SOLAR-POWERED CENTURION GOAL OF NASA; AIRCRAFT COULD BE VALUABLE TOOL.

Byline: Associated Press 

Nineteen miles above the Earth - on a wing and a solar glare.

That's the goal of engineers conducting test flights of a remotely piloted 206-foot flying wing they hope will someday make a slow ascent into the cold, thin air of the stratosphere using only sunlight.

Scientists want aircraft like the Centurion for atmospheric research. Meteorologists may be able to use them for tracking major storms. There's also interest in versions that could stay aloft for weeks performing the same functions as satellites at a far cheaper cost.

``To fly in level flight at 100,000 feet will be higher than any nonrocket-powered airplane has flown,'' said Ray Morgan, vice president of AeroVironment Inc., which is developing Centurion under NASA's Environmental Research Aircraft and Sensor Technology program.

With 14 propellers and a wingspan bigger than a Boeing 747, Centurion is a leap in size over predecessors. Yet it weighs just 1,175 pounds and cruises at about 20 mph.

Eventually, the electrical power will come from panels of solar cells atop the wing. For now, it's running on conventional batteries during low-level test flights above Rogers Dry Lake at Edwards.

Morgan said there is discussion of extending the wingspan an additional 45 to 100 feet.

The wing is so stable that it could be cut into a half-dozen sections and each would fly. In flight, the wing's flexibility sometimes makes it look like an ocean swell, with a wave running down to one tip and then running back.

``It works like many aircraft flying in close formation, but they do happen to be structurally interconnected,'' Morgan said.

Extensive automation of the control system is essential, not just because Centurion is unmanned, but because the potential for problems increases with the length of the span, Morgan said.

For example, because the wing is so long and its speed is so slow, a turn could cause ``tip stall,'' when the wingtip on the inside of the turn stops moving forward and essentially stops flying.

AeroVironment of Monrovia was founded by Paul MacCready, a pioneer in super-light aircraft who gained fame for designs used in human-powered flights.

Centurion follows that tradition. Construction materials include carbon fiber, Kevlar, Styrofoam and plastic film. The step up to Centurion follows tests of smaller solar-powered planes: Solar Challenger, Pathfinder and Pathfinder Plus.

Pathfinder Plus, with a wingspan of 121 feet and eight motors, reached an altitude of 80,285 feet in August during testing over the Pacific near Hawaii. The altitude was a record for a propeller-driven aircraft.

NASA's ERAST program is developing a variety of unpiloted aircraft suitable for research at various altitudes and capable of adaptation to commercial uses.

Scientists' interest in high-flying, solar-powered aircraft is based on the need for atmospheric sampling without altering the very air that is being collected.

Jets have topped 100,000 feet, and the X-15 rocket plane flew three times that high. But such speed affects atmospheric samples.

``Once you start going supersonic, it's no longer of great value, the reason being that the heating associated with the compression of the air as it moves through it changes the chemistry,'' Morgan said.

Balloons are also used in high-altitude research, but they tend to ``off-gas,'' making it difficult for sensors to get unbiased readings, he said. Balloons also have problems with altitude and location control.

Morgan said developing the series of solar-powered planes has cost about $30 million, and it will take more to finish Centurion. Only one high-efficiency solar panel, costing about $1.5 million, has been acquired. The program will need about $7 million more to acquire four more panels.

From a technical standpoint, Centurion could be ready to attempt 100,000 feet as early as the year 2000, he said, but it will probably be later.

Centurion is to be followed by Helios, designed to be able to stay aloft for great lengths of time, using solar power during daytime and solar-charged batteries at night.

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Photo

PHOTO NASA's Centurion soars above Edwards Air Force Base in a test flight of the remotely piloted 206-foot flying wing now powered by batteries.

Gene Blevins/Special to the Daily News