There's no guarantee that the United States will be around 200 years from now.

Only a large-volume market like space travel can attack the barrier of high costs.

If we go back to the moon, we're guaranteed second, maybe third place because while we are spending all that money, Russia has its eye on Mars. Landing people on the moon will be terribly consuming of resources we don't have. It sounds great - 'Let's go back. This time we're going to stay.' I don't know why you would want to stay on the moon.

Because of his military service, Dad was buried in Arlington National Cemetery.

Instead of planning the retirement of the Space Shuttle program, America should be preparing the shuttles for their next step in space: evolving, not shutting them down and laying off thousands of people.

There's a tremendously satisfying freedom associated with weightlessness. It's challenging in the absence of traction or leverage, and it requires thoughtful readjustment. I found the experience of weightlessness to be one of the most fun and enjoyable, challenging and rewarding, experiences of spaceflight. Returning to Earth brings with it a great sense of heaviness, and a need for careful movement. In some ways it's not too different from returning from a rocking ocean ship.

I'm convinced that sending people to Mars is so expensive that if you go once and bring the people back and then go again and bring the people back, we're eventually going to run out of money. But what if we send people the first time and they don't come back? What if they stay there?