Thinking about this, the interesting part is what happens when there is no air to heat and expand? From my understanding, in a chemical explosion the explosive itself releases a pressure wave of gas from the burning of the explosive. The air surrounding a chemical explosion helps carry the pressure wave further out.
But what physical material is ejected from a nuclear explosion and can it create a pressure wave? I was under the impression that the main component of a nuclear explosion is heat. Lots and lots of heat in the form of photon energy in a rainbow of EM spectrum. The destructive pressure wave is a result of the air/material around the detonation being violently heated to millions of degrees in mere microseconds.
Of course even in the vacuum of space anything within "ground zero" (can you say that in space?) of a nuclear explosion will still vaporize, producing expanding gases which can create a pressure wave. This is how I imagine a nuclear "asteroid buster" would have to work. The bomb would have to be on the surface or damn close to vaporize material from the object to influence its trajectory.
I had to double-check with the Atomic Rocketship website. You are correct in that the energy released by a normal nuclear detonation in a vacuum would follow the inverter square law, and would not transfer force as effectively over distance as it would in a fluid medium.
Note that I said "normal" nuclear weapon. ;-) The Atomic Rocketship page describes something called a Casaba Howitzer. This is basically a shaped charge version of a nuke, that discharges its energy in a beam or cone shape. Details beyond that are still classified.
Anyway, there's more than you ever wanted to know here:
But what physical material is ejected from a nuclear explosion and can it create a pressure wave? I was under the impression that the main component of a nuclear explosion is heat. Lots and lots of heat in the form of photon energy in a rainbow of EM spectrum. The destructive pressure wave is a result of the air/material around the detonation being violently heated to millions of degrees in mere microseconds.
Of course even in the vacuum of space anything within "ground zero" (can you say that in space?) of a nuclear explosion will still vaporize, producing expanding gases which can create a pressure wave. This is how I imagine a nuclear "asteroid buster" would have to work. The bomb would have to be on the surface or damn close to vaporize material from the object to influence its trajectory.