The need to maintain relative station keeping without the need for
   tethers or propulsion was one of the hallmarks of Loon tech.

   On Sun, Jul 25, 2021, 9:40 AM jim bell <[1]jdb10987@yahoo.com> wrote:

   On Sunday, July 25, 2021, 01:17:03 AM PDT, grarpamp
   <[2]grarpamp@gmail.com> wrote:
   On 7/24/21, jim bell <[3]jdb10987@yahoo.com> wrote:
   >> The balloon could use hydrogen. [1]
   >> day electrolyzing
   >That's two fun energy sources (H + solar), plus buoyancy.
   >If tethered then you're not spending much if any energy
   on stationkeeping, only on keeping the RF gimbal
   aimed at a target, or none if using omnidirectional-RF.
   If not tethered then you have a lot of energy expense
   just to keep in range of target.
   I see no need at all to do station-keeping.  The balloon could simply
   detect its GPS location, and using that re-calculate what its optimum
   aim for the antenna(s).  The people 'watching' the microwave signal
   would see only a slight change in azimuth., presumably not enough to
   require them to re-aim.
   >Are liquid hydrogen tanks light enough to replace
   their weight with gas volume then jettison?
   No, that's totally impractical.  That's why I suggest creating new
   hydrogen,  in gas form, storing it into the huge balloon, and using a
   bit of it, at night, to generate electricity in the fuel cells.  I've
   never worked with fuel cells, but I believe it's fairly simple, because
   the components already exist.
   >Not much altitude is needed to reach out 12NM
   with any system, so your tether might also carry
   whatever you need.
   > The water could be obtained by dessicating it out of the
   > atmosphere with a deliquiescent dessicant, perhaps concentrated
   sulfuric
   >Reagents and catalysts would need refilled too.
   I don't think so.  The article says that the lifetime of the balloon
   would be relatively short, was it 7 months?  The dessicant (I proposed
   concentrated sulfuric acid) wouldn't evaporate, so it would never run
   out.  The catalysts in the fuel cell would be essentially permanent for
   the life ot the balloon's million.
   >See about making water from atmosphere via
   free sun/shade/dewpoint condensation methods.
   I assume the altitude will be about 40-50,000 feet.
   >Solar-day battery-night powered planes already exist,
   but they cost a lot more than simple balloons.
   [4]solar powered 24hr plane at DuckDuckGo
   That's one reason to use a hydrogen-filled balloon, doubling for life
   and fuel-cell fuel storage.
   >If you're already hanging out at 12NM with a tether
   or base station, surely you can also just run whatever RF
   system you want from the boat deck that will cover that
   distance, no balloons or planes needed, assuming your
   target has matching RF gear.
   I don't see an obvious need for a boat.  just an anchor.  One big
   reason is that any boat would stick out by radar, directing the enemy
   Cuban military  to try to cut the tether.     I think that there could
   actually be multiple tethers, maybe even 5, tied together at perhaps
   5,000 altitude, and each anchored at perhaps a mile apart, so that if
   one gets cut by a passing plane, the rest will take over the
   function.

References

   1. mailto:jdb10987@yahoo.com
   2. mailto:grarpamp@gmail.com
   3. mailto:jdb10987@yahoo.com
   4. https://duckduckgo.com/?q=solar+powered+24hr+plane