HELIOS TESTS ON TAP CRAFT COULD STAY ALOFT FOR DAYS, EVEN WEEKS.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - In a step toward developing aircraft capable of flying for weeks or even months, NASA's solar-powered flying wing Helios this summer will test a fuel-cell system for flying at night.

Two years after setting an altitude record of 96,863 feet while flying on solar power, Helios will attempt to stay aloft more than 40 hours, with at least 14 hours above 50,000 feet altitude, over the Hawaiian island of Kauai.

Helios will use solar cells for daylight flight and an experimental fuel cell that uses hydrogen and oxygen for night flight.

``For the last eight or nine years, we've been working at proving the concept of solar flight in general,'' said John Del Frate, Helios project manager at the National Aeronautics and Space Administration's Dryden Flight Research Center. ``This takes the concept a step further. When the sun goes down, the plane doesn't have to come down.''

The 743-pound fuel-cell system combines oxygen from the atmosphere with hydrogen gas contained in two pressurized tanks mounted on Helios' outboard wing sections. The hydrogen and oxygen are fed to a series of proton-exchange membrane fuel-cell ``stacks'' mounted in the central landing gear pod.

The experimental fuel cell is expected to generate 15 kilowatts to power the aircraft's 10 electric motors that turn propellers.

A 15-hour checkout flight June 7 found leaks in a cooling system and in an air-feeder line going to the fuel cell. The fuel cell itself was not turned on.

``It was a shakedown flight,'' Del Frate said. ``We were expecting things like this to happen.''

Another checkout flight will be held, possibly as early as the week of June 26, prior to the endurance flight.

Helios' flights are from the Navy's Pacific Missile Range Facility at Kauai, which has lots of sun and test ranges closed to other air traffic, NASA said.

Helios is only 12 feet long, but it has a 247-foot wingspan. The airplane's cruising speed ranges from 19 to 25 mph.

The airplane is made of lightweight composite materials, such as carbon fiber and graphite epoxy, which are used in the B-2 stealth bomber, and Kevlar, which is used in the making of bulletproof vests.

The flight testing is being conducted under NASA's Environmental Research Aircraft and Sensor Technology program, which is overseen by NASA Dryden. ERAST is aimed at developing technologies that allow companies to build unmanned aircraft that can carry out the dull, dirty or dangerous missions that would be impossible or impractical for manned aircraft.

One of the program's goals is to develop technologies allowing aircraft to fly at high altitudes for days, weeks or even months at a time. Such aircraft could be used almost like satellites, assisting with telecommunications or serving as platforms for instruments to study Earth and its atmosphere.

NASA describes the two-day endurance flight as the crowning achievement of the 10-year-old ERAST program, which will conclude in September.

The Helios prototype was built by AeroVironment Inc. of Monrovia as part of the ERAST program.

There are plans for a follow-up program to further develop the fuel-cell system. Researchers are looking at developing a regenerative system that would break down water molecules into hydrogen and oxygen gases.

Such a system could allow an aircraft to stay aloft for months at a time.

Researchers are looking at flying such a system in 2006.

Researchers are also interested in a system that would use liquid hydrogen that would allow an aircraft to stay up for as long as two weeks. That system would be useful in areas like Alaska, where sunlight conditions are not suited for solar flight.

Helios is slated for a telecommunications relay demonstration project in September. The craft will carry advanced broadband Internet connectivity and antenna systems developed by Japan's Communication Research Laboratory and the Telecommunications Advancement Organization of the Japanese Ministry of Public Management, Home Affairs, Post and Telecommunications.

Jim Skeen, [phone]

james.skeen(at)dailynews.com

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Photo:

Helios is a solar-powered flying wing that incorporates a fue l-cell system for night flying.

NASA