Do youhave a gantry model?  Nasa has one for download on their 3d model site if you do not.  [NASA 3d model downloads.](http://www.nasa.gov/multimedia/3d_resources/models.html)

My suggestion is to model your smoke in Hexagon or another poly modeler.  Then use a volumetric cloud material on it in Bryce.

I started a similar scene and then stalled out on it.

Free men do not ask permission to bear arms!!