With modern, flexible envelope materials, pressurisation is all that's needed to impart the necessary rigidity to the airship body. Only local reinforcement structures for the engine and payload attachment are necessary. The airships are equipped with an engine for mobility and stable positioning against stratospheric air currents. The altitude of 20km is high enough to give local or regional communications coverage to a circular 'footprint' of about 100km in diameter. Positioning the craft any higher would place it in the path of dangerously high winds.
Clean power is provided by solar cells covering the upper portions of the airship skin.
From there would be drawn the necessary power for nighttime propulsion and operation of the vehicle. The ESA and other HALE supporters figure that Earth observation is a domain where the craft can play an important role. Such observations could either be permanent or ad-hoc. Besides obvious long-term environmental monitoring, a HALE system could, for instance, offer temporary assistance in a disaster management scenario. The airships could be used to guide rescue operations in the event of a flood or earthquake, when local telephone connections, including terrestrial cell networks, fail, and rapid local observations of the disaster area are vital.