I'd like to strickly restrict this to Main Battle Tanks, as I'd rather ask about Infantry Fighting Vehicles later, in another thread.

 

In short, how the 1990s Tank?

 

Sincerely yours,

 

Aussie_Mantis


Well well well(come to the forum!), I’m curious to watch this video that brought you here, got a link? Also, I hope you’ve read the posting guidelines: 

 

As for “designing a tank”, it’s not so cut and dry… at all. Every aspect of a tank effects another aspect of the tank, I.e. gun size effects ammo and turret size (turret size effecting hull size, and both effect how much armor you need to protect them from enemy fire, etc). Not only that, but each bit of technology usually has its own uses in certain situations: gas turbines have great power to weight, but annihilate fuel; diesels are just good and reliable; and petrol is for people who don’t understand the torque requirements in an armored vehicle :P. From my (slightly educated) perspective, there’s a lot of going back to things you’ve already done, having to give up some requirements to meet other requirements, and it gets frustrating. I will say, we do have a “semi-biannual” design competition for fun, which was almost exclusively for armored vehicles, but the next comp is an aircraft, so no luck. That doesn’t mean you can’t just do stuff or ask questions, though, but I’m not sure just how much of a “creativity forum” this is, as compared to something like shipbucket. 

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23 hours ago, Aussie_Mantis said:

Hi there!

I'm a new user, and found this forum by way of a video on the so-called "reformers". The video also included a screencap of a thread in this forum about some guy called "Black Tails Defense" or something, in which the strangest tank was shown- something with a 145 millimeter... howitzer

 

The... sheer tomfoolery of putting a long-barrel world war one era howitzer with eighty rounds of ammunition in a forty-ton vehicle somehow designed to also float... I personally enjoy entertaining the concept of designing fictional tanks for fictional universes. However, I'm critically aware of how limited my knowledge on this subject is. 

 

Honestly, I was more really concerned with the external appearance of the tank to look as "realistic" as possible- no shot traps, no funny "turrets" like on whatever that Scorpion-thingy from HALO was, as well as worrying about details like how to make sure the tank doesn't break down mid-combat and the placement of critical systems like Optics, but I'd also like to know what kind of systems should you use (e.g. Turbine or Diesel, Horstmann or Torsion bar, etc etc) 

 

There's a little thing that I'm doing where I draw up tanks et cetera within the confines of Mid-Late 80s-90s - early 2000s doctrine, and I'd like to ask you, what makes a real tank tick for tanks of this era? How should you go about designing a tank? I'm aware of the fact that one should always design inside-up (critical components such as engine, gun, et cetera up), but what are some of the caveats and nuances inevitably intertwined into it? How should one go about the design process for designing a tank?

 

What's a rough list of features you want to have, and others that you can sacrifice for any given role of a tank? I'm aware that this is like asking, "what should I put on a plane", but let's assume that it's for a tank stuck in, say, the Mid-late nineties, around the Gulf War - Kosovo period.

 

Also, in addition to this, some common questions that I'd also like settled are;

- Diesel, Turbine, or Petrol? Where/When/How should these engines be implemented?
- Rifle or Smoothbore? This debate goes on forever and I'd like some sort of concrete answer. As far as I know, the only forces that use rifled guns use them either out of necessity or reliance on a certain specific type of round.
- Why in god's name would you ever put a 145 millimeter howitzer on a tank?

- Caliber: Is there an upper limit? Is it really worth going above 120mm/maybe 130mm at a stretch when combat won't even happen above the ranges that these guns are effective due to the distances that you can see with optics? At range, Artillery and Missiles have traditionally been more efficient.

- Whither the Autoloader, or Nay? I've seen the Chieftain's video on it, but I personally would like your opinions on it.

- Barrel loaded ATGMs- are they really all that they're cracked up to be? Why/why not?

 

I'd like to strickly restrict this to Main Battle Tanks, as I'd rather ask about Infantry Fighting Vehicles later, in another thread.

 

In short, how the 1990s Tank?

 

Sincerely yours,

 

Aussie_Mantis

 

Welcome to the forum. Go check out the various competition threads down in the Competitions subforum. We've done... Oh, four or five tank design comps? Should be illuminating.

 

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I’ll third the welcome and second the recommendation to check out the past design competitions.

Having said that, I’m going to chance my arm by saying the fundamental factor determining tank design is doctrine; i.e. what is your tank supposed to do and how is it intended to fight?

Another question regarding your scenario: is this a new design for 90s production for the “end of history” environment or is it a legacy Cold War platform tasked into that environment?

If the second and western, it would look almost exactly like Abrams or Leo 2.

If the first, you might well go for lighter overall, accepting say a 105mm L7 based gun and lighter base armour protection which theoretically could be up armoured… and it would look like an XM8.

There are better educated amateurs on this forum who can quantify the trade offs, not to mention professionals who work in relevant fields. These folks can give more specific responses than I can - I am, at best, a dilettante.

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On 1/4/2022 at 2:49 PM, Aussie_Mantis said:

/.../

In short, how the 1990s Tank?

 

Sincerely yours,

Aussie_Mantis

 

   Few questions:

What kind of fiction we are talking about? Is tech more advanced in those alternative 90s than it was IRL?

What country this tank design belongs to? Doctrine under which it was designed?

Backstory and situation description for conflict that it is going to participate is also going to be useful.

 

On 1/4/2022 at 2:49 PM, Aussie_Mantis said:

Honestly, I was more really concerned with the external appearance of the tank to look as "realistic" as possible- no shot traps, no funny "turrets" like on whatever that Scorpion-thingy from HALO was, as well as worrying about details like how to make sure the tank doesn't break down mid-combat and the placement of critical systems like Optics, but I'd also like to know what kind of systems should you use (e.g. Turbine or Diesel, Horstmann or Torsion bar, etc etc) 

 

There's a little thing that I'm doing where I draw up tanks et cetera within the confines of Mid-Late 80s-90s - early 2000s doctrine, and I'd like to ask you, what makes a real tank tick for tanks of this era? How should you go about designing a tank? I'm aware of the fact that one should always design inside-up (critical components such as engine, gun, et cetera up), but what are some of the caveats and nuances inevitably intertwined into it? How should one go about the design process for designing a tank?

   If you are concerned more about external appearence and aim to make something not outlandish, using few real life MBTs common design features is going to produce more or less believable vehicle.

   List of those features:

  • Torsion bar suspension is popular for a reason. No weirdo layout of tracks, rollers, spacing bewteen rollers, drive sprokets located way too high or too low that forces tracks to do big turns.
  • Diesel engine, engine in the back, air grills on engine deck roof. Basically no stupid "Merkava hull with Leopard turret cause they are real and people know about them, if i combine them together it will work great!".
  • Turret in the middle part of the hull. Turret should not be too big (or even bigger than hull), just enough to accomodate cannon guts and breach, space to move it (elevation and some amount of depression), location for crew and in certain designs - space for ammunition in the rear part of the turret. Cannon should be located in the center of turret "face"
  • Hull design should avoid too many "steps" in hull roof section (some tanks have rised engine decks, for example), no weaponry mounted on the hull, no firing ports and space for dismounts or any other additional humans other than a crew. Vertical sides is prefferable, front and rear can be angled.
  • Details - optics for driver should be small enough to not be an easy target to hit, can be 1 to 3 vision blocks. Gunner station should be next to gunner's optical sight, same story with a commander. Commander hatch can be equipped with cupola with additional vision blocks and some sort of sight or optical observation device that can be rotated. Pieces of tank should be done with minimum amount of weld seams, no rivets in construction of hull and turret itself, some sort of rivets or bolts can be used for add-on hardware. Hull roof and hull bottoms can have complex-looking features in specific places, to accomodate parts of suspension and engine.
  • Add-on hardware can be blocks of ERA, boxes for tools and storage bins, additional protection measures such as ERA modules, hull bottom mine protection plates, mine rollers, and smoller stuff.

    Sticking to those should give you something decent-looking for the most part.

 

Example for complex looking shapes of tank hull:

Spoiler

trumpt-64a20.jpg

   T-64 hull. You can see how turret ring shapes hull around it, including hull side plates. This is done to accomodate relatively big turret for a hull of such size.

 

Amusing%2BHobby%2BT-72M2%2BSlovak%2BMBT.%2BModerna%2B2.JPG

   Hull bottom of the T-72. It is made as a big stamping, so it can be more than just smooth single surface.

 

Zvezda 1/35 T-90 Main Battle Tank Build Review Image

   T-90A turret. Looks busy, but it is rather simple from external design. 2 big angled boxes in front to accomodate layered armor package, space for cannon and moint points between then, space for crew of 2 (gunner and commander) and turrets ends after volume for humans ends. Gunner have sights in front of his hatch and his working station, commander have additional vision optics and whole cupola is rotatable, so big boxy sight can be used for 360 visiblity devise.

 

 

On 1/4/2022 at 2:49 PM, Aussie_Mantis said:

Also, in addition to this, some common questions that I'd also like settled are;

- Diesel, Turbine, or Petrol? Where/When/How should these engines be implemented?
- Rifle or Smoothbore? This debate goes on forever and I'd like some sort of concrete answer. As far as I know, the only forces that use rifled guns use them either out of necessity or reliance on a certain specific type of round.
- Why in god's name would you ever put a 145 millimeter howitzer on a tank?

- Caliber: Is there an upper limit? Is it really worth going above 120mm/maybe 130mm at a stretch when combat won't even happen above the ranges that these guns are effective due to the distances that you can see with optics? At range, Artillery and Missiles have traditionally been more efficient.

- Whither the Autoloader, or Nay? I've seen the Chieftain's video on it, but I personally would like your opinions on it.

- Barrel loaded ATGMs- are they really all that they're cracked up to be? Why/why not?

  • Petrol is not used for any tanks for many years AFAIK. Multifuel deisels are go to engine type. Gas Turbines are not that great for a ground combat vehicle, at least they were.
  • This is not even a discussion to have. Rifle guns are in the past. Smoothbore gun barrel have longer service life, potentially a bit cheaper to produce, can provide higher muzzle velocities from same propellant charge. If you want to fire shells that needs to spin - add angled fins on your shells.
  • This one trick will allow you to rule the world! Just add this one feature on your...
  • Cannon calibers on modern tanks are 120 and 125 mm, but guns in 130, 140, 152 mm calibers were developed. You probably can go to something bonkers, like 300 mm, but this is stuff for deviantart. Militaries don't like to change calibers for logistical reasons. Any change should be big enough to accomodate shell growth potential for a decade or 2 in best case. Ability to see enemies in your optics is not a limiting factor for choosing gun caliber, main reason is amount of energy your cannon can pump into armor piercing projectile and amount of explosives filler can be put in an anti-infantry shell. With modern shells you can't just increase speeds on existing guns without getting into hard-to-solve issues. Also, tanks can into inderect fire without having direct LOS with them. T-90 gun max range is 12 km, range is limited by max gun elevation.
  • Autoloader is the only option for future designs. Question is only in specific design. Crew isolation from explody stuff is just one of driving forces to go auto.
  • They are commonly called GL-ATGMs (Gun launched ATGMs). GL-ATGMs are limited by a caliber of main gun and space inside of the vehicle, but have an advantage of using same loading system, ammo storage and a fact that they are located under main armor of the vehicle. Externally-mounted ATGMs on tanks exists (North Korean tanks are example of that), they are good for many reasons - existing ATGMs can be used, including infantry-carried one, design of ATGM is not limited by internal volume and layout of an AFVs, launcher can be designed into a module that can be added as an upgrade package for older gen tanks. Externally-mounted ATGMs have negatives sides as launcher usually are made to not be too heavy, so their armor may be not that great, they increase size of a turret, harder to reload or/and require to operator to get outside or expose some parts of his body.  

 

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On 1/4/2022 at 6:49 AM, Aussie_Mantis said:

 

Honestly, I was more really concerned with the external appearance of the tank to look as "realistic" as possible- no shot traps, no funny "turrets" like on whatever that Scorpion-thingy from HALO was


I think it should be pointed out that shot traps pretty much don’t exist anymore, APFSDS doesn’t bounce or ricochet any appreciable amount, and you can safely ignore shot traps for the time period you’re concerned with. What does make angled armor less attractive is that your protection is not homogeneous across your profile, being thickest at the tip and thinner as you move towards the base, such is the geometry of triangles. I suspect this is why the Leopard 2SG and PL have more square faces than the 2A5. 
 

As for “funny turrets”, if it works for what you need it to, then don’t worry about aesthetics. Teledyne’s low profile turret is “funny”, as compared to practically every other tank out there, but it works, as proven by the M1128 (somewhat). There’s also the “Elke” technology demonstrator, mounted on an M551, that’s even crazier, and I would very much enjoy seeing something like that work. What’s wrong this the halo tank is that the crew is practically exposed, the tracks are complicated as hell, and the ammo seems to share space with the engine. 

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4 hours ago, LoooSeR said:

no shot traps

 

Others have said/alluded that "shot traps" aren't really a thing anymore, but I wanted to add that a big part of the reason for this now is that for the most dangerous threats a lot of the tank is simply "all or nothing". Yes it's true that fin doesn't ricochet so much, but a part of this that is forgotten is that modern tank armor is absolutely bursting at the seams, it's as much armor as anyone can stand a vehicle to have, and it's all directed at stopping the biggest threats from only so generous an angle. A really good book to read if you want the story on how tank design went from "okay we'll protect against this threat everywhere" to "we really need to be making compromises here" is Hunnicutt's Abrams, specifically the section after MBT-70. That's when designers in the West had their come to jesus moment.

These armor arrays are so huge that shot traps are simply a cost of doing business (albeit, again, not a terribly costly one in the current environment), because there's no practical way to make a NERA-box that had flush armor arrays like an M48 has.

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As LoooSeR said, context is important.

During the 1940s, tanks were simple enough that relatively small countries could design and field reasonably competitive designs on their own.  The expertise required for tanks largely overlapped with either other armament industries (tank guns were often adapted naval, AA guns, or field artillery and the engines were often modified aircraft powerplants), or civilian heavy industries (much of the casting/welding and transmission design could be readily adapted from car/train/ship making industries).

By the 1990s, however, tanks were much higher tech and a lot of that tech was much more tank-specific.  It should be possible to adapt a helicopter turbine or heavy prime mover engine to work in a tank.  Fabrication of the hull could still probably be done with expertise from other industries.  Production of the special armor packages, transmission and running gear would require tank-specific knowledge but not necessarily tank-specific industry.  Production of the gun, fire control systems, and other combat electronics would by that point require very specific knowledge and would overlap relatively little with too many other things already in production if it were a nation's first tank.

I think it's instructive to look at the smallest/poorest countries that have produced their own tanks.  Romania was able to produce the TR-85, albeit in somewhat limited quantities, and they didn't design their own gun, and the turret and hull design are at least based on the design of the T-54/55 albeit very heavily modified.  As far as I can tell they did design their own engine and transmission, which is quite impressive, but this took some time and all the while they were cribbing notes off of foreign designs.  No shame in that; high specific output diesels are not easy to design.

Israel designed the Merkava, which has a completely original hull and turret design, locally designed suspension and tracks, and locally designed special armor packages and fire control on the later models.  The engine is either US or German designed, and the transmissions have been US, German or Israeli designed based on the mark.  The gun was a straightforward clone of the M68, and later a locally designed version of the German 120mm smoothbore.  Both of these guns are compatible with the wide range of ammunition in either caliber, although Israel has a local ammunition industry capable of designing and producing its own tank gun ammunition (which in some cases has been widely adopted outside of Israel).

South Korea has produced two MBTs locally, the K1 and K2.  The former had a great deal of assistance from Chrysler, but the latter appears to be a largely local effort.  Early K2s had a German designed engine and transmission, but these are eventually to be phased out and replaced with locally-designed equivalents.  I believe the tracks are German-designed.  Not sure about the suspension.  The armor packages and fire control system are locally designed and manufactured.  The gun is some sort of version of the German 120mm, although again South Korea is capable of designing and producing their own ammunition.

Turkey, which has roughly the same size economy as South Korea if we discount their current economic woes, has had a much harder time developing their own MBT.  Despite considerable help from South Korea, they have struggled to develop their own engine and transmission and are currently dependent on political good will from Germany if the project is to go forward quickly.  I don't want to give the impression that Turkey has a weak local manufacturing sector or is a stranger to high tech industries.  Neither is true; they are actually capable of producing their own helicopter gas turbines, combat UAVs, missiles, and a variety of other quite challenging materiel.  Turkey has, current monetary woes aside, a well diversified and fairly well developed economy.  They're just not a match for South Korea, which has an extremely well-developed heavy industry and electronics sector relative to the country's size, natural resources and population.  Israel has an even smaller population and GDP, but their defense industry is outrageously well-developed for a country of that size for some mysterious reason, and there is abundant local expertise in the design of complex weaponry.

So, any country that is plausibly going to mass-produce a 1990s tech-level tank (and let's be honest, that's not dramatically different than a 2022 tech level tank) is going to need a fairly robust economy, well developed local heavy industry, and a large number of mechanical and electrical engineers.  I think the poorest of the countries I just listed is Romania, with the 39th largest GDP in the world (out of 190-something).  By the 1990s, being able to design and produce a tank on ones own was a privilege reserved for a fairly small number of countries.  Even countries that could plausibly design their own engine, transmission and tracks frequently farmed these out to Germany's Renk and Diehl, respectively.  Alternatively, you might say that Brazil in the 1980s represents the floor economy of a nation capable of designing and producing its own tank, although the entire turret on that vehicle is a British design from Vickers.

So that would be the first thing I would say about designing a 1990s tank; it's not for small nations, and even the rich ones frequently used foreign components.

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As for what a 1990s tank would realistically look like, by the 1990s most tanks were really samey.
 

Powerplant:  The earliest tanks with diesels were experimented with in the 1930s, I believe either the Japanese or the Soviets were the first.  By the 1940s the advantages were obvious, but de-rated aviation gasoline engines were reliable and already in mass production, so many countries stuck with those.  I'm less clear on the rationale for the Germans keeping gasoline motors as theirs were not aeroderivative.  In any case, there actually was a German tank diesel program, it just went nowhere.

By the 1990s there were pretty much two realistic possibilities for a tank powerplant; either a turbodiesel or a gas turbine.  1990s MBTs are about half armor by weight, so they're very sensitive to the compactness of things.  Turbocharged diesels don't have amazing power density, although with a lot of careful engineering they can be made competitive, but they have very low fuel consumption and lower waste heat rejection requirements than gasoline engines.  Once you factor in the volume of the engine plus the volume of the fuel plus the volume of the cooling fans, and the strategic mobility advantage the fuel-sipping diesel, it's definitely coming out ahead of the gasoline motor.

Gas turbines do not scale down particularly well.  Very large gas turbines like the 33,000 horsepower Rolls Royce WR-21 naval gas turbine in the Type 45 destroyer achieve 42% thermal efficiency, which is like middling efficiency by diesel standards.  A gas turbine that will fit inside of a tank is much less efficient; realistically about a match for a gasoline engine in terms of specific fuel consumption when it's at design point and much worse if it's idling or doing any kind of stop and go.  Gas turbines also need beefier air filters than diesels due to much higher mass airflow through the engine.  However, there are still a number of advantages that must be taken into consideration.  Gas turbines are (very nearly) completely self-cooling, so while there will still need to be cooling fans to keep the transmission cool, the total powerpack losses to cooling power will be smaller and the ballistic windows from the ventilation will be much smaller.  Gas turbines with a free power turbine (which is most of them) have a very different torque/RPM characteristics from a diesel; they produce max torque at their lowest RPM and max power at their minimum torque.  These are very favorable characteristics if you want to keep the transmission small (although the Abrams' XR-1100 transmission was, as I understand, designed to work with both the AVCR-1360 and AGT-1500 so it likely does not take much advantage of this effect).  Gas turbines are easier to start in the cold.  Gas turbines have very little vibration because their moving parts rotate rather than reciprocate.  Gas turbines are actually multi-fuel, no questions asked and no mucking around with adjusting the engine to suit the fuel.  The Brayton cycle uses continuous, constant-pressure ignition which simply does not care about octane numbers or cetane numbers.  Finally, it's easier to design gas turbine fuel burners so they produce very little smoke than it is to ensure that a diesel produces very little smoke due to the much different fuel burn stoichiometry of a gas turbine.  It should be noted that not all gas turbine designers have actually succeeded in doing so, however.

A gas turbine good enough for a tank would be roughly similar to a turboshaft for a helicopter, albeit tweaked more for better fuel consumption than for absolute power to weight ratio.  The list of countries that can design very good turboshaft engines is quite short, but then so is the list of countries that can make high specific power diesels.  If tank-sized gas turbines performed as well as ship-sized ones this would be no contest, but they don't so either choice is competitive and it's pretty ambiguous which is "best".  But most countries in the world realistically do not have the luxury to pick and choose between a top of the line diesel and a top of the line turbine.  Interestingly, the UK is in a position to make such a choice and they still managed to fuck it up somehow by fielding a tank diesel that's 300 horsepower short of its stablemates.  The French hyperbar engine is a turbocharged diesel, just tweaked for very fast throttle response and compactness at some expense to efficiency.

Armament:  By the 1990s, advances in digital fire control systems largely rendered gun-launched missiles obsolete.  There was probably still a case for them as a sort of long-range precision round for swatting at helicopters and the like, but that role could also be filled with something like M830A1.  There were various flirtations in the mid Cold War era with sorta-kinda howitzer like armament for tanks in the form of medium pressure guns and gun/launcher hybrids, but by the late 1970s there was basically a consensus amongst all sensible people that the tank armament of the future would either be the Rheinmetall 120mm or would look a lot like it.  Even British engineers were aware of this:

ehoiVGY.png

In any event, the Soviets taking their toys and going home meant that the world did not suddenly fill with various super-tanks, and tank lethality ended up being more economically improved by advances in ammunition design rather than arming the tanks with larger guns.

3H8wBLX.png

You can't go too much larger than current 120mm without requiring an autoloader.

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