There's a good TV show about Project Orion ("To Mars By A-Bomb") which pops up over here every so often. It includes footage of the prototype flying (using conventional explosives!)
The real thing would have been enormous. With chemical rockets you need to keep the weight down, but with Orion you can make it as big as you like. Not quite a flying battleship, but not far off.
Arthur C Clarke's opinion is that the idea isn't crazy, but using it is.