But it was unclear if the privately funded Cosmos 1 was in space or had crashed to Earth, with the U.S. backers of the project saying the craft was sending faint signals, possibly from a lower orbit.

"The unique solar sail spacecraft was not delivered to its planned orbit because the engine of the first stage of the "Volna" rocket shut itself down 83 seconds into the flight," Russia's Federal Space Agency said in a statement.

"Unfortunately, this is the second unsuccessful attempt to launch a solar sail craft on a journey through space," the agency added.

Separately, Russia's Itar-Tass and Interfax news agencies quoted an unnamed Russian space agency source as saying the craft had crashed in the Barents Sea close to where it had been launched Tuesday from a Russian submarine.

But controllers at the Pasadena, Calif.-based office of The Planetary Society, the mission's U.S. backers, said the craft appeared to be "alive" and sending signals to tracking stations.

"We have no evidence that anything is wrong with the spacecraft at all," Bruce Betts, the Planetary Society's director of projects, said late Tuesday.

The Planetary Society, the world's largest private space advocacy group, hoped the mission would show that a group of space enthusiasts could kick-start a race to the stars on a shoestring budget of $4 million.

Cosmos 1 blasted off in a converted Russian ballistic missile from the Barents Sea on Tuesday. But the disc-shaped craft lost contact with its controller almost immediately. For several hours, Cosmos 1 was believed lost.

A spokesman for the Russian Space Agency said they could not determine whether Cosmos 1 had crashed to earth or was in orbit. He referred inquiries to the Russian military but a representative could not immediately be reached.

However, weak signals received by tracking stations in the Pacific Ocean, Russia and the Czech Republic seemed to show it had made it into orbit.

Mission controllers discovered after reviewing data recorded by the stations that the craft had signaled its passage during what had been believed to be several hours of radio silence, said Planetary Society co-founder Bruce Murray.

"The good news is we have reason to believe it's alive and in orbit," said Murray, a former director of the Jet Propulsion Laboratory. "The bad news is we don't know where it is."

The signal appeared weak probably because the orbiter had veered off course during its final rocket burn, and ground antennae were now trained on the wrong part of the sky, Murray said.

For that reason, it was not clear whether planned communications sessions with the spacecraft would help mission managers find Cosmos 1, he said.

They planned to enlist the help of the U.S. Strategic Command, whose job is to monitor the skies for signs of incoming missiles and other threats.

If the craft is still in space, mission backers still face the prospect that it is in a deteriorating orbit and may eventually fall back to Earth, or that the orbit is so irregular that the solar sails cannot deploy properly.

Cosmos 1 was to unfurl a 100-foot petal-shaped solar sail to power its planned orbit around Earth and show that photons--light particles emanating from the Sun--would propel the craft forward at an ever-increasing rate of speed.

The mission's goal is to raise Cosmos 1 to a higher orbit above the Earth by "sailing" the spacecraft on streams of photons.

The project started as a dream by Planetary Society founders Murray, Carl Sagan and Louis Friedman, a former NASA engineer who proposed sending a solar sail craft to Halley's Comet in the 1970s.

Sagan's widow, Ann Druyan, provided most of the funding for the mission through her entertainment company, Cosmos Studios.