Collimatrix

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:



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.



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

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.

A few FN Evolys have been delivered to French special forces (in both 5,56 and 7,62).
 
http://www.opex360.com/2022/01/12/les-forces-speciales-francaises-ont-recu-la-nouvelle-mitrailleuse-ultra-legere-evolys-de-fn-herstal/
 
https://www.linkedin.com/posts/thierry-roger-3a07a949_première-livraison-de-la-nouvelle-mitrailleuse-activity-6884570994216837121-KlVo/
 
Probably just for testing purposes for now, like the British army.
While concerns regarding sustained fire capability are important for the regular army, it is probably less so for SF (which would likely rank the reduced weight higher on the priority list).

Indian DRDO tested their infatry ATGM (F&F, 2.5 km range).

 
 

11th Maneuver Division training at the KCTC 
 
K2

 
K21 

 

Just going through some older documentaries on the ROK Army Consolidated Maintenance Depot and discovered what I would consider some neat shots of the K1.
 
Something that you don't get to see clearly often is the hydropneumatic suspension on the K1.

 

This is from a 2013 even held by the Verein Schweizer Armeemuseum. The man in the photo is Walter Lanz, who some may know from the Lanz-Odermatt formula.
 
https://www.armeemuseum.ch/thuner-schiessplatz-anekdoten-rueckschau/

Elements of Tank Design (Page 35)
 
https://www.benning.army.mil/armor/eARMOR/content/issues/1983/NOV_DEC/ArmorNovemberDecember1983Web.pdf

Fragmenting behavior of large caliber PELE.

Absolutely. Korea awarded a development contract with Chrysler (eventually became General Dynamics Land Systems hence on most pictures of the XK1s have GDLS marked on them) for a tank which would eventually become the K1. 
 
You can get a general overview of the development from this page scan from Janes IDR:
 
 
XK1 PV-1 and PV-2:
 

ADS in Lazarev's hands.
 
   Interesting bit - long rail version are used in this video. MoD RF footage of firing ADS and older "underwater" guns umm... under water is also sprinkled here and there in this video.
 
   Gas regulator have "air" and "water" settings. "Underwater" bullets also works in the air. Dioptrical iron sights are build-in into the rail. Grenade launcher-rifle selector is located on the left side of the gun. Grenade launcher have separate trigger, so i guess this selector was made according to MoD requirements. GL trigger have an interesting additional "safety" feature (on 10:30 mark you can see it) - a circle piece that you push away with a finger.
   Video also shows a close up how spent casing ejection works and it is a bit unusual (around 8 minute 30 seconds mark). Spent cases are pushed into a "holder" above pistol grip on right side, facing forward-ish and only ejected after next shot or bolt carrier moved by hand. This was done according to MoD requirements.
   Charging handle can be easily moved from to other side of the gun by simply rotating it (10:52), and looks like it is even faster and easier than on ARX, lol.

Swiss 140 mm HEAT-MP-T :
 

Armor magazine, January/February 1986 edition

ROKMC M48A3Ks of the 2nd Marine Division during a recent training.
 

 

K9, K10 and Redback share same transmission.
 


 
https://thedeaddistrict.blogspot.com/2021/11/automatic-transmissions-for-k9-k10.html

Just a reminder that Mike Spark's website is a high-level cognitohazard and should not be read without a protective layer of alcohol to prevent brain damage.

1. Introduction
 
Stealth is one of those buzz-words that everyone knows. Stealth makes aircraft invisible to radar, allowing a stealth plane to sneak up and punch other aircraft or SAM sites with impunity. Stealth is widely acknowledged as one of the most fundamental technologies that all new combat aircraft need to have. Stealth is also, like SH's old friend NERA, mostly completely misunderstood. This thread will attempt to change that, at least a little.
 
HUGE DISCLAIMER: I know, at best, the basics of what is essentially one of the darkest arts in an already black magic-heavy field (radio and radar engineering). I'll be relying heavily on others to correct my obvious mistakes, but this is and will be the lies-to-children version of the field, as told by another child. Still, given the state of knowledge out there, it's probably better than nothing.
 
2. The most basic basics
 
Okay, you ask, what is stealth then if we're all misunderstanding it? Here I think that the best analogy is that stealth is like camouflage, but for aliens. Camouflage famously entails the 5 (sometimes expanded to 7 with speed and spacing) S's: Shape, Shine, Shadow, Silhouette and Sound. Each operates on somewhat different principles, and can be more or less important in different scenarios, but are united in terms of how human senses work. We are pattern-finding creatures with passive senses, so anything that breaks up visual or auditory patterns, blends one into the background, or limits the amount of noise or reflected light one gives off will make you harder for another human to spot.
 
Radar, however, is generally not passive. Instead, a radar set sends out a beam of electromagnetic energy and looks for an echo. There's a huge amount of complexity in how this can be done (what frequency to use, how to generate and send the beam, how to track the returns and so on), but that's radar at it's most basic. So, like camouflage, ways to avoid radar will be united in trying to trick or defeat this basic mechanism. These principles are, roughly: Absorption, Redirection, Scattering and Emissions. Finally, and just to complete a fun acronym, there's also the side issue of radio-related Shenanigans. Taken together, these measures can significantly reduce how easy an aircraft is for a radar to "see" from certain angles.
 
Absorption is simple in concept: if something eats up the radar waves before it can get reflected, then the receiver doesn't get to pick up a signal and the plane doesn't get found. There's a whole realm of sneaky material science that goes into this, but from my understanding the two most common techniques currently being used are non-metallic structural components (which can be more or less transparent to radar) and foams or paints with nanomaterials in them (the famous grey stealth paint job generally being a weather coating instead of the magic material itself). These can be used in all sorts of clever ways: for instance, by making the forward edge of your wing out of radar transparent composite and then packing the area behind it with cones made out of radar-absorbing foam. Absorption can't make a non-stealthy design stealthy, however. It's more of a "cut 10% off our already-low radar return" sort of strategy.
 
Redirection is one of the single biggest reasons why stealth aircraft have their characteristic look. Generally the principle here is to make as many surfaces on the aircraft as parallel as possible, in order to direct the majority of your return to one or two places rather than scattering it all over the sky. Since the most common place you don't want returns to come back to is directly to the front, this also means that swept wings and tails are a must. It's also why flat bottoms are preferred: if someone is looking at your aircraft from below, then a flat bottom is the one shape guaranteed not to provide a good return until you are right above them.
 
The major enemy of this approach is the dreaded corner reflector, which is where any right-angled surface will reflect a return straight back to it's source. This is why stealth aircraft all have angled fuselages, hard chines and cranked tailplanes, and also why even things like landing gear hatches and bomb bay doors end up with saw-tooth profiles (note: not 90-degree saw teeth if you can help it, because corner reflector). The other major enemy of this approach is aerodynamics, which inherently prefers rounded frontal profiles that are great at reflecting returns back along an entire wing or fuselage segment. So stealth aircraft also tend to have aerodynamic features (sharp-nosed, flat-bottomed airfoil profiles, for instance) that make them a bastard to fly.
 
Scattering: if you're doomed to reflect something in an unwanted direction, then it helps to make the surface convex in order to disperse the return. This is seen in the shallow, curved fuselage profiles of stealthy aircraft which, along with their beaky fronts and hard chines, gives them a sort of alien bird quality. It's also really useful when designing air intakes for the engines you've sensibly buried inside the fuselage (seriously, the front of a jet engine is like a disco ball for creating noticeable radar returns): an S-shaped intake reflects about half as much energy as a straight intake with a similar profile.
 
Emissions are more or less self-explanatory: if you're trying to hide in the dark, then don't bring a flashlight with you. This means no big radio sources or old-school radar sets that a receiver can easily pick up on. I've heard that modern AESA radars are harder to spot for {electronic black magic} reasons, but the principle still stands.
 
Shenanigans are what you resort to in the corner cases where one or the other approaches described above are not possible. These usually make use of unintuitive electromagnetic wave-specific physics like half-wave resonance. The intake screens on the F117, for instance, seem to be sized so that the radar wave "sees" it as a solid surface and bounces off while still allowing at least a trickle of air in to feed the engines. These tricks tend to be fiddly, however, and can go very wrong when faced with radar systems that use frequencies much higher or lower than the ones that they were designed to counter.
 
3. Artists are dumb and wrong
 
So, having learned the barest minimum about how stealth works, let's point and laugh at the mistakes of artists who ape the form of stealth without understanding the content. Note: it's now almost impossible to grab high-resolution images off of websites, so you'll just have to google these things if you want to see them in any sort of level of detail.
 
Example 1: the F-19 from model kits in the late 80s
 
A fictional stealth plane from the time where people could be forgiven for not knowing a damn thing about stealth. The top-mounted air intake and engines are a good idea, but the rounded wings/fuselage profile and anhedral wingtips look like a great way to get returns from every direction. 5/10 for effort at a time when nobody knew what stealth really was.
 
Example 2: F/A-37 Talon from the movie Stealth
 
Considering that the damn movie is called "Stealth", the Talon is a remarkable example of a bunch of artists googling stealth aircraft and then adding enough greebles so that the result is neither stealthy nor much of an aircraft. It has intakes everywhere, a bunch of curves but few parallel lines, a swing-wing setup that I can only imagine puts a bunch of nooks and crannies into the airframe that reflect well, random greebles off at right angles and on and on. 0/10, the aircraft plays Incubus when it's angry and is therefore canonically a moody teenager.
 
Example 3: XA-20 Razorback from Tom Clancy's giant, throbbing brain
 
It's an F-20 that's inexplicably been converted into a CAS aircraft (presumably because, in the dark future of 2020, transaircraft rights are now government policy). That idiocy aside, it's more or less fine. Turns out that when you crib directly off of someone else's work you won't fuck things up too badly.

Training for SyAAF MiG-29 pilots with AA missiles launches.
 
 
 

Just a reminder that Mike Spark's website is a high-level cognitohazard and should not be read without a protective layer of alcohol to prevent brain damage.

Just a reminder that Mike Spark's website is a high-level cognitohazard and should not be read without a protective layer of alcohol to prevent brain damage.

Mid 1980s experiment with using exhaust from the gas turbine to decontaminate vehicles in an NBC environment:


 

Mid 1980s experiment with using exhaust from the gas turbine to decontaminate vehicles in an NBC environment:


 

Nigerian Vickers Mk.3

 

Shooting with Metis ATGM. Interesting moment when camera shows flight path from behind gunner, they launched missile way higher than a target and then guide it to the target below initial flight trajectory.
 

Hanwha display setup for AUSA 2021