ERA: how it works, how it could work

So as an extension to the original armor penetration thread, I'd like to discuss ERA (explosive reactive armor) and how it works & could work in Arma 3. This isn't a purely theoretical discussion, after all the armor thread lead to the Real Armor Mod.

How it works now in Arma 3 currently:

• It doesn't; unless I'm missing something, there is no representation of ERA or special armor of any kind (unless you count explosionShielding, which is far too general to fit the bill).
  

An idea of how it "should" work (IMO):

• BISURF (armor materials) should have 3 more variables: kineticResistance & HEATResistance; by default they = 1. These are a multiplier to thickness vs. kinetic/HEAT weapons. The 3rd variable is depletionType, with the default value being 0 (the armor does not deplete, e.g. regular armor or "electric ERA"); "1" indicates the armor is an ERA panel that disappears after being hit, "2" indicates depletion with residual aplique effect (e.g. "Kontakt-5").
  
• Weapons should have one more variable: HEATStrength; the default value is 0, which means it is not a HEAT weapon. Regular HEAT warheads have a value of 1, while special warheads (tandem, etc.) will have values>1. This value is a multiplier to the weapon's "caliber" (penetration) vs. any armor with HEATResistance >1.
  
• ERA would be modeled in a vehicle's P3D Fire Geometry just like any other armor. Thus covering just where it belongs and nowhere else.
  

How it could be made to work:

OK, BIS is probably not going to follow my code advice, so let's consider possible workarounds.

• Investigating now as I work on the Real Armor Mod... I will update this post with results.
  

I'm a firm believer in Occam's Razor: the most parsimonious solution is the best one. So if you can think of a more elegant solution to modeling ERA (either in code, or as a workaround, or a script), feel free to post. (Bakerman has given a lot of thought to this and will probably post here. But if he doesn't, look him up to see his exciting work on the subject. I'm looking into a simpler approach that might complement Bakerman's work.)

Edited January 25, 2014 by Olds

I agree with everything

I'm really not sure I understand your approach.

This either requires scripting or BIS re-writing their configs to help you. I'd be shocked if there was any way to distinguish between KE and HEAT ammo in the game.

And if you use scripts, you might as well just do what ACE did, so you can simulate everything. ACE just gave AT ammo types an RHA value and variables for HEAT, KE or Tandem warhead. And tank armor had an RHA value with ERA that would be depleted with each hit.

Excellent points, all maturin.

I'm really not sure I understand your approach.

This either requires scripting or BIS re-writing their configs to help you.

No, I'm not expecting BIS to do anything (except maybe read the thread :) ). But it's worth trying to figure out how it would work if it was coded--if for no other reason than it might help you think through how you would approach it with scripting.

I'd be shocked if there was any way to distinguish between KE and HEAT ammo in the game.

Almost certainly not, but worth finding out exactly what is in there. After all, it only took a few judicious config workarounds to completely transform the armor/penetration system (not that I think we'll be that lucky with ERA).

And if you use scripts, you might as well just do what ACE did, so you can simulate everything. ACE just gave AT ammo types an RHA value and variables for HEAT, KE or Tandem warhead. And tank armor had an RHA value with ERA that would be depleted with each hit.

I used to think this but not anymore. I wouldn't do what ACE did with Arma 2. The ballistics simulation has changed and it makes sense to take advantage of the new features it offers rather than simply reinvent them with a script. For example, I think it'd be redundant to start adding RHAe values into weapons & armor. Also treating tandem as a flag rather is overly limiting, IMO, when there are different degrees of "tandem" out there--which is why I suggested a scalar value.

You could argue different ways, I certainly wouldn't suggest my idea is the best one.Besides, I'm far too new to scripting to do anything like this myself.

The idea of this thread is just to move the conversation forward to the way Arma 3 works. And hopefully spread the knowledge of a) how precisely the ballistics simulation works now and therefore b) how to take advantage of that in the most performance-efficient way possible.

I like this.

You've done the hard work with laying out the idea, now it just needs to be implemented and tested.

The system is capable of knowing who killed what, so it shouldn't be a stretch to assume that it knows the weapon/bullet involved.

...

I'm a firm believer in Occam's Razor: the most parsimonious solution is the best one. So if you can think of a more elegant solution to modeling ERA (either in code, or as a workaround, or a script), feel free to post. (Bakerman has given a lot of thought to this and will probably post here. But if he doesn't, look him up to see his exciting work on the subject. I'm looking into a simpler approach that might complement Bakerman's work.)

This approach alone deserves applause. I am very much looking forward to see if something simple and beautiful comes from this, hopefully to result in improving the existing vehicles along with future content. Especially with the selective ability to apply these surfaces to the appropriate areas on a vehicle, taking careful aim at an enemy target will become more useful.

As an intermediate step, this is more useful than attempting to make the Active Protection work. I am looking forward to seeing what you guys can come up with, hopefully BI will take what you've discovered and if at all feasible, bring it to the native game. Community-Developer synergy, hopefully.

A better way to deal with those variables--more in keeping with the current BISURF values--would be to change "HEATResistance" to "HEATPenetrability". And change it from a multiplier value to a penetration value just like "bulletPenetrability".

I guess you could also dispense with kineticResistance altogether and simplify everything. "bulletPenetrability" effectively represents the same thing already (I think).

The point is that certain armors--Chobham, ERA, etc. are more resistant to HEAT penetration than they are to kinetic penetration. The damage system should reflect this differentiation. Whether an armor is depletable (ERA) or not (Chobham) or in-between (Kontakt-5) is a separate issue and that is reflected by the "depletionType" value.

P.S. Yes, I know if we get pedantic we can say all armor is depletable to varying degrees. But that'd be getting needlessly detailed. :)

P.P.S. I don't think tandem-penetrators and other anti-ERA measures have any effect on composite armors. So HEATstrength values over 1 should probably only be applicable to ERA.

Edited February 3, 2014 by Olds

Just a little note that most of this will be incorporated into the next version of RAM... I guess that would be Alpha 0.0.5. (Heck I might even call it beta after that!)

See, I told you it wasn't just a theoretical discussion! :p

Ok, some explanation about ERA and how it works.

ERA is one of several types of vehicle protection that can be named as dynamic protection.

@Olds, you made actually a mistake in statement that for example "Kontakt-5" is something between normal ERA and "Chobham" (but in fact such thing as Chobham armor, development program was codenamed "Burlington" and all different types of armors developed within it, were not codenamed).

Every type of ERA, be it "Kontakt-1", "Kontakt-5", "Relikt", "Knife" or "Duplet" are depletable. Which means that a single cassette or module that is struck, explodes and disintegrates.

Another misunderstanding of how ERA works is that it's protection is meassured in RHA equivalent. ERA does not adds RHA protection, it just reduces penetration capabilities of projectiles. In case of shaped charge jets (HEAT), the main mechanism is to cause spaciation of the jet itself. Smaller jet fragments have very low penetration capabilities compared to continous jet.

In case of APFSDS ammunition, mechanism is actually very similiar, heavy or universal ERA, causes APFSDS rod to bend, break etc. So smaller fragments of the rod, have smaller penetration capabilities.

And there is another aspect, some types of ERA, can actually defeat tandem HEAT warheads, for example Ukrainian "Duplet" can do this, also Russian "Relikt" is reported to have such capabilities or Polish ERAWA-2.

So it might be problematic to simulate ERA.

Actually it can be also problematic to simulate composite armor as well. This is because we have actually two types of composite armor, passive like soviet "Combination K" used on tanks such T-64, and we also have dynamic type, which can be called as composite variant of NERA, such armor is used for example on M1 Abrams tanks, Leopard 2, T-72B, T-90 or Merkava Mk4. NERA actually works very similiar to ERA, but does not explodes and have a multi hit capability. Also modern NERA which includes composites can be very efficent.

I hope that at least some of my knowledge might help. :)

don't forgot on the market is active era and not active ( no expositions )era. for example on merkaba , ifv puma .

Thank you for a more detailed discussion Damian--I agree with everything here! However, we should keep the big picture in mind. While I'm talking about improving the armor realism pretty dramatically... I don't think it's practical to turn the game into a scientific armor simulator. Measuring any complex armor in RHAe is--of course--a simplification. Not even the most hardcore armor game (e.g. Steel Beasts Pro) does much more than this AFAIK.

I don't think it's practical or even desirable to go beyond the standard practice of expressing armor protection in terms of mm of RHA equivalence. And we follow the standard of splitting RHAe into values vs. A) kinetic weapons & B) HEAT warheads. "TE-KE" & "TE-CE" if you will.

Now let's dig in to some details...

[apologies, armor nerd discussion :p]

@Olds, you made actually a mistake in statement that for example "Kontakt-5" is something between normal ERA and "Chobham" (but in fact such thing as Chobham armor, development program was codenamed "Burlington" and all different types of armors developed within it, were not codenamed).

Sorry, I didn't mean to imply that K-5 was a composite like Chobham, merely that is was somewhere between depletable and non-depletable. (Technically there may be a minor applique effect that remains after the explosive cell has fired).

Every type of ERA, be it "Kontakt-1", "Kontakt-5", "Relikt", "Knife" or "Duplet" are depletable. Which means that a single cassette or module that is struck, explodes and disintegrates.

Indeed. All armor ablates and gets weaker at varying rates--ERA just much faster than most. :) (P.S. Regarding the name "Chobham": multiple generations of Western composites are colloquially referred to by that nickname--even in military manuals--so I merely follow the tradition :)).

Another misunderstanding of how ERA works is that it's protection is meassured in RHA equivalent. ERA does not adds RHA protection, it just reduces penetration capabilities of projectiles. In case of shaped charge jets (HEAT), the main mechanism is to cause spaciation of the jet itself. Smaller jet fragments have very low penetration capabilities compared to continous jet.

Yes and no, but it's a good point. There's real life and there's simulating in a game like Arma. The key question is: which mathematical method will give us the most reasonable results? Having ERA reduce penetration by a simple factor (say %50) will not give reasonable results: you will end up with the smallest warhead penetrating ERA (when it would be fully disrupted IRL). Having ERA add to TE-CE--while certainly a simplification--will give much better results. Would you like to propose a more realistic alternative? Keep in mind that we are working with a simple formula:

(Arma penetration in mm) = speed*caliber*bulletPenetrability

And there is another aspect, some types of ERA, can actually defeat tandem HEAT warheads

Now tandem vs. ERA needs more thought. Do we treat tandem's as simply having more penetration? What about the fact that some weapons--e.g. top-attack--don't fire both jets into exactly the same "hole" and thus help vs. ERA but don't simply add the two penetration values together? My proposal above attempts to sort-of reflect that variation, but it's far from well-cooked...

[/apologies, armor nerd discussion]

Now I look forward to your contributions to the NATO-Pact mod I'm planning! That's where the RAM improvements will really be put to work as I'll be able to model armor types and thicknesses in all their glory! We'll have lots to discuss then I hope! :)

Thank you for a more detailed discussion Damian--I agree with everything here! However, we should keep the big picture in mind. While I'm talking about improving the armor realism pretty dramatically... I don't think it's practical to turn the game into a scientific armor simulator. Measuring any complex armor in RHAe is--of course--a simplification. Not even the most hardcore armor game (e.g. Steel Beasts Pro) does much more than this AFAIK.

I don't think it's practical or even desirable to go beyond the standard practice of expressing armor protection in terms of mm of RHA equivalence. And we follow the standard of splitting RHAe into values vs. A) kinetic weapons & B) HEAT warheads. "TE-KE" & "TE-CE" if you will.

Well you are right that ArmA engine is not the best one for armor simulation.

Sorry, I didn't mean to imply that K-5 was a composite like Chobham, merely that is was somewhere between depletable and non-depletable. (Technically there may be a minor applique effect that remains after the explosive cell has fired).

Nope. I know what you mean that there might be left some applique effect, and I know from where it comes. I think you read it at old internet site made by Vasili Fofanov? I know Vasili, he said once to me that he just never updated his site, and actually he was mistaken. "Kontakt-5" after explosion does not leave any applique effect, whole cassette or module is just blow off from armor. I might provide you with photos of T-90A tank after ballistic tests, preaty much where projectile hit and there was ERA, ERA just blows off. A hell with it, here is photo:

http://s13.radikal.ru/i186/1102/5b/d8fb3b294b60.jpg

Indeed. All armor ablates and gets weaker at varying rates--ERA just much faster than most. (P.S. Regarding the name "Chobham": multiple generations of Western composites are colloquially referred to by that nickname--even in military manuals--so I merely follow the tradition ).

Well, if you are interested in some historical insight in to UK/US special armor development, I have a good, incredibly reliable source, however these articles are in Polish, and I don't know if you can read in it. These are two articles by Paweł Przeździecki, made for our army's military history review. I may send you these, so you can try luck with translator?

Yes and no, but it's a good point. There's real life and there's simulating in a game like Arma. The key question is: which mathematical method will give us the most reasonable results? Having ERA reduce penetration by a simple factor (say %50) will not give reasonable results: you will end up with the smallest warhead penetrating ERA (when it would be fully disrupted IRL). Having ERA add to TE-CE--while certainly a simplification--will give much better results. Would you like to propose a more realistic alternative? Keep in mind that we are working with a simple formula:

(Arma penetration in mm) = speed*caliber*bulletPenetrability

Well I had idea how to make this more realistic. If we have for example armor surface, with protection of RHA equivalent of 800mm vs KE, and we have projectile capable to penetrate only 500mm of RHA and this is kinetic energy projectile, then normally armor should be impenetrable for it. I think this is the most close to reality as we can get. And it would also force players to play more tactically. For example using more often hull down position, as well as trying to hit sides of vehicle or weak spots like gun mantle?

Because yeah, some types of tanks have in some places armor that is impenetrable for current generations of weapons.

But of course this is only idea.

Now tandem vs. ERA needs more thought. Do we treat tandem's as simply having more penetration? What about the fact that some weapons--e.g. top-attack--don't fire both jets into exactly the same "hole" and thus help vs. ERA but don't simply add the two penetration values together? My proposal above attempts to sort-of reflect that variation, but it's far from well-cooked...

Ah, this is a good point. Indeed it is a problem I was discussing a lot in the past. Well, in theory some tandem warheads have precursor charge placed in line with main charge, so in theory precursors should create a clean path for main charge before it's own erosion will made it ineffective. In such case indeed, good idea might to just increase overall penetration capability. For simplicity and engine limitations sake.

Warheads with assymetrically placed precursor and main charge might be more problematic, same with top attack ATGM's with EFP charges instead of HEAT.

Now I look forward to your contributions to the NATO-Pact mod I'm planning! That's where the RAM improvements will really be put to work as I'll be able to model armor types and thicknesses in all their glory! We'll have lots to discuss then I hope!

No problem, I can help with my knowledge, especially that in the past with friends we made some armor thickness estimations (and our are very close to reality) as well we have some estimations of real modern tanks turret armor, Leopard 2. So if you needs something, I will gladly help. :)

Just a quick link to a post on the subject of how HEAT warheads work IRL.