The science behind tethered drone technology
Small-scale drones work with electric motors and batteries. The energy density (energy per weight) of current batteries is more than 10 times lower than the energy density of fuel, which significantly limits the flight time of hovering drones. This problem is obviated by our tether system.
In the simplest case, a tethered drone is connected to a mooring point via a mechanical cable or tether that restricts the spatial position of the drone, physically preventing it from flyaways. However, a tethered drone is more frequently related to an electro-mechanical tether that connects the drone to a large source of electricity (battery or grid) via a ground station. This enables the drone to hover on station for a much longer period of time compared to the 15-20 minutes allowed by on-board batteries. The tether could also comprise an optical cable for high bandwidth data transmission, e.g. ultra HD video, which is not currently achievable using wireless networks.
Even though balloons take advantage of buoyancy to create almost free lift, they lack all-weather reliability. This is because for the same payload (e.g. a camera), balloons are much larger than drones, which makes them more vulnerable to wind drift and more difficult to keep on station. This lack of maneuverability makes them not suitable for applications that require station-keeping capability.
Power is transmitted using high voltage direct current (DC) electricity. High voltage permits efficient power transmission using thin, lightweight conductors with low wind drag. The combination of all these properties allows for tethered hovering at altitudes not attainable with low-voltage tethers. A surface power supply converts standard AC power to the higher voltage DC power for tether transmission, and a lightweight DC-DC converter on-board the drone provides the lower voltages needed for operating the electric motors and the camera/gimbal system.
A winch autonomously launches and recovers the drone by managing the tension of the tether.
The tethered platform can hover up to 400 feet above the ground, depending on the platform size and the payload employed.
If, for some extreme reasons, the tether breaks or the ground power source goes down, an on-board backup battery can supplant the tether for autonomous and safe landing.