CIWS-Safe

With the increase in rocket and missile attacks on civillian populations, countries are investigating putting in C-RAM (Counter Rocket Artillery and Mortar) systems. One of the preferred implementations is the same as the Naval Close in Weapons System (hence the title). This is essentially one or more automatic gatling guns that track and shoot down the incoming munitions.

One problem with this approach is that in dense civillian populations, all of these thousands of bullets are going to come back down, potentially doing severe (or even lethal) damage to anything under them, including the civillian populations you are trying to protect.

I suggest, therefore, that these bullets be equipped with small spring loaded flaps along one side. These flaps are designed to be held aerodynamically closed as long as the bullet is moving along its axis above a certain speed (and are held closed inside the barrel). This allows the bullet to travel normally along the path to its intended target.

Once the bullet slows sufficiently near the peak of it's travel, the flap pops open. Once open, they push the bullet off-axis, preventing it from remaining spin stabilized and increasing it's tumble. This slows the bullet during it's return to earth, minimizing harm to anyone who finds themselves in the wrong place at the wrong time.

There obviously would be significant design challenges to work out (eliminating bullet imbalance and tumbling from the effects of holding the flaps closed), and there would be a minimum effective angle (if enough of the starting velocity isn't upwards, it won't slow enough before turning back down). I'm pretty sure all of that could be dealt with, however, and the end result should be something that could be placed in/near heavily populated areas without nearly as much fear of collateral damage.