Serge

That's essentially the same as with the Marder, with the difference that the MILAN launcher on the Marder was mounted at the commander's hatch during travel and could be used to engage heavily armored targets. Once the infantry left the vehicle, the missile launcher was carried by the AT team. For the Puma the ATGM launcher will be fixed, but both the infantry squad and the IFV will share the same stock of missiles.
 
 
Can you elaborate? I've never heard of any "great powers" (USA, Soviet Union, NATO?) stopping any cooperation between the Scandinavian countries.
 
 
The Netherlands were offered to buy the Puma IFV or cooperate in the development during a very early stage. They opted for the CV9035 instead, because of their wish for a 35 mm gun, the lower cost of the CV9035 and the earlier possible introduction.
 
I am not sure how deep the cooperation between the Netherlands and Norway is, but I'd imagine it wouldn't be as deep as the cooperation between the Netherlands and Germany currently is - though it might have been a closer cooperation at the time the CV90 was chosen. The Dutch tanks are semi-integrated into the German Army (and located in Germany), while just recently a new cooperation on air-defence was made. The FlaRakGruppe 61 will be subordinated to the Dutch Air Force, while the procurment of future air defense systems will be made jointly - that means the Netherlands might buy MEADS/TVLS at some point in the future, while both countries look for a VSHORAD system to properly fill the gap left since Gepard/PRTL Cheetah were decommissioned (maybe Skyranger on Boxer?). The current systems relying on Stinger SAMs only (i.e. Fennek and Wiesel) are not capable enough for protecting moving convois. The German naval infantry is part of the Dutch Korps Mariniers, while the Luchtmobiele Brigade is subordinated to the German Division Schnelle Kräfte.
 
At the same time Germany and Norway are buying submarines together, but the Dutch are not interested in the U212 class. So European military procurement is still in a pretty bad shape, where cooperation is limited and rarely used when it could save costs.
 
 
Well, the title of the topic is a bit biased and certainly makes it look like this is a bashing topic only, I didn't have the intention to bash anything for no reason. The CV90 is a popular choice and it is not inferior to most other IFVs, but it is often praised for questionable reasons and has a large fanbase, that sometimes doesn't look at the facts. In so far I think the title chosen by Serge, "Why so much love?", seems to be quite fitting. I once posted in another forum that the the basic CV90 (Strf 9040) armor should protect against 14.5 mm/23 mm AP in the frontal arc only (both rounds with the same penetration), but then was told by another poster that the CV90 clearly had better armor and all-round protection against 14.5 mm ammo, while the frontal armor should resist 30 mm APDS. The Norwegian CV9030 with composite armor then would resist 30 mm APFSDS ammo frontally and APDS ammo at the sides...
Now, BAE Systems' own presentation says something against such myths, together with the armor schemes from the UDES 09 prototype (23 mm LFP armor, 6-10 mm side armor). I've seen people posting in forums that the Strf 9040 is the best IFV!
 
Not being as good as claimed by fanboys doesn't mean that the CV90 is bad, it is just not very good either. It is average and has a number of advantages (low size, seven roadwheels pairs, separated fuel tanks, low costs) over other IFVs from the same time; however if rating vehicles only by armor protection, FCS or power-to-weight ratio, the CV90 is certainly not the best IFV. The fact that the CV90 won the Swiss evaluation by price and reliability, but not by performance is something that surprised me when reading; I never considered the Warrior 2000 to be something special and I also didn't think that Kuka's M12 (E4) turret was superior to the CV90's E30 turret at that time.
 
The Norwegians essentially dislike(d) all things that the Swiss also disliked on the evaluated CV9030: low troop compartment size (that's why tthe SPz 2000 has an enlarged one), bad thermal imagers (thats why the CV90 Mk II has second generation thermal imagers) and no hunter-killer capability (too expensive to fix for the Swiss Army).
 
____
 
Not very well known, but Germany actually tested an upgraded version of the CV9030CH in late 2001/early 2002. It was rejected for several reasons, which is why the Puma development was started in Fall 2002. I am still searching for more info on that, but there is an archived question in the Swiss parliament, where a member of one party questions the value of the CV9030CH in the Swiss Army based on the German critique. I.e. it appears that the CV90 in Germany was fitted with a mine protection kit, which was still found unsatisfactory. The basic conception of the vehicle has been claimed to be based on the ideas of the 70s and 80s. The weight of nearly 30 tons of the up-armored variants was too close to the weight limit of the chassis, limiting the growth potential and upgradability of the CV90 in thte future. The exact wording of the Swiss MP says that the CV90 got "the last place" in the evaluation, suggesting it was tested against other vehicles (or concepts for future vehicles). I'll try to look into that topic.

At the request of @anwaralsharrad a topic about non-initiating precursor shaped charges.
 
Basic principle of non-initiating precursors
 
As the name implies, these are specialised shaped charges designed to not initiate something, which in this case is an ERA sandwich. The purpose of this is to punch a hole through the ERA sandwich for the main charge to go through, without setting the ERA off. Achieving this means that the detonation of the ERA sandwich cannot influence your projectile in any way shape or form.
The explanation on how this works is fairly simple: Every energetic material (explosive) needs to be initated, if it isn't initiated it will act like any other material when hit by a projectile. In our case the initiation is done (or not done) via an impact. For an explosive to not initiate by impact, the impact energy needs to be lower than the critical energy* of the explosive. So you basically throw something at the ERA sandwich fast enough to punch a hole through it, but not fast enough to introduce critical energy in the explosive.
 
This is usually achieved by using a special liner material, usually something lighter than copper (in theory you can make the jet slower to make it non-initiating, but then the main charge might catch up with your precursor jet, which you don't want). I've seen PTFE thrown around as a liner material for a non-initiating precursor warhead. The formula for kinetic energy is Ek=0.5*m*v2,, the kinetic energy of something is half the mass multiplied by the square of its velocity. So to lower the energy you can either go lighter or slower.
 
* The impact/shock initiation point of explosives can be quantified by multiple units like J*cm-2, v2d, u2d, ρv2d, √ρv2d, Pd, and probably a whole bunch more. In this topic I will keep it simple and try to not use units.
 
Things that influence non-initiating precursors
 
However, it is quite tricky to get right since a plethora of factors influence the initiation point of an explosive. For starters, the type of explosive used in the ERA block is important:

(Table from "A General Model for the Shock Initiation of Explosives" by F. E. Walker and R.J. Wasley)
 
As you can see, explosives can have wildly varying critical energy points. Although these values are for pure explosives and not the desensitised explosives used in ERA, but this should give you an idea about not all explosives being equal. So a precursor might be non-initiating versus one type of ERA, but not versus another type of ERA simply because they use different types of explosives.
 
A different graph showing the same thing:

(Figure from "The Legacy of Manfred Held with Critique" by EV2 Florian Bouvenot)
 
Furthermore, the impact velocity to initiate an explosive changes when the explosive is protected by a barrier of another material. The effectiveness of this barrier, which in the case of ERA is a flyer plate, depends on its thickness:

(Figure from "The Legacy of Manfred Held with Critique" by EV2 Florian Bouvenot)
 
In this graph everything above the line means "Boom" and everything under it means "No Boom". So to initiate an explosive protected by a barrier, you can either go faster, or go heavier. And again, this means that a non-initiating precursor might not be non-initiating because one type of ERA might have a thinner flyer plate than an other type.
Even the material used for the barrier has an effect:

(Figure from "The Legacy of Manfred Held with Critique" by EV2 Florian Bouvenot)
 
Again, a non-initiating precursor might be an initiating precursor depending on the material of the flyer plate. There has been research about using glass or ceramic flyer plates. It might be that a precursor that's non-initiating versus a steel flyer plate, is initiating versus a glass flyer plate.
 
Another thing to take into account, is whether or not the explosive is confined on all sides. For example, Nozh has a non-uniform confinement, so Nozh might react differently to a non-initiating precursor. The effect looks like this:

(Figure from "The Legacy of Manfred Held with Critique" by EV2 Florian Bouvenot)
 
 
But the most important one for us, is projectile material:

(Figure from "The Legacy of Manfred Held with Critique" by EV2 Florian Bouvenot)
 
As you can see, the lower the material density, the faster the projectile has to go to initiate an explosive. This is what we want, because we want to punch a hole without initiating an explosive. However, a lighter material also means that it has less penetration compared to a liner with a heavier material. ...but a lighter material can be accelerated to higher velocities, which means a higher penetration than a slower jet with the same density. So basically, whether or not a non-initiating precursor is actually non-initiating depends on a significant amount of variables, each of which influences the other. Basically it's a giant mess of variables to keep an eye on, but the desired result is clear: Punching a hole through a metal-explosive-metal sandwich without setting off the explosive. After that you can throw whatever you want through that hole without having to worry about setting off an explosive, which means that you can use the best penetrator you can make.
 
... @anwaralsharrad does this answer your questions? If not, feel free to ask anything.
 
 

more of Mechem Krokodil




 
and G6 based SAM

 
 

UDES 09 armor layout:

 
CV90 base armor (various versions):
 
CV90 and Bradley. Making an IFV taller than the Bradley would be a real challenge.

Now about some good stuff, heavy armor.

T-72M1, we have around 350 these tanks in total, with around 159 in active service. No upgrades are planned for them, and are meant to be replaced as soon as it will be possible.

PT-91 "Twardy", Poland have around 232 of these in active service. Improvements over standard T-72M1 include, new 850HP diesel S-12U, new explosive reactive armor ERAWA-1 and ERAWA-2 (I will post separate informations about them later), fire control system Drawa or it's improved variant Radew, improved TPD-K1 day sight and also thermal sight, there are two variants of thermal sights, older Israeli made TES, and new Polish 2nd gen FLIR KLW-1 "Asteria". Vehicle is also equipped with self defense system SSP-1 Obra-3 which includes both laser warning receivers, and new smoke dischargers Tellur mounted on the both sides of turret. Other major improvements were only included in export variants PT-91Ex, PT-91M and PT-91P. There was also a technology demonstrator called PT-16 that is a proposal for T-72M1 and PT-91 tanks upgrade, however the proposal contains two solutions for turret, either rebuild + addon armor for existing turret, which was presented on the technology demonstrator, and second, probably new welded low profile turret based on the UMPG Anders design.


PT-16 technology demonstrator.

Poland purchased from Germany 142 Leopard 2A4 tanks, currently upgrade codenamed Leopard 2PL is developed by Rhinemetall and polish industry.

Leopard 2PL technology dekonstrator.

Besides Leopard 2A4's, also 105 Leopard 2A5's are in service.

BWP-1 as BMP-1 is called here, we still have around 1268 of these antiques in service, tough replacement for them is currently in development, codename "Borsuk". It is still uncertain if "Borsuk" will be based on domestically designed chassis, or on foreign one purchased via license, both options are currently considered, also issue with amphibious capabilities are debated, initially there was requirement for new IFV to be amphibious, but after intelligence reports from Ukraine, now it's considered that perhaps heavier armor is a better choice.
 
Also new IFV "Borsuk" will be equipped with unmanned turret ZSSW-30. Armed with 30mm ATK Mk44, 7,62mm coax, and Spike ATGM's. Same turret is also intended as upgrade for Rosomak wheeled IFV.


Early concept model of IFV "Borsuk".

Now about Rosomak, this is the basic Rosomak M1 variant which is literally just wheeled IFV, equipped with manned turret Hitfist-30P armed with 30mm Mk44 and 7,62mm coax, there is also planned upgrade for these turrets to equip them with Spike ATGM's launchers.

Here is also IFV variant with unmanned turret ZSSW-30 prototype on the firing range.
 
There were many more specialized variants of Rosomak developed. For example fire support variant with 105mm gun or 120mm gun, yet these are not ordered by Polish Army, tough 120mm variant might be eventually ordered.

Rosomak/Wilk armed with 120mm gun.

Rosomak-M with upgraded Hitfist-30P turret, as well as new addon armor acting also as buoyancy elements improving vehicles amphibious capabilities.

Experimental Rosomak-XP with improved suspension and armor protection + some minor improvements.

Rosomak WRT, you can consider it as ARV variant of Rosomak family.

Rosomak WEM.
 
Of course there are many more variants in development.
 
Another interesting R&D program was UMPG Anders for modular tracked platform.

Single technology demonstrator was build and later to prove it's modularity reconfigured in to several variants, these were.

Light tank with 120mm gun in low profile manned turret.

Light tank with 105mm gun in CT-CV turret.

IFV variant with Hitfist-30P turret.

IFV with unmanned Hitfist-OWS turret.

Unmanned autonomous tank destroyer with Spike ATGM's in AMUR weapons module.

Improved IFV variant with new version of Hitfist-30P turret with Spike ATGM launchers.
 
 
 

So, recently I stumbled upon something fairly interesting. Most of the people here know about shaped charges and how they work, the principles behind it are fairly well known. Recently however, there has been research about a new 'class' of shaped charges: Reactive Liner Shaped Charges. As the name implies it's a shaped charge with a liner made out of a reactive material.
 
Please note that I still do not fully understand the workings of Reactive Liner Shaped Charges, this post may be changed or updated depending on new information and/or discussions.
 
What is a reactive material, you say? One of the papers explains it like this:
(Demolition Mechanism and Behavior of Shaped Chargewith Reactive Liner, Jianguang Xiao et al., 2016)
 
In simple terms, it's a material that only explodes when you hit it really really really really hard with a hammer. Or when you fire it into a solid material at several kilometers per second. I dunno. It's one of the two.
 
What this amounts to is a shaped charge which forms an exploding jet. Neato.
 
But... why should you care? We already don't fire explosives at an armoured target because it's not very efficient, so why suddenly care now? To answer that I have to compare it to normal shaped charges and explain a few things about explosives. The most important thing to understand is that no explosive detonates instantly, there is always a slight delay. This delay is (almost) negligible at normal projectile velocities, but become important at high velocities. Think hypersonic velocities, like with... shaped charge jets!
The main thing I am not completely sure about is whether the detonation of the shaped charge initiates the liner, or the impact with the target. The self-delay of the reactive material used in most of the tests is ~0.85 and depending on the liner angle the jet can move 2.8 to 5.2 meters before actually exploding. Of course this distance will be a lot less when penetrating because the material slows down. A reactive material with a too low self-delay might detonate during the formation of the jet, or before it actually managed to penetrate the armour (but this only applies in the situation where the reactive liner is initiated by the shaped charge). This is of course not something you want, you want the liner to detonate inside the target to do the maximum amount of damage.
 
And that's the main reason you should care about shaped charges with reactive liners. They do a fuckton of damage.
 
This is your brain: This is the result of a shaped charge with an aluminium liner:

 
This is your brain on drugs: This is the result of a shaped charge with a reactive liner:

To give a sense of scale, that's a 1520 by 1520 mm concrete cylinder. The shaped charge had a diameter of... 81 mm.
 
As you can see the reactive liner does a fuckton more damage compared to a normal liner, this is because the jet literally detonates when it's inside the armour. Concrete is one of the materials that cannot deal with certain forces, which makes it weak versus explosives detonating inside of it. Steel for example cares a lot less about it, but even steel will suffer more damage from a reactive liner than a normal copper liner. The entry hole for a reactive liner is around 0.65 CD whereas for a copper liner it is 0.5 CD. A paper also states the following:
The paper however does not show or describe the "tremendous increase in steel target damage". It does however give some basic information and show photos of the entry holes:
 

 

 
The penetration capabilities of reactive liners in steel targets were "sacrificed slightly" compared to copper liners, but the paper does not elaborate any further.
 
Here's some more information and pictures about the effectiveness of reactive liners against concrete targets, just for shits and giggles:

A 'Bam Bam' is the same warhead as the 81mm one (1.8 kg) from the first photos, except scaled to 18.1 kg. The 81mm charge is called Barnie, by the way. The target is the same ~1500 mm too.
 

As you can see the Bam Bam charge is capable of fucking up massive parts of asphalt roads/runways. A 21.6 cm shaped charge completely destroying around 42 square meters of asphalt.
 

 
But hey, a 21.6 cm charge is fucking massive, lets tone it down slightly.
 
Charges:

 
Test setup:

 
Results:

Sadly there's a bunch of information missing in the tables. It is highly likely that different liner thicknesses were used, but these aren't given in the tables.
Results can be found in the full version of Table 1:

...that's around 9-10 square meters of concrete fucked up by a ~1 kg warhead. That's fucking insane.
 
 
Some other things to note is that due to the materials used in these tests (an aluminium-polymer mix) the jet velocity is significantly higher and the jet length longer than comparable copper liners:

 
So the reactive liner used (26% Al, 74% Teflon) has a jet tip velocity that's around twice as high for shallow charges, but drops to around 1.6 at higher angles. The difference in jet tip velocity is most likely due to the lower density of the reactive liner. This is what Wang et al. said about this:
This poor ductility also increases the probability of fragmentation (jet break-up), which can be seen here:


 
So because the reactive liner has a lower density, it forms a jet quicker, but because of its poor ductility it starts to break up very quickly. Tests have shown that a stand-off that's longer than 2 CD is undesirable, whereas normal liners do not really care about a longer stand-off.
 
However! The research done to make the Barnie warhead show that it is undesirable to have cavitation during the formation of the jet. This cavitation is visible in the above simulations, but can better be seen in this one:

It is very well possible that Wang et al. had a sub-optimal liner design, since the final Barnie jet looks like this compared to a comparable aluminium liner jet:

They are quite similar and the Barnie jet does not have the 'blobs' visible in the simulations from Wang et al..
 
 
 
And last but certainly not least, Xiao et al. calculated the TNT equivalence (RE factor) of the reactive liner:

 
In simple terms, the kaboom-effectiveness of this reactive material is 3.4 to 7.7 times as high as TNT. But since these values on their own are kind of meaningless, lets compare them to other RE factors!
The RE factor of C4 is 1.34.
The RE factor of RDX is 1.6.
PETN? 1.66. 
Torpex? 1.3.
Amatol? 1.1.
ANFO? 0.74.
The explosive with the highest detonation velocity (Octanitrocubane)? 2.38.
THIS FUCKING ALUMINIUM/TEFLON MIX!? MOTHERFUCKING 7.77.
 
Interestingly the theoretical energy contained in the aluminium/teflon mix is only about 4 times as high as TNT. The higher values are most likely due to the addition of kinetic effects.
 
 
So yeah... huzzah for reactive liners. 
 
I might add some stuff to this post later, depending on whether or not I forgot something.

Free Piston linear generator. 

Crappy wikipedia link: https://en.wikipedia.org/wiki/Free-piston_linear_generator
 
 
And two videos:
 
 
 
Not sure where to post this, but I think this could be a really good option for Series Hybrid electric AFVs. 

The frontal section of the Leopard 2's roof is sloped and thicker, supposedly 70 mm thick, because it has to resist incoming APFSDS rounds to such a degree, that they shatter and ricochet. In this area the additional "roof armor" double acts as a storage box with relatively thick coverplate. The proper roof armor covers only the flat section of the roof, which is has thinner base armor (est. 20 to 40 mm).
 

 
To complement the aesthetics, at the left and right of the new roof armor section, additional storage boxes are installed ontop of the side armor of the turret. There are some photos showing the storage boxes open on a Swedish Strv 122, but I cannot find them ATM.
 
On the Spanish Leopardo 2E, the frontal storage box was shortened for some reason, so a small portion of the turret roof (above the breech block of the gun) seems to be exposed:

 
PS: found one

You have storrage all around the armored roof. 

I've found it :

I've found it :

Kurganets-25 with its modular side armour removed.

The Armored Combat Vehicle Puma started as a privat-venture betwen Krauss-Maffei and Diehl in 1983. The two first prototypes were ready first in spring 1986 with a Kuka 20mm two men turret and second in autumn with a Diehl 120mm mortar turret. 
ACV-Puma was intented as an export armored vehicle of the 16-28 t class. 
 

 
By 1983 original concept, it was offered with two engine options (400/600hp) to cope with the level of armor protection asked.
The running gear was a mixt of both Leopard-1 and 2 components :
- Leo-1 : road wheels, track support rollers, torsion bars and even the driver's seat ;
- Leo-2 : track adjuster, cooling system components and sproket hub.
It was possible to run the engine outside of its compartment. 
 
In 1988, the concept was improved further :
- the class range reached 38t ;
- the engines offer was 440 or 750hp strong ;
- the chassis was now available in two length (5/6 road wheels) and  hight/low profil hull (20cm).

The ACV-Puma was a contender at the Norwegian IFV programme from 1991 and the Turkish 1987 relaunched TIFV programme.
Norway chose CV-90 and Turkey, the AIFV.
(If anyone have information about how it was a serious contender, I'm interested)
It was also evaluated by the Swiss army in 1991. I don't know if it took part to the Char de grenadiers 2000 programme. 
 

In 1983´s concept, the difference betwen the low profil hull and the 20cm higher hight profil hull was obtained by a "box shape vertical raised" rear compartment. With the 1988's design, the front slop is now different to achieve a better ballistic protection. 
 
When considering documentations of this period, it's important to note the mine/IED protection was not a priority like today. 
 
I'll post soon a scan showing general layout of the troop compartment. It's a Marder/BMP old fashion one with soldiers facing outside. 
 
Even if it was not a success at exportation, I think ACV-Puma must be known because of both :
- the outdated combat beliefs of the 80's (still vigourous today) ;
- and advanced proposal  such as the differential hull length from the drawing board. 
 
I have a question :
Does anyone known if a 6 road wheels chassis was ever built ?

The Armored Combat Vehicle Puma started as a privat-venture betwen Krauss-Maffei and Diehl in 1983. The two first prototypes were ready first in spring 1986 with a Kuka 20mm two men turret and second in autumn with a Diehl 120mm mortar turret. 
ACV-Puma was intented as an export armored vehicle of the 16-28 t class. 
 

 
By 1983 original concept, it was offered with two engine options (400/600hp) to cope with the level of armor protection asked.
The running gear was a mixt of both Leopard-1 and 2 components :
- Leo-1 : road wheels, track support rollers, torsion bars and even the driver's seat ;
- Leo-2 : track adjuster, cooling system components and sproket hub.
It was possible to run the engine outside of its compartment. 
 
In 1988, the concept was improved further :
- the class range reached 38t ;
- the engines offer was 440 or 750hp strong ;
- the chassis was now available in two length (5/6 road wheels) and  hight/low profil hull (20cm).

The ACV-Puma was a contender at the Norwegian IFV programme from 1991 and the Turkish 1987 relaunched TIFV programme.
Norway chose CV-90 and Turkey, the AIFV.
(If anyone have information about how it was a serious contender, I'm interested)
It was also evaluated by the Swiss army in 1991. I don't know if it took part to the Char de grenadiers 2000 programme. 
 

In 1983´s concept, the difference betwen the low profil hull and the 20cm higher hight profil hull was obtained by a "box shape vertical raised" rear compartment. With the 1988's design, the front slop is now different to achieve a better ballistic protection. 
 
When considering documentations of this period, it's important to note the mine/IED protection was not a priority like today. 
 
I'll post soon a scan showing general layout of the troop compartment. It's a Marder/BMP old fashion one with soldiers facing outside. 
 
Even if it was not a success at exportation, I think ACV-Puma must be known because of both :
- the outdated combat beliefs of the 80's (still vigourous today) ;
- and advanced proposal  such as the differential hull length from the drawing board. 
 
I have a question :
Does anyone known if a 6 road wheels chassis was ever built ?

The Armored Combat Vehicle Puma started as a privat-venture betwen Krauss-Maffei and Diehl in 1983. The two first prototypes were ready first in spring 1986 with a Kuka 20mm two men turret and second in autumn with a Diehl 120mm mortar turret. 
ACV-Puma was intented as an export armored vehicle of the 16-28 t class. 
 

 
By 1983 original concept, it was offered with two engine options (400/600hp) to cope with the level of armor protection asked.
The running gear was a mixt of both Leopard-1 and 2 components :
- Leo-1 : road wheels, track support rollers, torsion bars and even the driver's seat ;
- Leo-2 : track adjuster, cooling system components and sproket hub.
It was possible to run the engine outside of its compartment. 
 
In 1988, the concept was improved further :
- the class range reached 38t ;
- the engines offer was 440 or 750hp strong ;
- the chassis was now available in two length (5/6 road wheels) and  hight/low profil hull (20cm).

The ACV-Puma was a contender at the Norwegian IFV programme from 1991 and the Turkish 1987 relaunched TIFV programme.
Norway chose CV-90 and Turkey, the AIFV.
(If anyone have information about how it was a serious contender, I'm interested)
It was also evaluated by the Swiss army in 1991. I don't know if it took part to the Char de grenadiers 2000 programme. 
 

In 1983´s concept, the difference betwen the low profil hull and the 20cm higher hight profil hull was obtained by a "box shape vertical raised" rear compartment. With the 1988's design, the front slop is now different to achieve a better ballistic protection. 
 
When considering documentations of this period, it's important to note the mine/IED protection was not a priority like today. 
 
I'll post soon a scan showing general layout of the troop compartment. It's a Marder/BMP old fashion one with soldiers facing outside. 
 
Even if it was not a success at exportation, I think ACV-Puma must be known because of both :
- the outdated combat beliefs of the 80's (still vigourous today) ;
- and advanced proposal  such as the differential hull length from the drawing board. 
 
I have a question :
Does anyone known if a 6 road wheels chassis was ever built ?

ARA
 
 
The AMX-30B2 Brenus uses BS-G2 reactive modules,  here is a picture of a scale model of a M60A1 fitted with BS-G2 :
 

 
 

I think there are multiple factors that need to be considered. Shtora and Sarab are effective nowadays, but only against older missile types. Why are these systems effective? Because there was enough time to analyze the existing missile systems, that was quite hard back in the Cold War. The Soviets with Shtora faced a much greater amount of competition, still the system appeared rather late (~1985) and failed to intercept the TOW and MILAN missiles during the Greek tests. So it seems rather questionable, that a 1970s tank (a tank "prior to the adoption of the Leopard 2") could make good use of a Shtora/Sarab system.
 
One thing to consider: The majority of opposing ATGMs in the 1970s and even in the 1980s still were MCLOS missile systems, at least for the Warsaw Pact countries. The Soviet Army could afford all the new and fancy stuff, the other countries in the Warsaw Pact not so much. For example East-Germany received the Fagot ATGM in 1975, the Konkurs and Metis were delivered in 1983 and 1984, while the gun-launched Bastion ATGM was adopted in 1988 and the Shturm missile was adopted in 1989. Even then the Malyutka remained the most numerous missile, though apparently a number of them were upgraded to SACLOS systems. The SPG-9 and RPG-7 were considered to be the main tank killers though.
The Soviet Union adopted Shtora, because they faced a very different opposition. West-Germany alone had something in the area of 3,000-4,000 SACLOS launchers (316 Jaguar 1, 165 Jaguar 2, 170 Wiesel with TOW, ~2,100 Marder with Milan, several hundred Fuchs and Wolf with Milan, 212 PAH-1 helicopters, + several infantry systems).
 
I can understand that it's a bit sad that most modern vehicles don't have an APS, but even the Soviets had a reluctance when it came to adopting APS. No system is perfect, so when you don't have to invest lots of money into a system of potentially limited value, then you won't do it. Even before the Israelis used Blazer for the first time, there was an ERA package being tested on the Leopard 1, which provided protection against 105 mm APFSDS ammo. Just think about that, an armor that could have a Kontakt-5-like impact on tank and gun development a decade earlier!
 
I think it comes down to NATO not having access to enough data on Soviet tanks and missiles. The existence of the T-64 was pretty much unknown during the 1970s, while info on the T-72 was extremely scarce... I have an old edition of Jane's, where the author assumed that the T-64 and T-72 were both the same tank (blaming different reporting names from UK and US for the two designations) and were fitted with either a 115 mm or 122 mm rifled gun, while not a single word about composite armor is mentioned...
NATO believed that ATGMs could deal with all Soviet tanks and that the larger number and higher sophistication of NATO ATGM systems would mean that Soviet tanks were even less likely to survive.
 
When it became clear that the Soviets had composite armor and had developed more modern missile systems, the NATO tanks all were upgraded. The US Army's M60 was meant to receive ERA, but after the M1 Abrams became widespread, it was considered cheaper to not buy it. The ERA package adopted on the M60A1 of the USMC (originally designed for the US Army) is btw. not Blazer, but made in France (it's called something like "ACA" or" AAC"). The AMX-30 received a version of the same ERA system to protect against ATGMs. The Leopard 1 was meant to receive composite armor, but that was canceled after the Soviet Union was gone.
 

*cracks fingers*

Something that has interested me for a while, are shape stabilised projectiles. As in, projectiles that are stable due to their shape. Everybody has heard of rotation stabilised and fin stabilised projectiles, but shape stabilised is kind of different. I guess most of you here have seen shape stabilised projectiles without actually knowing how and why they work.

Geek sidenote: Fin stabilised projectiles are actually fin and rotation stabilised.

As I said, shape stabilised projectile have a stable flight path due to their unique shape.

Figure 1: A 84mm Carl Gustav shape stabilised HEAT-round

Note the slightly ogive front and the stand-off, which are characteristic of shape stabilised projectiles (SSP). Both features are absolutely crucial for the SSP to work.
I'm going to throw you guys into the deep end by showing a .gif of the airflow in front of an SSP.
Here's a link because I can't embed .gifv apparently
The first thing you should notice is the air circulating in some-sort of pocket, and that this airflow is subsonic. Before I continue, here's the airflow in front of a blunt projectile: Clicketyclick
While that projectile has a subsonic airflow in front of it as well, it is not circulating.

Here's the airspeed of both projectiles as a normal picture:

Figure 2: Airspeed in front of an SSP


Figure 3: Airspeed in front of a blunt projectile

It's clear that an SSP has a ogive-shaped subsonic airpocket in front of the projectile. This basically emulates the ogive of a normal rotation stabilised projectile. In other words, it makes it more aerodynamic. But does that airpocket stabilise the projectile?
No it does not.

So why is this projectile stabilised? The key is in what happens when it starts to tumble. Right now, there is nothing stopping the projectile from tumbling, and that's the interesting thing. There is literally nothing stopping the projectile from tumbling, except...


the projectile itself.

Lets take a look at what happens when an SSP starts to tumble. (If I remember correctly, I rotated the projectile 10 degrees)
First off, the airflow in front of the projectile. It's fairly obvious that the airflow has changed. Lets check that again, but this time as a picture.

Figure 4: Airflow in front of a tumbling SSP

Again, it's obvious that the airflow has changed. The subsonic pocket has mainly shifted to one side and the air itself isn't really circulating in the pocket. This change causes a huge change in the Cd of the projectile. Let me show you why.

Figure 5: Pressure in front of a tumbling SSP

Next, the pressure in front of an SSP flying straight.

Figure 6: Pressure in front of an SSP flying straight

Please note the approximate pressure in front of both projectiles. The tumbling projectile has, on one side, twice the pressure as the projectile that's flying straight. Very interesting. What's even more interesting is that the pressure occurs on the opposite of the side it's turning to! The projectile is turning upwards, but the pressure builds up at the bottom. This pressure forces the projectile to start turning down again, forcing the projectile in a state where the pressure on all sides is equal.

Voila, a shape stabilised projectile.


But... why does it work?

The subsonic airpocket is created by the stand-off and that little flange, or whatever you want to call it. The dimensions and placement of both are equally important. The stand-off and its side create the airpocket and the flange give the airpocket the required shape. The stand-off size can vary, but the flange size and placement is very important. If the flange is too far forward or too far back, the airpocket will be either too small or too big. Why does the size of the pocket matter? Because of this:

Figure 7: Subsonic pocket in front of an SSP

I changed the parameters slightly and made all airflow above Mach 1 red. Whatever is not red, is trans- or subsonic. The interesting thing to note here, is the pocket extends to the edge of the projectile (if I made the projectile better it should be exactly on the edge). (Sidenote: Here's the same picture of an SSP at a 10° angle)
While the airpocket does not start at the flange, the flange determines where the pocket starts. If, at this velocity, the flange was further back, there would be supersonic flow hitting the front of the projectile, massively increasing drag. If the flange was further forward, the airpocket would be further forward too. This would mean the airpocket would not end at the edge of the projectile, but further out. Creating an airpocket which is wider than the projectile. This would allow the projectile to tumble a bit, because pressures wouldn't change much unless there is supersonic flow hitting the projectile.

It is also possible to change the size of the airpocket by changing the front of the projectile itself. If the radius connecting the front and the stand-off is too big, the airflow inside the pocket would disrupt the circulation. The same would happen if the radius is too small. The angle of the front is important as well, but I haven't expermented that much with it so I don't know how important it exactly is, but it has an effect on the airflow.

By the way, if the flange did not exist at all, the airpocket would start at around a third to half of the stand-off. Which would completely ruin the airpocket. Without a flange, the stand-off itself would have to be way bigger and longer to create the same kind of airpocket.

But Bronezhilet, I hear you cry, if the airspeed changes, the pocket changes as well!

I'm glad you brought that up, because you are right.

A shape stabilised projectile only works properly within a certain flight envelope. If the projectile is moving too fast, the airpocket would compress allowing supersonic flow to hit the front of the projectile. Which in turns increases drag. By a lot. If the projectile is moving too slow the airpocket widens, allowing the projectile to tumble a bit before it would stabilise.

I've been brainstorming with Colli a bit, and we've come to the conclusion that is why some projectiles are both shape stabilised and fin stabilised. When the projectile is moving too slow for shape stabilisation, the fins would keep it pointing in the right direction.



And that concludes today's lesson. Thank you for reading.

I never even took the words "depleted", "spent" or "bleed energy" in my mouth. Maybe you should read carefully?
 
Kobylkin also says this (in the same paper):
 
Mickovic:
 
Hazell:
 
Hazell, again in a different publication:
 
Kobylkin, again:
 
Held:
 
 
Eehhh... hello? Eroding a penetrator is a basic hydrodynamic interaction principle? Unsupported by any research? Fuck me sideways, hydrodynamic interaction between a penetrator and armour is where any decent researcher will start. If someone doesn't understand hydrodynamic interactions it's nearly impossible to understand the penetration mechanics behind APFSDS and HEAT.
 
The penetration formula for a HEAT jet is basically the same fucking formula as the one used for hydrodynamic penetration:

^ HEAT jet penetration formula
 

^ Hydrodynamic penetration formula
 
Both formulas are from Hazell's excellent book called "Armour; Materials, Design, and Theory".
 
Hello again, are you even reading what you type? You're literally giving the answer to your own question: ｖｅｃｔｏｒｓ
 
Do you understand how those work?
 
Evidently not.
 
Hey here's a hint: THE JET IS MOVING TOO
 
LIKE
 
REALLY REALLY FAST
 
Maybe you shouldn't base your rambling on a single source you apparently do not even have access to which is also fully focussed on figuring out a single aspect of HEAT vs ERA interaction. Shit, if you actually properly read the conclusion of the paper you linked you'd have noticed that it starts with "It is proposed that [...]". For some reason you read that as "IT ABSOLUTELY AND TOTALLY IS THIS".
 
Since we're apparently going to sling journals and papers around, here's a thing for you to read (well, multiple things actually): Everything a fellow called Manfred Held has ever written on ERA, since he was one of the people who invented the fucking thing.
 
But anyway, you just stay you and keep claiming that ERA works by magically interfering with the jet. You correctly said that an impact will create a larger crater than the diameter of the penetrator. Which means that if the plates aren't moving into the path of the jet, ERA/NERA will have no effect. As can be seen in the picture I've posted before:

See? No effect on the penetrator what-so-ever. 
 
But guess what, if you angle the ERA/NERA so that the plates will actually intersect the jet, things happen!

 
So no, ERA/NERA does not fucking work if you don't feed material into the jet.

The bit I quoted from Kobylkin was directed at your question about why the FMP has a different effect than the BMP, not at whether or not feeding material into the jet lowers penetration.
 
Anyway, yes, the main reason why ERA/NERA works is due to feeding material into the jet. Since a penetrator can only penetrate a finite amount of armour, you can lower the thickness of main armour it can penetrate by feeding material (armour) into its path.
 
The faster a plate moves, the more material it can feed into the jet before the jet has passed the plate. A plate basically looks like this after the jet has gone through it:

And the faster the plate goes, the longer Lslit will be. To be specific, it can be calculated with this formula:
 
The jet will also pass through more material if the angle of the ERA/NERA is increased:

 
And what happens when you increase the thickness of the FMP and BMP?


(Note that the BMP in the FMP test is 8 mm thick while the FMP in the BMP test is 1 mm)
 
Anyway, there's lots more I want to say, but I'm a bit ill at the moment so staring at journals and papers isn't the smartest thing to do, I'm already getting a headache and yet I only have a few journals open:

 
I'll get back to this when I'm feeling better, I'm sorry for not being able to give a concise answer at the moment. Or maybe @Collimatrix can take over, he knows about as much as I do on this subject.
 

The explosive compound in ERA (well, any military explosive compound) will only detonate when a certain pressure is reached. If the impact does not reach that pressure, the explosive will not detonate. As long as the pressure doesn't go above a certain threshold it doesn't matter what's hitting the explosive, it simply won't explode. I suppose there's a way to poke a hole through ERA without setting it off, but I haven't yet figured out how exactly.
 
It is. 
 
If you look at various tests with actual ERA, you'll see that the jet isn't noticeably being yawed/deflected, no matter the ERA angle:

You can however see that the higher the angle of the ERA compared to the jet, the more disturbed the jet is. This is simply because the ERA is capable of feeding more material into the jet, degrading it.
 
Actually, here are a bunch of photos of a shaped charge jets versus NERA at different angles:

 
And again, the more material is fed into the jet, the worse it becomes. 
 
 
However, ERA and NERA do actually deflect the jet, but only very slightly. I'm talking about ~50 m/s down for a 55 degree angle ERA sandwich. 50 m/s might sound a lot, until you realise that these jets move forward at a few thousand meters per second. So the downward velocity is negligible.

 
 
The reason the forwards moving flyer plate caused more damage to the jet is because of... vectors, basically..
 
Or as Kobylkin and Dorokhov put it:
 
Also, this is what the paper says about the pictures you linked:

 
Here are the pictures in higher res by the way, for future use:

The EGS also had a torsion bar suspension. According to cross sectional drawings, there are two elastomer mounting elements: one around the support bearings, which connect the running gear module to the hull and one around the torsion bar, acting as air-tight seal. Unfortunately I am not sure if this is the correct translation of the German terms.
 
 
Here is a image from a patent showing a vehicle with a decoupled running gear (and diesel-electic drive). The elastomer connection is marked as 10. On the drawings of the EGS suspension, there is another elastomer connection/seal at the torsion bar. I suspect the M113 might have a similar system.
 

Shared pleasure.
 
And the period is plenty of very interesting news.
 
I just have to find an avatar (It will be Mars-15. ;))

This is the French Vextra demonstrator with a TML-105 turret. 
 

It's made by Tamor. 
10 scops, 1 hatch.