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.

http://www.popsci.com/science/article/2011-01/interstellar-travel-wont-be-possible-least-200-years-according-new-calculations

http://arxiv.org/ftp/arxiv/papers/1101/1101.1066.pdf

I'd like to think we'd come up with a new way of harnessing energy by then.

Or a way to source energy on the journey. There are indigenous tribes who figured out thousands of years ago it's easier to gather stuff as you go than carry it all with you from the beginning.

Jon

There is the bussard ramjet which will work pretty well if they can build it. http://en.wikipedia.org/wiki/Bussard_ramjet

It's just a maths exercise as far as I can see. As we won't have current tech then if we make it that far.

The maths will be obsolete before the 200 years is up. By then we’ll have either nuked ourselves, or will have entered a new Dark Ages driven by suspicion, superstition and religion.