It's Science Fiction Week on Short Wave, earthlings! So strap on your zero gravity suits and polish your light sabers because we're about to get nerdy ... starting with today's episode. It's one of our science fiction myth busting favorites from earlier this year. Contrary to sci-fi depictions in shows like Iron Man and Star Wars, getting from point A to point B in space is a tough engineering problem. NPR Science Correspondent Geoff Brumfiel, with help from scientist Naia Butler-Craig, explains how space propulsion actually works, and why some new technologies might be needed to get humans to Mars and beyond. (Encore episode)