PASADENA, Calif. (AP) -- Though their history-making endeavor stalled, organizers of a bold attempt to fly the world's first solar sail spacecraft say they have no regrets and that future efforts will benefit from what they learned.

The Planetary Society, the Pasadena-based group that orchestrated the $4 million launch of Cosmos 1, all but conceded Wednesday that the spacecraft's launch ended in failure.

Russia's space agency said with ''some definitiveness'' that Cosmos 1's booster rocket failed 83 seconds after its launch from a Russian nuclear submarine in the Barents Sea on Tuesday. Ground tracking stations continued to scan the heavens.

"We all rate it as a 1 percent probability of something like that, but stranger things have happened," said project director Louis D. Friedman, a veteran of military and civilian space programs including NASA's Mariner, Voyager and Magellan projects.

The Planetary Society and its backers had hoped for a revolutionary demonstration of a technology envisioned for interstellar flight.

"We have no regrets over what happened," said Bruce Murray, a former director of NASA's Jet Propulsion Laboratory who founded the group with Friedman and late astronomer Carl Sagan. "We've learned a lot and I think we've shown what can be possible and what might be able to be done."

The solar sail vehicle weighed about 240 pounds and was designed to go into an orbit more than 500 miles high. It was designed to be powered by eight 50-foot-long sail structures resembling the blades of a windmill.

"This may be the down part of the story rather than the triumph we'd hoped for, but I really don't think the story is over," said Sagan's widow, Ann Druyan, whose Cosmos Studio was the project's principal backer.

"No matter what the fate of Cosmos 1, I really do think that all of us involved in this mission are going to stay in the exploration business," she said.

Past attempts to unfold similar devices in space have failed.

In 1999, Russia launched a similar experiment with a sun-reflecting device from its Mir space station, but the deployment mechanism jammed and the device burned up in the atmosphere. Russia tried again in 2001, but the device failed to separate from the booster and burned in the atmosphere.

Yet, there may be hope for Cosmos 1.

Tracking stations on Russia's Kamchatka peninsula, in the South Pacific and in the Czech Republic recorded signals that seemed to be transmissions from the craft, Planetary Society officials said, leaving the possibility that the vehicle made it part way around the globe or actually was in orbit, waiting to be found.

"All we can do is investigate further," Friedman said.