74 hours non-stop flying on only solar power

 747-Sized Drone flies 74 hours non-stop on only solar power

US-based aerospace startup Skydweller Aero has successfully flown its solar-powered drone for nearly three days straight in recent tests. The aircraft, which has a wingspan wider than a Boeing 747, flew entirely on solar and battery power, and then did it again. And it did it fuelled by nothing but photons and electrons for the entire time. The company's stated goal is to eventually achieve "perpetual" flight, in which the drone would only have to land once it needs maintenance. “In back-to-back missions, Skydweller, the world’s largest solar-powered aircraft, stayed aloft for 73 and 74 hours, powered entirely by sunlight,” said the firm. “Over the course of four recent flights, the aircraft logged 222 total hours in the air, validating its endurance, resilience and transformative potential.” This represents significant progress toward the company’s ultimate goal of achieving “perpetual” flight. Because Skydwellers are solar-powered, they are green with zero carbon footprint.

The recent tests were conducted by the Naval Air Warfare Center Aircraft Division (NAWCAD), the drone's first potential customer. The Navy is interested in what a Skydweller could bring to its operations in Southern Command (SOUTHCOM), which encompasses Mexico, Latin America, and all nearby waters. Loaded up with a variety of sensors, a Skydweller could sweep for piracy, drug trafficking or any other illegal activity.  The US Navy is assessing the Skydweller for long-duration intelligence, surveillance and reconnaissance (ISR) missions within the vast US Southern Command (SOUTHCOM) area. Of course, lots of drones and other aircraft already exist which can do that. Skydweller's party trick is its flight time, which is just outrageously good. For reference, the RQ-4 Global Hawk drone, which has a wingspan of 131 feet, can only fly for around 30 hours. The Skydweller's recent tests got as far as 74 hours. That mostly has to do with how the two are refuelled: where the Global Hawk has a turbofan engine which requires good old-fashioned jet fuel, the Skydweller is fully electric and solar.

The aircraft’s performance is a result of its power system and lightweight construction. Its airframe is built from carbon fibre and its expansive wings are covered with 17,000 solar cells which can generate up to 100 kW of power. While the Air Force does have in-air gas stations, in the form of the KC-135 and the newer KC-46 planes, Global Hawks and other drones are not equipped to receive fuel from them. There is a logic to that: since drones are often operating in hostile areas and hoping to stay undetected, flying a jumbo jet over to it doesn't make a lot of sense. The Global Hawk therefore has to fly back to base to get its petroleum fix. During daylight hours, this electricity drives the drone’s four propellers and on board systems while also charging a 1,400-pound battery system. After sunset, the aircraft draws power from these batteries, allowing it to continue flying through the night until the sun rises to recharge the system. 

By contrast, the carbon fibre Skydweller has no gas tank at all, but rather 1400 pounds of batteries, fully 25% of the maximum capacity weight. But even better are what's on those enormous wings, 17,000 solar cells, making 100kW of power. During the day, that's enough to power the four propeller's, avionics and up to 800 pounds of sensor equipment. It's also enough to charge up those batteries, which it then flies on during the night. Recharge mid-air the next day, fly another night; recharge mid-air the next day, fly another night. That's what these recent tests demonstrated. Again, the goal is perpetual flight, and that opens up a whole Pandora's box of opportunities. “Skydwellers are made out of carbon fibre and are capable of uncrewed perpetual flight, typically staying aloft for 30-90 days or longer,” highlighted the company.  This means the aircraft would only need to land for mechanical maintenance, not for fuel. Besides, this drone can carry payloads of up to 881 pounds (400 kg). This significantly improved over previous solar UAVs, which had limited use because they couldn’t carry heavy loads.

For the military, the use cases here are pretty clear. Need to observe an enemy base constantly,  have a Skydweller fly in circles nearby forever. Or is there a place where a terrorist commander will probably show up, someday, maybe? Just park a Skydweller there and have it alert you if he ever shows up. Neverending patrols are another good option, as is a kind of backup GPS capability. Such a capability would allow for a continuous presence over a target area with fewer aircraft and lower operational costs compared to conventional fleets. The ability to provide unbroken monitoring over large swaths of ocean and land could aid in detecting activities like drug trafficking and illegal fishing. The Skydweller platform offers a different operational model than existing ISR assets. The jet-powered RQ-4 Global Hawk, for example, has a flight time of around 30 hours before it must return to base for fuel. While the military operates refuelling tankers, using them for uncrewed aircraft in sensitive areas is often not tactically feasible. The Skydweller’s self-powering design circumvents this logistical constraint.

“Our customers are planning to deploy Skydwellers for long-duration missions like detecting drug smugglers and pirates at sea, providing continuous aerial coverage above war zones, surveilling naval activity in contested waters without risking flight crew’s lives, and tracking wildlife migration and poaching in Africa,” concluded Skydweller. Its AI-driven data processing enables on board target classification, dramatically reducing data loads sent to ground control and enabling efficient bandwidth use, which is critical for long-duration autonomous missions. Beyond government use, Skydweller Aero plans to enter the commercial sector. The drone could be equipped with sensors for scientific applications, such as atmospheric data collection or environmental monitoring. Skydweller Aero makes it clear that it has commercial ambitions, too. For example, sensors could be used for scientific research, too. Meanwhile, SpaceX's Starlink promises the internet to anyone anywhere, but it's also blinding our telescopes and congesting low earth orbit, it accounts for 60% of all satellites! Skydwellers could hang out in far-flung areas and provide customers with high-speed internet without either of those issues around the world.