You need propellants to accelerate toward Mars, then to decelerate at Mars, again to re-accelerate from Mars to Earth, and finally to decelerate back at Earth. Accordingly, the mass of these required propellants, in short, drives our need for innovative launch vehicles.

I would rather people understand that there is a very, very fortunate American who was given the opportunity, and was in the right place at the right time to have the moment of a lifetime. My mother was born - her name was Marianne Moon. And she was born in 1903, the year that the Wright Brothers first flew.

I know: If you're looking down at Earth, you're looking through an atmosphere that has a bit of haze in many places and not just occasional clouds.

Not everyone will understand this need for America to lead the world in space.

Unless we are able to commit to a permanent growing settlement [on Mars], then I don't think just going there with humans and coming back is worth doing. The expense of planning to come back is like the people who left Europe to come to America and then to turn around and go back to Europe, it really doesn't make any sense at all.

Space architectures capable of supporting a permanent human presence on Mars are extraordinarily complex, with many different interdependent systems.

Apollo 11 will probably go down in history as one of the major responses of two nations facing each other with threatening technologies - sometimes called mutually assured destruction. It was also the America's response to the apparent superiority of the Russians in putting objects into space before USA could.