Pokestake: The Russian engineers didn't go into too much detail regarding their tethered balloon. I did look at an actual piece of their balloon fabric and several photos.
A tethered balloon or aerostat for high altitude telecommunications is not very practical. The tethers are highly prone to lightning strikes. Static buildup along 20 miles of cable also presents a problem.
The ideal tether cable would be the filaments spun from the spinnerets of Black Widow spiders. It is one of the strongest known to man. If we could synthsize it, we could actually put tethered satellites into low geosynchronous orbits on a leash.
By the way, I live in Yucaipa, CA. During WWII, the worlds deadliest woman lived here. They called her the Spider Lady. She had a shed in her yard that was infested with Black Widow spiders. She somehow got a government contract to install spider web filaments as the + in the sight windows of the Norden bombsights.
Little Norton is still alive and doing well. A few weeks ago, I found one of his white feathers in my front yard. I have it here on my desk. He has a girlfriend now and hangs out with her across the street.
Norton couldn't fly very well when he was rescued by the GTE assembly crew. He was beat up pretty bad by that marauding crow. I occasionally see him flying with the other pidgeons and he is now squadron leader.