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I am more suprised about how much space is occupied by the mounting brackets for the NERA. There are a number of possible armor layouts that don't need such brackets.

 

Perhaps the standoff space is deliberate; e.g. to give the penetrator/jet more room to yaw or break up.

 

Or perhaps the metal elements move quite a bit during penetration and need that room to flex.

 

I would be surprised if that design were actually inefficient and due to incompetence.  On the early Abrams you could maybe suppose that a sub-par armor package was installed because the early Abrams was supposed to be a cheap tank (cheaper than the MBT-70 anyhow).  But as I recall, pictures of damaged Abrams from Iraq still show those giant mounting brackets, and the armor package has been quite comprehensively re-designed at least on the turret (M1A1 turret cheeks overhang the driver's position noticeably more).

 

So I guess that it's deliberate.

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It could be they were leaving room for a better armour array in future. Adding more on the front of the hull affects mobility, whereas a redesigned with bigger NERA boxes only adds to weight

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The fact that a group as insanely knowledgeable as the posters on this forum are still actively debating said features and the motivation and intent behind them really does say a lot about just how much of a leap forward the Burlington and Burlington derived armor packages truly were.

To my mind that alone goes a long way towards justifying the long time even a document like this stayed classified!

I'm sure several of you god damn technological wizards will bang out FEA and other analysis tricks and pin down the true reasoning behind the brackets by at the latest three weeks from now, but that's just because you guys are a fucking critical mass of super geniuses that regularly remind us normal genius types that compared to all y'all we're window licking helmet wearing short bus riders ROFL

seriously you guys are ... Astounding and I love this place even if it regularly reminds me I'm nowhere near as smart as I think I am LOL

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Perhaps the standoff space is deliberate; e.g. to give the penetrator/jet more room to yaw or break up.

 

Or perhaps the metal elements move quite a bit during penetration and need that room to flex.

 

I would be surprised if that design were actually inefficient and due to incompetence.  On the early Abrams you could maybe suppose that a sub-par armor package was installed because the early Abrams was supposed to be a cheap tank (cheaper than the MBT-70 anyhow).  But as I recall, pictures of damaged Abrams from Iraq still show those giant mounting brackets, and the armor package has been quite comprehensively re-designed at least on the turret (M1A1 turret cheeks overhang the driver's position noticeably more).

 

So I guess that it's deliberate.

 

 

I guess it could be related to the way the NERA array is mounted, allowing easier replacement (repair) of damaged armor modules. I have been wondering (based on the following photograph) if the Abrams' side armor modules are inserted from the side, rather than cutting of the roof as done on the Leopard 2. This might make sense due to the M1's sight systems and hatches overlapping over the weldline of the armor cavity roof.

 

2lw0s5s.jpg

(M1 Abrams turret structures during a upgrade process - note how the side armor of the crew compartment was cut open at the sides)

 

e2994b49d0b60e35bad77813944a5f77.jpg

 

British Burlington armor designs don't feature a mounting bracket or a large empty space betweem the NERA layers and the base armor. Well, there is a slightly larger air gap in front of the base armor, but it's only ~ 2-3 times as large as the spacing between each NERA layer.

2865253585_f79f4cc7e2_b.jpg

 

The air gap in front of the base armor of the US design is 5-6 times as large as the air gaps between the sandwich plates.

 

I haven't seen any photo of a damaged M1 Abrams with such mounting bracket, do you happen to know a link to one?

 

It could be they were leaving room for a better armour array in future. Adding more on the front of the hull affects mobility, whereas a redesigned with bigger NERA boxes only adds to weight

 

I don't think your theory is correct, based on the M1IP and M1A1 requiring new turrets with thicker frontal armor.

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We haven't seen the armor layout of the turret cheeks, but we have seen the armor layout at 4 different places. The two places where the armor is integrated (hull front and turret bustle side), there is such a mounting bracket. On the two other places, the armor is fitted into modules can easily be detached.

 

I find it hard to assume that the frontal turret armor suddenly follows a completely different layout - in general it should provide (on the oriignal production model) the same level of protection as the turret along the frontal 60° arc. The fact that the hull armor stayed at the same size, while the turret armor thickness increased is related to how armor upgrades distributed more mass to the turret; that still doesn't mean that the function of the mounting bracket was to provide volume for future armor arrays.

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Frontal hull armor and frontal turret armor inserts being different is sort of normal thing for Soviet MBTs like T-64s, T-72s and T-80s.

 

On the earlier tanks, yes. But on the T-80UD and late T-72B/T-90 hull and turret armor follow the same technology, the shape of the inserts was just adapated to the shape of the hull.

 

Aren't the DU inserts in the later M1s only in the turret cheeks?

 

Some sources suggest so, other sources however disagree. There are at least five M1 Abrams tanks with DU armor in the hulls located in the US Army schools - but it seems possible that DU armored hulls were not adopted in US Army service (yet).

 

x0nmoij.png

 

From a document of the US Army TACOM Life Cycle Management Command Safety Office to the  U.S. Nuclear Regulatory Commission.

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Something that just occurred to me: how much difference does the quality of steel and rubber used make?

 

Because I will die a bit inside if the super secret sauce turns out to be mild steel plate and vulcanised rubber sheet.

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On 1/31/2017 at 4:15 AM, Toxn said:

Something that just occurred to me: how much difference does the quality of steel and rubber used make?

 

Because I will die a bit inside if the super secret sauce turns out to be mild steel plate and vulcanised rubber sheet.

 

I suspect that the metal in the NERA package does make a difference.  The latest M1 variants and IIRC latest T-90s are supposed to use titanium in the fancy tryhard frontal composites.

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I have a different guess about the DU in the M1A1HA.  The DU has been described both as a "mesh" and as being placed on top of some sort of preexisting composite array.  Also, materials with very high densities have poor ME against CE threats.

Given the above, I think it is most likely that the DU elements are placed in front of the armor array and are designed to work like perforated armor.  Perforated armor schemes work best with materials that have high density, as the greater inertia means the penetrator decelerates more when it collides with them.

The DU in the M1A1HA is also described as being encased in graphite.  This, I suspect, is to protect it from fast neutrons.

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57 minutes ago, Collimatrix said:

I have a different guess about the DU in the M1A1HA.  The DU has been described both as a "mesh" and as being placed on top of some sort of preexisting composite array.  Also, materials with very high densities have poor ME against CE threats.

Given the above, I think it is most likely that the DU elements are placed in front of the armor array and are designed to work like perforated armor.  Perforated armor schemes work best with materials that have high density, as the greater inertia means the penetrator decelerates more when it collides with them.

The DU in the M1A1HA is also described as being encased in graphite.  This, I suspect, is to protect it from fast neutrons.

That... would suck.

Then again, if your neutron flux is enough to cause your armour to be a fission danger then your day has thoroughly gone to shit already.

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19 hours ago, Collimatrix said:

 

I suspect that the metal in the NERA package does make a difference.  The latest M1 variants and IIRC latest T-90s are supposed to use titanium in the fancy tryhard frontal composites.

I wonder what titanium gets you over steel, beyond weight?

Is there any word on how well aluminium alloys work?

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55 minutes ago, Toxn said:

I wonder what titanium gets you over steel, beyond weight?

Is there any word on how well aluminium alloys work?

AFAIK Titanium alloy used in armor provides some advantages over steel besides weight. Some materials to read.

http://c.ymcdn.com/sites/www.titanium.org/resource/resmgr/2005_2009_papers/Gooch_Final_2007.pdf
http://c.ymcdn.com/sites/www.titanium.org/resource/resmgr/2010_2014_papers/GoochWilliam_2010_MilitaryGr.pdf

 

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59 minutes ago, Toxn said:

I wonder what titanium gets you over steel, beyond weight?

Is there any word on how well aluminium alloys work?

I've heard that aluminum alloys suck vs high velocity threats like shaped charge jets and KEPs, but work quite efficiently against low velocity threats like artillery fragments.

 

1 hour ago, Toxn said:

That... would suck.

Then again, if your neutron flux is enough to cause your armour to be a fission danger then your day has thoroughly gone to shit already.

The whole point of neutron bombs is to bring the joy and happiness of fast neutron radiation to people inside of tanks.

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40 minutes ago, Collimatrix said:

I've heard that aluminum alloys suck vs high velocity threats like shaped charge jets and KEPs, but work quite efficiently against low velocity threats like artillery fragments.

 

The whole point of neutron bombs is to bring the joy and happiness of fast neutron radiation to people inside of tanks.

Graphite won't help much with that.

Better that you get cooked by your armour turning into a makeshift reactor than live long enough to see your skin fall off your necrotic flesh.

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Why not?  Graphite is a pretty damn good moderator.

DU only fissions appreciably under fast neutron bombardment.  If you can thermalize the little bastards then at least you don't need to worry about your own tank's armor dosing you with gamma rays.

I would agree that you're still having a bad day.

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I have seen these rumors about "a DU mesh" acting like perforated armor at other places. However it was always either Wikipedia (without mentioning a source) or another website/forum quoting Wikipedia. There seems to be no reputable source describing the DU armor in the Abrams' turret as mesh or perforated plate.

DU supposedly has a higher ME against shaped charges than steel (old source on tank-net, unfortunately Google blocks access due to phishing claims). I have never seen perforated armor against anything larger than HMG bullets. It works well against bullets, but longrod penetrators should behave quite a bit different than those. Probably the tip might break away when impacting a heavy metal perforated armor system, but the majority of the rod might stay intact. Furthermore I wonder if a perforated DU plate would be a feasible option in terms of protection per weight compared to a NERA-based array.

The Leopard 2 is rumored to incorporate tungsten and titanium in it's armor since the 2A4 variant, while the Leclerc according to some books features a "tungsten-titanium non-explosive reactive armour system".

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A perforated armor scheme for use against a long rod penetrator wouldn't work quite the same way as perforated armor screens on APCs work.  Those are mainly to stop 12.7mm and 14.5mm AP projectiles, and the defeat mechanism is often by breaking the penetrator in half.

Against a long rod penetrator the mesh would be designed to take advantage of the fact that LRPs yaw into sloped surfaces:

vbBqIT2.jpg

 

Even a very slight angle of attack of the LRP would enormously reduce its sectional density and make it much easier for the rest of the armor array to stop the penetrator.

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