As part of the Missile Defence Network the US have developed these little critters.

http://www.engadget.com/2008/12/08/t...ing-nightmare/

Apparently these guys are supposed to move to an intercept path of a ballistic missile and the collision alone is supposed to destroy the missile. They carry no armament.

So a 40T missile hurtling thru the sky at 8 kmps, is supposed to be destroyed by a tiny little hovering speed bump. Fail.