I think it's inevitable that there will be Earthlings establishing a presence on Mars. And I would say that it would certainly take place by 2050 or shortly thereafter.

The energy varies with the square of the velocity, so if you need five times the velocity, that's 25 times the energy.

I was lucky enough to have been born on this planet earth, in this admirable country of the United States of America.

My first biography written in '73 was not 'Journey To The Moon.' It was 'Return To Earth.' Because for me, that was the more difficult task - disappointment.

I wrote 'Reaching for the Moon' because I wanted to tell kids that all of us have a moon, a dream, that we can strive for. Even if you don't attain it, you can at least reach for it.

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.

Once you've been first, it cannot be done again. Not by you, not by anyone else.