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[0054325 & 0054326] APHE incorrect damage zone and fragmentation power


This is a joint work of @Ulatersk and me.

 

I would like to thank @arczer25, @Hornet331 and @KH_Alan for help with this report. :salute: 

 


Fragmentation Zone part in this report is outdated. You can find updated version here:

 

Hello,

 

I would like to report a few incorrect behaviors of all armor piercing rounds with HE filler - I will refer to them as APHE rounds in this report, although it is not only about rounds labelled as APHE in War Thunder. In my opinion those issues are not only making those rounds' effects incorrect and unhistorical, but also giving them huge advantage over all other ammunition types. Considering that not every tank and not every nation is using APHE rounds, those issues are largely affecting the balance in the game.

 

The main issues I would like to report are: 

- damage zone - the area where fragments from HE filler explosion are distributed

- filler explosion power - ability to kill tankers by HE filler

 

For starters - for all readers - short introduction and explanation of APHE type rounds.

 

DESCRIPTION OF APHE

The idea of APHE round is to combine penetrating capabilities of AP round with damage from high explosives. This is the example of the APHE round, the american M82 round.

Spoiler

JPzlEI6.jpg

You can see the round has a shape similar to AP, but it's rear part is drilled to be filled with explosive material and it’s closed with fuze. The fuze is detonating explosives in some amount of time after round hits something, so the explosives will explode inside of the tank, not before penetration. In game we have this time delay transferred into distance after penetration of the armor, after which the round will explode. So the real distance between point of penetration and the point where round explodes depends on remaining velocity, which most probably is not calculated. For now, I’m going to ignore this issue, although it might be reported in the future - fixing it would require a lot of programming work and game changes, while I want to focus on issues that affects game the most.
 
Now let's analyze the explosion itself. First, the amount of explosive power is very different for different rounds, for example the round caliber tells lot about the weight of explosives used (but that’s not the rule). Also the amount of explosives is correlated with round's penetration power - the more explosives are used, the less penetration the round has. That's why 100 mm Soviet round has less explosives than 85 mm, because designers started to care more about penetration.

 

To illustrate the power of filler explosion from APHE rounds, please imagine a hand grenade attached to round, and exploding inside the tank. Standard Soviet hand grenade from WW2 was this one "F1 Hand Grenade". It contains 60 grams of TNT. The American "Pineapple" had two ounces of TNT (57 grams). It is dangerous weapon, but it's definitely not powerful enough to kill entire crew, or cause any explosion of ammunition or damage of parts like gun breech. 75 mm PzGr for KwK 40, which we will be using for testing has bit less than 30 g TNT equivalent, while 88 mm PzGr from Tiger has a bit more than 100 g.

 

1. DAMAGE ZONE

One of the most important things that should be revised in HE filler explosion in WT is the zone of the fragmentation. According to fragmentation zones of HE explosives, we can see how explosion is "escaping" from the round. I'm using this 75mm T3 HE shell explosion zone analysis, because it's the most detailed one

Spoiler

V8qgiph.jpg


This image is taken from the document:

Fragmentation effects of the 75 mm  HE shell T3 (M48)
http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0702233

 

The other document that contains similar analysis of explosion zones is:

Handbook of Ballistic and Engineering Data for Ammunition. Volume 2

http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA955369

 

Interesting picture we can find on the page 26 of the second document. We can see how the explosion zone looks like, when HE round will hit the ground, and the ground is blocking the frontal explosion. In similar way the APHE nose should be blocking the explosion to the front, so the frontal cone is questionable, but not impossible, that’s why my proposal of new APHE damage zone contains two options for frontal damage zone. As we can see in the first document, on pages 30, 31 and 32, the damage zone depends on the round velocity - the higher the velocity, the bigger the front zone is, and the rear zone gets smaller. Side zones are equally big, just their direction is a bit different, being influenced by round movement. I want to make things realistic, but also simple, therefore I’m recommending using just the last graph to model APHE explosion zones. There is possibility that the round will detonate in stationary state, but this will not affect gameplay very much, because it mostly affects HE detonating on the armor surface. The crucial thing is to model correctly the explosion inside the tank, so when the round still has some remaining velocity. The 1085 ft/s, or 331 m/s is quite reasonable velocity of the round after penetration - it could be even a bit bigger. The 75 mm PzGr 39 from Pz IV F2 has 120 cm fuze delay in game. In fact fuze delay is given in time, and this round’s fuze delay is 0,003 second. That means that game is presuming 400 m/s velocity after penetration. The difference between 331 and 400 m/s we can ignore, the influence on the damage zone shape would be minor.


This is fragmentation zone simplified to what we can easily implement to the game. 

Spoiler

The sections drawn in T3 HE zone:

 

HE_zones.png.eb37c1fa83886ce7c884b3cb30a

 

The same values put into 3D sketch:

 

sketch.thumb.JPG.b360c32596eb21293d79aac

 

 

Therefore, I’m proposing new APHE damage model, divided into three zones.

58a6e71898d74_crosssection.JPG.45be92d0e

 

Option 1:

 

Front zone
Cone angle = 20 degrees
Fragments amount = 18
Range = 100

 

Side zone
Zone is between 120 degrees cone and flat surface perpendicular to shell's axis
Fragments amount = 39
Range = 90

 

Rear zone
Cone angle = 40 degrees
Fragments amount = 30
Range = 60

 

In this option the round is exploding completely, producing the frontal, side and rear cone of fragments. This is actually the fragmentation shown in the picture above.

 

Option 2:


Side zone
Zone is between 120 degrees cone and flat surface perpendicular to shell's axis
Fragments amount = 39
Range = 90

 

Rear zone
Cone angle = 40 degrees
Fragments amount = 30
Range = 60

 

In this option there is no frontal cone, but the round is still going through, with less penetration power (because of decreased mass). The remaining power should be about 50% of round’s power after penetration, but before detonation.

 

Option 3:


Front zone
Cone angle = 20 degrees
Fragments amount = 18
Range = 100

 

Side zone
Zone is between 120 degrees cone and flat surface perpendicular to shell's axis
Fragments amount = 39
Range = 90

 

Rear zone
Cone angle = 40 degrees
Fragments amount = 30
Range = 60

 

In this option the round is still going, like in Option 2, but also there is frontal fragmentation, like in Option 1.

 

Please note that fragments amount, and range are taken directly from T3 HE graph, so they may be different for individual round models.

 

All options could be used for different rounds, or just one can be picked - this is up to Dev Team. As we could see on fragmentation of M61 round, the nose of the round was not destroyed. In that case the round should be still moving forward after HE filler explosion, unlike it’s working right now.

Spoiler

UG8ujde.jpg

 

 

 

This is cross section of the APHE damage zones with use of Option 1 and 3. Option 2 would remove frontal cone and put the round to continue traveling.

APHE 3D (2).PDF

(You might need to download the pdf file to Your computer and open it with Acrobat Reader, some browsers are having troubles with 3D pdf files)

 

Graphics made by @KH_Alan

 

A little bit of physics to prove the point:
After fuze will ignite the explosive material inside the shell, the explosion is causing a massive increase of internal pressure. We can easily assume that the pressure is equal in every fragment of HE filler gap. That also means, that pressure is creating force F that is applied to whole area of the filler gap equally. The force applied to small fragment of area is directed perpendicular to the surface of that fragment.

All that what was said is giving us one important conclusion - most of the force, that is created by internal pressure, is applied to biggest surfaces of the HE filler gap. That means the shape of the gap is affecting the distribution of said force. That’s why hand grenade has usually shape of the ball - to equally distribute the force, and spray fragments all around the grenade, in every direction.

 

Now, War Thunder is a game, and we have to make things simple. Therefore it is not a place for complicated calculations of the force distribution according to the shape of the gap. Fortunately, most of gaps in APHE rounds have similar shape - a tube with height greater than diameter, so the damage zones will be similar to each other. Not identical, but I think we can ignore the differences.

 

This is simple graphical explanation of the force distribution. You can see that most of the force is directed to the biggest area of the gap - the sides. Red lines are representing a equal fractions of the force F created by pressure. Note, that if the force distribution would be drawn on 3D model, even more lines would be directed to the sides of the projectile.

Spoiler

he_filler.jpg.26901f0fd287816d14ef8be05b

 

Of course many thing would affect the final shape of zones of fragmentation, like: gap shape, shell walls thickness, fuze thickness, size of the gap in relation to whole projectile size, depth of the gap in relation to whole projectile length, material used for the round, explosive material type and many more. But as I said - this is not an “explosion simulator”, it’s a game, and therefore it have to be simple, as long as simplification is not changing the nature of the event, or is not significantly increasing or decreasing the performance.

 

Current model of HE filler damage zones is actually the example of such simplifying that changes the performance a lot. To accent the rate of the over performance - the overall volume of those three damage zones (proposed in Option 1 and 3) is only 28,8% of the volume of the current model - sphere. It means that current damage zone, in form of sphere, is covering almost 3,5 times more area than it really should! Think about APHE exploding in the middle of the tank turret. Currently the filler explosion would fill the whole turret with fragments, which usually kills everyone in the turret, damages a lot of turret modules. In proposed model about 2/3 of turret space would be safe, allowing more crew members to survive the shot. That would make APHE post penetration performance a lot more realistic and historical.


2. HE FILLER EXPLOSION POWER

Second issue I would like to report is the HE filler explosion power. By “power” I mean ability to kill crew members and ignite the tank interior. The fires inside the tank is another complex problem, so I will address it in another bug report. Now I want to focus only on ability of HE filler explosion to kill crew members.

 

What I'm going to do, is:

  • Calculate average number of tankers killed by single APHE shot by using data from WO 205/1165
  • Evaluate the possible number of tankers killed by APHE explosion
  • Perform tests in War Thunder using APHE rounds.
  • Compare real life data with WT tests and draw conclusions.
  • Verify the results with other documents

 

CALCULATION OF AVERAGE NUMBER OF TANKERS KILLED BY SINGLE SHOT

 

Using "A survey of casualties amongst armoured Units in N.W. Europe by Capt H.B. Wright RAMC and Capt R.D. Harkness RAMC" I’ve made a summary of post penetration effects of various German rounds, mostly 75 mm and 88 mm. I will refer to this document as "WO 205/1165 reports" or simply "WO".

http://discovery.nationalarchives.gov.uk/details/r/C3186871

The document was put into digital data here:

http://ww2talk.com/index.php?tags/wo-2051165/

 

I've picked only a part of cases, to achieve best possible results. Therefore I used this rules to filter the cases:

 

  • Non-penetrating shots are not taken into account, because that would artificially lower the statistics.
  • Penetrating shots that didn’t caused damage to crew compartment were also excluded. Mostly it was shot stopped by gearbox, or penetrated the engine compartment. In the second scenario tank always catches fire, but the crew was never hurt and successfully bailed out.
  • Non-penetrating rounds that killed crew members (mostly by head injury, for example tanker was driving with his head outside) were excluded, as they are not a part of WT realm.
  • The penetrating shots, where crew already bailed out, were not used.

 

Basically, I’ve picked only the cases where gun-fired projectile hit the crew compartment, while whole (or almost whole) crew was inside.

 

Tankers were divided into categories: unhurt, burned, wounded, killed by hit, killed by fire, killed, not in tank. Few rules here:

 

  • Tankers are considered ‘killed by hit’ only if it was confirmed by description, with few exceptions where the report is not saying it, but it’s obvious - for example if the penetration was through machine gun port, and killed co-driver who is seated right behind machine gun.
  • If the cause of death was at least partially uncertain, it was described as ‘killed’, which I will consider later as possible HE filler explosion casualties. 
  • If tanker was killed outside of the tank, he is considered as wounded/burned/unhurt - depends on what was his state when he was leaving the tank.
  • Tankers burned and wounded are described as wounded

 

 

The information I got from WO 205/1165 report:

 

  • tank type
  • type of round that penetrated the tank
  • penetrated part of the tank (hull/turret, left/right/center/rear)
  • effect of the penetration on every tanker
  • occurrence of fire (minor fire was not considered as fire)
  • direct hit to ammunition stowage
  • short description or important information

From all cases described, I was able to pick 62 penetrating shots, and put the details into the sheet.

https://docs.google.com/spreadsheets/d/1jUX4nTyHbwvc6b4QjH_-FqCIe9h0KpKzyx-5XQA6vEo/edit?usp=sharing

The total number of killed tankers is 57, which is giving the average of almost 1 killed tanker per 1 penetrating shot.

 

 

EVALUATION OF NUMBER OF TANKERS KILLED BY HE EXPLOSION

 

Out of 57 killed tankers, 10 were killed by fire. Most of them didn’t manage to leave burning tank fast enough. Note, that 5 of them was killed in one particular situation. On average, only 0,16 tankers were killed by fire per shot, that is one killed tanker in six penetrations. Most common cause of death was direct hit by the round, or penetration fragments/spalling. 36 tankers were hit directly, so 0,58 tankers per shot. Every second shot killed one (in fact 1,2) tanker by hitting him directly.

 

The rest of killed tankers is 11 soldiers. Their cause of death could be everything we’ve already discussed (fragmentation, spalling, fire, explosion, wounds), and also could be an effect of HE filler explosion. This is 0,18 killed per shot, which means every 5-6 successful penetrations of crew compartments one tanker was killed in uncertain way. Even if we would count all of them as victims of HE filler explosion, that means that every 5-6 successful penetrations APHE is killing one additional tanker (means - one more that similar AP round would).

 

If those shots wouldn’t have HE filler, still 46 of 57 tankers would be killed. We can assume that all 11 tankers were killed by HE explosion, but we can also assume that none of them was killed by explosion, and they all died because any other reason given earlier. Assuming that all 11 tankers were killed by HE filler is too exaggerated, but that’s maximum difference between AP and APHE we could calculate out of those reports. There is also possibility that none of those soldiers would survive if tank would be hit by AP rounds.

 

Summarizing those results, the conclusions are:

 

  • AP rounds would kill at least 80% of tankers killed by APHE (46 of 57)
  • AP rounds would kill at most 100% of tankers killed by APHE (57 of 57)
  • Both extreme assumptions can be averaged (from 80% and 100%) to safe statement that AP rounds would kill about 90% of tankers killed by APHE shots

 

 

WAR THUNDER TESTS - APHE

 

Let’s see how those situation would be simulated in game, with use of 75 mm KwK 40 gun mounted on Pz IV F2 tank, the most common gun we can find in the reports. I’ve shot few variants of Sherman tanks 52 times. Shots were fired from the front and from the sides, to different parts of tank. 

 

  • First four shots to center of the hull are already giving dramatic results. 5, 4, 4 and 4 tankers killed. Next trial - upper part of hull center:  5, 4, 5, 4. Out of 62 shots in real life only six of them killed more than two soldiers!
  • Shots to hull’s side parts of frontal armor produced a bit less, but still huge amount of casualties. 4,1,4,4 shooting to right side, and 3,3,2,3 shooting to left.
  • 8 shots to low part of the hull, centered. 22 tankers killed. 
  • Then I’ve made shots to Turret’s front, 4 shots on the right side, four on the left, four on the various edges. 19 tankers killed in 12 shots.
  • As we may expect, side shooting produced similar amount of casualties. 6 shots to hull - 20 tankers killed. 11 more tankers killed in 6 shots to turret’s side. Last 4 shots, to turret rings of M4’s - no less than 16 killed tankers.

 

All shots, including extra tests with Tiger and 8,8 Flak are here:

 

 

 

 

 

Let’s compare the results.

 

Shots to hull from the front.
WT tests: 3,375 killed per shot (81 killed in 24 shots)
Reports: 0,375 killed per shot (3 killed in 8 shots). In those 8 shots two of the crew members were not in the tank. If we would add them to casualties (one of them we have to add, shot went through his seat) we have 0,625 from 5 killed in 8 shots.

 

Shots to hull side.
WT tests: 3,333 killed per shot (20 killed in 6 shots)
Reports: 0,727 killed per shot (8 killed in 11 shots). Adding tankers that were not inside the tank (5) do casualties, we have 1,182 from 13 killed in 11 shots.

 

Shots to turret front.
WT tests: 1,583 killed per shot (19 killed in 12 shots)
Reports: 0,714 killed per shot (5 killed in 7 shots). Adding missing tanker will give us 0,857 killed/shot. In one report there is more missing tankers, but they could not kill anyone beside commander (which was killed).

 

Shots to turret side.
WT tests: 2,7 killed per shot (27 killed in 10 shots)
Reports: 1 killed per shot (5 killed in 5 shots). In this case, we have to add two tankers to casualties - we have 7 killed per 5 shots, so 1,4.

 

As we can see, test’s hull shots produced 3,367 killed per shot vs 0,947 in real life. 
Turret shots produced 2,091 killed per shot vs 1,083 in real life. 

 

We can clearly see, that despite the differences are huge, the results are much more closer to each other when it comes to turret shots. The crew is much closer to each other in turret, so we could predict that it will give us more casualties per shot in real life (although the difference is very small). The biggest problem is enormous amount of killed tankers by shots to hull - this is because APHE fragmentation can spray around the whole tank including the turret, while shot exploding in the turret is limited by turret ring - still driver and co-driver are not completely safe. In real life no driver or co-driver was killed by shot to turret from any side!

 

Please take a closer look at certain, similar situations:

 

Shot between driver and co-driver

Spoiler

In WO reports we have two situations, where shot went between driver and co-driver (22 and 40 row in sheet). Both hull tankers survived in both situations - first time both were wounded, in second situation only driver was wounded. No one was killled.


In WT tests we have 3 set of results:

  • shots to center of hull killed 17 tankers in 4 shots (4,25 per shot)
  • shots to lower center of hull killed 22 tankers in 8 shots (2,75 per shot)
  • shots to upper center of hull killed 18 tankers in 4 shots (4,5 per shot)

 

Shot left or right side of hull's front

Spoiler

In WO reports we have 3 situations, where shot to hull was not to the center, but a bit aside, directed at one of the hull crew members. In two situations tankers hit directly were killed, in third situation the co-driver was outside the tank. In only one of those situations the second soldier was wounded, two times he was unhurt. Fourth shot, went very close to the side, and hit the ammo rack. The loader was killed, suposedly he was near the ammo rack and was hit directly. Every shot killed just one tanker, one shot didn’t killed neither driver nor co-driver. Average is 1 killed per shot.


In WT tests from shots to sides of frontal armor we have:

  • shots to right side killed 13 tankers in 4 shots (3,25 per shot)
  • shots to left side killed 11 tankers in 4 shots (2,75 per shot)

 

Shot to hull's side (around the center)

Spoiler

In WO reports we have 16 cases of hits to hull’s side. Let’s try to find the ones close to center of crew compartment. Surprisingly, this should be one of the safest shots for the crew, because it is behind the driver's’ positions, and below the turret crew. We can find few situations like this, in rows 5, 16, 18, 39, 44, 60 and 63. Those 7 shots killed 4 tankers - 0,57 killed per shot.


In WT tests shots to hull left side killed 20 tankers in 6 shots - 3,33 killed per shot.

 

Shots through mantlet

Spoiler

In WO reports we have 3 shots to gun mantlet (rows 8, 15, 20). In first situation commander was not in the tank, so let’s assume he would be killed by this shot. In two other situations one tanker was killed by each shot. The very interesting and important fact is - beside those killed ones no other crew member was even hurt. Average value is 1 tanker killed per shot.


In WT tests shooting to mantlet gave such results:

  • shots to right side killed 5 tankers in 4 shots (1,25 killed per shot)
  • shots to left side killed 8 tankers in 4 shots (2 killed per shot)

 

Shots to center of turret from side

Spoiler

In WO reports we have 3 situations where shot hit the central part of turret side (10, 57, 61). 5 tankers were killed in 3 shots (1,67 killed per shot).


In WT tests shots to turret side:

  • shots to center of the turret killed 7 tankers in 3 shots (2,33 killed per shot)
  • shot to frontal part killed 2 tankers - while situation from row 21 killed no one
  • shot to radio bulge killed 1 tanker - while situation from row 14 killed no one
  • shots to turret ring killed 16 tankers in 4 shots (4 killed per shot)

 

The differences are clear, and huge.

 

 

WAR THUNDER TESTS - AP

 

To prove the claim that HE filler should not be killing tankers in such numbers, I made tests with use of M3 gun mounted on M4 tank, shooting solid AP M72 shot. You can find the details of tests in the sheet below (as well as APHE tests details) but in summary we have:


16 shots to hull front killed 22 tankers, so 1,375 per shot
8 shots to turret front killed 9 tankers so 1,125 per shot
4 shots to hull side killed 9 tankers so 2,25 per shot
4 shots to turret side killed 6 tankers so 1,5 per shot

 

All pictures from AP tests are here:

 

 

This results are much closer to real life effects of APHE, which proves the point - APHE rounds were killing mostly tankers who were hit directly by the round or penetration fragments, or fire caused by the round. HE fragmentation of such small caliber wasn’t a significant cause of death It seems that APHE rounds were more efficient in causing fire, but the deadliest fires inside the tanks were caused by directly penetrated fuel tanks.

 

We can see more similarities between real life performance of 75 mm APHE and WT 75 mm AP round, when we will compare the statistics about how many tankers were killed by single shot.
 

Spoiler
Number of killed tankers by shot
  AP in War Thunder APHE from WO reports APHE in War Thunder  
no one 8   26   3    
one tanker 18 60% 23 64% 9 18%  
two tankers 8 27% 7 19% 8 16%  
three tankers 4 13% 5 14% 10 20%  
four tankers 0 0% 0 0% 18 37%  
five tankers 0 0% 1 3% 4 8%  
               
  30   36   49    

 

You can see how the well proportions of WT AP effects are matching WO reports, while APHE data is completely reversed, and not related to reality.

The table is also showing the distribution in efficiency for WT APHE, WT AP and WO. Again, WT AP and WO reports are very similar, and APHE is way off.

 

There is big difference between number of shots that killed no one from WO and AP (23 against 8). This might suggest that in WT AP fragmentation is a bit too wide, but let’s leave it for now. Let’s assume for a moment that most of the shots that killed no one in real life were to edges to crew compartment, or some fortunate shots that I didn’t recreated in my tests.

 

If we would ignore the shots that didn't kill anybody, we would have:

WT APHE killed 147 tankers in 49 shots, so 3 tankers per shot
WT AP killed 46 tankers in 30 shots, so 1,53 tankers per shot
WO APHE killed 57 tankers in 36 shots, so 1,58 tankers per shot

(This values are only to compare rounds, it should not be treated as real killed/shot ratio!)


Again, WT AP performance is very close to WO reports.

 

Details about WT APHE and WT AP tests You can find in sheets here:

https://docs.google.com/spreadsheets/d/1NZ11X0epzYPpH4aLMZIqaDfyrrKPHzwNg2gKY4rtU9Q/edit?usp=sharing

 

 

VERIFY RESULTS WITH OTHER DOCUMENTS

 

The average "1 killed per shot" value is confirmed in many documents, statistics and reports

In the same WO 205/1165 we have a lot of statistics about casualties in tank crews.

http://ww2talk.com/index.php?media/albums/tank-casualties-survey-nwe-1945.205/

 

CHURCHILLS

On this page we have a bit simpler version of "tank by tank" casualties for Churchill tanks.

http://ww2talk.com/index.php?media/tank-casualties-survey-nwe-1945.16214/full&d=1368621734

 

Overall number is 21 tanks, but note, that in this summary we have only tanks destroyed with at least one crew member hurt, so average value of all penetrating shots might be a bit lower. Here we have only shots to the turret, to make comparing to game easier. Total number of 23 tankers were killed, so 1,1 tanker per shot. Very close to what we had from WO 205/1165. Unfortunately there is no detailed description of cause of death, so we can't assess which one was caused by hit, fire or else.

 

Also, in next table (http://ww2talk.com/index.php?media/tank-casualties-survey-nwe-1945.16215/#media) with penetrations to hull, with a bit more casualties (1,69 killed per shot), but there are situation with few penetrations (and no information about crew bailing out). Also, we have tankers killed by things not happening in War Thunder, like machine gun mounting driven through the tank with dramatic results, and quite often shots to ammunition.

There is also a table where place of penetration was not known. It seems like it was the most catasrophic cases, where tanks were destroyed so much that it was impossible to find the place of penetration. It those cases 21 people was killed in just 10 situations.

 

So all in all - shots to turret killed 1,1 tanker per shot. Shots to hull killed 1,69 tanker per shot. In what seems to be the report of most tragic situations - 2,1 tanker was killed by 1 shot. WT tests gave us 3,5 tanker per shot from 4 shots to turret. Two shots were to turret front, one to frontal top of the turret, and one to turret ring. Out of 14 tankers killed in tests, 3 of them were from the hull, which means 21%. In real life it was less than 9%. Again, the differences are huge.


Another statistics about Churchills:

http://ww2talk.com/index.php?media/tank-casualties-survey-nwe-1945.16213/#media

Casualties inside the tank - 19%. 19% of 5 crew members is roughly 1 tanker.

 

CASUALTIES IN BURNING AND NOT BURNING TANKS

This is VERY interesting. It shows us the tank casualties in two situations - in tanks that was burning after the penetration, and in tanks that did not catch fire.

http://ww2talk.com/index.php?media/tank-casualties-survey-nwe-1945.16205/#media

In first scenario (with fire) we have total number of 108 tankers exposed, which means we are probably talking about 22 tanks. 33 tankers were killed.

In second scenario (no fire) we have total number of 104 tankers exposed, probably 21 tanks. 11 tankers were killed.

We can clearly see that there is a lot more killed tankers, when tank catches fire, 1,5 killed per shot vs 0,52. But the most important part - all in all we have 44 tankers killed in 43 tanks. Again - average 1 tanker per shot!

In addition, we can see some interesting things about APHE ammunition.

Spoiler

aphe_explanation.jpg.50497440f6553561929

First of all - this confirms my estimations, that APHE rounds would not kill much more people than AP rounds. I've said - AP would kill at least 80% of tankers killed by APHE. That means that APHE would kill 25% more than AP at most! Here the estimations are "even if whole excess of casualties was due to this (...) not more than 20%", so even less than I've said!

Second thing - it is stated, that APHE rounds are not always exploding, which is also confirmed in one of the tank reports, where the commander found the not-exploded Panther round in his tank, on the turret floor. Adding small chance of APHE not exploding should be considered.

But overall conclusion from this document is - in most cases AP rounds would cause the same amount of damage than APHE rounds actually did.

 

Another statistics, with one important thing difference between 75 mm and 88 mm APHE rounds

http://ww2talk.com/index.php?media/tank-casualties-survey-nwe-1945.16196/#media

Again - 19% killed by single penetration of 75 mm. 24% killed by non-disclosed APHE rounds (1,2 killed per tank), and 35% killed tankers by 88 mm APHE shots. We know that Tiger's shots were much more powerful than Pz IV. But 35% means 1,75 tanker killed by single penetration by 88 mm gun, while in War Thunder 75 mm gun is causing almost 3 kills per shot!

 

This is summary of casualties form many differents type of rounds and guns.

http://ww2talk.com/index.php?media/tank-casualties-survey-nwe-1945.16195/#media

The sample is quite big - total number of tankers exposed is 593, and 143 were killed. If we assume the tank = 5 soldiers, then we have 119 tanks and 143 tankers killed. Ratio is 1,2.

 

BIG SAMPLES OF CASUALTIES

Another book is ORO-T-117, Survey of Allied tank casualties in WW II

http://www.worldcat.org/title/survey-of-allied-tank-casualties-in-world-war-ii/oclc/21347186

 

We can see a big sample of tanks with casualties, and we have even smaller percent of tankers killed. I believe that this statistics are counting also situations like shot into engine compartment, which usually ends up with no tankers killed. I did not took those situations to my calculations or tests. If I would, most probably the results would be like here: 12-15%, so 0,6-0,75 killed per shot.

Spoiler

4m7CwXV.jpg?2

 

 

 

 

SUMMARY AND CONCLUSIONS

 

Basing on WO 205/1165 reports, I've calculated number of tankers in tanks of British Army killed by German AP rounds of 75 mm and 88 mm. The result is no more than 1 tanker killed per shot on average. This result was confirmed by few other statistics from the same report, it's also confirmed in other sources. It is clear that 88 mm projectiles are causing more casualties, but still the average number is smaller than 2 tankers per shot, while 88 mm projectiles had over 3 times more explosive power, and the round itself had more kinetic energy.

Thanks to detailed descriptions in WO reports I've estimated that AP rounds would kill about 90% of the tankers killed by AP rounds, and not less than 80%. That means APHE could kill (maximum) 25% more tankers than AP, while WO reports have estimation of maximum 20%.

 

Tests done in War Thunder with 75 mm AP rounds from M4 tank produced very similar results, with average of 1,2 tanker killed per shot.

 

Tests done in War Thunder with 75 mm APHE round from Pz IV F2 tank produced 2,8 tankers killed by single shot. This is 300% of the real, historical values for this gun and this round.

 

There are very small samples of killing power of other tanks, but still 2,8 is more than any German round from WW2 produced!

Extreme examples:

KwK 43, a King Tiger's gun shot down 9 tanks, killing 16 tankers. 1,8 tanker per shot.

Flak 44 (most probably it's PaK 44, 12,8 cm Jagdtiger's gun) shot down 2 tanks, and killed 5 tankers - 2,5 tanker per shot.

 

We used PzGr 39 for KwK40 - 1,86 MJ of energy and 30 g TNT equivalent.

Jagdtiger was shooting PzGr for PaK44 - 12,1 MJ and 700 g of TNT equivalent.

 

Problem can be solved in rather easy way:

Because AP effects in War Thunder are almost identical as real APHE performance, HE filler fragmentation power should be decreased to the level where 75 mm APHE will not kill any tanker with HE filler explosion, only with penetration fragments/spalling and direct hit. Tankers should be wounded, and accumulation of wounds that would cause death should be rare situation - we know that AP would kill 90% of tankers killed by APHE, we can say that APHE should cause death for 1 out of 10 tankers wounded by filler fragmentation.

 

This amount of power should be obviously higher for the rounds with greater TNT equivalent. Jagdtiger shot should probably kill most, if not all of the soldiers that would be hit by fragmentation. Unfortunately I wasn’t able to document this, but the killing power of Jagdtiger APHE rounds should be comparable to what we saw in tests, of course within the new damage zones. In WO reports we can find two cases when HE round were detonated inside the tank. None of them killed the whole crew, but first was detonated in the frontal part of hull, and hull crew was killed, the second time explosion was placed in the center of the hull, below the turret - and this time turret crew was killed, while drivers left the tank alive.


 

 

SUMMARY 

 

Fragmentation zones for APHE round is incorrect

 

 

PROBLEM: Fragmentation of HE filler explosion is incorrect

WHAT IS INCORRECT: The HE filler explosion damage zone is in form of sphere. It means that explosion can scatter fragments all around the point of explosion

HOW IT SHOULD BE: The explosion should scatter most of the fragments to the side of the round, and rest to the rear and to front in narrow cones. Also, the round should continue to fly (with less mass), because the nose should not be destroyed by explosion.

PROOF: Damage zone of 75 mm HE round (T3), with addition of zones for: M42A1, M71 and M1 rounds. APHE fragmentation of M61 proves that the round nose is not destroyed by explosion.

FIX: Change spherical damage zone of the APHE rounds into 3 sections of explosion - frontal, side and rear. Three Options are proposed:

Spoiler

Option 1:

Front zone
Cone angle = 20 degrees
Fragments amount = 18
Range = 100

Side zone
Zone is between 120 degrees cone and flat surface perpendicular to shell's axis
Fragments amount = 39
Range = 90

Rear zone
Cone angle = 40 degrees
Fragments amount = 30
Range = 60

In this option the round is exploding completely, producing the frontal, side and rear cone of fragments. This is actually the fragmentation shown in the picture above.

 

Option 2:

Side zone
Zone is between 120 degrees cone and flat surface perpendicular to shell's axis
Fragments amount = 39
Range = 90

Rear zone
Cone angle = 40 degrees
Fragments amount = 30
Range = 60

In this option there is no frontal cone, but the round is still going through, with less penetration power (because of decreased mass). The remaining power should be about 50% of round’s power after penetration, but before detonation.

 

Option 3:

Front zone
Cone angle = 20 degrees
Fragments amount = 18
Range = 100

Side zone
Zone is between 120 degrees cone and flat surface perpendicular to shell's axis
Fragments amount = 39
Range = 90

Rear zone
Cone angle = 40 degrees
Fragments amount = 30
Range = 60

In this option the round is still going, like in Option 2, but also there is frontal fragmentation, like in Option 1.

58a6e71898d74_crosssection.JPG.45be92d0e

This can be also used to create HE rounds fragmentation (with additional frontal cone, a lot wider, but also very short).

 

 

 

HE filler fragmentation is too powerful in terms of killing crew

 

 

PROBLEM: Fragmentation of HE filler have huge damage power

WHAT IS INCORRECT: The crew members and modules hit by HE filler explosion and fragments are being killed/damaged/detonated way too much than they should. Most of the crew members hit by even small amount of fragmentation are killed, which is unreal and unhistorical behavior.

HOW IT SHOULD BE: The fragments from HE filler fragmentation should be only additional cause of damage, not main. The HE filler killing power should be reduced. Crew memeber hit by fragments of 75 mm PzGr 39 from KwK40 should be only wounded, not killed, unless he will be hit by massive amount of fragments (for example whole frontal cone), or by the round directly. This should be done for every round with similar (~30 g TNT equivalent) or lower explosive power. Projectiles with more explosive power should have adjusted killing power. Probably Jagdtiger's projectile should kill all tankers inside the damage zone.

PROOFS:

  • WO 205/1165 "tank by tank" reports shown the average 1 tanker per shot
  • Various statistics from the same document are confirming 1 tanker per shot for 75 mm gun, 1,7 for 88 mm and 2,5 for 128 mm
  • Detailed analysis of "tank by tank" reports showed that AP round would kill at least 80% of tankers killed by APHE, most probably about 90%. WO Reports gave APHE maximum 20% more casualties than AP rounds.
  • War Thunder test results: 75 mm AP round killed 1,2 tanker per shot, but 75 mm APHE round killed 2,8 tanker per shot. This is around 300% of historical values.

FIX: Change the HE filler fragments power as follow:

  1. PzGr 39 from 7,5 cm KwK40 (or weaker) HE filler power should be almost unable to kill tankers (unless tanker will be hit by massive amount of fragments, for example whole frontal cone). On average 1 in 10 tankers hit by fragments could be killed.
  2. PzGr from 12,8 cm PaK44 (or stronger) HE filler power should be killing all tankers inside the damage zone, with no exceptions. 10 of 10 tankers hit should be killed.
  3. All rounds with power within range 30-700 g of TNT Equivalent should have interpolated power between power of rounds from points 1 and 2.

 

To make it simple, we could use inear interpolation, the results would be like this:

100 g of TNT equivalent - 19% chance to kill

200 g - 33%

300 g - 46%

400 g - 60%

500 g - 73%

600 g - 87%

700 g - 100%

 

Those simple changes will make APHE round performance a lot more realistic and historical.

Also, it would make the game much more balanced, because in current state APHE is way more powerful round than any other in the game, including most modern APFSDS or HEAT-FS. But our main goal is still historical accuracy.

 

THE END

 

 

 

 

Congratulations for all folks who have read it to the very end! :salute:

Thanks for attention and Your time. Possibly, a few more works like this one will be made in the future :)

Ulatersk & Godman

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Thank you very much for taking the time to create such a detailed report. 

 

This topic has been divided into two separate reports

 

Fragmentation zones for APHE rounds are incorrect - ID: 0054325

HE filler fragmentation is too powerful in terms of killing crew - ID: 0054326

 

This thread will remain unlocked for one week (7 days) so that anyone with additional information\evidence\examples will have a place to post as well as if the Developers require more information.
 

After this time the report will remain active but this topic will be move to Documented Bug Reports. 

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