The US Navy is developing an uncrewed solar-powered aircraft to fly for 90 days at a time. The Skydweller aircraft could be used as a communications relay platform or a constant eye in the sky to escort surface ships.
The testbed aircraft adds new software and upgraded hardware to Solar Impulse 2, a piloted solar aircraft that flew around the world in 2015-16. The new plane is made by US-Spanish aerospace firm Skydweller Aero. The company was awarded a $5 million contract to develop the aircraft.
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Skydweller Aero CEO notes that previous Solar Impulse flights had to break up circumnavigation of the planet into hops of no more than five days because of the limitations of the human pilot.
鈥淲hen we remove the cockpit, we are enabling true persistence and providing the opportunity to install up to about 400 kilograms of payload capacity,鈥� says Miller.
The Skydweller aircraft is radically different from other high-altitude solar aircraft under development, sometimes known as high-altitude platform systems or pseudo-satellites. These are lightweight and fly at extreme altitudes with small payloads.
The Skydweller plane is much heavier and has 72-metre wings covered in solar cells. The developers say it may later be fitted with hydrogen fuel cells for an additional boost. The aircraft is gradually shifting to unpiloted operation.
鈥淲e are currently following our plan to test autonomous flight, then autonomous take-off, then autonomous landing and finally our first fully autonomous flight,鈥� says Miller. 鈥淥nce all this has been proven, we will move into long-endurance testing with the goal of operating for 90-plus days.鈥�
The US Navy currently operates airliner-sized MQ-4C Triton drones with an endurance of 30 hours on maritime patrols, but seeks longer flight times.
鈥淭he biggest advantage of long endurance is not having to make repeated transits to and from the operating area,鈥� says at UK security think tank Royal United Services Institute. Bronk also says that the Skydweller aircraft appears more robust than other solar aircraft.
鈥淭hat makes sense for the US Navy in particular, which faces some pretty serious weather at high altitude over the Indo-Pacific region,鈥� says Bronk. 鈥淗ydrogen fuel cells make sense as a backup if you need to climb rapidly if there is bad weather intruding.鈥�
Miller says that, in the longer run, the largest market may not be the military but commercial telecommunications, with solar drones providing 5G or other services at a fraction of the cost of satellites.
鈥淚t may still not have enough power for an active sensor like radar, but it could be useful for passive sensors such as cameras, or as a communications node,鈥� says Bronk.
