Drone aircraft able to remain aloft in the stratosphere for months or years at a time are under development.
(Successful December, 2018 flight of Zephyr)
Subsidiaries of Airbus SE, Boeing Co., and Japanese tech conglomerate SoftBank Group Corp. are developing stratospheric drones, which could fly unaided for months and take pictures or beam down internet services some 60,000 feet or more to the ground. They are betting the technology could create markets with military or commercial customers.
It hasnít been an easy start. A March flight of the Zephyr S drone from Airbus, which is using an airfield in northern Australia as its first stratospheric port, was cut short after the drone encountered bad weather as it ascended through lower parts of the atmosphere. The aircraft, which resembles a glider, was destroyed, a spokesman for Australiaís aviation regulator said. Airbus plans another test flight for later this year.
One challenge is designing a drone that is lightweight, but has relatively long wings, so that it can generate sufficient lift while flying slowly in the thin stratospheric air. Regulators must also be convinced the aircraft are safe before possibly hundreds take to the skies.
...after much experimentation by the Westinghouse and the Glenn Martin people a satisfactory substitute was found in the high-flying planes. A few of these planes, spotted around the country, handled the whole television load nicely. Known as Stratovideo planes, they were equipped with studios; many programs originated in the air and were transmitted directly, others beamed from the aircraft to ground stations and then relayed. The planes flew continuously, twenty-four hours a day, were refuelled in air, and dropped down to ten thousand feet every eight hours to meet the Contact planes and take on a new shift of workers.
I should also mention the solar-powered aircraft from John W. Campbell's 1930 story The Black Star Passes, which is the earliest sfnal reference that I know about to a heavier-than-air solar-powered aircraft.