Don't know if you've seen this rendering work by Rhys Taylor of Orion before, but I'm gob-smacked...

http://rhysy.plexersoft.com/orion/index.html

...and his fictional Orion-powered space-fleets around Callisto...

http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/

...plus a 3-D animation of an Orion launch...

http://www.nuclearspace.com/gallery_orion_movie.htm

...quite impressive really. Quite dire in other respects - nuclear Cold-War space-fleets have an Apocalyptic feel.

Another link is an interview with Steve Howe discussing his nuclear  rocket work and  his antimatter sail concept for a very light probe (10kg) to Alpha  Centauri...

http://www.nuclearspace.com/article/Sview/HOWE_view.htm

...needs 0.017 kg of antimatter which is a BIG ask presently, but doable given some dedicated accelerators on the Moon *sigh*