By 1931, after a few years' experience of flying scheduled airlines, those planes were operating at roughly 600 times the safety of the space shuttle. I look at safety not in terms of fatalities per passenger-mile, but when you get in and close the door, what is the risk of dying on this flight?

There is a rampant tendency in any industry where someone is trying to sell something with a bunch of data, where they cherry pick a little bit... bias a little bit. This becomes quite easy when there is an enormous amount of data to cherry pick from.

In the coming era of manned space exploration by the private sector, market forces will spur development and yield new, low-cost space technologies. If the history of private aviation is any guide, private development efforts will be safer, too.

I believe that research, that you can claim that you're doing research only if half of the people, and I'm talking about half of the experts, believe that the goal is impossible.

In 12 or 15 years, there will be routine, affordable space tourism not just in the U.S. but in a lot of countries.

We didn't have practical model rockets in the '50s. The ones we made were very dangerous and the kids that played with them didn't have all their fingers, and sometimes were blind in one eye.

Science is not about consensus, and consensus is not science.