The urge to explore has propelled evolution since the first water creatures reconnoitered the land. Like all living systems, cultures cannot remain static; they evolve or decline. They explore or expire. . . . Beyond all rationales, space flight is a spiritual quest in the broadest sense, one promising a revitalization of humanity and a rebirth of hope no less profound than the great opening out of mind and spirit at the dawn of our modern age.

This has been far more than three men on a mission to the Moon; more still than the efforts of a government and industry team; more, even, than the efforts of one nation. We feel this stands as a symbol of the insatiable curiosity of all mankind to explore the unknown.

I believe that space travel will one day become as common as airline travel is today. I'm convinced, however, that the true future of space travel does not lie with government agencies -- NASA is still obsessed with the idea that the primary purpose of the space program is science -- but real progress will come from private companies competing to provide the ultimate adventure ride, and NASA will receive the trickle-down benefits.

I don't think we're going to build a 50-person spacecraft or a 100-person spacecraft.

A space program that truly goes somewhere! With his deeds, not only words, President Obama has revitalized our struggling space program.

I think both the space shuttle program and the International Space Station program have not really lived up to their expectations.

History will remember the inhabitants of this century as the people who went from Kitty Hawk to the moon in 66 years, only to languish for the next 30 in low Earth orbit. At the core of the risk-free society is a self-indulgent failure of nerve.