Cosmos 1, a $4 million experiment intended to show that a so-called solar sail can make a controlled flight, lifted off at 12:46 p.m. PDT as organizers of the private project monitored the launch from Moscow and California.
There was no immediate confirmation that the spacecraft reached orbit. Russian space officials in Moscow said it was unclear if Cosmos 1 had successfully separated from a booster rocket.
A ground station in Russia said a signal from the spacecraft broke off at about the time the rocket's final stage would have ignited. The spacecraft was not detected by another station in the Marshall Islands in the Pacific.
Bruce Murray, co-founder of the Planetary Society, confessed earlier to butterflies about the mission, because of the complexity of the new technology. The spacecraft was launched atop a converted missile.
"There is a significant chance of failure," Murray said of the launch and subsequent events the spacecraft was designed to carry out. "This will be a great leap forward if ... it succeeds."
If all goes as planned, the spacecraft will unfurl its eight triangular sails, each nearly 50 feet long and just a quarter of the thickness of a trash bag. Controlled flight, achieved by rotating each blade to change its pitch, would be attempted early next week.
Solar sails are seen as a means for achieving interstellar flight by using the gentle push from the continuous stream of light particles known as photons. Though gradual, the constant light pressure should allow a spacecraft to build up great speed over time, and cover great distances.
Such a craft would not have to carry chemical fuel to propel itself through space, and, according to advocates, would eventually achieve greater speed than a traditional spacecraft.
Cosmos 1 was expected to orbit Earth once every 101 minutes and operate for at least a month.
The project was organized by The Planetary Society, a Pasadena-based organization founded by the late astronomer Carl Sagan; Murray, who is a former director of NASA's Jet Propulsion Laboratory; and JPL veteran Louis D. Friedman, the society's executive director and Cosmos 1 project director.
Funding came largely from Cosmos Studios of Ithaca, N.Y., a science-based entertainment company that was founded by Sagan's widow, Ann Druyan.
Built in Russia by the Lavochkin Association and the Space Research Institute of the Russian Academy of Science, Cosmos 1 was under the control of a mission operations center in Moscow.
Japan tested solar sail deployment on a suborbital flight and Russia deployed a solar sail outside its old Mir space station, but neither involved controlled flight.