Given that humanity must one day flee the solar system to the nearby stars to survive, or perish, the question is: how will we get there? The nearest star system, Alpha Centauri, is over 4 light-years away. Conventional chemical propulsion rockets, the workhorses of the current space program, barely reach 40,000 miles per hour. At that speed it would take 70,000 years just to visit the nearest star.