Spurred on from an earlier post over here. The general consensus was that if a depleted uranium round is coming your way, don't be in its way. And if you do get hit, disperse the damage as much as possible.
Essentially, with the introduction of long rod tank rounds (think like APFSDS- Armor Piercing Fin Stabilized Discarding Sabot), armor will have a tough time with those rounds slamming into it. Especially as the speed of those rounds increases. Someone in the other thread made an interesting point, essentially shells don't behave like normal projectiles at much higher speeds.
Modern armor designs are more of a system than a slab of metal these days i.e. ERA (explosive reactive armor) on top of solid composite armor etc. Something that was also brought up was that a long rod penetrator isn't going to do as much damage if the round is tumbling and hitting the armor on its side (ie long rod doesn't strike armor with its tip).
Using this principle, how feasible/effective would a system that intercepts long rod penetrators(LRP) to induce a tumbling or structural damage be. Target acquisition aside, imagine a system that shoots out either a projectile or an explosive to cause the incoming round to tip over and tumble. Currently the Israeli trophy system doesn't work against long rod types. Russia's Afganit supposedly intercepts kinetic rod weapons, however that fires a large heated mass to physically break apart the rod.
Two systems that I had floating in my head were:
A foam type weapon that detonates in a wide pattern and sticks to an LRP to cause aerodynamic instability or even detonates to cause structural damage.
A malleable explosive that's shaped larger in surface volume to an incoming round (think like size of a small pizza or a large pie dish). Upon hitting and wrapping around the tip of a penetrator, it detonates (imagine punching raw pizza dough, sure you go through it, but it gets stuck on your arm and stretches with your fist for a moment) to either cause a flight change or damage structural integrity. Or just immediately detonates when making contact with the tip of the LRP.
These are just ideas to help visualize what I mean, system can be anything really. So long as it goes out to meet the incoming projectile to destabilize the projectile. destroying it is a plus not a requirement.
Its main use case would be on a tank, whereby it would intercept or destabilize long rod penetrators so that if they do hit, then the rest of the tank's armor package can absorb it with relative ease. You'd be able to carry more of these small interceptors than the enemy can shells (enemy is single tank for question's purpose) due to the massive size difference the ammunition sizes of enemy round and interceptor round.
Ignoring target acquisition and assuming the speeds are anywhere from 1.8 ~ 4km/s would a system that works on destabilizing a long rod penetrator either by damaging its flight path or structural integrity be feasible. Or is this a developmental dead end. The system doesn't have to be perfect, just like existing active protection systems. Just good enough to increase survivability by a meaningful factor to warrant its inclusion as part of a tanks comprehensive defense package.
One major constraint is that laser systems to vaporize a shell isn't an option. Anything capable of eating through that much dense metal would be a weapon in its own regard, not an active defense system.