Travel to the Stars -- When?

How soon could humanity launch a mission to the stars? That's the question considered today by Marc Millis, former head of NASA's Breakthrough Propulsion Physics Project and founder of the Tau Zero Foundation which supports the science of interstellar travel.

This is a question of increasing importance given the rate at which astronomers are finding new planets around other stars. Many believe that it's only a matter of time before we find an Earth analogue. And when we do find a place with the potential to host life like ours, there is likely to be significant debate about the possibility of a visit.

The big problem, of course, is distance. In the past, scientists have studied various factors that limit our ability to traverse the required lightyears. One is the speed necessary to travel that far, another is the cost of such a trip.

By looking at the rate at which our top speed and financial clout are increasing, and then extrapolating into the future, it's possible to predict when such missions might be possible. The depressing answer in every study so far is that interstellar travel is centuries away.…