“For decades, people have known the chemical-propulsion approach to space travel is really not going to get us that far. Chemical propulsion is essentially like the horse-and-cart approach to the exploration of the American West, instead of the steamboat or the railroad.” PeopleSpaceKnownFutureApproachHorseWestDecadesExplorationChemicalsPredictionsRailroadsSpace TravelCartsAmerican WestPropulsionSteamboats Author:Franklin Chang Diaz