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As this is being written, technicians on the Hawaiian island of
Kauai are preparing NASA's Helios Prototype, the giant solar-powered wing
pictured above, for take off in an attempt to set a new altitude record
for nonrocket aircraft. The vehicle, which reached 76,200 feet (about
23,450m) in a test flight in July 2001, is expected to attain an altitude
of 100,000 feet (30,770m). In contrast to the Space Shuttle, which
can climb to that height in just a couple of minutes, Helios will take
eight hours to reach its peak altitude. With a wingspan of 247 feet (76m
-- greater than a Boeing 747) and a length of only 12 feet (3.7m), Helios
cruises between 19 and 25 miles per hour (30-40 kph).
The aircraft, which weighs only about 1,500 pounds (about 680 kilograms) is built of carbon fiber and graphite epoxy composite material, as well as Styrofoam, Kevlar fabric, and a plastic film covering. It is driven by 14 propellers each powered by an electric motor which uses electricity generated by the 66,000 solar cells that cover its upper surface. Eventually, in 2003, NASA hopes to send Helios up on flights lasting four days. In order to do this, it will need a means of storing the solar energy it generates so that it can fly at night. NASA is developing a fuel cell storage system that will use a portion of the electricity its solar cells generate during the day to convert water into hydrogen and oxygen, store the gases in pressurized tanks, and recombine them in a fuel cell during the night to provide electricity for the plane's engines. The ultimate goal of the program is to develop an aircraft that can remain in flight at 60,000 to 70,000 feet (18,500 to 21,500m) for weeks or even months at a time. This would permit scientists to monitor weather systems, pollution, and other atmospheric phenomena on a continuous basis. In addition, Helios's developer, AeroVironment, hopes to use such aircraft to circle over population centers and provide broadband communications capabilities, supplementing space satellites and earth-bound systems. |
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 = highly recommended
Helios's telecommunications potential, from AeroVironment, the California firm that built the Helios Prototype under contract to NASA. Tracking and update site for Helios flights. "Helios Prototype Aces Last California Test Flight," by Andrew Bridges, Space.com (Dec. 8, 1999). This flight was powered by batteries. Subsequently, the craft was reconfigured to run on solar power, then taken to Hawaii for further testing. "Robot Aircraft Shoots for Altitude Record," by Space.com staff (Aug. 10, 2001). "Helios, Taking Power from the Sun," on NASAExplores, an educational site with materials suitable for kindergarten through 12th grade. "Helios readied: Solar aircraft aims for record altitude above 100,000 feet in Hawaii," by Alan Brown, on NASA Dryden X-Press (May 31, 2001). Angel Technologies Corporation, a competing approach to airborne stratospheric communications using high altitude, long-duration piloted aircraft. |
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