posted on Jul, 23 2005 @ 05:12 PM
The French have a bomb called a 'Durandal' bomb which is dropped from medium to high altitude and is used to take out runways.
As it falls to the ground, a clockwork motor arms a small rocket motor which is feulled by a solid propellent. When the bomb reaches a pre-determined
height the rockets fires, driving the bomb deep into the ground.
I would go with this method and use a more powerful engine. Should do the job no problem!