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

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.

Pascal Lee is a true pioneer of Mars exploration.

Kids, help your parents if they don't know how to use a smartphone.

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.

The decision to go to the moon is now appreciated and associated with President Kennedy's speech, but somebody else had told him it was a good idea. It turned out to be a good commitment, but it was a unique situation.

It's not easy to get human beings into orbit. So far only three nations have been able to do that, with all the resources that they put together. And I'm just a little skeptical that that's going to be done by the private sector without making use of what has been done by the government.