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#Solar planes? But for what purpose?
Transportation Transportation Battery

Facebook’s (soon to be) solar-powered, wifi serving, laser mesh network drone, the Aquila, is retiring to the V&A – the world’s leading museum of art and design – in London.
The plane has completed two successful test flights, one each in 2016 and 2017. Facebook’s goal is to create a broad network of technology to deliver internet connectivity to the 1.6 billion on earth without access.

The plane was built in Somerset, England and is returning home for display. Facebook believes its high altitude platform stations (HAPS) program, that includes the drone, will fill in where cellular towers are uneconomical.
The carbon fiber plane’s wingspan of 141 feet is greater than a Boeing 737. Half of the planes 900 lbs is dedicated to batteries. The goal is to fly the plane between 60-90,000 ft. Standard operating energy demand was approximately 5,000W in the plane’s first flight. When in cruise, the usage of the plane fell to 2,000W. When flying upwind, the unit moves at 10-15 mph – max speed is 80mph. The final design hopes to have a plane that can fly without human intervention or refueling for 90 days straight.

The units will communicate with each other and users on the ground using lasers and millimeter wave hardware. In testing in 2015, the lasers were able to deliver ’10s of Gb per second to a target the size of a dime from more than 10 miles away.’ A single unit hopes to deliver data across a 60 mile wide diameter.
Aquila first flew on June 28th 2016 at the Yuma Proving Ground in Yuma, Arizona. The flight was scheduled for 30 minutes – but lasted 96 -and reached a height of 2,150 feet. The goal of the flight was to test aerodynamics, flight AI, electric performance and data collection.The unit suffered a structural failure seconds before landing. This occurred while the airplane’s AI pilot reacted to changing air conditions between 20-40 feet above ground.The combination of high airspeed and up elevon caused more bending and torsion than the structure could tolerate, resulting in a downward deformation and failure of the right wing. The craft was ‘substantially damaged’ per Facebook.
On May 22, the Aquila took off again. The plane flew for 106 minutes and landed perfectly this time. The unit climbed at a much higher rate than before, which Facebook said was a result of structural changes to the plane learned from the first flight. The unit flew up to 3,000 feet. If you look closely at the below video (and noted in the link above) you’ll notice only one of the four propellers stopped in the right position.
What I do greatly appreciate is seeing more use of design expertise that minimizes energy usage relative to solar production. Other groups are working to build a ‘solar powered perpetual’ flying drone. Some have flown a human being around the world using a solar powered plane. And now we have electric planes coming from the big boys. Seems like engineers have a thing for gliding among the clouds and feeding on the sun.

John Fitzgerald Weaver, @SolarInMASS

Solar-Powered Drone May Be Capable of Perpetual Flight

University researchers have developed a solar-powered drone capable of continuous flight. But what for?
Whether they're used in agriculture, inspection, surveillance, or search and rescue, drones tend to have a clear task at hand. It would seem foolish to keep drones hovering in the air when no flight path or activity is mapped out and required. Researchers from the Autonomous Systems Laboratory at Stanford and glaciologists from Swiss university Zurich’s ETH, however, have been exploring the advantages of keeping drones in the air, specifically using solar-powered unmanned aerial vehicles.

While the initial purpose of designing a drone, called the AtlantikSolar, was to determine whether it could stay in flight indefinitely, those behind the project eventually wondered what this perpetual flight ability could actually offer to the world. What are specific use cases for such an ability? Are there any functional applications of this technology? What are they?
The team got a clearer sense of what the future may hold for drones like the AtlantikSolar this past summer, when it completed the “first-ever solar-powered flight in the Arctic,” which lasted 13 hours, after which the solar-powered battery was still at more than 60 percent capacity.
ASL believes that this easily scales to a full day, according to the ETH. A mere month later, the ETH glaciologists piloted the drone in up to 6 meters per second vertical gusting and a sustained tail wind of 15 meters per second,” for five hours and a total of about 143 miles. It landed perfectly. 

How does this translate to practical, functional scenarios of use, you ask?

“Monitoring glaciers in polar regions is in pole position to become a primary application,” since the nightly availability of sun there allows for perpetual flights, which in turn can monitor the continuous changes of the ecosystem, providing us with a wealth of information of that region, according to the ETH. This isn’t even theoretical anymore, as the AtlantikSolar was able to map a big crevasse in the arctic’s Bowdoin Glacier, monitored it until complete collapse, and thereby provided scientists with data and information that would otherwise be unnoticed or collected.
With constant monitoring, in other words, there’s an extreme increase in data. If the required energy for these drones is freely collected from the sun, there seems to be no possible argument against this new-fangled method of sustaining perpetual flight. According to the ETH, that one little observation at Bowdoin Glacier gave researchers “a unique set of data—describing all the fracturing phases—for improving the numerical modeling of calving, a complex and still not fully understood mechanism, which play a major role in the sea level rise.” 

Marco Margaritoff's