[RightWhale]

A multi-generational city-sized space ark would be appropriate.

That's going to take significant time to build even before the expedition sets out. We better start today.

[petuniasevan]

Multigenerational ships may be the only way to go.

When you accelerate a body to relativistic speeds, you come upon some real problems. First, you are blue-shifting all background and stellar radiation into the high-energy realm. Somehow one must shield the delicate life-forms aboard from this constant blizzard of gamma and x-rays.

Second, if any matter is in the path of the craft, how will the craft avoid it? Almost as soon as its photons arrive to announce its presence the object itself will be hot on the heels of the "message".

Third, time will shorten considerably (depending on how close to c the craft accelerates). 6 months' ship travel time to HD70642 at 99.9% c still will be 90+ years here on Earth. Friends and relatives of the astronauts will be long gone when they return.

Sure, I prefer the physics of Star Trek, but I don't think it's practical; it may not even be possible.

[Aric2000]

If we started on an ark today, it would probably take 20 years to build, at LEAST, by that time, the entire technology it was based on would be obsolete, kinda like the shuttles.

What we need to do is put together a conglomeration of private companies to build it, then promise those companies the sole rights to minerals etc that was found, it would of course be a LONG term investment, but it would also force them to try and come up with a faster method of propulsion.

Private industry, the only way to REALLY get into space efficiently.