Skydweller Aero, a firm in Oklahoma, has developed an unmanned autonomous aircraft powered entirely by solar cells, that will be able to stay aloft more or less indefinitely. They have had two successful test flights recently, each lasting most of a day. The craft generates zero carbon emissions. DOD is one funding agency.
The Skydweller aircraft, made entirely of carbon fiber, boasts a wingspan larger than a Boeing 747 but weighs as little as a Ford F-150. These uncrewed solar-powered aircraft are designed to perform ultra-long duration missions, such as maritime patrol, monitoring naval activities, and detecting smuggling operations, all while leaving zero carbon footprint.
I can see these aircraft replacing geosynchronous satellites for certain applications. Putting these in the air has to be much cheaper than boosting a satellite into orbit. Needing to provide no human support, they can fly high above the weather with their enormous wings, circling gently over a point on the ground.
Afterthought: That carbon fiber body might not reflect radar waves, turning a big target into a little one.
