Helios reaches record-setting altitude of 96,863 feet Aug. 13. NASA Photo

Reaching new heights
Helios soared to an altitude of 96,863 feet in record-setting flight Aug. 13

NASA News Services

The unique Helios Prototype solar-powered flying wing, developed by AeroVironment, Inc., for a NASA program managed by Dryden, reached an altitude of 96,863 feet during a maximum-altitude flight Aug. 13 from the U.S. Navy's Pacific Missile Range Facility (PMRF) on the Hawaiian island of Kaua'i.

The Helios Prototype flies by the western shore of Nl'ihau, which is also known as the "Forbidden Island." The island is privately owned, but the Helios team has agreements to land on several locations in backup scenarios. NASA Photo / Carla Thomas

Although short of the 100,000 feet altitude that project officials hoped for, the altitude is the highest ever flown by a non-rocket powered aircraft in sustained horizontal flight, and well above the current world altitude record of 85,068 feet for sustained horizontal flight by an aircraft, set by a U.S. Air Force Lockheed SR-71A reconnaissance aircraft in July 1976. It also surpassed the existing altitude record for propeller-driven aircraft, 80,201 feet, set by the Helios Prototype's predecessor, the Pathfinder-Plus, in August 1998. The 96,863-foot record altitude remains unofficial, however, until certified by the National Aeronautics Association's board of records and standards.

NASA Administrator Daniel S. Goldin, hailed the achievement as "a ground-breaking accomplishment which will advance this technology to new heights."

"This is like going to the Olympics and setting a new world record for engineers," added John Del Frate, solar aircraft project manager at Dryden. "This achievement did not come easily. Thousands of things had to work right for something like this to come together."

The Helios Prototype returns from its record altitde flight. NASA Photo by Nick Galante

Due to shortening hours of daylight, a reduced sun angle as the summer waned in the northern hemisphere and low cloud cover during the morning which delayed takeoff by about 36 minutes, the Helios Prototype's time-to-climb was limited to about seven hours. The aircraft reached its maximum altitude shortly after 4 p.m., when the sun angle had already dropped to less than 45 degrees and Helios' climb rate dropped to zero. Even with the reduced angle, however, the solar arrays atop the Helios' wing were still producing about 24 kilowatts, or about 70 percent of their maximum rated output of 35 kilowatts at mid-day.

The Helios Prototype Team consists of, row one, from left, Derek Lisoski, Bob Curtin, Rik Meininger, Claire Olores, Marshall MacCready and Meadowsweet Levi. In the second row are Casey Heninger, Bob Barta and Jim Daley. Row three includes Casey Donohue, Jenny Baer-Riedhart, Ken Cross, Ed Teets, Win Banning and Vince Nishina. In row four are Ken Carbine, Dale Tietz, Mandy Cannone, Bart Rusnak,Brian Matsu-mura, Greg Faith, Shaun Arakaki, Wolfgang Kniedl and Kirk Flittie. The fifth row features Mark Shipley, Dana Taylor, Cliff Cates, Greg Kendall, Jason Mukherjee and Stefano Paris. The back row consists of Patrick Wright, John Del Frate, Ray Morgan, Wyatt Sadler and Earl Cox.

The Helios Prototype flew for more than 40 minutes above 96,000 feet altitude before beginning its descent. It was in the air for almost 17 hours on the record flight, having lifted off the PMRF runway at 8:48 a.m. and landing at 1:43 a.m. the following morning after a 9 1/2-hour descent. Electrical power for post-sunset flight was provided by the generating capability of the motors using the windmill effects of the propellers as the aircraft glided down.

Project officials report that Helios' propulsion, avionics, environmental and flight control systems worked flawlessly during the flight. Temperatures encountered ranged from 80 degrees F at takeoff to a low of minus 85 degrees F at 58,000 feet, but all systems stayed within their temperature limits.

The remotely operated aircraft had reached 76,200 feet during its first checkout flight from PMRF under solar power a month earlier on Saturday, July 14. The Helios Prototype flew six low-altitude airworthiness validation flights on battery power at Dryden in the fall of 1999.

AeroVironment's Brian Matsumura and Casey Heninger work on the official weighing of the Helios Prototype in preparation for its record-breaking altitude flight.

Since then, the aircraft underwent major upgrades, including the installation of high-efficiency solar cell arrays across the wing, navigation and emergency lights, and improved avionics. AeroVironment technicians also completed upgrades to the ground control station, the tracking antennas, and updated operational procedures. More recently, AeroVironment developed a new propeller design that is both stronger and more efficient than the propellers that drove the Helios Prototype during its earlier test flights. The new propellers were used on both the record flight in August and the earlier checkout flight in July.

Dryden's Casey Donohue and PMRF's Dick Nagoshi prepare a weather balloon for flight.

The maximum-altitude flight was one of two major flight milestones set for the craft by NASA, the other being a four-day non-stop endurance demonstration flight above 50,000 feet planned for 2003. Development of a regenerative hydrogen-oxygen energy storage system which would make the multi-day continuous flight possible is progressing at AeroVironment. The system will use excess power generated by the solar arrays during the daytime to run an electrolyzer that separates water into its component parts, hydrogen and oxygen, which are then stored under pressure in specially-designed tanks. At night, the hydrogen and oxygen will be recombined by the fuel cells, producing electricity as a by-product to power Helios' motors and systems.

Production variants of Helios might see service as long-term Earth environmental monitors, disaster monitoring, as well as communications relays, reducing dependence on satellites and providing service in areas not covered by satellites. The record-altitude flight also provided NASA and AeroVironment with information on how an aircraft would fly in a Mars-like atmospheric condition, since the atmosphere at that altitude above the Earth is similar to the atmosphere near the Martian surface.

The 247-foot-span ultralight flying wing's development is being funded and managed under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) project.

Responsible NASA Official: Steve Lighthill
For questions, contact: Jenny Baer-Riedhart
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