Boris B asks
Kind of. Mostly it is the result of the huge overkill of nuclear weapons. While a megaton bomb may in fact destroy the center of its action a thousand times more efficiently than a kiloton bomb, it certainly does not create a blast radius a thousand times larger. Dresden was more thoroughly destroyed than Hiroshima, even though it was not hit by as much explosive force. The firestorm that was caused resulted from the placement of the bombs, not the power of them.
It also doesn’t take vaporization to compromise the usefulness of most of the accoutrements of civilization. Simply knocking them down, and setting them on fire is, in a military sense at least, sufficient. When you consider that concrete and steel are among the things which get set on fire in the firestorm which *follows * a nuclear explosion, you can understand why a little one is really all you generally need, in a given township.
If you want to sterilize, and obliterate a very large area, for some reason, you are far more likely to be successful if you place kiloton bombs on half mile centers over a five or six mile radius, than if you drop a big whomper in the center. For the same bang, you can set the entire five mile circle ablaze in a firestorm which will thereafter sweep outward for a mile or more, and the resulting counter blast of returning air will re-ignite anything which managed not to burn in the first holocaust.
Ideally you want your bombs to go off a thousand feet (assuming you are using 1 KT bombs) or so in the air, as well, since the fireball will rebound off the ground to a great extent, and even many megatons won’t vaporize all that much country rock, or reinforced bunker. The higher center allows your fireball to rebound in a more outwardly pointed vector, reinforcing the power of the blast, and the heat moves over a larger area of target. Secondary fires will be more widespread as well. Keeping the fireball from touching the ground will reduce the fallout by some amount, if that matters. Getting it above the troposphere will increase the EMP (electromotive pulse) effect, if that matters.
Now using nuclear explosions for propulsion is a bit different. You have to get up real close and personal, in space. The portion of the blast which moves away from the object to be accelerated is not a factor in the equation, and the further from the object, the higher that fraction is. Getting it above 50 per cent would mean having a concave target, and some spiffy impact reinforcements on that side of the object. If your asteroid is a big hunk of iron, all in one piece, it could work. If it is a pile of ice and gravel meandering around in space together, you create some amount of high speed shrapnel, and the rest of the pile moves along as before.
<P ALIGN=“CENTER”>Tris</P>
What goes: Clop, clop, clop, clop, Bang! Bang! Clop, clop, clop?
An Amish drive-by shooting.