Have you ever watched an action hero fly through the air, propelled in slow motion by the massive explosion erupting behind them? This slice of cinematic cheese gives you a decent taste of how NASA considered propelling spacecraft in the 1950s and 1960s.
Dubbed Project Orion (not to be confused with NASA's more recent Orion spaceship project), this crazy-sounding propulsion system depended on nuclear warheads. You read that right, not mere nuclear power but actual nuclear detonations.
According to NASA, the plan called for the craft to dump "five bombs a second" out the back. These would detonate and the resulting shock waves would slam into the craft's shock plates to heave it through space.
How many bombs would the craft need? According to science historian George Dyson, son of theoretical physicist Freeman Dyson, designs called for a payload of 2,000 5-kiloton yield bombs. To put that in perspective, the Little Boy atomic bomb that decimated Hiroshima in 1945 was a 15-kiloton weapon. The largest ship design called for an 8-million-ton (7.2-million-metric-ton) vessel to carry all the warheads, each the size of a small car and specially formed to shape the explosion in a single direction.
Dyson says it would have taken 800 detonations just to get into orbit. Here's his excellent TED talk on the topic (he also wrote this book): [youtube=http://www.youtube.com/watch?v=3l2QopJbDBs]
The U.S. Air Force reportedly loved the program, but NASA wasn't quite that enthusiastic. Oh, maybe it was the list of side effects for such a propulsion system, which includes such apocalyptic symptoms as deadly nuclear fallout and electronics-decimating electromagnetic pulses. Plus, there's the titanic cost and political hurdles involved in constructing such a world-wrecking colossus.
The Project Orion designers dreamed of flying to Mars and Saturn by the 1970s. Instead, NASA killed the project. But what might the 21st century have looked like had the project progressed? Space-faring culture or post-apocalyptic ruin?