The logistic requirements for a large, elaborate mission to Mars are no greater that those for a minor military operation extending over a limited theatre of war.

The greatest gain from space travel consists in the extension of our knowledge. In a hundred years this newly won knowledge will pay huge and unexpected dividends.

There are flying grandfathers. But I intend to be an orbiting grandfather.

I believe that the time has arrived for medical investigation of the problems of manned rocket flight, for it will not be the engineering problems but rather the limits of the human frame that will make the final decision as to whether manned space flight will eventually become a reality.

We can lick gravity, but sometimes the paperwork is overwhelming.

If we continue at this leisurly pace, we will have to pass Russian customs when we land on the moon.

Science and religion are not antagonists. On the contrary, they are sisters. While science tries to learn more about the creation, religion tries to better understand the Creator. While through science man tries to harness the forces of nature around him, through religion he tries to harness the force of nature within him.