What are the uses and limitations of moored (powered) balloons? (Compared to GEO, sounding rockets et c.)

Question

Why aren't moored helium balloons hoovering a few kilometers over many cities as a competing alternative to expensive satellite launches? They could provide services with local advantage such as: high powered radio communication, precision navigation, live traffic observation, micro meteorology and more which takes advantage of the low altitude and local adaptions.

Some benefits I can think of:

• unlimited access to cheap electric power through the ground cable, which could constantly power payload and even rotors to achieve extra altitude and control (an electric chopper in a leash),

• reusability and therefor much lower cost,

• no space graded equipment needed and therefor much lower cost again,

• serviceability of payload and therefor higher reliability,

• high degree of adaptation to specific local and current demands.

What is it that makes moored balloons apparently incapably to exist as a competitor with commercial (and military) geostationary satellites, GPS, LEO-satellites? Where's the deadly flaw?

In particular: SOFIA is an IR telescope on a Bo747 which is used at 12 km altitude in order to get over the clouds and most of the IR distorting atmosphere. Could moored balloons with similar payload capacity reach as high? "Telescope installation weight: 17 tons"

Answer 1

Balloons can be interesting as comms relay, in fact the French satellite builder Thales is developing balloons for comms relay (note it is not moored in order to reach higher altitudes)

http://translate.google.com/translate?hl=en&sl=fr&u=http://www.sciencesetavenir.fr/high-tech/20140307.OBS8892/stratobus-le-ballon-autonome-futuriste-de-thales.html

The problem is the communications market is not asking for it: if you want comms around cities, you put a few antennas on hilltops. If you want comms in the middle of nowhere, you use a satellite.

Weather can also be a concern at low altitudes so you would not have coverage 100% of the time.

Answer 2

I suspect the major objection to large numbers of moored balloons would be the mooring cables themselves, as they would interfere with other aircraft. This was the intended function of barrage ballons over London in World War II.

That having been said, free-flying high-altitude balloons have been and continue to be studied for communications (Google and others) and surveillance (DARPA) purposes.