When Solar Impulse had just completed its round-the-world tour without a drop of kerosene, using only the energy of the sun, a similar exploit was launched: the first flight of the giant UAV Aquila, propelled by solar energy and capable of flying for three months at an altitude of 18,000 metres without interruption. A crazy project launched by Facebook to connect the whole of humanity to the Internet.
It was just over a year ago that Facebook unveiled its prototype solar drone. The aim of the operation was to bring high-speed Internet to areas with poor or no access. After several months of tests on small models, the first flight of Facebook's life-size UAV was a success.
Called Aquila (for eagle in Latin), the gear is impressive by its shape. It is a single carbon fiber wing with a wingspan of 42 meters, more than that of an Airbus A320. A thin and elegant wing but particularly light: the whole aircraft weighs no more than a third of an electric car. To give an order of magnitude, the Renault Zoé weighs around 1,500 kg unladen.
Like Solar Impulse, this aircraft flies without a drop of fuel. The UAV operates on solar energy produced by the photovoltaic cells it is covered with. The aircraft's electricity consumption at night does not exceed 5000 watts, the equivalent of three hairdryers. Thus equipped, Aquila is capable of flying for three months, without interruption, at an altitude of between 60 and 90,000 feet (18 to 27,000 metres). Needless to say, there is no pilot on board. The aircraft is automatic and flies at a speed of 40 km/hour.
To achieve the expected performance, the engineers embarked on a race against the weight. As a result, the machine has no landing gear. It takes off with a pyrotechnic device and takes off only with its autopilot. The Aquila tests are not yet complete; the performance of the high energy density batteries, the resistance of the aircraft in real atmospheric conditions and the very shape of the craft will be the subject of numerous tests.
Eventually, the idea is to launch squadrons from Aquila, to create a network of solar drones flying at high altitude in a geostationary manner. The drones would be equipped with a laser transmission system. This will allow the Internet signal to be received from the ground and relayed from one UAV to another to spread the connection over large areas.
The choice of the social network to use laser transmission is particularly daring. Indeed, according to our colleagues in Futura-SciencesThis technology requires a high degree of precision, which is all the more complex as the device is in motion. Researchers at Facebook's Connectivy Lab recently published a description of a light sensor that connects the drone to the ground in the journal The Optical Society. It would be a kind of light bulb made from fluorescent plastic fibres, which would absorb one colour (blue) and emit another (green). According to the authors of this publication, the time between emission and re-emission would thus be reduced to 2 nanoseconds. The first tests of this technology have reached 2 gigabits/sec. In July 2015, the team announced that its laser system could achieve a data transfer rate of several tens of gigabits per second in invisible infrared radiation.
The project's ambition is to provide an Internet connection to 4 billion people, i.e. 60 % of the world's inhabitants who do not have access to it, particularly in emerging countries. Facebook specifies that today, " 1.6 billion people live in regions without mobile broadband networks. Connecting these parts of the world with existing technologies such as buried fibre optics or microwave links is often too expensive. ".