There is another thing to consider. At that attitude there is quite some radiation. So more shielding is needed...
All things considered, I dont think the concept would work very well in the end. The sphere wouldnt change its attitude much and you would still need some other type of transport to get onto it.
I think the future of air travel is in flying wings. No matter what kind of engine you use to propel yourself, its the aerodynamics that limits you to certain speeds and power requirements. Making a plane with less drag compared to what it carries it the way to go. And another thing. Flying wings have more or less flat top. So it would be easier to fir PVs onto it.
I think the specs could be generally inserted into an equation, which will wait for now I think.
