Oops that's a great point. I completely forgot about sidewall stiffness. My messing around with treads was probably just me adjusting things to make myself look good then!
Great point. I wasn't even thinking of this in a larger context. I wonder if the downside is more important than the upside. So if it's just me trying to build an experimental aircraft, at worst I die. If I'm a city planner, I can make a bunch of lives miserable. Not sure what the upsides would be in either case, but the number of people affected by the downside is pretty easy to tell. So maybe the fewer people affected by a bad outcome, the more radical your ideas can be.
As the author of the article, maybe I can explain why I think it’s a good example. I’ll just say - I absolutely could have chosen something that was more of a slam dunk great idea (in hindsight) with tons of follow-on success. I mostly chose it because the Rotary Rocket and SpaceShipOne sit next to each other in Mojave and got me thinking about this in the first place.
As you said yourself, it was a good design to win the prize. That to me is the key. It did everything it set out to accomplish. Your comments all relate to the scaled up SpaceShipTwo - a completely different vehicle - which I agree that the jury might still be out on. But to me, that’s like saying that a hang glider is a bad idea if someone tries to make a hang glider for ten people. Is it the hang glider that’s the bad idea or the fact that someone’s trying to scale something that maybe doesn’t scale well?