Interstellar travel won’t be possible for at least 200 years, according to a former NASA propulsion scientist who has some new calculations. And by then, the spaceships we would design for the trip will be obsolete.
Forget cost, political will and all the other variables — simply obtaining enough energy will take until 2196, according to Marc Millis, former head of NASA's Breakthrough Propulsion Physics Project and founder of the Tau Zero Foundation, which supports interstellar travel research.
In a few months, NASA scientists and the press will note the passing of the 30th anniversary since the launches of Voyagers I and II. By now, both interstellar probes have passed beyond Pluto's orbit and are speeding out toward neighboring star systems, carrying with them copies of the Golden Record, a phonograph record full of images, music and recordings of life on Earth intended for any extraterrestrials who might happen upon the probe and wonder who sent it. It's the same idea behind the plaque that was bolted onto the Pioneer 10 and 11 spacecraft, both of which are currently gliding out of the solar system behind the Voyager probes.