"the researchers identified 500 watt-hours per kilogram as an important threshold for the energy density of a solar stratospheric aircraft’s battery. At that level, they argue, persistent flight becomes viable across many parts of the world where atmospheric conditions allow…..By comparison, today’s commercial electric-vehicle batteries sit in the roughly 250 watt-hour per kilogram range, while experimental or specialty cells in the 400 watt-hour per kilogram range are already available. “We’re almost there,” Mascarenhas said. “Those cells are very expensive right now, but they’re getting cheaper very quickly.”"

​ It's a truism that war accelerates technology development, and we are certainly seeing it with the current Ukraine & Middle East wars. Now it seems another fundamental breakthrough is around the corner.…