Today, Verne's glimpse of a far-flung future finally is edging closer to reality. At 12:46 p.m. PDT Tuesday, the world's first solar sail spacecraft, called Cosmos 1, is scheduled to take flight.

Cosmos 1 represents a unique and intriguing prototype for space exploration: a vehicle that is powered by light, not fuel. Eventually, solar sails could even offer a way to reach the stars.

Tuesday's expected launch is more modest in scope. The Planetary Society, the nonprofit group based in Pasadena, Calif., that designed the sail, says Cosmos 1 likely will remain in orbit for only a few weeks.

"We're not sure what the full length of time will be," spokeswoman Susan Lendroth said. "We're hoping a month." Eventually the pressurized gas that keeps Cosmos 1's ribs in place will leak, and the small spacecraft's orbit will decay until it burns up in the atmosphere.

Solar sails work by capturing the minuscule momentum of light particles emitted by the sun. Over time, the spacecraft can maintain a mild but constant acceleration--unlike the more powerful but briefer burst produced by chemical rockets. Some proponents have even speculated that orbiting lasers could be trained on the sail for propulsion when the spacecraft is far away from the sun.

While there have been some preliminary tests of solar sail technology from NASA and from a Japanese institute, Cosmos 1 will be the first spacecraft powered by one.

If all goes well, Cosmos 1 will be launched from a Russian Navy submarine in the Barents Sea north of Norway and Russia and fly atop a Volna rocket into orbit at an altitude of about 520 miles. The solar sails--made of the same material as Mylar balloons, only thinner and more delicate--will deploy four days later.

The Planetary Society and its partners (funding is coming from Cosmos Studios, which was founded by Carl Sagan's widow, Ann Druyan) have erected two ground stations along the eastern edge of Russia and the Marshall Islands in the central Pacific Ocean. Mission control will be based in Moscow, with a link to the group's offices in Pasadena.

The Planetary Society suffered a major mishap during a July 2001 preliminary test of its solar sail. The package launched from a submarine in the Barents Sea but never separated from the third stage of the rocket, so the sails could not deploy.

Space travel buffs say that Cosmos 1 marks a new trend toward private research and exploration and less government control of the heavens.

Microsoft co-founder Paul Allen funded SpaceShipOne, which won the Ansari X prize by flying to the near edge of space. Amazon.com's Jeff Bezos founded Blue Origin, which seeks to create an "enduring" human presence in space. Other private-sector space pioneers include Richard Branson and Burt Rutan.

"It shows that the private sector can do a lot of interesting things and come up with innovations," said Ed Hudgins, editor of the book "Space: The Free-Market Frontier."

"It will be the private sector that will turn us into a space-faring civilization, but only if government gets out of the way."

Science fiction works after Verne's "From the Earth to the Moon" have elaborated on the concept of a solar sail. In 1951, Astounding Science Fiction published a nonfiction account titled "Clipper Ships of Space." Nine years later, Cordwainer Smith published "The Lady Who Sailed The Soul," a story about a romance between two legendary solar sailors.

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