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.

A NASA-funded study estimates that if the price of a ticket to space approached $100,000, close to a million people would buy one. That's a $100 billion industry. Microsoft cofounder Paul Allen gave me $20 million in startup funding to go after that market.

At various times over 20 years, I did preliminary designs for aircraft like the Stratolaunch. For that whole time I was encouraging us to do something that almost everyone else felt you could not do.

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.

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.

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

Space travel is the only technology that is more dangerous and more expensive now than it was in its first year. Fifty years after Yuri Gagarin, the space shuttle ended up being more dangerous and more expensive to fly than those first throwaway rockets, even though large portions of it were reusable. It's absurd.