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Pathfinder-Plus for hanging in the National Air and Space Museum's Steven F. Udvar-Hazy Center. (Dane Penland)

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The heaviest object in the Steven F. Udvar-Hazy Center in Chantilly, Virginia, is undoubtedly the space shuttle Enterprise. The prize for most unwieldy, however, goes to a 700-pound, 121-foot flying wing, Pathfinder-Plus, a January addition to the Hazy collection.

In August 1998, the solar/electric-powered, propeller-driven wing flew at a record 80,201 feet. (The highest altitude achieved by a propeller aircraft is 96,863 feet, reached in 2001 by Helios, a direct descendant of Pathfinder-Plus.)

NASA developed Pathfinder-Plus with AeroVironment, a California-based manufacturer of unmanned aerial vehicles led by inventor Paul MacCready. Ever since he was a boy growing up in Connecticut, MacCready has been fascinated with flight. He started AeroVironment in 1971 as a company devoted to building environmentally friendly aircraft. “MacCready’s creations are so innovative, clever, and unique,” says National Air and Space Museum curator Bob van der Linden. “And they work. The Pathfinder-Plus is a high-lift, low-speed airfoil. The potential for that kind of aircraft is tremendous. It could perform long-term reconnaissance or function like Landsat [Earth-observing satellites].”

Several of MacCready’s inventions are already in the Smithsonian’s collection: the human-powered Gossamer Condor and its successor, the Gossamer Albatross; the solar-powered Solar Challenger; and the Sunraycer solar race car. In 1985 the Smithsonian commissioned MacCready to build a remote-controlled flying model of a pterodactyl (a flying dinosaur), which later appeared in the IMAX movie On the Wing.

MacCready designed Pathfinder in 1983 to explore high-altitude, long-duration flight. It evolved into Pathfinder-Plus in 1998 with the substitution of more efficient solar cells and the addition of a center wing section with a high-altitude airfoil, which added more than 22 feet to the wingspan. Developed as part of NASA’s Environmental Research Aircraft and Sensor Technology project, the aircraft were technology demonstrators for flight at the low end of the speed regime. Despite having eight electric motors, Pathfinder-Plus didn’t go anywhere quickly: Its top speed is only 25 mph.

Navigating the ungainly wing into the Hazy Center was quite a feat. But perhaps the biggest triumph of logistics was in coordinating a crew from AeroVironment to arrive along with the two trailers that hauled Pathfinder-Plus. Reassembling the aircraft required the specialized knowledge of the AeroVironment team, says Robert Mawhinney, a museum specialist at the Paul E. Garber Preservation, Restoration and Storage Facility in Suitland, Maryland. Mawhinney has participated in most of the hanging installations at the Hazy Center, and says this one was the most complicated.

“The airplane is extremely fragile,” he says. “The leading edge is built from Styrofoam about the thickness of a coffee cup. It’s the kind of airplane you have to work on without touching or leaning on it.”

Pathfinder-Plus was reassembled directly beneath the place in the Hazy Center where it was to be hung—once it was assembled, it couldn’t be moved because it’s so flexible it might bend until reaching its breaking point. Still, “the engineers said it was possible to bend the entire airplane so the tips of the wings would touch without snapping,” says Mawhinney. “Hanging it was like hanging a wet noodle.” As Pathfinder-Plus was lifted into place, it was supported on the joints of the wings and its pylons—rigid structures along the wing where the engines are attached.

“We did the best we could as far as simulating normal flight attitude,” Mawhinney says. “It’s a bit more U-shaped in actual flight, but it looks fairly realistic.”

 

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