intercepting an impactor with presumably a nuke is not going to be easy or even possible in many of the likely scenarios asteroid impactor is moving to fast and we see it to late,or not at all. asteroid impactor is solid nickle iron asteroid impactor is too large to destroy or deflect

The timing of an explosion will be tricky, as the combined speed of the asteroid and the nuke will be huge,the only possible intercept is head on, and the detonation will need to be timed to the pico second(dont know, but its way less than a micro). Too early, and we get hit with a slightly warm asteroid, too late and we get hit with a radioactive asteroid. Then the actual asteroid nuking rocket has to sit ready,after of course getting built, the summs involved will of course be thematicaly consistant, for whoever can insist that they get to build and maintain it,in perpetuity.