Two questions regarding the T-72

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Arbalest 4/19/2008 12:53:48 AM

The answer to your second question is not known to me.

I can only give you a generic answer to your first question.

Sloping armor always has some effect, the question is, how much effect? The answer depends on several things; Armor material and thickness, projectile type (size and weight, material, construction, etc.), and impact angle and impact velocity.

Impact velocity is primarily dependent on muzzle velocity, projectile aerodynamics, and range.

Impact angle is the angle, at the point of impact, between the projectile trajectory and the normal vector at the point of impact. The normal vector is a line that points straight out from the point, sort of like a flagpole in front of a building, or a nail nailed straight through a piece of wood.

So for a flat plate of armor that is vertical (90 degrees), the normal at each point points to the side (0 degrees), so the armor has no vertical slope.

The turret of the British Cromwell tank is a useful example. When seen from the front, or slightly off center on the side, the turret armor has no (zero) slope. All sides are vertical (but it actually has 6 sides, so when seen from the side, the sides have 5 or so degrees of horizontal slope). The German tankers in WW2 North Africa would approach at an angle, to get 10 or so degrees of horizontal slope.

Impact angle is a combination of both horizontal and vertical slope.

The value of slope (for steel armor) was considerable in 1942. The T-34 was essentially invulnerable to all deployed German AT guns. A combination of larger guns (88s and long 75s: heavier projectiles) and high velocity shot for the 50L42 and 50L60 was the answer.

Fast forward to today. It turns out that current long-rod penetrators might bounce at a 75 degree impact angle, otherwise, they go into the armor.

15 degrees of slope equates to about 10% more armor thickness; essentially free, probably worth doing, but only is a small increase. 750mm of protection (assuming steel armor) would require 675mm of steel armor. This is thicker than the Yamato?s turret face armor. 45 degrees is only 40% more. 60 degrees doubles the thickness, and 375mm is on the verge of do-ability, but only over small areas.

But there?s a question of size and volume. Sloping the side window 15 degrees on a passenger car might be an inconvenience, but maybe not. Sloping the side windows the same as the front (or back) windows is problematical (and this still isn?t yet 60 degrees). Either the car becomes unacceptably large (much wider), or there is no usable internal room.

The previous words are simply to clarify the answer: APFSDS does not negate slope, APFSDS simply requires more slope to defeat it.

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oli 4/19/2008 6:15:42 PM

Well in then in theory the T-72 would have around 500-600mm, is there really any way to tell from the current info available how much armour (RHAe) the T-72 has against KE?

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Arbalest 4/19/2008 7:48:17 PM

Depending on the model of T-73, 500-600mm might be the value that agrees with the published reports. Check some of the late 2006 and early 2007 Armor threads for references and links to published values. Other sites and Google are likely to provide similar links and values. How good these values are is anyone's guess, but most people take them as useful values.

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Herald12345 4/19/2008 7:51:33 PM

Source 1:

Basic discussion which I find interesting about Russian and US metallurgy and tank armor in WW II.

Source 2:

Armor data table.

The two T-72s shot through may have been through the side of the turrets where the armor is thin enough for machine cannon to pierce . Hull armor through the side is also possible. Do you know how much armor you need to stop a six mega-joule shot?

Herald

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oli 4/19/2008 9:41:53 PM

Will read Source 1 tomorrow (bed time here).

Source 2 seems to show that an M829A2 (630mm @ 60 degrees @ 2000m*) would go through a T-72M turret (330mm) out the back with relative ease with what I assume still enough energy to punch a hole in the second T-72M.

*From the results found of the M829 series it looks as if it penetrates more against slopped armour than vertically angled armour.

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00_Chem_AJB 5/27/2008 1:56:23 PM

Arbalest and Herald nailed the first question, I'd have to agree with Herald about the side armour penetration, the DU round splinters was it penetrates armour due to friction/resistance from the metal, (the mechanism I am not sure on) and as uranium is pyrophoric these splinters burst into flames (this mechanism I know) so by the time the sabot has went though the frontal arc of the tank it is nothing more then a burst of white hot flaming sharp uranium pieces, so it's entry is similar to that of a HEAT round penetration, these hot fragments thus kill the crew and cause any thing flammable or explosive to go up in flames or bang. Now as there is less armour on the sides, and less resistance, what fragments there are cause utter havoc and there should be enough of the DU round to pass out through the other side and into another tank, again through the side or rear.

As for your second question, yes the FCS of the Iraqi and most former Warsaw pact tanks is primitive mainly the stabilisation of the gun and poor aliened sights, thus when firing the tank would have to slow down or stop in order to hit, but lack of a ballistic computer, again poor optics and a bad range finder meant even when they could get an accurate shot off, it was at much lower ranges than that of the M1 or Challenger. So while it alot of it was poor quality the flaw was in the design. Iraqi T-72s were either ex Czech or Czech supplied kits assembled in Iraq, so while these problems are less prominent in Soviet built models such as the T-72A and T-72B they were in client state tanks or monkey models as they are dubbed. Soviet models of the time had by the early 1980's up to date laser range finders and by the mid to late 1980's up to date ballistic computers as well as integrated and improved gun stabilisation and better optics but still generally relied on Luna IR night vision like their Iraqi counterparts thus limiting their range to what they can see, which is around 1000m (IR signatures could also be detected alerting a crew to the presence of an enemy tank) while the M1s and Challengers could use thermal imaging and hit targets as they could in the day. These days however the Russians using French and domestic technologies have thermal imaging, but many tanks still rely on the old Luna IR.

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Claymore 5/28/2008 1:06:39 AM

I head that the British L7 105mm (Used by the US and other NATO nations) would not penetrate the T-72's front armor. However it would send so much energy that it would shatter all the gauges and the the crew.

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WarNerd 5/28/2008 2:10:38 AM

Arbalest and Herald nailed the first question, I'd have to agree with Herald about the side armor penetration, the DU round splinters was it penetrates armor due to friction/resistance from the metal, (the mechanism I am not sure on) and as uranium is pyrophoric these splinters burst into flames (this mechanism I know) so by the time the sabot has went though the frontal arc of the tank it is nothing more then a burst of white hot flaming sharp uranium pieces, so it's entry is similar to that of a HEAT round penetration, these hot fragments thus kill the crew and cause any thing flammable or explosive to go up in flames or bang. Now as there is less armor on the sides, and less resistance, what fragments there are cause utter havoc and there should be enough of the DU round to pass out through the other side and into another tank, again through the side or rear.

There is a huge difference between the dart from an APDSFSDU and the jet from a HEAT round penetrating.

The HEAT round penetration sends a few ounces of material jetting thru the armor at velocities of 4000 - 6000 m/sec into the vehicle. The jet will generally damage anything or kill anyone it its path plus there is some additional fragments from hull material that spalls off around the penetration. If the HEAT round is large enough (opinions vary, but generally over 80mm in diameter) it may also cause enough internal overpressure for a concussion kill on the crew. Generally though spectacular kills only occur from a direct hit on the ammunition, hydraulics, or fuel.

The APDSFSDU on the other hand typically enters the vehicle as several kilograms of small metal incendiary fragments at 500 - 1000 m/sec, depending on the residual energy left after penetrating the armor. These burning fragment ricochet around inside the vehicle chopping up the crew and usually finding any exposed ammunition, hydraulics, of fuel to ignite and converting the vehicle into a spectacular flaming wreck.

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00_Chem_AJB 5/28/2008 10:52:48 AM

There is a huge difference between the dart from an APDSFSDU and the jet from a HEAT round penetrating.

I know the mechanisms are different, one is a molten jet and burst of super heated gas, the other is a a spray of flamming metal, I was merely say they would appear similar form the point of view if you were in the tank, eithey way both are bad news.

As for the L7/M68 I heard that in Lebanon Isreali Centurion tanks had hard times defeating T-72s on the frontal arc with APDS, but fell victim to the 125mm gun, the Centurion's blazer armour would make little difference against a APFSDS, but what you seem to be describing is a HESH or HEP impact.

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Bluewings12 5/28/2008 5:05:59 PM

I jump in because it' s interesting .

00_Chem knows his stuff :-) Some of his remarks are well worth reading .
I slightly disagree with Herald on some points . His second link is only giving some gross aproximations and most of them are wrong . Nevertheless , it is a rather known and good link to start with if you have some interest in armor and round penetration .

Arbalest is very good too and I like what he says :-)

Oli :
""I read that an M829A1 went through 2 T-72's""

It was me who did talked about it here on SP a long time ago and I see that the word spreaded , lol .
It did happen in GW1 during the Easting 73 battle . The round was a M829A1 "silver bullet" fired at 600m , it was a flanking shot . The round went through the 1st T-72 's back turret , kept going (leaving a wrecked tank behind) and did hit the 2nd T-72 in the space between the turret and the hull (if I remember well) . Both tanks did catch fire and burned .

Since the discussion has switched to the DU "side effects" , it 's good to remember that it works both ways : the round and the armor .
By that , I mean that the pyrophoric effect affect the crew when the round is made of DU but it is even worse if the armor is made of DU . It works both ways ! When a DU armored tank is penetrated (even by a tungsten alloy round) , the inside goes burned pear shape . It is why the Abrams has a Halon system to cope with the inside fire , and the system does it well if I may say , but it is still highly dangerous !
The Abrams is using (on the front turret only) a plate of DU in between layers of poor steel . The Challenger is using DU nuggets (Dorchester) and a better steel which is safer and better . Why ?
Because the incoming round is deviated sideways by the nuggets (more armor to go through) and does not bring with itself some DU inside the tank in case of penetration . As simple as that .

The German Leopard and the French Leclerc do not use DU in their respective armor . They use a steel twice stronger as the one used on the Abrams and also use a mix of ceramics and composites . It makes the Tank stronger and lighter . As a exemple , a double tandem warhead fired from a RPG-29 (HEAT) will have a very bad time against composites like Phenolic type material.or steltexolites or ceramics like Alumina [AL2O3] .
The Abrams and the Challenger have been penetrated by such warheads .

Cheers .

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Herald12345 You aren't qualified to comment. 5/28/2008 5:34:15 PM

I'm not on armor, YET, but I'm getting there.

Herald

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Bluewings12 5/28/2008 6:04:05 PM

It 's you Herald who 's not qualified to comment as you say so .
You are free to challenge me on Tanks matters and Tank warfare if it is your wish .
I 'll be there ...

Cheers .

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LB T-72 Ammo Matters 5/28/2008 6:07:28 PM

Reportedly Iraq had a factory that produced 125mm ammo for it's tanks. Quality control was not nearly as good as Soviet/Russian ammo. This is at least what Russian and Chinese weapon reps told those who would listen to at least partially explain the performance of Iraqi T-72's during the Gulf War. There's probably some truth to it and the piss poor standard of Iraqi tank crews also make the T-72 look worse than it actually is. That said it's not in the same league as modern (M-1, Leo, etc) tanks in any terms. OTH what the 125mm can really do with a good FCS and good ammo is a bit of an open question.

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Bluewings12 5/28/2008 6:47:07 PM

LB :
""OTH what the 125mm can really do with a good FCS and good ammo is a bit of an open question.""

Not really , we know a lot about the Russian rounds . The Chinese rounds are tested right now by the West ;-)
Don 't ask me how we did get them , it is classified .

The main problem they have with the 125mm is with the sabot and the length of the penetrator . It seems that they cannot get the thing right . They understood that the riffled gun is of no use (they do not have the British know-how) and they are actually trying a smooth bore gun in 2 different calibers : 120 and 140mm .
The other problem they are dealing with is the inside gun liner (Brits are good at that) .

No probs so far for us ;-)

Cheers .

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00_Chem_AJB 5/28/2008 7:56:33 PM

I missed these arguments on who is a expert and who is not, I'm no expert I'm just well informed on what I know, and that is Soviet armour, and of course chemistry. Herald has proved himself when it comes to mechanics (mathmatics) and physics, never dismiss him, he takes the time to work things out, thus he has the best and final argument, the battlefield is ruled by physics, design specs are nothing untill they have been proven in combat.

I jump in because it' s interesting .

00_Chem knows his stuff :-) Some of his remarks are well worth reading .
I slightly disagree with Herald on some points . His second link is only giving some gross aproximations and most of them are wrong . Nevertheless , it is a rather known and good link to start with if you have some interest in armor and round penetration .

Arbalest is very good too and I like what he says :-)

Oli :
""I read that an M829A1 went through 2 T-72's""

It was me who did talked about it here on SP a long time ago and I see that the word spreaded , lol .
It did happen in GW1 during the Easting 73 battle . The round was a M829A1 "silver bullet" fired at 600m , it was a flanking shot . The round went through the 1st T-72 's back turret , kept going (leaving a wrecked tank behind) and did hit the 2nd T-72 in the space between the turret and the hull (if I remember well) . Both tanks did catch fire and burned .

Since the discussion has switched to the DU "side effects" , it 's good to remember that it works both ways : the round and the armor .
By that , I mean that the pyrophoric effect affect the crew when the round is made of DU but it is even worse if the armor is made of DU . It works both ways ! When a DU armored tank is penetrated (even by a tungsten alloy round) , the inside goes burned pear shape . It is why the Abrams has a Halon system to cope with the inside fire , and the system does it well if I may say , but it is still highly dangerous !

How do you make a leathal situation worse? If the sabot round has entered the crew compartment the crew is dead, due to boiling metal fragments being sprayed around, burning if the round is DU. DU or not any fragments of armour which enter the crew compartment are leathal projectiles and easilly hot enough to ignite anything flammable, the heat comes from friction. The point of a fire supression system is to prevent any fire leading to an ammo cook off, what you are implying is closeing the stable door after the horse has escaped.

The Abrams is using (on the front turret only) a plate of DU in between layers of poor steel . The Challenger is using DU nuggets (Dorchester) and a better steel which is safer and better . Why ?
Because the incoming round is deviated sideways by the nuggets (more armor to go through) and does not bring with itself some DU inside the tank in case of penetration . As simple as that .

Last time I checked even the basic production M1s used Chobham, which is a lattice of cermaic plates and steel/tungstan rods*, hardly the poor steel you describe, the DU itself might be encased in steel, but the neither the M1 or Challenger relies on just steel with added DU.

The German Leopard and the French Leclerc do not use DU in their respective armor . They use a steel twice stronger as the one used on the Abrams and also use a mix of ceramics and composites . It makes the Tank stronger and lighter . As a exemple , a double tandem warhead fired from a RPG-29 (HEAT) will have a very bad time against composites like Phenolic type material.or steltexolites or ceramics like Alumina [AL2O3] .
The Abrams and the Challenger have been penetrated by such warheads .

Ok last I checked both the Leopard and the LeClerc featured spaced metal/cermaic(composite) armour as part of their module armour package, a key component, as this limits the effectiveness of HEAT warheads, forcing the jet to bore through one layer, yet dispurse when it hits the second layer thus reducing it's engery enough so it can't penetrate the whole armour package. This is great at stopping HEAT rounds but what about sabots? If the armour is configured and shaped correctly I'm sure it can. The chobham armour package is a dence lattice using dence materials which is effective at stopping HEAT rounds but also stopping sabots, remember chobham is a product of the late 1970s, while spaced module armour is from the late 1980s to early 1990's and is thus more efficent at weight reduction but both are effective in their desired role.

*The compostion is still classified, so that may be a load of horse crap, again I'm no expert just informed and with so logical thinking.

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