My first inclination is to be a bit skeptical about the claims that human-produced carbon dioxide is the direct contributor to global warming.

The guys who walk on Mars are going to be historic.

I want people to go into space, to orbit around the world a few times, even to stay there for 24 hours and then come back to where they took off. And I also want people with a low income to be able to do that, not only rich people.

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.

Nobody ever asks who was the seventh person on the Moon. The only thing they know is who's number one and who's number two. Does anybody know who the last man was?

I think humans will reach Mars, and I would like to see it happen in my lifetime.

All the Chinese have to do is fly around the Moon and back, and they'll appear to have won the return to the Moon with humans. They could put one person on the surface of the Moon for one day and he'd be a national hero.