There is a system of AIS to broadcast position, course and speed of marine vessels. Perhaps one could combine this with a mesh relay network to forward packets to boats in the direction of land. An AIS and long range WiFi-like system running on top of sailor’s masts would be a fun community to bring together. Software defined radios could come in handy to handle multiple frequencies and protocols.

https://www.marinetraffic.com/en/ais/home/

something like http://aprs.org

If you care about speed aprs isn't your boat. 1200bps in almost all cases, zero FEC, bandwidth rapidly disappears depending on how many digipeaters overlap.

It's good for brief beacon based things but most of the RF tech around it is still stuck in the 80s.

Absolutely agree... but an aprs2 that incorporates some modern tech and modern thought could be interesting. What if every TNC was also a digipeater and they all coordinated to route their traffic via the shortest/best route to shore?

BTW: this conversation has convinced me to buy a LimeSDR Mini. It can handle Marine VHF, (probably AIS with a GPS source) and even LTE. I figure having a couple of these might be great on a boat since you can reuse them for a variety of purposes and having backups are key. They even fly LimeSDRs on micro satellites.

If high endurance air drones are advanced enough, you can coordinate sea and air nodes to make a mesh that avoids clouds and line of sight all-together so you don't have to string the network over the sea level horizon. Maybe have autonomous platforms that allow both to refuel too if they use hybrid systems.

Balloons, maybe.

Apart from wind moving it to the side, it would not be a fundamental problem to fly a tethered blimp with a pair of single mode fiber and a thin aluminum wire that is driven in resonance [0] with the surface capacitance the blimp has, relative to earth, up to about 20-50 km. The breaking length of the fiber comes out at ~120 km, and you have to spare some tensile strength to hold the aluminum wire.

This is not hard, and for 8km height you could manufacture them for under $2k/piece. Even if they'd be made to work with hydrogen, as that raises the demands on the construction. If you'd find the FCC to be willing to allow something like this and are able to handle both thunderstorms and just the general wind load on the tether, this should not be hard.

[0]: https://en.wikipedia.org/wiki/Single-wire_transmission_line

Lightning + aluminium wire is a problem. I suspect an electrical current will form in the wire even w/o lightning because of static electricity. Also the wire is a hazard if it breaks and falls down. It will probably cut everything in its path.

Yes, probably. Maybe you'd have to fly it at a place where you don't need to worry about lightning. But that seems rather restricting. Though, for high-bandwidth applications, it might then be necessary to fly local power, and have the whole system sit over the cloud layer, at about 50km.

Regarding the damage from it when falling down, you have to remember that each fiber weighs 50g/km, and the wire is also below 1kg/km, even for rather low heights. This should not be a problem, considering the ease of breaking an optical fiber optic at any remotely sharp edge. A small bird (the size your cat can catch) could probably snap it if he hit's it with some force.

It will create a lightning discharge path regardless if you fly it over the cloud layer.

1 kg/km • 50 km • 9.8 m•s^-2 • 50 km = 24.5 MJ

10 MJ = kinetic energy of the armor-piercing round fired by the assault guns of the ISU-152 tank

I think that's just about enough energy to cut just about any living thing in half. Maybe it work if the cable was made of spider silk or Kevlar.

If you are at a high enough altitude clouds would never get in the way so solar power works much better.

Careful, you're almost a satellite now and the original idea was to eliminate the cost of satellite data! Alternatively, if such a UAV was cheaper than a satellite, that would be a whole competitive business in itself!

That's interesting. 70 meters is a pretty dang tall aerial for something with that small a footprint to hold aloft, though. That plan also limits their range of movement severely to keep the network intact, but I guess they could use satellite as a backup.

Maybe a kite of some kind, but how do you reliably launch and retrieve it? I dunno, I think in practice the satellite may be cheaper.

Or a blimp with a thin wire in resonance and two fibers? If you don't need much power, the thing should weigh in at under 50g, which would allow a blimp the size of a large kitchen trashcan (50l).

https://en.wikipedia.org/wiki/Single-wire_transmission_line

Disposable paper hot-air balloon for lift, retractable antenna? Or perhaps better yet: disposable paper kite?

Your comment, while I assume you earnestly meant, is enigmatic of the gap between what the lay person may think works at sea and the very harsh and unforgiving reality of the Sea.

Source: my father was an engineer at a marine engineering company

Hehe. I left out that I was thinking of a system that used all the environmental monitoring to deploy such a disposable contraption only in calm/good weather - but then it would not be a substitute for satellite data - mote an opportunistic system for bulk backup.

I like the wording of your comment, but I think you mean emblematic instead of enigmatic.

Yes, you're right. That's embarrassing.

Caveat wind issues, raising a balloon would work. But still you would need a big enough balloon to hold 70m of coax up and the antenna. On the plus side you could slowly electrolysize water with the solar panels to fill your balloon with hydrogen :-). So you would only need to carry spare envelopes rather than a bunch of helium tanks.

The engineering choices are interesting here.

Can you cover most conditions with a balloon and a kite? Can you make a kite which can be inflated to turn it into a balloon? (Looks like clever people have already been here: Kytoon – a balloon with a couple panels of fabric to make it behave like a kite in wind and a balloon in calm.) A two string kite can also be used for propulsion in many conditions.

Depending on transmitter power, I have to think that in 2018 a transceiver is lighter than 70m of coax cable compared to a power pair. Put a relay at the top and talk to it from the boat. (10 watts over 30ga for 70m at 48v is about 66% efficiency for a mass of only 30 grams. You can trade off mass with power, wire size, and respect for the life of you maintenance technicians. The product always looks better at 200 volts!)

While crazy, you could just use radio up to the blimp too ;) In fact, apart from the pollution aspect, you could just launch a balloon with a radio and let it drift... As a disposable radiointervju in the sky...

You could build this type of system with more sparsely placed nodes if you used HF communications, at which frequencies the waves reflect off the ionosphere [1].

[1]. https://en.wikipedia.org/wiki/Skywave

In most political regions the max data rate for HF transmissions is very, very low.