Sorry folks, it looks like only our grandkid's grandkid's grandkids will be able to take advantage of interstellar travel. Why so long? Because a NASA scientist says it'll take at least 200 years to obtain enough energy to make the journey.

Marc Millis a former NASA propulsion scientist, analyzed 27 years of data on energy trends, mission energy requirements, individual energy use and any and all things involving energy to come up with his professional guesstimate, which involved a heck of a lot of extrapolation.

Millis looked at the amount of energy the US has used to launch the shuttle over the last thirty years or so, as a fraction of the total energy available to the country. He assumes that a similar fraction will be available for interstellar flight in future.

[One] mission is a human colony of 500 people on a one-way journey into the void. He assumes that such a mission requires 50 tones per human occupant and that each person will use about 1000W, equal to the average amount used by people in the US in 2007.

From this, he estimates that the ship would need some 10^18 Joules for rocket propulsion. That compares to a shuttle launch energy of about 10^13 Joules

So, damn! Interstellar travel requires a shit ton of energy, of what we don't have. And when you throw in all the politics and legislature and brouhaha into the mix, it's bound to take even longer. [Technology Review via Pop Sci]