The February issue of Discover Magazine has an interesting article about Project Orion: a project that was developed during the ’50s and ’60s to build a spaceship that was as big as a skyscraper, weighed eight million pounds, and was propelled by—get this—nuclear bombs.
While Discover’s article was good, focusing more on the people and policies involved, Wikipedia’s Project Orion page is excellent, and delves much more into the hard science. It sounds on the one hand totally insane and on the other hand perfectly logical and obvious. But you gotta wonder at the audacity of a design that would have required 800 (or more) nuclear explosions just to lift the ship into Earth orbit 300 miles up…
Interestingly, an Orion ship is a major plot point in one of my all-time favorite science fiction books, Footfall by Larry Niven and Jerry Pournelle. A great book, probably the best alien invasion story out there, period—Niven and Pournelle simply rock. What else can I say? I totally recommend it. It would make a perfect movie, done right, but if nothing else, read the book.