How to calculate HE penetration?

[Little_Black_Devil]

Okay - this question has plagued me long enough.

How do you work out the penetration capability of HE rounds?

Are they just treated as solid shot (until a certain point at which they finally detonate)?

At what point during the "penetration" process does the fuze pack it in and detonate the explosive filler - or do we always assume that the ranges are so short so as to preclude the fuze from arming yet?

I think its great that we have this feature in game, its certainly served me well a couple of times - I just wish I knew how to mathematically work it our for myself.

Anyone know what the *secret* forumla is?

Thanks

[Little_Black_Devil]

I don't wanna know how Cadbury gets the caramel into their chocolate bar - I just wanna know how to figure out HE penentration for myself.

Anyone....?

[Sergei]

Only a terrorist would ask such things. Now you die.

EDIT - oh, I thought you were asking how Cadbury gets the caramel into their chocolate. Okay, sorry to sound threatening. :cool:

[ September 25, 2003, 02:12 PM: Message edited by: Sergei ]

[Redwolf]

LittleBlackDog,

all penetration data, including that for AP, is just rules of thumb.

The formulas we use for AP, even the complicated ones, have *not* been computed from physics up. People came up with them by looking at lots of existing data and then guess suitable formulas to fit the existing data.

Same for HE.

I have the Rexford book at home, if you remind me I'll have a look if and what he is saying about HE.

[ September 25, 2003, 05:56 PM: Message edited by: redwolf ]

[Little_Black_Devil]

Well - I've got Rexfords book as well, and while I'm at work at the moment - I don't recall seeing anything specific regarding HE rounds.

Were HE rounds penetration abilities on par with AP - then I don't think there ever would have really been a need for AP.

Aside from measuring the weight of the projectile, its velocity, the range, the relative facing of the targets armour (and what kind of armour it is), the armour's thickness, I think HE rounds also have to consider things like the fact that they are not solid shot, and also utilize a variety of fuzes - which may ultimately dictate a variety of behaviors on or after impact.

I'm only really interested in the reaction between an HE rounds set on "superquick" or detonation on impact and ones set on (standard) delay of about 5 seconds (the standard settings on an M739 fuze for a conventional HE round as fired by a 105mm Howitzer for instance).

While it would be iteresting to consider other projectiles and fuzes - I'm only after HE at the moment.

I think its great that the game offers HE penetration statistics vs armour. I'm just curious as to how they determined those figures - what formula(s) were used to calculate them?

Thanks again

[flamingknives]

The HE round will always have less penetration than a true AP round, as the explosive filler is less dense and weaker than steel, so the more HE you have, the less weight and strength your shell has.

[Little_Black_Devil]

makes sense.

[rexford]

Armor piercing projectiles have very hard noses and hardened shell casings, which are designed to rip through hard armor.

HE shells are designed to hit something and then explode into lots of pieces shortly thereafter.

My book did not go into HE penetration stats. The only HE penetration figures I've seen are German ones which Mark Diehl published in AFV-G8 maagazine a long time ago.

I think but am not sure that the thin armor penetrated by HE shells is based on actual penetration of the armor by the projectile nose or body, which would have to occur fairly quickly.

[Scheer]

Hi all,

I always thought that HE is to " soft " to get through the hardened steel.

Just like throwing a tomatoe against a windowpane, it just squishes. If you throw a stone on the other hand ...

[ September 27, 2003, 03:58 AM: Message edited by: Scheer ]

[Little_Black_Devil]

So basically, HE armour penetration is heavily dependent on the diameter of the projectile (and subsequent mass) to penetrate armour then - as opposed to hardened noses/bodies?

[rexford]

Penetration data for German 75mm L43 gun is available at PzKpfw IV Universe site:

http://ourworld.compuserve.com/homepages/willphelps/Specs-03.htm

Vertical penetration by 75mm L43

APCBC

126mm at 500m

113mm at 1000m

HE

47mm at 500m

42mm at 1000m

The HE round is fired at 550 m/s while the APCBC is launched at 740 m/s. The DeMarre equation for penetration versus velocity predicts that a round fired at 550 m/s will penetrate about 65% of the same ammo at 740 m/s.

So some of the difference between HE and APCBC is due to a lower muzzle velocity.

126mm at 500m for APCBC x 0.65 = 82mm.

I would guess that the difference between 82mm penetration at 500m by APCBC (if fired at 550 m/s muzzle velocity) and 47mm at 500m for HE is due to:

1. softer steel with HE rounds

2. lighter HE round (12.6 pounds for HE vs 15 for APCBC)

3. a larger HE burster cavity in the HE shell (which weakens the projectile structure so more of the impact energy is absorbed by the HE round compared to APCBC)

4. nose shape differences.

So there are the differences between HE and APCBC that account for less HE penetration, plus lower muzzle velocity for 75L43 HE.

Panther 75L70 fires APCBC at 935 m/s, shoots HE at 750 m/s.

Tiger II 88L71 fires APCBC at 1000 m/s, rips off HE rounds at 700 m/s.

Tiger I 88L56 unloads APCBC at 780 m/s and HE at 810 m/s.

[Redwolf]

The fact that HE penetration decreases over distance is also a strong hint that the penetration is not from the explosion of the HE round, but that kinetic energy of the round before its explosion plays a big or the only role.

[Little_Black_Devil]

Thanks Rexford - thats what I was looking for.

[rexford]

A U.S. report on Russian weapons and vehicles give hardness data for Russian HE and armor piercing rounds.

Russian HE shells ranged in hardness from 180 to 250 Brinell Hardness, while the noses of the armor piercing ammo averaged about 480 Brinell Hardness. So Russian HE ammo was softer than the homogeneous armor carried by most German tanks but was still harder than regular structural steel used in buildings and bridges.

As noted in a previous post by Redwolf, HE shells appear to penetrate by pushing through the armor they hit using the same mechanisms as armor piercing rounds.

[ September 30, 2003, 01:49 AM: Message edited by: rexford ]

[rexford]

Originally posted by redwolf:

The fact that HE penetration decreases over distance is also a strong hint that the penetration is not from the explosion of the HE round, but that kinetic energy of the round before its explosion plays a big or the only role.

That's a good connection that sums up what goes on.

The drop-off in 75L43 penetration with range is about the same with APCBC or HE, where APCBC loses 10% of its penetration from 500m to 1000m and HE loses 11%. This suggests that impact velocity is driving penetration of both ammo types.

When the HE burster inside armor piercing rounds is defective, such as on U.S. 90mm APCBC tested in England just before D-Day, the rounds detonated on the surface of the armor they hit and failed to penetrate easy targets.

To penetrate successfully, the HE inside a shell or shot must not detonate until the round has passed through the armor.

[ September 30, 2003, 01:55 AM: Message edited by: rexford ]

[K_Tiger]

@Rexford

Tiger I 88L56 unloads APCBC at 780 m/s and HE at 810 m/s.

Is there a special reason why the HE from Tiger I`s hade such a high MV? Is it possible that they used Anti-Air Projektiles against Ground Units?

[flamingknives]

Being as the 88L56 is basically the Flak 88, mounted in a tank, it does seem likely that they used the same ammo as the AA configuration.

As I presume this uses the full charge the case is capable of holding, it makes sense that the heavier AP round would be slower, asit would use the same charge.

I was able to talk to a veteran of the 10th Royal Hussars (served in France, NA and Italy) a little while back and he described the German 88 gunners using the time-fused AA shells as shrapnel shells against allied tanks, in order to get TCs or even to get some shrapnel into the tank through open top hatches

[Mr. Tittles]

Originally posted by redwolf:

The fact that HE penetration decreases over distance is also a strong hint that the penetration is not from the explosion of the HE round, but that kinetic energy of the round before its explosion plays a big or the only role.

This is a very astute observation.

The data from the Mk IV website also sheds some light because:

1. L24 gun in table is using same HE(34) round

2. Its HE velocity is less than L43/L48 (420m/s vs 550m/s)

3. its HE penetration is much less and also decreases with range.

This particular HE round has a very large high explosive content from the data. could this then have thinner steel construction? the L24 has a higher HE velocity than its AP round also; interesting.

I would think SOME of the penetration is caused by the HE explosion. Since KE is 1/2MV^2, velocity is a primary factor in HE penetration from this data. If the velocitys at the ranges were known, a formula could be graphed. Face hardened armor would be very effective at defeating these HE shells I would think.

High velocity HE rounds also have a tendency to crack welds. russian test firing of 100mm, 122mm HE rounds on panther/tigerII armorcould crack the welds and make the vehicle structurally unsound so that it would be unreparable.

I would imagine the crew effect of HVHE also being deadly/injuring humans.

[ September 30, 2003, 01:06 PM: Message edited by: Mr. Tittles ]

[flamingknives]

HE tests carried out on the Conqueror HY gun tank showed that 120mm HE was insufficient to penetrate the tank from the front and sides, but a lucky shot on the turret front blew the drivers' hatch open, allowing blast and fragmentation to enter the crew compartment. (in this specific instance, the driver would almost certainly have been killed but the rest of the crew would have been safe.

Other than that the HE had little or no effect behind armour, while comparable calibre AP round caused extensive damage to Gun Control Equipment inside the turret, despite not penetrating

[Mr. Tittles]

Some interesting math:

Take the ratio of point blank penetration of 75mmL24/75mmL48 (30/52)=0.576

Take the ratio of point blank V^2 (75L24_vel^2/75L48_vel^2)=0.583

it can be surmised that velocity squared accounts for penetration increase.

One could also extrapolate-surmise that the 75mmL48 HE round at 2500 meters is traveling at 420m/s. a little math suggests the L24 HE is traveling at 297M/s at this same range.

[Mr. Tittles]

The Panzer IV website:

A funnything about this data; it suggests that reinforced concrete is tougher than steel? Perhaps a typo?

[ October 01, 2003, 11:03 AM: Message edited by: Mr. Tittles ]

[Mr. Tittles]

http://www.752ndtank.com/TheRock.html

this website is interesting as far as HE vs armor.

1. a sherman tank takes an indirect fire 105mm HE round. Little damage is done (it was not a top hit but hit the side of the turret) but a major sub-system is taken out; the power traverse.

2. Same tank battles a stug III at close range. Sherman fires a HE at stug. Supposedly not penetrating but cracks armor. followup AP round devastates stug.

If CMXX is developed, I would like to see these type of effects. HE taking out things like radio, power traverse, crew casualties, etc. Crews could also be stunned, backing away, "pinned" etc.

[ September 30, 2003, 05:51 PM: Message edited by: Mr. Tittles ]

[Mr. Tittles]

Originally posted by flamingknives:

Being as the 88L56 is basically the Flak 88, mounted in a tank, it does seem likely that they used the same ammo as the AA configuration.

As I presume this uses the full charge the case is capable of holding, it makes sense that the heavier AP round would be slower, asit would use the same charge.

I was able to talk to a veteran of the 10th Royal Hussars (served in France, NA and Italy) a little while back and he described the German 88 gunners using the time-fused AA shells as shrapnel shells against allied tanks, in order to get TCs or even to get some shrapnel into the tank through open top hatches

I read in a book on Tiger tanks that the tiger I had an electric firing mechanism. The back of the cartridges had a circuit element that would heat up quickly and fire the shell instantaneously. The ground mounted 88s did not have this. if the Tigers were to use Flak shells (which they could probably get from army flak bns) they would have to be compatible with the electric setup. These time fuze shells would also have to be preset for distance.

[Horncastle]

I suppose its similiar to wearing body armour and being hit by a rifle round, though the round wont penetrate and exit it will cause internal damage. Were there HESH rounds in WWII? I know they work on the principle of spreading over a large area and detonating HE to cause major internal armour flaking, so maybe penetration per se is not what one should be looking at, more the shockwave caused and its effect on the inside of the vehicle

Good idea about the tank damage, though maybe its already covered sufficently in just the generic "abandonded" tag. I would like to see details on crew injured more though much like you can see whose down in a squad be good to see if you say lost your driver then became imobile, lose the commander and you can barely shoot!

[Mr. Tittles]

I think the HE and HESH are very different. The HESH has to have a low velocity also if I recall correctly (this may have been solved though). The HE can be high velocity but I am starting to think that the HE detonation must be delayed. Rexford mentioned this with the 90mm AP rounds with small HE. The shell must be on its way through before the blast. The blast will jettison much of the mass of the shell (especially in HE) and interrupt penetration.

The HESH has a very soft nose, the HE has a very hard nose. The HESH is designed to direct the blast towards the front; HE blast/shrapnel goes to the sides. HESH spreads the explosive into a putty-pancake against the armor and then detonates it, HE always has the front part of the shell between the HE and armor (unless the shell has penetrated).

HE can still can pop rivets, crack welded armor, blow away antennas, etc. I would venture a bet that cast armor is very effective at defeating HE.

HESH is more a modern round I believe. The British still use it as a multipurpose round in tank guns and claim very longe range kill/soft-kill with it in rifled tank guns.