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If we use tethered balloons (aerostats) with wireless gateways fitted on them (let's say for Cellular or LPWAN communication), they can provide much more coverage owing to the height they can reach (e.g. while towers usually reach a maximum of 2000 feet, tethered balloons can usually reach a maximum of 4.5 km). And increasing the height of a gateway can increase the coverage surprisingly, since at a sufficiently good height, the Fresnel Zone gets good clearance giving clear line of sight. And it has been recently demonstrated using LoRa when someone created a record of 702 km coverage with a high-altitude balloon.

I wonder why are tethered balloons then not used for communication?

While there are many instances of high-altitude balloons (like Google's Project Loon, Space Data SkySite® or this question on this StackExchange), I could find scarce resource on low-altitude tethered balloons. What I could find was this work done in 2008 (IEEE Conference Paper) by a research lab. Another recent conference paper (2016) is this from another lab. The first paper also demonstrates that the tethered balloons turn out to be lower cost in the long run.

Some reasons that directly come to mind are:

  • Balloons would require more maintenance (and may turn out to be expensive)
  • Cost of balloons would increase dramatically as the weight of the wireless equipments is quite high
  • Balloons would struggle under winds (however since they'd be tethered, exactly how would wind affect them?)

What I would like to know is some solid engineering answer on this, with some numbers to back the claim. What exactly restricts their usage from RF, Communications, Aerodynamcis or Mechanical point-of-view, as compared to fixed towers? Or perhaps is it just that beyond 2000 feet (maximum tower height), you do not get any benefit in Fresnel Zone clearance?

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  • $\begingroup$ Have you checked for similar questions on here? $\endgroup$ – Solar Mike Nov 10 '18 at 7:01
  • $\begingroup$ Your entire premise is that higher transmitters are somehow the most beneficial. If this is true, why are there different height towers now? Shouldn't everything be on the tallest tower possible? i.e. radio/tv towers are much taller than cell towers. $\endgroup$ – hazzey Nov 10 '18 at 22:29
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They would be a great hazard to air traffic; The umbilical would be essentially invisible to passing aircraft. In spite of regulations not to fly here or there.

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  • $\begingroup$ Yes +1. That is one valid point I missed. So, we can probably then never have as many balloons as towers (e.g. in urban areas closer to airports). But in (rural) areas farther away from airports, balloons should be a better option, shouldn't they? $\endgroup$ – shivams Nov 11 '18 at 0:30
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Tethered balloons were actually used to ward off air attacks in WW II - so I imagine a lot of passenger aircraft would be lost if this took place.

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  • $\begingroup$ I think this problem could be solved by warning lights. $\endgroup$ – peterh - Reinstate Monica Dec 10 '20 at 21:11
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Tethered baloons are clearly the way to go, the heat emitted can even aid in the buoyancy of the baloon by heating the gas inside, the baloon itself might prove lucrative for advertisers (using an internal projector for night advertising).

And given enough tension in the tether, the baloon can stay fixed in place, especially if it were designed aerodymically like a blimp, which can rotate with the wind, and wind at high altitudes should be less turbulent, albeit stronger.

And if the baloon was to be located somewhere harsh it can be fixed to the ground using 3 or more tethers under tension resulting from the upwards force from the baloon, and since steel is stronger in tension than in compression it could even prove to be more economical than the common moment frame.

And with indicator lights and reflectors along the tethers it would be visible for aircraft.

This concept is already being used by the US army. But I can see it being deployed in cities, and in the country, economically and effectively. And it will be less of an eye sore as an added benefit.

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  • $\begingroup$ Tethered balloons were one method of air defence... and up to 4.5km really? $\endgroup$ – Solar Mike May 2 '20 at 21:24
  • $\begingroup$ I don’t see how this answers the particular question. $\endgroup$ – Teo Protoulis May 3 '20 at 15:39

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