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The Honolulu Advertiser
Posted on: Saturday, June 7, 2003

Wing uses hydrogen to stay aloft

By Jan TenBruggencate
Advertiser Science Writer

MANA, Kaua'i — The Helios solar-powered flying wing, scheduled to take off from Kaua'i's Pacific Missile Range Facility this morning for a 20-hour flight, is breaking new ground in hydrogen fuel cell technology.

The Helios solar-powered wing will take off from Kaua'i for a 20-hour flight this morning. It will fly on solar power until dark, when it will switch to fuel cell power.

NASA

The flight is the first of several that the wing's developers hope will demonstrate they can keep an unmanned craft flying through the night and into the next day.

"We're leading up to a long-endurance demonstration," said Alan Brown, public affairs officer at NASA's Dryden Flight Research Center in Edwards, Calif.

Future improvements in the system could achieve a NASA goal of having an unmanned aircraft that can stay aloft indefinitely to function much like a satellite, relaying images of Earth, serving as a communications platform or any of a multitude of applications. It would be much cheaper than a satellite and could be landed for reconfiguring its payload and mission.

AeroVironment of Monrovia, Calif., builds and flies the wing as a contractor to NASA's Environmental Research Aircraft and Sensor Technology project.

The flying wing program started several years ago with the 98-foot Pathfinder, a battery-powered, unmanned wing. Helios, which is covered with solar panels, has a 247-foot wingspan. From front to back, the plane is only 12 feet.

In 2001, Helios flew to 96,863 feet above Earth using solar power and batteries to run 14 motors that operated 14 propellers. The batteries are too heavy to keep the plane aloft overnight, when the solar panels are useless.

The newest version of Helios, with 10 motors and rotors, has moved to a fuel cell system, which can be lighter than batteries.

The system uses a standard General Motors automotive fuel cell core but has high-altitude components, so it can function at 50,000 feet. NASA's Brown said the aircraft will have a 180-pound fuel tank of hydrogen gas at each end of the wing.

The plane also has a small bank of standard lithium batteries for emergency backup power.

The wing already made a "hop" on the Pacific Missile Range runway under fuel cell power, so scientists know it works at sea level. If the flight takes off today as planned, Helios will soar to its test altitude under solar power, then switch to fuel cell power when it gets dark. It will fly on fuel cell power until about midnight, then begin its slow descent for a pre-dawn landing tomorrow.

If all goes as planned, AeroVironment and the National Aeronautics and Space Administration hope for a 40-hour flight in about a month, taking the plane to altitude on solar power, running it on fuel cell through the night, then on solar power again all the next day before bringing it down.

Brown said that this Helios system is not a regenerative one, meaning the solar panels will not be used to make hydrogen to fuel the night flight. There are applications for nonregenerative flights, such as over the Antarctica when there is little sunlight.

But a major goal is the development of an entirely regenerative fueling system, with solar panels capable of powering motors and creating hydrogen at the same time, so that the plane can stay aloft for days, weeks or even months.

The Helios team is using proton-exchange membrane fuel cell technology, both for its efficiency and because it has few moving parts.

"These systems have the potential of very high reliability," said a NASA fact sheet on the process.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.