When you have a transportation system that the price of propellant is essentially negligible something is very wrong. If you look at any other transportation system, a car, a motorcycle, a train, an oil tanker, an airliner, you name it; about a quarter to a third of the operating cost is buying the propellant.

I spent about seven years during the Vietnam War flight-testing airplanes for the Air Force. And then I went in and I had a lot of fun building airplanes that people could build in their garages. And some 3,000 of those are flying. Of course, one of them is around-the-world Voyager.

The Russians did much bigger space launch vehicles for launching satellites and for getting men in orbit. They did that much sooner than America because America was very good at something else.

Achieving something that has never existed in manned spaceflight and that is high volume and public access.

There was a wonderful little short four-year time period when marvelous things happened. It started in 1908, when the Wright brothers flew in Paris, and everybody said, 'Ooh, hey, I can do that.' There's only a few people that have flown in early 1908. In four years, 39 countries had hundreds of airplanes, thousands of pilots.

It's not good enough for us to have generations of kids that ... look forward to a better version of a cell phone with a video in it. They need to look forward to exploration.

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?