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From Gareth.Bull@cc.monash.edu.au (Gareth Bull)

Bernt.Budde@its.uu.se (Bernt Budde) wrote:
> ttelenko@mail.phoenix.net wrote: 
>>   There was some speculative articles in the Defense Technical press about 
>> using shaped charge explosives inside an armor array to cut up -- 
>> "guillotine" -- APFSDS rounds as they are penetrating.  This sectioning of 
>> an APFSDS round takes away the secret of it's success -- intense cross 
>> sectional energy density.
>> 
>>   Western Armor designers never followed up on this line of research due to
>> the success of Chobham and the practical problems of venting explosive 
>> gases from the main armor array without blowing up the tank the array was 
>> protecting. 
>Shouldn't this be much less heavy than Chobham? Could you realistically
>get the sides protected as well? (It's only the front that's almost
>"invulnerable" on the M1A1?) 
>British and US tanks use Chobham? The old Eastern Bloc used this special
>active armor. What do the Leopard (and others, like the new Indian) use
>instead? Nothing? Secret?

The Leopard 1 uses conventional hardened steel armour. The Leopard 2
uses Chobham and was the first Chobham armoured tank into mass
service. In the last few years there have been modifications to the
Leopard 2, particularly the turret, to protect against improved
anti-armour weapons that have been developed in more recent years.

As for India, They got into the tank business building copies of
Russian designed T series tanks, including the T-72. They certainly
won't be using Chobham, but they might have something similar. More
likely they use something more conventional, perhaped spaced hardened
steel. 

>What would happen if a 40 millimeter cannon with HE shells started
>shooting at a T72 with all those neat explosives?

Reactive armour charges are designed not to detonate from light
weapons or shrapnel, but a heavy enough hit would set them off. The
25mm Brushmaster used on the M-2 and LAV would set off reactive
blocks.

>(Do you *have* to cut the penetrator in two? Wouldn't it be enough to move
>the piece of armor that was being penetrated so that the round wasn't
>coming in exactly straight?)

The idea is to deflect the energy in some way. Reactive armour works
best against HEAT/HESH weapons. Solid penetrators such as APDS (Sabot
of whichever kind you prefer) are a different problem, and a reactive
armour charge *might* push the penetrator rod off course enough to
make it bounce off, but the trend has been to make solid penetrators
faster, giving them more energy when they hit (which make them harder
to deflect with a counter-explosion), and to make them out of denser
metal  (tungsten and depleted uranium) to give them better penetration
capability against heavy armour.

The NATO answer to high velocity solid penetrators is to make the
armour very dense (The M1-A2 uses Chobham armour made with depleted
uranium instead of hardened steel. The German and Dutch Armies have
added extra armour to their Leopard 2's. I don't know what the British
do). This also makes the tank very heavy, and more difficult to
transport from place to place as a result.

Look at the German "super-tanks" of WW2, they had very powerful guns
and very tough armour, but could only travel very slowly. They weren't
much more than slow moving bunkers in reality. The Panther was
generally considered to be one of the "best" tanks of WW2, because it
had a particularly good balance of armour, firepower and mobility.
Mobility is probably the most overlooked quality of a tank. The most
powerful gun and toughest armour in the world are wasted if you can't
get the tank to the place it needs to be.

                      Gareth Bull
               Gareth.Bull@CC.Monash.edu.au
    I'm just a jaywalker on the Information-Cul de sac