My experiences with science led me to God. They challenge science to prove the existence of God. But must we really light a candle to see the sun?

A good engineer gets stale very fast if he doesn't keep his hands dirty.

Man is not made for space. But with the help of biologists and medical doctors, he can be prepared and accommodated.

We should remember that science exists only because there are people, and its concepts exist only in the minds of men. Behind these concepts lies the reality which is being revealed to us, but only by the grace of God.

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.

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.

It takes sixty-five thousand errors before you are qualified to make a rocket.