[meatloaf]

They aren’t until you calculate the terminal velocity and determine the kinetic energy.

[FredZarguna]

Incorrect. They really aren't particularly destructive. The terminal velocity is about Mach 10. To get to nuclear weapon yield, you need >Mach 300 at the point of impact, minimum.

That will be possible when we attack the people living on the other side of the Moon, or take out the Martians. It isn't happening on a planet with atmospehere; it's >100 km/sec. The fastest meteors, moving perfectly against the Earth's rotation, hit the top of the atmosphere at < 75 km/sec.

MOAB is a better alternative.