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

It will free man from the remaining chains, the chains of gravity which still tie him to this planet.

I have learned to use the word 'impossible' with the greatest caution.

I only hope that we shall not wait to adopt the program until after our astronomers have reported a new and unsuspected asteroid moving across their fields of vision with menacing speed. At that point it will be too late!

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

I'm convinced that before the year 2000 is over, the first child will have been born on the moon.

Conquering the universe one has to solve two problems: gravity and red tape. We could have mastered gravity.