Chuck sez...
Rethinking it, a 1-kilometer object could be reduced to small rocks, rubble, and dust with repeated detonations of conventional explosives- no nukes needed.
As a former little boy, I can certainly see the appeal in blasting the living s*** out of a threatening asteroid or comet. But I'm a long way from being sold. When I think of the tons and tons and tons of material (or materiel) to be lifted to quite distant moving targets, it just doesn't add up for me. Just like the whole so-called "Star Wars" missile defense, it shares more with the Maginot Line than with a successful plan. The French squandered their treasury on the Maginot Line and the Germans just drove around it. I think that if we got our minds set on a big blow-em-up strategy, we'd miss out on cheaper and potentially more effective tricks. Of course the big defense contractors would love it. Job security for decades. Cost Plus. For a 'what it' scenario, imagine you've got to get rid of a Temple-Tuttle class comet. Boost up a few truckloads of soot and spread them over the thing. Let the sun take care of it over a few years. Or imagine a big microwave emitter with solar cells. Land the thing on the comet (or just orbit) and point the emitter down toward the surface. Maybe sprinkle a little popcorn on it, too. For an asteroid, send a few ion drive engines. Use a few to damp the rotations and another to gradually nudge the orbit. It mighttake decades to move it. These may be the dumbest ideas yet, but the point is not to be crippled by the only techniques we know.