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Operation_Ivy

[BUG REPORT] 20mm HE Ammunition

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A little update, Han replied to my message:

 

According to him, HE damage is based on "accumulated practical data" which is translated into simple parameters like HE load, calibre and mass.

 

I have absolutely no clue what "accumulated practical data" means and i did not get an explanation when asked. As far as i am aware there is next to no data of 20mm HE damage tests except for the one mentioned in this thread. Also i think that Han only skipped over this post sadly, because he did not understand the intention of it in the first place. Then again, i guess it says a lot about how busy he is when he replies on a message after nearly 3 month.

 

As far as my tests and my short conversation with Han goes, i am of the opinion that the 20mm HE damage is more or less decided on a whim and a very debatable topic to say the least. 

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The game has AP and HE ammo at the actual state? Looks like, Minengeschoss needs a new way of Damage calculation + extended damage model.

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It was far from an automated message, yet it left important questions unanswered. Everything points towards that the damage values of the different 20mm HE rounds were decided on a whim more or less without any actual valid data.

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Not just sturdier planes. The damage model is much more diverse now. For example, fuel tanks in the wings are a serious weak point now. However this thread is not supposed to be about the damage model. 

 

In terms of the 20mm HE it seems that there weren't any changes done to it and the changes don't affect how they perform.

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2 hours ago, III./JG5_seaflanker819 said:

in 3.008 seem every plane need more shell to destroy, the plane increase or the cannon decrease?

 

Possibly both. The DD mentioned changes to the plane, for instance that there was a bug double counting the damage on certain kinds of hits.  It also mentions that the angle of the hit now affects the damage: although I am not quite clear on what that means, it could result in a round hitting and doing less average damage that it used to, at certain angles, whatever the plane.

 

Whichever it is you have to look at both when testing.

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A good read thank you for you time and efforts . Hope this gets the attention it deserves .  

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One of the most professional posts which I ever seen on this forum. 

Hats off. 



 

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Very well stated! 

This is one of the reasons I did my post grad studies in statistical analysis - numbers do not lie!

 

People can distort, misrepresent or misinterpret them - but with a well represented argument, it is hard to not agree with the posters findings.

 

I like that he didn't go any further with a "conspiracy theory". He kept this factual!

Edited by JG7_X-Man

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Do we have any further updates on this topic? It would be nice if the devs replied to such an on going and old thread. 

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This test and all the accumulated data is fantastic, thank you for your hard work.  I would also like to know if there has been any update or will be one concerning the issue.

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There has been no update on the issue and i don't think the devs are viewing it as such. 

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On 6/2/2019 at 3:43 AM, Operatsiya_Ivy said:

There has been no update on the issue and i don't think the devs are viewing it as such. 

 

In the absence of dev intervention and Chemical damage modeling, is it possible to tweak the existing values to get damage modeling more historically correct, and release it as a mod?

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On 6/8/2018 at 12:11 AM, Ehret said:

Energy amounts are useful for "physical accounting" but it is momentum and pressure which break things. Rounds' total E gives some insight but doesn't explain what is actually happening or what should happen.

 

The shot's speed may affect explosive effects as well - the shock wave could be modulated by the round's original vector and shell shape. Explosives differ in more ways than the energy content per gram (like detonation velocity). Then we have fragmentation with multitude of variables...

Energy takes into account momentum E=1/2mv^2 and p = mv. E =  p^2/2m. p = sqr(2mE). More energy equals more momentum. 

Edited by =BLW=Tales

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On 9/7/2019 at 4:10 PM, =BLW=Tales said:

Energy takes into account momentum E=1/2mv^2 and p = mv. E =  p^2/2m. p = sqr(2mE). More energy equals more momentum. 

 

Still, more mass at lower velocity will get you more momentum at the same J.

That's why citing just energy content is not whole story. The hit from a heavy club may have just a fraction J of a bullet but can kill just as well. The modern fighter AA cannon rounds are much more similar to the historic Hispano 20mm than the M-shells and the same goes for AA missile warheads. Sizable shrapnel/fragments tend to work better than HE alone.

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Actually it is work that breaks things - force times distance. Because to break something, you have to stretch it over a certain distance with a certain force until it fails. The unit for work is J. It is not a coincidence that it is the same as energy. Momentum's unit is kg*m/s, which has nothing to do with Joule or how to break things.

 

Also, missiles use shrapnel because they are expected to work from proximity, not from penetrating hits. And then modern aircraft are not comparable to WW2 aircraft regarding structural details and critical components. Armament develops as aircraft do.

 

But yes, citing energy is far from the whole story.

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11 hours ago, JtD said:

Actually it is work that breaks things - force times distance. Because to break something, you have to stretch it over a certain distance with a certain force until it fails. The unit for work is J. It is not a coincidence that it is the same as energy. Momentum's unit is kg*m/s, which has nothing to do with Joule or how to break things.

 

There is no way that you can do work at 100% efficiency and that's exactly why you want more momentum - heavier projectile (or fragments) will travel longer distance (including in target's material) before stopping thus can do more useful work for the same input J.

 

Besides it's all compromise with advanced primer ignition blow-back gun like the Mk-108 - you can only have high cyclic rate or ballistic performance with it; not both. Understandable considering it hand fit in such small air-frame like the 109 - all had to be light and fast firing because the targets were big and robust and available time very short because of those pesky escort fighters. There was no other option for relatively light 20-30mm rounds than fill them with HE filler as much as possible.

 

There is another thing which is actually very well represented in the game - lots of HE on target results in huge amount of debris and that's is even worse when you have shot from short distances because of poor ballistics. That would be a big no with faster modern jets with powerful air hungry yet delicate jet engines.

Edited by Ehret

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47 minutes ago, Ehret said:

There is no way that you can do work at 100% efficiency and that's exactly why you want more momentum - heavier projectile (or fragments) will travel longer distance before stopping thus can do more useful work for the same J.

 

Gas in a contained environment like the inside of a wing or fuselage will work at a far higher efficiency than any solid high speed object like splinters. It's the main reason mine shells can rip structures apart whereas splinters can only punch some holes. The amount of aluminium ripped apart (and thus transferred and absorbed energy) is maybe a factor of 10 higher with gas pressure of a mine shell than it is with splinter damage from a HE shell. That's not just because of higher initial energy, it's also because of a much more efficient energy transfer. And, of course, gas pressure will automatically attack the weakest points of a structure, splinters will randomly punch holes.

 

Seeing that this is the bug reports section, I'll leave it at that.

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2 hours ago, Ehret said:

Besides it's all compromise with advanced primer ignition blow-back gun like the Mk-108 - you can only have high cyclic rate or ballistic performance with it; not both.

But you can enlarge the chamber. The Oerlikons/Hispanos were were API as well (all „Becker based“ guns) and some of them had pretty decent ballistics and fire rates, at least concerning practical purposes.

 

AFAIK the MK-108 sacrificed ballistics for building the gun especially light and compact. They could well have given it better ballistics, but the higher gas pressure would have required a longer barrel and a significantly heavier bolt (and stronger spring). But you do not require that when all you want is getting a lot of grenades 400 m ahead of you.

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On 9/13/2019 at 5:19 AM, Ehret said:

 

Still, more mass at lower velocity will get you more momentum at the same J.

That's why citing just energy content is not whole story. The hit from a heavy club may have just a fraction J of a bullet but can kill just as well. The modern fighter AA cannon rounds are much more similar to the historic Hispano 20mm than the M-shells and the same goes for AA missile warheads. Sizable shrapnel/fragments tend to work better than HE alone.

Mgeschoss is not a parameter for modern aircraft because rate of fire. But destructive Power per round is greater than hispano. Modern airfight requires supremes rate of fire because high aircraft speeds. There is compromises in rate of fire when shoting more massive rounds and vice versa. But in case of multiple barrel autoguns like the A-10 Cannon this problem of overheat while firing large and massive projectiles at high rate are overcome.

On 9/13/2019 at 5:19 AM, Ehret said:

 

Still, more mass at lower velocity will get you more momentum at the same J.

That's why citing just energy content is not whole story. The hit from a heavy club may have just a fraction J of a bullet but can kill just as well. The modern fighter AA cannon rounds are much more similar to the historic Hispano 20mm than the M-shells and the same goes for AA missile warheads. Sizable shrapnel/fragments tend to work better than HE alone.

Energy already takes into account mass and speed. You should have more mass to compesate less speed and vice versa. A-10 gun has much more to do with mgeschoss than hispano.

Edited by III./SG77-G_Boelcke

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2 hours ago, III./SG77-G_Boelcke said:

A-10 gun has much more to do with mgeschoss than hispano.

 

No it does not. The A-10's 30mm Autocannon it is designed for use against armour, not aircraft, and has nothing whatsoever to do with mineshells. It is a very high velocity weapon that fires mainly shells with a depleted uranium penetrator plus an HEI round with standard fragmentation and incendiary effects.   

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