Six out of seven times we landed successfully [on the Moon]. I wanted to be a part of that and I was a part of that, so my personal feeling is of great gratefulness for having somehow been in a position to have been given the opportunity to be on that first landing. That's a marvelous experience for a little kid that grew up in New Jersey. So I'm very thankful, and I asked the whole world to give thanks once we successfully landed.

Mars is there, waiting to be reached.

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

As we reflect back upon the tragic loss of Challenger and her brave crew of heroes who were aboard that fateful day, I am reminded that they truly represented the best of us, as they climbed aloft on a plume of propellant gasses, reaching for the stars, to inspire us who were Earthbound.

Absolutely the United States should lead in space, for the survival of the United States. It's inspiring for the next generation. If we lose leadership, then we'll be using Chinese capability to inspire Americans.

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.

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