I was motivated to improve the U.S. strategy of going back to the moon in 1985. That's a long time ago. Going back to the moon would be a great achievement for tourism adventure flights.

Ray Bradbury is one who is contributing to the understanding of the imagination and the curiosity of the human race.

We have the ability, at such high fidelity, to simulate the physical world through computers. But when the spiritual world or human behavior comes into play, we don't have a very good model for that at all.

As time goes by, I'm increasingly impressed by how very special and timely it was that we got the degree of national commitment needed to put people on the Moon. For the first time, this nation was united in trying to develop an interplanetary capability. We've been trying to repeat that situation ever since.

When we can demonstrate that we can take off horizontally and put something into orbit, then we can begin to talk about increasing the amount of payload. But to say, 'I'm going to do that and put people into orbit' is a real leap.

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.

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.