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

I want to reach a new generation. That's why I am Twittering now. I have a BlackBerry, an iPhone and a Mac.

Mars has been flown by, orbited, smacked into, radar examined, and rocketed onto, as well as bounced upon, rolled over, shoveled, drilled into, baked and even blasted. Still to come: Mars being stepped on.

Mars is there, waiting to be reached.

I don't believe any pair of people had been more removed physically from the rest of the world than we were.

Dwelling on an engine failure for a pilot as he rolls down the runway is NOT what he should be thinking about - it's obtaining a smooth liftoff! But in the back of his mind, he knows exactly what to do (or pretty much) and in many cases, if he's alone in the fighter aircraft, he has to leave that aircraft in an ejection seat in a big hurry!

There's no doubt who was a leader in space after the Apollo Program. Nobody came close to us. And our education system, in science, technology, engineering and math, was at the top of the world. It's no longer there. We're descending rather rapidly.