The Helios comes down to Earth - a winner
Date: 16-Aug-01
Country: USA
Author: Joan Conrow
The $15 million experimental aircraft, powered by 14 tiny propeller motors that have been described as having the strength of blow dryers, surpassed the horizontal flight record of 85,068 feet (25,930 metres) set in 1966 by a Lockheed SR-71 jet.
It took Helios about 5 hours to set the world altitude flight record and 9 1/2 hours to return home, making a perfect landing at 1:42 a.m. Hawaiian time (7:42 a.m. EDT) on the Hawaiian island of Kauai.
Robert Curtain Jr., vice president of AeroVironment, the southern California company that made the Helios with NASA, said the flight was successful even though it just narrowly missed its target goal of 100,000 feet (30,480 metres), about three times higher than a jet airplane flies.
NASA engineers and the weary ground crew, which was on duty for 27 hours piloting the craft from a command station on the ground, were pleased.
"This is like going to the Olympics and setting a new world record for engineers," said John Del Frate, project manager for NASA's solar-powered aircraft.
NASA engineers say the craft can reach altitudes of 103,000 feet (31,390 metres) under ideal conditions.
TAKE-OFF DELAYED
Cloud cover delayed the craft's take-off for about 40 minutes on Monday morning and by late afternoon, the slanting rays of sunlight were not giving the Helios the solar power it needed to plow through the thin, cold air of the Earth's stratosphere.
It took 36 minutes for the Helios to climb the last 1,240 feet (378 metres), compared to an earlier climbing rate of about 300 feet (91 metres) per minute.
When it reached a "zero climb rate," engineers brought it back to the U.S. Navy's Pacific Missile Range Facility on Kauai before its back-up batteries were depleted.
The Helios also surpassed the 1998 altitude record of 80,201 feet (24,440 metres) for solar-powered and propeller-driven aircraft set by its predecessor, the Pathfinder Plus. Only rocket-powered craft have flown higher.
The aircraft depends on its 62,000 solar cells to create electricity to power its flight. It was drawing its maximum solar power of 31 kilowatts at the upper altitudes.
The Helios, with a wing span of 247 feet (75 metres), is designed to reach high altitudes and stay aloft for up to three months. It is intended to function like a "poor man's satellite," providing telecommunications and other services at a fraction of the cost a satellite, said AeroVironment project manager John Hicks.
Now that engineers have demonstrated the craft can reach its target altitude, they will work to develop a lightweight fuel cell system that will allow it to store the excess solar power it generates for night operations. Currently, the Helios has batteries that allow it to stay up for just a few hours after sunset.
The solar cells generate about 40 kilowatts of power - about the amount used each day by four to six homes - to drive 14 propellers on the craft, which looks like a single, boomerang-shaped translucent wing.
When fuel cells are installed by summer of 2003, the Helios will be able to stay aloft for months at a time, Hicks said. It can also remain in one spot over the Earth's surface for an extended period of time.