It's interesting that NASA has resurrected the "Orion" moniker for their latest moonshot. Before Apollo (and even before NASA was NASA) the US floated the idea of spaceships powered by atomic explosions. The idea was not only plausible, but on the drawing boards! It turned out to be not-so-popular, esp. in light of their incredible destructive power. Physicist Freeman Dyson was one of the scientists who worked on this project. His son George Dyson detailed the early exploits of the original Orion project in his book "Project Orion." Another good clearinghouse for Orion info: orion.ttsw.com
