All kinds of inventors and gagdeteers have come up with all kinds of ways to try to stop rocket-propelled grenades before they slam into a Humvee. The U.S. Army wants to blast the thing with a foot-long mini-rocket. The Brits think they can do with with a massive electrical charge. And a company called Aoptix Technologies wants to "apply... high energy light based weapons" to stop the things.

Reader NB has dug up a patent for a different type of RPG-stopper: one that uses a parachute.

When an incoming munition such as an RPG is detected by the tracking apparatus 12, the firing solution computer 14 determines the time of launch and the particular launch tube 16 and sends a firing signal to the igniter 24 of the appropriate launch tube 16. The igniter 24 initiates the propelling charge 22. As the propelling charge 22 burns, expanding gases 40 (FIG. 2B) that are sealed behind the obturator 26 push the mass 20 up the tube 16. The mass 20 continually accelerates in the direction of the arrow V until the obturator 26 exits the end of the tube 16. Soon after the mass 20 exits the tube 16, the cable 32 will be pulled taut. As the force acting on the cable 32 increases, the parachute 30 will be pulled from its storage container 18.

Simultaneously, the resultant force acting on the connecting ring 28 will cause the mass 20 to rapidly rotate as shown by the arrow w in FIG. 2D until the connecting ring 28 is facing rearward. As the mass 20 continues to fly forward, the parachute lines 34 and canopy 36 will be pulled from the storage container 18. Within a short period of time the parachute 30 will be fully inflated and flying directly towards the incoming RPG 38. The parachute 30 will remain inflated for a long time relative to the incoming projectile's 38 remaining flight time to impact, thereby alleviating the need for precise timing and fuzing systems. There are several mechanisms by which the collision between the parachute 30 and RPG 38 will render the RPG 38 less effective.

A significant amount of the momentum of the parachute 30 and mass 20 (which is similar to the momentum of the incoming RPG 38) will be transferred to the RPG 38, thereby slowing it and possibly causing it to miss the intended target. Secondly, the collision will cause damage to the RPG 38 such as breaking fins or crushing the nose cone. Damage to the fins and disturbance upon impact will cause the RPG angle of attack to grow, thereby greatly reducing its terminal effectiveness. Crushing the nose cone can short the RPG fuzing system, rendering the warhead inoperable. The collision between the parachute 30 and RPG 38 will take place well away from the protected vehicle 10. If the collision causes the warhead to detonate prematurely it is much less likely to hit or damage the protected vehicle 10.