Aerospace |
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Solar-powered
plane flies to record heights
Last week, AeroVironment announced that its "Pathfinder" solar-powered,
remotely-piloted aircraft flew to a record altitude of approximately 67,400
feet -- powered only by the sun -- and returned safely to the Pacific Missile
This altitude is approximately 400 feet higher than any propeller-driven aircraft has flown before, and 17,000 feet higher than the previous solar-powered altitude record. The Pathfinder airplane is a technology demonstration platform testing the viability of solar-powered aircraft for high-altitude, long-endurance flight. Derivatives of Pathfinder, incorporating energy storage for nighttime flight, will be capable of continuous flight for weeks or months at a time at altitudes of over 60,000 feet, powered only by the sun. The successful record flight in Hawaii marks another key milestone in the Pathfinder program, part of NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. Building on Pathfinder's previous record-breaking flight to 50,500 feet, achieved in September 1995 at NASA's Dryden Flight Research Center in California, this flight brings closer the vision of solar-powered aircraft as low cost, flexible, surrogate satellites for atmospheric measurement, reconnaissance and communications.
AeroVironment claims the Pathfinder aircraft is a truly remarkable engineering achievement. A "flying wing" with a span of 98 feet, Pathfinder weighs only 500 pounds and flies on a mere 8 kilowatts of solar power, about as much as five hair dryers use. The six highly efficient, electric-powered propellers are distributed along the wing. Pathfinder carried two payloads on this mission, a turbulence spectra sensor and a servo response frequency experiment. The flight began at 8:43 a.m. under partly cloudy skies with a battery assisted take-off. Avoiding scattered rainstorms and overcoming downward air currents, remote pilots guided Pathfinder steadily upward past the clouds, through air temperatures as low as minus 110 degrees Farenheit, and reached the peak altitude of 67,400 feet shortly after 4:00 p.m. An autopilot maintained stable flight from low altitude all the way to the peak. Mission planners constantly reworked and optimized the flight plans with the meteorologists and pilots, using the latest wind data and satellite photos of cloud locations. AeroVironment's SODAR acoustic remote sensing systems played a key role, measuring wind speed, direction and turbulence up to 4,000 feet. Two SODAR models, one for lower altitude and one for higher altitude, provided critical data to help plan the optimal take-off and landing times, to avoid areas of high vertical wind speed that inhibited climb or descent, and to prepare for large changes in wind direction and turbulence at different altitudes. The descent went smoothly at first but became more challenging due to strong trade winds at 15,000 feet, localized upcurrents and turbulence below 10,000 feet, and shifting cross winds as the plane approached ground level. With the help of SODAR wind data, the remote pilot was able to make a safe landing. The team will continue flight testing in Hawaii for the next several months to perfect operational procedures and demonstrate that Pathfinder is reliable enough to operate in FAA airspace. Pathfinder will also carry payloads for science missions, including monitoring of coral reef degradation and deforestation around the island of Kauai. AeroVironment has long been known for its development of efficient aircraft,
including the groundbreaking solar-powered "Gossamer Penguin"
and "Solar Challenger." In 1981, the Solar Challenger flew 163
miles from Paris to England, at altitudes up to 11,000 feet, powered only
by the sun. Solar Challenger is now owned by the Smithsonian Institute's
National Air and Space Museum. |
Range Facility
(PMRF) at Barking Sands, Kauai, in the Hawaiian Islands. The flight took
place on June 9th.
Ray Morgan, a vice president
of AeroVironment, noted that "we are particularly proud of this event
because we exceeded our milestone of 65,000 feet on the first flight day
at PMRF," a result that was made possible by "a lot of hard work
and planning by a dedicated team from AeroVironment, NASA and PMRF."