Cosmos 1, a $4 million experiment intended to show that a so-called solar sail can make a controlled flight, lifted off as organizers of the private project monitored the launch from Moscow and California.
Russian space officials in Moscow said it was unclear if Cosmos 1 had successfully separated from a 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. The spacecraft was launched atop a converted missile.
"The news is not good," said Bruce Murray, co-founder of the project's organizer, The Planetary Society. Data stopped during a pass
Plans called for the spacecraft to unfurl eight triangular sails, each nearly 50 feet long and a quarter of the thickness of a trash bag.
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. The constant pressure should allow a craft to build up great speed over time.
Cosmos 1 was expected to orbit Earth once every 101 minutes and operate for at least a month.
The Planetary Society is in Pasadena, Calif., and was founded by the late astronomer Carl Sagan, Murray, who is a former director of NASA's Jet Propulsion Laboratory, and Louis Friedman, the society's executive director and Cosmos 1 project director.
Built in Russia, Cosmos 1 was under the control of a mission operations center in Moscow.
