How fast can a space shuttle travel?

How fast are we capable of making a space shuttle travel? I'm asking because I was reading about the new planet, Gliese 581, which is said to have earth like habitation characteristics, but is 20.5 lightyears away-- impossible to reach in a human lifetime. So I would like to know how fast our space shuttles go (in lightyears, preferably), to see how much time it would actually take to reach that planet.

17,000 mph which is roughly .000025 light years.

fast

The shuttle goes 17,500 MPH. That speed is not high enough to escape from Earth orbit, but FYI, that is about 38,263 times slower than light speed. (Calculated as 186,000 miles per second times 3,600 seconds in an hour divided by 17,500 miles per hour.) So if the shuttle could leave Earth orbit and travel at 17,500 MPH all the way to that star, it would take 784,391 years to get there. (Calculated as 20.5 * 38,263.)

Well, the space shuttle normally cruises along at 17,000 mph. At that speed, assuming a straight line shot to Gliese 581, it would take 810,502 years to get there.

If we go back to the velocity of the Apollo missions to the moon (..about 45,000 mph..) we're down to a one-way trip of 305,706 years.

Theoretically, using an ion engine, we would be able to make it there in a human lifetime. The big problem with ion engines, it that its acceleration, which is quite slow.

But according to Einstein, one could travel at a velocity just short of the speed of light. Time and mass, however, would approach "near infinity" which may defeat the exercise.