Solar-powered planes for 3G and broadband

A US firm believes unmanned solar-powered aeroplanes could circle over cities for six months without landing and provide 3G and broadband Internet services

A US-based technology firm is planning to launch unmanned solar-powered aeroplanes that would provide broadband Internet access and 3G mobile services to whole cities from 70,000 feet above the ground.

SkyTower announced on Tuesday that over the last few weeks it had successfully carried out a number of tests that suggest broadcasters and mobile telecoms operators could use its stratospheric telecommunication platform commercially.

Working with NASA and the Japanese Ministry of Telecommunciations, SkyTower launched a solar-power plane called Pathfinder-Plus. After climbing to 65,000 feet above the Hawaiian island of Kauai, the unmanned Pathfinder-Plus transmitted several hours of third-generation mobile voice, data and video service to the ground, where it was received on a standard NTT DoCoMo 3G handset.

According to Stuart Hindle, vice-president of strategy and business development at SkyTower, the success of the tests shows that SkyTower's planes could complement, and in some cases supersede, satellite and terrestrial telecoms systems.

"The airborne platform, operating above the weather and commercial air traffic, is equivalent to a 12-mile-tall tower, which means significant advantages to telecom service providers and broadcasters," said Hindle in a statement.

Because the signal is being transmitted from directly or almost directly above, the SkyTower system will cover areas that cannot receive satellite or terrestrial signals because large buildings or other obstacles are obstructing them.

The upper wing of the Pathfinder-Plus vehicle is made up of solar panels, which generate the energy to remain in flight throughout the day. Currently, the plane must land at night but SkyTower is trying to create fuel cells that would store enough energy to allow the plane to stay in position circling a city overnight.

Such fuel cells could enable an airplane to stay in the air for up to six months at a time, SkyTower believes.

According to SkyTower, which is part of solar-powered vehicles pioneer AeroVironment, a commercial launch of its service could take place in 2005.

SkyTower claims that the extremely tight turning circle of the Pathfinder-Plus means that the plane stays within a small area throughout its flight -- so users on the ground won't have to keep moving their receiving equipment to track it.

This suggests that SkyTower's technology is ideal for broadband fixed wireless access and digital television services, but the company believes it should be of interest to 3G operators as well.

"Given the amount of money that wireless service providers have spent on spectrum licences for both fixed and mobile applications, these SkyTower tests should be of great interest," Hindle said. "Imagine launching a single platform, having instant metropolitan-wide market coverage, and eliminating the terrestrial costs associated with tower build-outs and backhaul," he added.

AeroVironment has been working on solar-powered plans for many years, including Helios -- a solar-powered plane somewhat similar to Pathfinder-Plus. Last year Helios flew to 96,500 feet, higher than any non-rocket-powered plane had ever managed before.

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