[GoLightly]

an energy release and shockwave comparable to the Hiroshima bomb

Know if it sent out an EMT pulse or would we only have to worry about that w/ a possible solution to a big one that gets in our way?

Don't know how reliable the info here is, but well... it's got pictures. ;o)

http://www.fas.org/spp/military/docops/usaf/2025/v3c16/v3c16-3c.htm

[SunkenCiv]

Thanks. Gene Shoemaker said that, once an object gets to a mile in diameter, the energy released by its impact on the Earth would exceed the energy released if one took all the nuclear weapons in the world, put 'em in a pile, and set them off simultaneously. Of course, that's give or take a dozen miles per second of terminal velocity. ;')