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.

To allow public access to orbit, we would need breakthroughs that would lower the cost by a lot more than an order of magnitude and increase safety by a factor of 100 as compared to every launch system used since the first manned space flight. I think airborne launch will be a significant part of the safety solution.

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.

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 like to call the difference between research and development. Some people use that interchangeably. They'll say R&D. They're two totally different things.

Everything looks nonsensical before it works.

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