John Ferrell wrote:
I think the electronics problems are trivial compared with the matter
of maintaining the platform at altitude and geosynchronous.

There is not much air for a lighter than air ship to float in at that
altitude. A quick estimate of 21km is about 65,000 feet. It would seem
to me that a platform that could hover at that altitude keeping pace
with the earths rotation could also circumnavigate the earth in 24
hours in the direction of the rotation.

The energy required to maintain that hover is going to be substantial.
Forget filling the Zep with Hydrogen. Even if you can devise a scheme
to fill an evelope with nothing (vacuum) It is going to be monstrous
in size to displace a hundred kilo's or so.

Count me out on the project...
John W8CCW

I agree, I've not actually seen any of the research about the platforms
themselves, but as well as the airships there are also some unmanned
solar powered wing planes have been tested too I think.

I'm sceptical myself, but it will be very interesting to see if it ever
takes off! (no pun intended ;-))

--
73, Iain M0PCB/P