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Google is Killing Its Solar-Powered Internet Drone Program (businessinsider.com)
An anonymous reader writes: Google's "moonshot" X division is ending its Titan drone program, which planned to use solar-powered drones to beam internet down to earth. Google bought Titan Aerospace in 2014. The company was developing solar-powered drones that could fly for several days at a time and take images of earth or beam down internet. When Google reorganized into Alphabet in 2015, Titan was folded into X, the Alphabet division that focuses on wild tech projects in hopes of stumbling on the next big thing.
Actually, building a solar airplane that can stay aloft as long as their business model demands, is a significant challenge. Reliability of servo actuators and electric motors is a major issue. Designing a structure light enough to minimize the power required to climb to very high altitudes, but robust enough to survive winds/gusts during ascent and descent, is a major issue.
Yes, good old balloons make much more sense if you just need to get up high and stay there. The whole "solar drones" thing reeks of a hype project combining two trendy technologies that are way inferior to a non-trendy, old-fashioned solution.
SJW: Someone who has run out of real oppression, and has to fake it.
More likely the regulatory/insurance climate is insane. I would bet that the money required to get the proper radio frequencies, get government approval for a drone holding pattern high enough over an urban area and insurance to cover any accidents would bankrupt a small country. There are most definitely also some technical hurtles but I would wager those are relatively minor in comparison. I think Musk summed it up when he was discussing the challenges of starting SpaceX, I believe he said something to the effect that the rocket science was easy, cutting through the red tape took a majority of their time/money. And that is for an industry that has existed for decades.
It's simpler than that: you just need to look up the typical windspeeds at the altitudes it would be cruising at (over 60m/s for much of the year). If you then work out the energy density required for overnight operation with achievable lift to drag (def less than 50, even for a stupidly long flying wing), you get a decent velocity of over 1.2m/s. This equates to an energy density of 12hours*9.8*0.6=510KJ/Kg, so even with state of the art lithium cells over 60% of the mass has to be batteries. If you assume that the props are 90% efficient, that the solar panels are effective late into the evening and early in the morning, so you actually need about 14hours of battery power, and that the battery efficiency is about 90%, then this becomes 87% battery mass fraction, leaving virtually nothing for structure, cells, motors, main power electronics, and finally payload. It's very clear that high altitude solar drones are not possible with existing battery technology.
If lithium sulphur cells ever leave the lab this may change, but currently they are suffering from dendrite formation after less than 100 cycles, and this seems like an almost intractable issue.
tl;dr : don't expect solar drones any time soon.