It's been one of the greatest challenges that ever came along in my life; it was one of the more difficult things to do.

I believe that space travel will one day become as common as airline travel is today. I'm convinced, however, that the true future of space travel does not lie with government agencies -- NASA is still obsessed with the idea that the primary purpose of the space program is science -- but real progress will come from private companies competing to provide the ultimate adventure ride, and NASA will receive the trickle-down benefits.

Let's not spend resources that we don't need to be sending astronauts back to the moon. Let's not spend expensive resources on bringing people who have reached Mars back again. Prepare them to become a growing colony.

Heavy lifting doesn't need to be heavy spending if we do the job right.

Anything we can do in the near future that begins to stimulate the interest of people - seeing somebody down the street have an opportunity to go into space - buoys up the whole neighborhood.

The universe is the way it is. It's not going to be changed by supplications.

I think there would be no shortage of applicants to the government astronaut corps to be settlers on the planet Mars. And I think this would be very inspiring.