Airships are set to make a return to our skies, but not for transport. The European Space Agency hopes to use large, high-altitude airships with solar-powered engines to carry aloft equipment for atmospheric research.
The first study into using a High-Altitude Long-Endurance (HALE) airship has been completed by the ESA and partners in the venture, Daimler-Chrysler Aerospace of Germany, Lindstrand Balloons Ltd of the UK and the Technical University of Delft in the Netherlands.
The HALE, as envisaged by the study, would be a cigar-shaped, helium-filled vessel that would work in the stratosphere 20 km up, where winds are relatively light. They would be 55 metres in diameter and at 220 metres in length, they would be about as long as two football pitches. The idea would be to launch them, then use an onboard solar-powered engine to move them about and then place them in a fixed position. Solar cells would cover the upper sun-oriented parts of the airship hull and would gather energy during the day to drive a large propeller, and also to charge batteries for night-time operation of the vessel.
Operating at such a high altitude, they would also be above the powerful winds of the jet stream, explained Mr Liam Burke, head of instrumentation and environmental monitoring at Met Eireann. "The density of the air is very low at those heights and there is little wind."
Met Eireann isn't directly involved in this project, but uses balloon technology to gather atmospheric information for weather forecasts, Mr Burke said.
Although similar in shape to the old Zeppelin, the HALE craft would not need an internal rigid frame, relying instead on internal pressurisation to keep its shape. Stationed 20 km up, it would be able to obtain visual information covering a 100 km radius. This regional coverage could be used for environmental monitoring or disaster management, or for recording data and relaying pictures from high up. It could also provide emergency or permanent telecommunications safe from problems at the surface such as earthquake or flood.
Hale's supporters also suggest the craft would be useful for future mobile multimedia services, be it Internet, radio or television. It would reduce the need for a network of antennas and ground-based relay stations. It might also be useful for radio-based gas, water or electricity meter reading or even traffic management.
Similar lighter-than-air research efforts are under way in Japan with its Sky-Net project and in the US with Sky Station International.
The technology is much cheaper and simpler than launching satellites to orbital altitudes and the HALE could be brought back to the surface for repair or to load new monitoring or telecommunications equipment.
