What is the effect of a nuke in space?
Since all a nuke (directly) is really good at is creating a lot of heat in a very small space, what does it do when there is no volume of air to heat and increase - dramatically - the volume of. [forgive the lousy sentence structure!]
Of course, there is blast produced just by the matter of the bomb, itself. How much shock/blast is caused by this?
And whatever it was close to (nearest part of the asteroid) would be vaporized, and add to the blast and shock, but this can be controlled by moving the bomb closer to or further from the body.