In the military use of drones, the challenges of rapid improvement of functionality and furthermore low cost have been overcome. A trend has emerged where private companies are using these improved capabilities and low costs. NTT Docomo has announced that it will commercialize “Hyper-Aerial-Base Stations” (HAPS), which fly unmanned aerial vehicles to communicate with the ground, in 2026. NTT will carry out these businesses in partnership with Airbus subsidiary Alto and Amazon.com Inc. (Amazon). NTT has partnered with Amazon in the satellite communications business. Amazon has a vision for a communications service using low-orbit satellites similar to Sterling. The two companies are trying to provide communications services using satellites and HAPS to corporations.
HAPS flies an unmanned aircraft equipped with an antenna into the stratosphere about 20 km above the ground. It is a system in which the drone is flown into the stratosphere about 20 km above the ground and transmits radio waves from the sky. The maximum range of radio waves is said to be 200 km in diameter. The problem is that this drone is powered by solar power, making it difficult to operate in high-latitude areas with short daylight hours. However, drone technology development is gradually solving this issue. The drone “Zephyr” currently being developed by Alto has the potential to overcome this hurdle. The “Zephyr” is a glider-type aircraft with a total width of about 25 m and a weight of only about 75 kg. This drone has a record of flying for 64 consecutive days, even with a large-capacity battery.
If a drone is equipped with GPS, it can fly to a designated location. If it flies with solar power generation, the weight of the communication equipment is also limited. The key is to overcome the challenge of reducing the weight of the solar energy generation device and increasing the weight of the communication equipment. To extend the flight time without using energy, it is important to use the wind as much as possible. The flying style of the albatross is a good reference. Albatrosses use almost no energy to fly. Albatrosses, flying just above the ocean surface, suddenly change direction into the wind when they slow down. When they catch a headwind, their body rises at a steep angle, which is called dynamic soaring. They fly repeatedly in this manner, so they use very little energy. The technology of dynamic soaring is being applied to technology that extends the flight time of drones. The stratosphere is an endless source of strong winds. With some ingenuity, it may even be possible to build a large airborne base.
