Leaks keep flying wing from using fuel-cell system
By Jan TenBruggencate
Advertiser Science Writer
An air leak and a coolant leak at 50,000 feet elevation caused engineers to bring down the unmanned Helios solar plane last week, before firing up its experimental fuel cell powerplant.
Advertiser library photo • Aug. 13, 2001
The flying wing flew for 15 hours, taking off and landing at the Pacific Missile Range Facility at Barking Sands, but did almost all of its flying on electricity generated by the solar photovoltaic panels in its wings. Its hydrogen fuel cell operation was canceled after on-board sensors detected leaks.
Helios, NASA's 247-foot, solar-powered flying wing, flew almost entirely on electricity last week when its hydrogen fuel cell operation was canceled after on-board sensors detected two leaks while the craft was at 50,000 feet.
Engineers are working to resolve the issue and hope to get the 247-foot wing back in the air as early as June 26 to test the fuel cell. If it functions normally, it will fly as scheduled in July to attempt to stay aloft overnight, using solar power during the daylight and the fuel cell at night.
On last week's flight, an air leak occurred in a line between the fuel cell and the compressor that delivers compressed air to it. The pressurized air is combined with hydrogen in the fuel cell to make power.
A second leak occurred in a coolant system used to reduce temperatures in the fuel cell, which heats up when in use.
Both leaks, identified using sensors, did not occur at ground level but appeared in the low pressure environment of the high elevations at which Helios was operating, said Alan Brown, spokesman for the NASA Dryden Flight Research Facility.
Helios flew to a record of more than 96,000 feet in 2001 with a total weight of 1,585 pounds. With the fuel cell and fuel on board, its overall weight is 2,328 pounds.
Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.
