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Subject: Question on armor defeat mechanisms
earlm    4/29/2010 7:03:03 PM
To defeat a KEP I am under the understanding that the projectile simply cannot be defeated by placing a mass in front of it regardless of what this mass consists of. Instead the projectile must be bent, broken, or blunted. 1. Are there materials that could defeat a competitive KEP simply by using up the energy as it passes through? I don't need the idiot level answer "Yes, but on a 150 ton tank." I'm looking at 70 tons as the limit. 2. What kind of probabilities are there for breaking, bending, and/or blunting? I assume that if it fails then the KEP goes right through.
 
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VelocityVector       4/29/2010 7:47:01 PM

A KEP is working on such small area and displacing such a small volume of matter that I believe your answer must be a canceling energy and not a material.  0.02

v^2

 
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earlm       4/29/2010 7:56:08 PM
Isn't that kind of how ceramics work?  They shatter, bounce off the backing plate and rebound into the HAT jet?  Do they do that against KEP?
 
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VelocityVector       4/29/2010 8:51:36 PM

I believe KEP working is majority in solid state; HEAT is not at all.  Given all the solid mass working and the real estate in the case of KEP I do not see how a single material within your 70 ton limit and requirement for field utility could break the individual atomic bonds to change state and cancel or redirect total KEP energy before KEp reaches a vehicle interior.  I truly don't know and have zero desire to attempt.  Sorry ;>)

v^2

 
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flamingknives       4/30/2010 2:41:08 AM
First off, what is a KEP?
In literal terms, a Kinetic Energy Projectile could be anything from a cannonball to an APFSDS.

Assuming that we are talking about APFSDS, then it can be stopped by homogenous armour, but the amount needed would be impractical for a tank to have any kind of comprehensive coverage.

Blunting, bending or breaking has the effect of spreading out the impact over a larger area of armour, so less mass hits any given point and that is more easily absorbed. Ceramics, High Hard Steel and similar hard material can act as a strike face, disrupting the APFSDS rod, while spaced armour provides drift space to allow the disrupted threat to break up before it hits the backing armour. Multiple disruptors at varying angles can add further lateral forces to the rod, encouraging breakup.

Modern ERA can also disrupt incoming APFSDS.
 
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Hamilcar    What FK said.   4/30/2010 4:11:08 AM
I add this, that you can plane the grain of the metal or plastics to resist cleave planes presented to 90 degrees to the the kinetic projectiles strike trajectory path. 
 
One more thing that FK alluded to, was to vary density zones, present angled hardened diverters in the armor blocks, a shock reflector back-plate, and varying voids and densities front to back (hard soft hard soft with planned voids and skipoffs in each armor face where practical.) You don't want to stop the dart so much as to bend it or snap it in two so that it will shatter inside an armor void.
 
H.       
 
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Mikko    slight sidestep   4/30/2010 5:05:09 AM
Good day,
 
If I may ask a question that goes hand in hand with the topic:
 
How small of a diameter bomblet / grenade does it take to be a threat to a MBT if entry angle is from the top? What are the limits in - say - cargo ammo to punch through the roof?
 
This is very general question but I am mainly considering cargo shells from artillery that could punch through. I understand there are bomblets that spray anti-personnell frags to the sides and push a shaped effect downwards on impact.
 
M
 
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Nichevo    Just for chucks   5/5/2010 5:15:32 PM
Put a wrecking-ball on a crane atop the MBT's turret.  Say a yard wide, or less as needed, of whatever interesting set of materials. Maybe not a ball, maybe a plate, maybe a plate with ERA.
 
Now, with antimissile systems you track the incoming rocket and fire a rocket, or a laser, or a buttload of ball bearings at it.  This system plots the path of the incoming penetrator and swings the wrecking ball, or plate, in its way, adding an optimal angle or rotational vector .  Defeats, deflects or slows the long-rod to where lighter armor can sustain the residual KE.
 
In the sense of armored cavalry as knights on horseback this would be known as a "shield."  If shield is destroyed, reload from a stack on the tank's rear.  Generally you won't be getting plastered with dozens at once.
 
Chief issues would seem to be reaction time, fine computation and brawny servos.  Oh, and CG I guess, though it could be laid flat for travel.
 
 
 
 
 
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Nichevo       5/5/2010 5:18:34 PM
If your computation were good enough the shield could be, say, a four-inch diameter, yard-long rod of armor swung to meet the projectile head-on.  Then again, maybe the tank could train its own turret and fire a sabot at the sabot.  Hmmm...
 
Anyway, you only need the armor where the warhead is coming in, is the idea.
 
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Mikko    of tank shields   5/6/2010 6:07:21 AM

If your computation were good enough the shield could be, say, a four-inch diameter, yard-long rod of armor swung to meet the projectile head-on.  Then again, maybe the tank could train its own turret and fire a sabot at the sabot.  Hmmm...
 
Anyway, you only need the armor where the warhead is coming in, is the idea.
Deflect. Sounds most fun. Three tanks could play ping pong and send the penetrator back to the shooter, ding-ding-ding-aaargh (kidding).

I like your idea. Though I can't make it work on paper yet doesn't mean it couldn't be done at all. The key issue would probably be the fact that the shield should be swung in such a speed and accelerated so fast to meet the incoming projectile, that the entire tank would become a batting servo and nothing more. Roger Federer on tracks.
 
And guess what the universal sceptic (that I am not) says next? "If you just took away the weight and cost of the moving parts and replaced them with ERA and steel of same effect, you'd get yourself a normal tank."
 
So the "bat" should be enormously light, hard and accurate to do the trick. Just imagine waving a metal rod to meet a projectile that's coming at you 800 meters a second. Not a small jerk to put it in motion and no small jerk to stop! Same with the tank cannon: I wouldn't want to be inside the turret when it swings 130 degrees in 0,1 seconds. My neck would snap and I'd make a grotesque corpse for my daughter to say goodbye to before cremation.
 
That's probably why shield systems are either counter projectiles or just sit waiting there.  Were I to work on a shield system, I'd investigate possibilities of a dedicated shield tank that would shoot ultra fast projectiles to defeat everything that flies towards your troops. Intercepting incoming AT-missiles could be within possibilities of accuracy and reaction time. Plausible maybe, but hardly cost effective. The mechanism should be so light that it would be scrap from one hit of a rifle round.
 
M
 
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Nichevo    ding-ding-ding-aaargh-LOL   5/6/2010 12:25:28 PM

 
 



If your computation were good enough the shield could be, say, a four-inch diameter, yard-long rod of armor swung to meet the projectile head-on.  Then again, maybe the tank could train its own turret and fire a sabot at the sabot.  Hmmm...


 

Anyway, you only need the armor where the warhead is coming in, is the idea.



Deflect. Sounds most fun. Three tanks could play ping pong and send the penetrator back to the shooter, ding-ding-ding-aaargh (kidding).

ROFL, Mikko, just ROFL.


I like your idea. Though I can't make it work on paper yet doesn't mean it couldn't be done at all. The key issue would probably be the fact that the shield should be swung in such a speed and accelerated so fast to meet the incoming projectile, that the entire tank would become a batting servo and nothing more. Roger Federer on tracks.

Well, shields were actually used against swords, spears, arrows.   Only circus acrobats and such can manage supersonic speeds under even controlled magic-trick conditions.  That's where computers come in.  The batting, to induce side vectors, is a refinement - we would be happy to place the center of a sphere or plate in its path.
 
 
And guess what the universal sceptic (that I am not) says next? "If you just took away the weight and cost of the moving parts and replaced them with ERA and steel of same effect, you'd get yourself a normal tank."

This could use ERA instead of a passive target.  If nothing else it would be taking the concept of spaced armor to a whole new levels - feet of void not inches - maybe a deflection that would be inches inside the Chobham would be feet with the shield and be a hull miss entirely.  This puts a ton of armor, say, directly in the path of the warhead, instead of around the 99% of the tank not under fire.  Like a shield is lighter than a suit of plate.  And the sphere or plate could itself be layered, use voids, etc.
 
 

 
Metal or alloy kg/cu.m
aluminium - melted 2560 - 2640
aluminium bronze (3-10% Al) 7700 - 8700
aluminium foil 2700 -2750
antifriction metal 9130 -10600
beryllium 1840
beryllium copper 8100 - 8250
brass - casting 8400 - 8700
brass - rolled and drawn 8430 - 8730
bronze - lead 7700 - 8700
bronze - phosphorous
 
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