Newsgroups: sci.military.moderated
From: jaremkow@hotmail.com (Andrew Jaremkow)
Subject: Re: T-90 verus M1A2
Date: Mon, 7 Jul 1997 16:34:53 GMT

On Mon, 30 Jun 1997 17:08:34 GMT, antispam@uvic.ca (Robb McLeod)
wrote:

>A good example of a OPFOR advantage that's never appeared is the inability of
>Western weapon systems to penetrate their armor.  I've always felt that was
>important:

Yet the OPFOR is granted unrealistic armour killing levels too. Do you
really expect the warheads in AT-4s and AT-5s (or even AT-11s) to
penetrate an Abrams? What about their archaic AP ammunition? The steel
BM-9s,  BM-15's with that tiny tungsten carbide slug, and even M735
clones like the BM-32 just can't manage M-1A1 armour. Yet, as others
have posted, they are given the ability to penetrate the Abrams. I'd
say the disparity is applied equally to both sides in this sort of
training.

>T-64:
>
>First ever production MBT to carry combinational armor.  It carried
>Combination K, which appariently is composed of glass fiber suspended within a
>plastic resin.

All indications I have seen (Zaloga, Ogorkiewicz, Janes...) state that
the T-64 used larger ceramic inserts, and not GRP. Have you a
different source, or is this speculation?

>DOI: 1966
>RHA verus APFSDS: 410 mm
>RHA verus HEAT: 500 mm

Zaloga, in his exhaustive work on Soviet armor design practices, gives
figures of  410mm, and 450mm respectively.

>T-80B:
>
>Along with the T-64B and T-72A, this vehicle substituted a Boron Carbide
>filled resin aggregate in 2nd generation Combination K, similar to the above
>mentioned GRP, but was more compact and provided better protection for the
>same weight.

Boron Carbide eh? Have you got a source, or are you just speculating?

	I'll bet your chain of logic went something like this:

1) T-72M1s produced in the mid 1980s apparently use a "pelletized
filler agent" in their armour (JA&A 96-97).

2)  Los Alamos has done work with ceramic aggregates (including boron
carbide and aluminum oxide) in polymer binders (Los Alamos Science,
Summer 1989).

3) Boron carbide has a high mass effectiveness against HEAT and AP
projectiles. (Ogorkiewicz IDR 4/1991, IDR 6/1995, or perhaps his
earlier work).

4) Therefore T-72M1s must use boron carbide. (Robb's own blind leap of
faith)

5) Since the foreign built T-72M1 of the mid 80s was an upgrade to
T-72A standards (Zaloga 1996) , the earlier T-72A of must have been
identical. (A much more reasonable leap of faith, but we can't be
certain. The Czech's and Poles liked to fiddle with Russian designs.)

6) Since the T-64B was developed even earlier than the T-72A (and by
different people) it too must have had the same armor. (Leap of faith
number 3)

7) Since the T-80B was an attempt to catch up with T-64B protection
levels (Zaloga, 1996) it too must have the same armor. (Leap of faith
number 4)

8) Therefore T-80Bs use boron carbide! (Robb's conclusion, which he
proceeds to disseminate as if it's a fact.)

But by all means, prove me wrong with a good source for your
assertion....

>DOI: 1978
>RHA verus APFSDS: 500 mm
>RHA verus HEAT: 580 mm

Not all T-80Bs are the same. The T-80B had a turret armour upgrade in
1982, and a glacis armour upgrade in 1984. Are your figures here for
early or late T-80Bs?

>T-80U:
>
>The first vehicle to carry Kontakt-5 EDZ, effective both against HEAT warheads
>and APFSDS.

Since you can put Kontakt-5 on almost anything (provided it has
sufficient armour to withstand the backplate) I don't think its
association with the T-80U has any special significance. Both happened
to come out in 1985, that's all.

> It also carried an applique armor pack which is composed of a
>frontal steel plate about 60 mm thick backed by an insert of three layers of
>inert interlayer reactive armor, composed of steel plates and penapolyurethane
>filler.

	For such a detailed assertion I definately want to hear a
source. Have you had the opportunity to measure one? Since you live in
British Columbia I rather doubt it. Are you guessing by the
photographs in some of the Jane's? Or are you just hypothesising based
on potential space available?
	 There is an interesting hypothesis presented by Zaloga (1996)
about the T-72B armor upgrade.  He writes: "These performance figures
and characteristics are similar to those made possible by the "bra"
armor developed by the NII Stali at this time for the T-55/T-62
upgrade program: it is possible that the T-72B's armor was based on
the same configuration, but integral to the turret casting rather than
as an applique." Now the Bra armor in question is composed of a
60-70mm front plate followed by steel plates in penapolyurethane. (I
have measured a cutaway example at the CFB Borden Military Museum.)
Does this sound familiar? Its essentially what was proposed in the
previous post.
	It seems we're looking at another big leap of faith here. Robb
is assuming that because the T-80U and T-72B are contemporary, and
despite the fact that they are designed by different people, they will
have the same armour. He is also assuming that they are using the
Bra-armor internally, despite the fact that this was only advanced as
a hypothesis. He next throws in a buzzword or two by claiming the
stuff is effective inert interlayer armor. This is then presented as
an established fact.
	I would be interested to see what evidence Robb has that his
"facts" are more than just a hypothesis on his part.

>Tests by a unified Germany in 1995 found this material to have an Em
>of about 5.0.

	Nonsense. The tests being referred to are reported in IDR
6/1995. These were German experiments with a variety of combinations
of interlayer armour, using different materials. They were not tests
on T-80Us, as Robb implies. They found that they could get a variety
of mass effectivenesses out of inert interlayer systems, ranging from
2.4 to 3 with elastomers and fiber reinforce plastics, up to "about
five" with a plastic "specially developed for the purpose" by
Deisenroth. These results were against HEAT, not APFSDS, and the mass
effectivenesses almost certainly don't include the backplate and
front-plates required to maintain the structural integrity of the
armor.

> Also had significant increases to vehicle survivablity in other
>areas, mostly the armoring and cellurization of ammunition storage and the
>incorporation of composite steel/GRP armor on the vehicle's flanks.

	I presume this refers to the uparmoured skirts on the front
half of the vehicle? I would be very surprised if they had fiddled
with the hull side itself.

>DOI: 1985
>RHA verus APFSDS: 820 mm
>RHA verus HEAT: 1 300 mm

	More estimation I presume?
>
>T-90
>
>The T-90 was the first vehicle to incorporate inert interlayer reactive armor,
>along with Kontakt-5, into it's armor system rather than relying on applique
>packs, lessening the number of null zones on the vehicle.

	I'll say it again. Source? I'm amazed you've been able to get
your hands on a T-90, enabling you to speak with such authority.

>
>Oh gee... The M829A1 can't penetrate the frontal armor of a T-80U, but it can
>kill a T-72G at about 8 km.

	And just what can the T-80U do to the Abrams? They're both
very much in the same boat, wouldn't you say?

>  Pitance that the guy who designed Air-Land battle
>doctrine, General Don Starry, says the same thing I do about the balance of
>technology.

	How very wise of General Starry... You meant to say that you
agree with General Starry, whose work you are parroting.

>The Sherridan conversions are all hot, and show up nicely on thermals,

	You've had a look, have you?

> even though the Russians have been incorporating thermal signature suppression in
>their vehicles since the T-80U and T-72B, circa 1985.

	Techniques such as? Running gear and tracks are by far the
most obvious heat sources on a tank from the important front and
front-side angles. The Russians haven't made any changes in this area.
The tank's shell is still a few inches of steel, which absorbs and
radiates heat quite nicely. No modifications there. The oblique
exhaust on the T-72 series, with its metal heat guard (hot and
noticable!), has remained essentially the same throughout the series,
and the T-80's turbine is actually a step backwards, with the
characteristic high temperature high volume exhaust of gas turbine
engines. Any improvements there might pull the thermal signature back
to parity with older designs. Improvements in the form of camoflauge
netting, matting, and other applique techniqes certainly aren't unique
to the Russians, nor to any vehicle class, so you couldn't mean that.
What did you mean?
	Thermal signatures are only significant with respect to the
thermal background, and the sensitivity of the imager. It is the
contrast between the target and the background that is important, not
absolute temperature of the target. A target may be very hot, but if
it matches the thermal background it is going to remain undetected.
The thermal background warms and cools depending on the season, the
weather, the terrain, and time of day.  Tanks are unusual objects in
the natural scheme of things (have you seen many 50 ton metal boulders
lately?) and don't act like the surrounding terrain thermally. Even a
completely inactive tank which has reached environmental temperatures
during the day or night will be revealed when it changes temperature
at a different rate than its surroundings at dawn and dusk. American
pilots made use of this to find dug in Iraqi tanks during Desert
Storm.



					Andrew Jaremkow
					jaremkow@hotmail.com

Newsgroups: sci.military.moderated
From: jaremkow@hotmail.com (Andrew Jaremkow)
Subject: Re: T-90 verus M1A2
Date: Tue, 15 Jul 1997 16:07:37 GMT

On Thu, 3 Jul 1997 16:44:42 GMT, antispam@uvic.ca (Robb McLeod) wrote:

>I have been told that the M111 "Hetz" could not penetrate the frontal armor of
>the T-72, and the real key to killing it was the "Shafta" warhead on the TOW.

Good for you. I can also provide sources that claim the M111 could
handle the T-72 at 3,500 yards. Which highly politicized claim from
the arms dealers would you like to believe?

>A couple of T-72M1s gave the USMC great trouble in Desert Storm for awhile.
>They proved capable of withstanding hits from Super Dragons to the front, and
>had to be taken out by a pair of AH-1W Super Cobra's firing Hellfires under
>the cloak of the burning oilfields.

Interesting. Where was this? Source?

>So, what's the formula to compute the penetration of long-rods?
>
>(T*[sec(theta)^0.75]/D) - 1 = (v^2/u^2)*[(D/L)^0.3]*(M/D^3)
>
>T = target thickness, in cm
>theta = angle of obliquity
>D = diameter of penetrator, in cm
>v = velocity of penetrator, in m/s
>u = penetrator constant
>L = penetrator length, in cm
>M = penetrator mass, in g
>
>'u' is about 4 000 for heavy steel penetrators and is about 3 500 for
>tungsten/Du penetrators.  I have better numbers but you can't have them.

	I have to laugh. If you think you're going to get anything
more than a general ballpark estimate from that formula you're wrong.

<Lecture mode on>

The formula was derived by a gentleman named DeMarro. It is a
simplified method of determining the penetration of long rods, and
ignores many very important factors. The formula includes values for
the rod's dimensions, mass (and thus density), and its velocity.
Unfortunately, rod penetration is governed by a host of other
variables as well.

The formula makes no mention of the strength of the rod and target
materials. These factors are quite important, and after density have
the dominant effect on penetration. Depending on which is stronger
(rod or target) and by how much the penetration characteristics can be
quite different. The difficulty lies in the fact that you need dynamic
strengths (the strength of the materials under the impact conditions),
not the static strengths. Dynamic strengths are very difficult to
measure, and vary depending on the materials, and the impact velocity.


The formula assumes that rod penetration can be described with a
constant velocity. Unfortunately this is not the case. As the rod
penetrates into the target elastic waves bounce back and forth within
the rod, slowing it down. This has been measured experimentally. As
the rod changes speed its penetration abilities will change. Not only
that, its dynamic strength will change. This means that for any
realistic determination of penetration value you're going to have to
determine the penetration bit by bit by bit as the rod slows down, its
strength changes, and its penetration method changes.

Unfortunately, that's not all. The shape of the rod's nose is quite
important in determining its penetration ability. Weapons engineers go
to great lengths to determine optimum nose shapes. Unfortunately,
there is almost no unclassified data about the effects of operational
nose shapes. The noses themselves are hidden under the pointed
windshields that are visible to the naked eye. There are cutaway
photos of various noses in Jane's, but can we really be sure which are
real, and which are representational? No. We can't. So this very
significant factor in penetration is essentially a guess on our part.

Furthermore, there are several stages of the penetration process, each
of which has different characteristics and durations, that are not
simulated by the equation above. Initially, the brief transient phase
is characterized by the intense pressures of the impact and formation
of the plastic shockwave. At the end of the penetration process there
is after-flow, where the crater continues to expand after the
penetrator has been consumed due to momentum effects. Neither of these
phases, which account for about a sixth of penetration at ordnance
velocities, are taken into account by the formula above.

Similarly, there are other material characteristics which will have
significant impact on the penetration process. How ductile is the
penetrator? How brittle is it? Is is susceptable to adiabatic shear?
None of this is taken into account by the above formula. Everything
except velocity, mass, and size is lumped into "u".  You need a
different U for each combination of
nose/strength/velocity/material/shape/etc. Do you honestly expect it
to be an accurate simulation?

What you've got on your hands is a curve fitting exercise. "U" is not
a real physical characteristic. It's an invented number to make the
curve fit the data points. As such it's only accurate in the limited
range of the original data. Attempting to use such a model outside its
data range is not going to produce good results.

For those who want the straight story, I'd suggest a set of three
books. One is called Impact Dynamics by Zukas et al, another is High
Velocity Impact Dynamics edited by Zukas, and the third is
Fundamentals of Shaped Charges by Walters and Zukas. They will give an
explanation that is heavy on the math, but worthwhile. You don't have
to follow step by step to understand the conclusions.

For those interested in where Robb learned his stuff, I'd suggest you
go to the Tanker's Forum (http://www.airfax.com/tanks) and have a look
at the Ammunition Chronology/Technology thread.

>M111 'Hetz'
>
>Mass = 3950 g
>Diameter = 3.07 cm
>Length = 36.7 cm
>Muzzle Velocity = 1 455 m/s

Let me guess. The dimensions come from advertising photographs showing
the round in flight, don't they? Since they don't come with a scale
bar that makes things difficult when you haul out the ruler and start
trying to measure...

>See above formula.  The effect yaw has on penetrator peformance is the only
>remaining factor on penetration, no?

No.

>The adiabatic shear mechanism whereby
>the long rod radially displaces the armor material and self-sharpens as it
>cuts down into the slope is accounted for.

Um, no it's not. It's just lumped into "u" along with everything else.
That's hardly "accounted for" in my book.

> Perhaps the dilatancy effect whereby ceramic armor erodes a penetrator
> should be explained?

Perhaps. Perhaps then you can also explain why it has no relevance in
the above formula...

> I really do understand this stuff

Evidently you don't understand enough.

>and I can compute the figures to a very high degree of
>accuracy when I have accurate figures, which is more and more the case
>nowadays.

Oh please.... Do you know the alloys involved? Sure it's W-Ni-Fe, but
precisely what alloy? Or perhaps it's W-Ni-Cu? Or Du-Ti? Have the
manufacturer's really released their formulae? What is the density?
How ductile? Just how have you gotten the dynamic strengths? The data
isn't let out, and you can't be sure. You can make impressive looking
estimates and extrapolations all over the place, but they remain just
that. Estimates.

>The Russians are very conservative in their armor estimates.  I know this from
>experience in working with the numbers.

Uh-huh.

> The Germans claim that Kontakt-5 shatters their Du penetrators, BTW.  Pity.

 Source? Is this Manfred Held in IDR?

>  Also, the testing method uses
>reduced charges fired in a evacuated underground chamber at a lesser range
>than is claimed.  This means that there isn't as much penetrator yaw at the
>claimed "range" than you'd normally expect, and penetrator performance is
>higher than the results you'd expect in real conditions.

	There are several techniques which allow the testing of yawed
penetrators, even when using reduced charge techniques. The rod can be
tilted by means of a jet of gas from an explosive placed beside the
flightpath, by means of an asymmetric muzzle brake, or by means of a
reflector plate placed alongside the flight path to nudge the rod with
its reflected shockwave (Zukas, 1990). The methods are well developed,
and the engineers can thus select velocity and yaw angle as required
for their tests.

>Waste of resources.  They deployed roughly 1 200 jamming units in East
>Germany, mounted in trucks and trailers.  If you drop on a jammer, a Smerch
>will hammer your MLRS.

Unfortunately, since the SMERCH only carries unitary HE (9N218F) or
fragmentation bomblet (9N218K1) warheads, it's not much of a threat to
an armored target with shoot and scoot abilities.

>So where'd the 280 mm come from that the Israeli's gave us?  Well, that's the
>thickness of the exposed lip of the glacis that projects beyond the side
>armor: 110 mm deep @ 68^.

	If anyone wonders where Robb came up with this figure, I'd
suggest they go to the Tanker's Forum, at http://www.airfax.com/tanks,
and have a look through the "Russian T-72" thread. That is the amount
of glacis armour visible above the weldline at the side on basic
T-72s. I've measured it on the T-72 on display at CFB Borden. I've
never seen the 280mm number listed from an Israeli source. It has been
used in Jane's for years, however, as the protection level for the
turret. It certainly looks like that's where the number came from, but
we don't actually know.

				Andrew Jaremkow
				jaremkow@hotmail.com