Going Online? Just Call Up the Nearest Laser Drone...
Worldwide, four billion people do not have Internet access – yet. But from an altitude of 27 km, huge drones are to ensure fast wireless Internet to the entire world with laser light that flashes up to one billion times per second.
One summer morning in 2016, the peace of Arizona’s desert is interrupted by four rotating propellers that accelerate along a runway, resting on a metal support on wheels. Shortly after, a 42-m-wide aircraft lets go of the metal support to take off, ascending up through the air layers. The craft is a drone shaped like a huge, thin boomerang whose ends bend upwards. In spite of its size, the drone is not to carry neither goods, nor humans. Instead, it will use laser beams to supply fast Internet to the four billion people in the world who do not have Internet coverage.
96 minutes later, the plane lands again, and so, the first test flight of Facebook’s huge Aquila drone has been completed. 112 years after the Wright brothers' first flight became the beginning of a more connected world, Facebook has reached an important milestone in its Internet.org project, which is to form closer connections between the people of the world together. Swarms of interconnected drones with a hyper-efficient, aerodynamic structure make up an important element of the ambitious plans, whereas the development of history’s first flying Internet network carried by fast-flashing laser transmitters makes up another one. In combination, they could be the solution to how to fill the Internet "gaps" in Africa, South America, Asia, etc., where insufficient infrastructure and impassable terrain make it unprofitable or impossible to lay down Internet cables.
Nothing is superfluous
Prior to the test flight, Facebook has spent about two years developing a drone, that, in its complete version, is meant to fly nonstop for 90 days – only powered by solar energy. The engineers aim to create a plane stripped of all unnecessary equipment such as a cabin and landing gear. The drone is propelled by four motors that consume 5,000 watts – corresponding to a mid-size heat pump. The energy is generated by solar cells covering the entire underside of the wing. The body is made of ultra-light carbon fibre, so Aquila only weighs 450 kg.
Usually, aircraft carry much more weight, requiring much more speed for the wings to produce sufficient lift. Aquila’s low weight does not only benefit the lift, it also allows the drone to manoeuvre at low speeds and very high altitudes. It can fly from 130 to 15 km/h up against the wind and at altitudes of up to 27 km. In comparison, a commercial airliner typically flies 700-1,000 km/h and never higher than 12 km.
Flashing laser light sends data
During Aquila’s first landing on a gravel plain in the desert, the landing calculations were interrupted by a wind gust, causing considerable bruises. So, engineers are still
optimising the drone, as they are developing the project’s second leg: combined laser transmitter and receiver units, which are to carry the Internet signal from one drone to the next – and the next.
They are working with a technology known as Free-Space Optical Communication, FSO. Laser light imitates radio waves which are normally used to transmit data between routers, smartphones, and more. In an ordinary WiFi network, data is converted into radio waves by adjusting the waves’ accurate frequencies and when they start and stop. A unit such as a smartphone decodes the waves, and shows the desired content in the display. In an FSO network, activated and deactivated laser light produces the 1s and 0s, which make up the bits, which combine into documents, images, and video on the Internet.
The laser units work by a diode sending a signal through the centre of a lens. At the same time, the lens focuses external laser light onto a photo detector behind the laser diode, which decodes the frequency and intensity of the light flashes, converting them into bits. The lasers of the Aquila drones flash billions of times per second and can hence send huge quantities of data very accurately between them across many kilometres. According to Facebook, they can hit an area the size of a coin from a distance of 10 km.
Altitude ensures free passage
As the name implies, Free-Space Optical Communication requires that nothing interferes with the light passing between transmitter and receiver. So, FSO data transfer has particularly been used for communication between satellites and in space. Close to Earth, the technology has been limited, because it is difficult to achieve high data speeds across long distances due to disturbing air particles such as fog and rain.
In this case, laser light is markedly different from radio waves, which can function through the walls of a house. This is because of the waves’ different lengths and frequencies. An ordinary WiFi router's radio waves are usually relatively long – such as 12.5 cm for the most ordinary frequency of 2.4 GHz. FSO data transfer uses infrared light, whose wavelengths are only 700-1000 nanometres and frequencies of 300 GHz-430 THz, near to visible light. Waves with such minor lengths face a greater risk of interacting with air particles and so weakening the signal. The particles block out the light, meaning that bits of the data packets fail, and the digital content such as an image will not reach the user in perfect shape. The problem disappears at Aquila’s working altitude of 18-27 km above Earth, where the concentration of particles only makes up 5 % of the concentration at sea level. So, FSO is very efficient. The drones can transfer data at up to 30 gigabits per second
between them – that is about 30 times faster than ordinary Internet connections on Earth, which rarely exceed 100 megabits/second.
High frequency, no bottlenecks
When the drones have taken flight, they are hooked up with the physical Internet via cables and antennas on the ground, and Facebook is also innovative in this respect. The company aims to send the signal to the drones from antennas by means of millimetre waves. They cover frequencies of 30-300 GHz and are a crossbreed between radio waves and infrared light. More specifically, they will make use of the E band, which uses frequencies of 60-90 GHz – unlike the WiFi network of about 2.4-5 GHz. The broad spectrum of frequencies ensures that the network will not be overloaded – such as the WiFi network of a café will easily be in case of many users at the same time. The E band has existed since the 1970s, but before Facebook’s engineers refined it, it was both energy and space-intensive: a technology that was not at all suited for a drone.
In the most recent tests with millimetre waves, Facebook has sent data to a plane at an altitude of 6000m at speeds enough to stream 4,000 HD films at the same time. It is also millimetre waves that are to send the Internet signal from the drones to the receiver units and on to the users’ smartphones or computers on the ground.
Tech giants connect the world
Facebook sees a major development potential in supplying Internet to all people in the world, getting four billion new potential customers. But the company is not alone. Other tech companies such as Google and SpaceX are developing balloons or satellites with the same aim. Aquila’s current climax was reached on 22 May 2017, when it flew in a clear, sunny sky for 106 minutes, before landing as it was supposed to on a plain almost unharmed. If Facebook reaches its goal of building drones that can fly for 90 days and communicate via FSO, it will be two major milestones for drone and communication technology, respectively. Moreover, Aquila can be used for scientific research, etc., which requires the monitoring and studying of large regions at the same time and over long periods of time.
However, the immediate intention of the global Internet solutions is to make sure that farmers in South Sudan have access to weather forecasts and girls in Pakistan have access to an encyclopedia – and to connect any desert, mountain peak, and jungle – in short, bringing the world closer together. So, Facebook or one of its major competitors will close the ring that the Wright brothers initiated in 1903.
The drone flew for 96 minutes. The aim is 90 days of non-stop flight.
Aquilla’s first test flight took place from a metal support on wheels pulled by a large vehicle.