Sun power is preparing for takeoff. The world's first piloted airplane flight fueled only by the sun's rays is scheduled to make a short, 15-m.p.h. jaunt this month.
And by this fall, Dr. Paul MacCready -- who was also responsible for the first human-powered flight across the English channel last year -- plans to have finished a solar-powered plane which will be flown 100 miles, from San Diego to Los Angeles.
Aviation, however, is not exactly on the brink of a solar age. In fact, Dr. MacCready explains, his planes are not expected to open new vistas in either commercial or recreational flight.
Instead, he says, he hopes his sunpowered flights will focus attention on development of alternative energy sources, and one source in particular: photovoltaic cells.
Like many scientists, Dr. MacCready says he believes that if there is a future in solar energy as an inexpensive fuel it will be in photovoltaic cells. The cells, which convert sunlight into electricity, are too costly for widespread use now.
But with continued development, which Dr. MacCready hopes to speed by increasing public awareness of solar-cell potential, researchers predict that within another 5-to-10 years photovoltaic cells may become one of the cheapest alternative energy sources available.
The cells -- paper-thin and about as large as a microscope slide -- are the key to the flights of both the Goassamer Penguin, which will be flown as soon as the weather conditions are right, and the Solar Challenger, which is still being built.
The Penguin, which will fly 10 to 15 feet above the ground, will be powered by 2,800 solar cells lined along what looks like a small billboard percehd on top of the plane. Electricity converted by the cells will run a tiny motor which turns the plane's rearmounted propeller.