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

I don't go through life verbalizing what I feel.

Weve got to go [back to the moon]. But we dont want to stay too long. ... The ultimate goal is Mars.

In my mind, public space travel will precede efforts toward exploration -- be it returning to the moon, going to Mars, visiting asteroids, or whatever seems appropriate. We've got millions and millions of people who want to go into space, who are willing to pay. When you figure in the payload potential of customers, everything changes.

Mars has a bit of air pressure; maybe we can build up that atmosphere to be a bit more accommodating to humans.

One of the major problems with long-term deep space human flight is the requirement for radiation shielding.

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.