metalgod, on Sep 14 2011 - 05:32, said:
Again, a modified T72. Russia needs to retire this design altogether, its not bad, but the magizine autoloader is horribly vunerable. Reactive armor works real well against shape charges and rpg style rounds, what it is nearly useless against is depleated uranium sabots like the Challenger 2, Abrams and Leopard 2A6 are using. Russia is well capable of building a great MBT (the Black Shark was a good start, just a bit too ambitious) so retire the worn out T72s and lets see some real Russian steel!!!
Strictly speaking, the autoloader magazine in the T-72-derived tanks is no more vulnerable than the reserve ammo boxes in the Leo 2 (located in left section of front hull) or that of the Leclerc (drum magazine in right section of front hull) or the Merkava (rear hull left and right sections). All these ammo storage schemes hold the same dangers because they are not isolated from the crew by bulkheads and their compact arrangement increases the possibility of sympathetic explosions in the event of a hull penetration. What makes the ammo storage scheme of the T-72 family truly horrible are two factors:
1. The rest of the ammo.
In all variants of the T-72 and T-90 to date every single piece of ammo not in the autoloader magazine is stored all over the hull and turret floor area and all are horribly exposed. There are two charge cases under the seats of the turret crew! This basically means that a single spark falling into the turret has much greater potential to ignite a charge than in Western tanks. The autoloader itself is well protected and has an armored cover. In most cases of autoloader carousel detonation identified, the actual explosion starts with one of the exposed reserve charges and results in sympathetic detonation of ammo inside the carousel, so it's not usually the carousel itself that causes disaster.
2. The inherent inability to isolate any ammo from the crew.
In the Leo 2, Leclerc, and Merkava, there is always the option of simply emptying the reserve ammo boxes (which is done by Leos in Afghanistan and Merks in most recent conflicts) and relying on the ready ammo rack, which is isolated from the crew by armored bulkheads and located in the turret bustle, thus equipped with blowoff panels. In the T-72 family, the carousel is by definition necessary for normal tank operations and must always be loaded with ammo. This means that there is always going to be a giant powderkeg underneath the crew with no way to vent overpressure in the event of charge detonation, let alone HE round explosion.
The Black Eagle (T-80UM2) MBT resolves some of these issues by having a turret bustle autoloader and (in one variant) a lengthened hull with additional frontal armor and a special section of the hull for storing the reserve ammo. The problem with the design isn't that it was too ambitious but rather that it used the T-80 hull as a basis. The T-80 was mostly produced in Russia by the Kirov and Omsk factories and in the Ukraine by the Malyshev (now Kharkiv-Morozov) factory. The costly gas turbine engine caused cash-strapped Russia to stop production after the Soviet collapse and the T-80UD diesel-engined version designed by Morozov bureau (of T-34 and -54/55 fame) was produced mainly in the Ukraine so is now basically another country's product. The T-72, on the other hand, is quite numerous and production capacity remains in Russia. The T-90 being an upgrade of the -72 gives it a lot of logistical and political advantages over the T-80-based Black Eagle tank. The T-80 simply went out of favor in Russia, and the Black Eagle shared its fate. Then Omsk Transhmash went bankrupt due to financial mismanagement and development stopped completely.
There are proposals for a bustle autoloader for the T-90 derived from the Black Eagle's autoloader, so hope is not lost yet. Future generations of T-90 might incorporate this scheme.
As for reactive armor effectiveness against sabot round, it is true that traditional flying plate type reactive armor is useless, but modern Russian reactive armor like Kontakt-5 and Relikt actually use a shearing plate mechanism, which is why they are always angled on the tank's front hull. In this scheme, the reactive plate is not thrown against the impacting projectile but rather shears its way at an angle to the body of the projectile. With long sabot rounds, this would impart a tangential velocity component to the body that may cause it to break. This would separate the round into a shorter sharp-edged penetrator and a longer blunt-edged shaft (or even more pieces). The sharp-edged penetrator can stab through armor but lacks the mass to impart significant momentum to the tank's body. The blunt edged shaft has the mass, and therefore ability to impart momentum, but lacks the sharp edge that would allow it to stab through. With some luck both segments would be stopped by the static armor behind the reactive armor. This is why Russians claim that their modern reactive armor adds 200-500mm rha-equivalent to protection against kinetic energy rounds. Another way to look at it is that the reactive armor splits a round into a wimpy arrow and a clumsy battering ram, neither of which can punch through the steel wall behind it.
With that said, the US M829E3 sabot round is probably too long to be stopped by this mechanism.