| Helios is an unmanned solar powered aircraft, jointly developed by NASAs Environmental Research Aircraft and Sensor Technology (ERAST) program and AeroVironment at a cost of $15 million. It is intended to help NASA understand flight conditions at this altitude,which are though to be similar to those present on Mars, as well as having possible implementations as a 'poor mans satellite', or as an environmental monitor.
Powered by 62,000 solar cells capable of generating 40 kilowatts of power, a prototype version of Helios hauled its 74-metre wingspan from a runway at the US Navy's Pacific Missile Range Facility on the Hawaiian island of Kauai to a height of 75,000 feet, before performing a controlled descent. Later on this summer the craft should smash the current world altitude record, currently standing at 79,000 feet set in 1998 by Pathfinder Plus, when it is expected to reacha a height of 98,500 feet.
The crafts designers hope that Helios would eventually be able to stay aloft for months at a time, using fuel cells to store excess solar power for use at night.
Helios potentially presents many advantages over current satellite technology. Apart from being considerably cheaper to launch, it does not have to stay in orbit like a satellite, and can easily be brought down for maintenance and payload changes.
Update 14/08/2001
Helios has now broken the world altitude record for non-rocket-powered aircraft when it reached a height of 25,530 metres (85,100 feet), slightly less than the expected 30,000 metres (100,000 feet), apparently due to thinning air and slanting sunlight which limited its potential for power generation.
Sources include
news.bbc.co.uk
http://www.dfrc.nasa.gov/Projects/Erast/helios.html
http://www.aerovironment.com/
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