Lofty Goals Set for Solar Plane

Powered by 14 electric motors not much stronger than hair dryers, a massive flying wing made mostly of plastic wrap will attempt next month to go where no airplane has gone before.

Although it will take about eight hours to get there, lumbering at a maximum speed of 25 mph, the Helios solar plane is expected to shatter altitude records and help scientists understand how to fly on Mars. It could ultimately usher in a new era in satellite telecommunications.

Developed by AeroVironment Inc., a pioneering aerospace firm in Monrovia, with funding from the National Aeronautics and Space Administration, the remote-controlled aircraft will attempt to reach 100,000 feet, an aviation feat no jet or propeller airplane has accomplished.

“It’s one of our most exciting projects,” said Alan Brown, spokesman for NASA’s Dryden Flight Research Center, which is overseeing the test flights and has played a role in many aviation advances, including the shattering of the sound barrier.

If the $15-million Helios can reach its objective, it would set the first new altitude record in 25 years. The highest reported altitude by an airplane was achieved by the jet-powered SR-71 spy plane, which flew to 85,068 feet in July 1976. Only short-duration rockets have flown higher, NASA said.

A predecessor to Helios--the Pathfinder-Plus, also built by AeroVironment--flew to 80,201 feet in August 1998.

Besides aiming for the history books, next month’s flight also will give scientists tantalizing clues to flying in an atmosphere similar to that of Mars, aiding NASA’s quest to have humans explore the planet.

At such height, the sky is black, the curvature of the Earth is clearly discernible and the air is so thin--only one-tenth the density at sea level--it is incapable of supporting life, let alone a sustained flight.

“A 100,000-foot altitude record would be the icing on the cake,” said John Del Frate, project manager for solar-powered aircraft at Dryden, in California’s Mojave Desert.

NASA’s primary interest in the aircraft is seeing how much higher it can take sophisticated science equipment to study the atmosphere for climate change and ozone depletion. But the bonus will be the fact that at 100,000 feet, it would be similar to flying in Martian atmosphere.

“In a way, we are going to school on these flights to learn what the aerodynamics are like in these conditions,” Del Frate said.

The aircraft was assembled in pieces at the company’s Simi Valley facility and shipped to the Hawaiian island of Kauai, where it flew to 76,200 feet this month in the prelude to next month’s attempt.

The island was chosen for the record-shattering flight because it provides the best angle to the sun’s radiation and offers a large expanse of unrestricted airspace, NASA officials said.

The plane’s 247-foot wingspan is more than 30 feet longer than that of Boeing Co.’s 747-400, the world’s largest commercial aircraft, and is laden with 65,000 solar cells that provide the electric power to its propellers.

Its developers envision Helios, named after the sun god in Greek mythology, as a high-altitude aircraft that can stay aloft for months at a time and be a cheap alternative to satellites.

NASA officials are still studying the data from last week’s successful test flight and don’t know exactly when the record-breaking attempt will be, although they are aiming for a launch of Aug. 8.

“It went very, very well,” said John Hicks, a NASA program manager. “The aircraft came back in great shape and is ready to turn around and fly again.”

Plane Would Act as Small Satellite

If all goes according to plan, the flight also would give a major boost to AeroVironment’s plans to market a low-cost alternative to commercial satellites. The plane would be able to loiter high above the clouds and commercial aircraft traffic and relay ultra-fast Internet, television and telephone signals directly to homes like a miniature satellite. Its power would come from the solar panels.

Since there are few moving parts--each motor has only one--and no need for refueling, the aircraft could stay in the air six months or more. It would be brought down mainly for maintenance.

“We’re basically developing an airplane that is equivalent to an 11-mile-high tower,” said Stuart Hindle, vice president for strategy and business development for SkyTower, a company AeroVironment formed last fall to market the plane.

Hindle said the telecommunications system, including the airplane, the communications equipment and a backup plane, are estimated to cost $20 million, about one-tenth the cost of sending a satellite into space. It also would be about one-third the cost of establishing cable or digital subscriber line service to a community.

Hindle said the plane would be able to provide service to an area 40 to 400 miles in diameter with data speeds of as much as 20 gigabits per second to about 250,000 customers, each of whom could then access the Internet at 2 megabits per second. That’s about what a DSL connection provides, but without the degradation associated with heavy use.

“The airplane was designed with telecommunications in mind,” Hindle said.

The first plane isn’t expected to go into production until at least 2003, but Hindle said the company has signed up several telecommunication companies, which he declined to identify.

“We’re working with some of the leading satellite communication companies, but I can’t tell you who they are right now,” he said. “Hopefully, it will be in the near future.”

AeroVironment, founded in 1971, has a distinguished record in the alternative-power field. In 1979, its Gossamer Albatross gained worldwide acclaim when it flew across the English Channel, powered only by the pilot pumping away at bicycle-like pedals to turn the propellers. The aircraft is on permanent display at the National Air and Space Museum in Washington.

2 Decades of Design Changes Led to Helios

Two years later, the company’s Solar Challenger made the first sun-powered flight across the channel, and its Sunraycer solar-powered car won a race across Australia in 1987, beating the nearest competitor by two days.

In addition to solar-powered planes, engineers at Aerovironment’s lab are working on a number of cutting-edge designs, including miniature airplanes that would fly like hummingbirds.

AeroVironment has been working on Helios prototypes for nearly two decades and already has gone through several generations. The first generation was the Pathfinder, developed in the early 1980s with a wingspan of 98 feet. The plane grew in size with each successive generation, mainly to gain the capability for higher altitude and more payload.

The Helios prototype, which weighs about 2,000 pounds, is constructed mainly of Kevlar, Styrofoam and transparent plastic film to cover the wing.

Five pods connected to the wing house the motor and the fuel cells, which would be recharged during the day by the solar panels on the wing and provide electricity to the propeller motors at night.

The fuel-cell system, still under development, uses excess power generated by the solar panels during the daytime to run an electrolyzer that separates water into hydrogen and oxygen that are stored in pressurized tanks. At night, the hydrogen and oxygen are combined, producing electricity.

Because there is no rudder, turning is controlled by speeding up the motors on one side of the wing while slowing down those on the opposite side. Pitch control, or up and down movements of the aircraft, is achieved with 72 tiny elevators spanning the wing.

Though cutting edge in many ways, the airplane also relies on back-of-the-garage engineering that has typified AeroVironment’s ingenuity. The landing gear on each pod is made of wheels taken from mountain bikes and scooters.