Solar-sail mission reflects past and future

Arguing over history
The California-based Planetary Society has been working on the Cosmos 1 project for five years, with technical assistance from Russian partners and financial backing from Cosmos Studios. The project's leaders claims that Cosmos 1 is "the world's first solar-sail spacecraft" — sparking a debate over just how much of a first it represents. In an odd way, the fact that a debate has arisen over Cosmos 1's future place in history serves as a measure of how realistic the technology has become.

"I am not certain why the Planetary Society makes the claim," Keith Cowing, editor of the independent NASA Watch Web site, said last week. He pointed out that there have been previous solar-sail tests, including a Japanese mission last August during which a small rocket lofted a test payload on a suborbital trajectory and briefly unfolded a solar-sail structure.

Cowing's complaint drew a quick response from Louis Friedman, the Planetary Society's executive director as well as Cosmos 1's program director. He said the Japanese team "did not either build a solar sailing spacecraft or attempt to fly under sunlight pressure. Those latter two goals are unique (thus far) to The Planetary Society project.”

Friedman acknowledged that there have been previous flight experiments with thin-film deployment, but he said none of them actually tried to use sunlight to steer through space.

Indeed, the Russians have twice deployed "sails" from spacecraft, back in the 1990s. One was fully unfurled and reflected sunlight down from the evening skies over central Europe, where it was visible as a bright, fast-moving star. A second deployment failed when Russian Mission Control forgot to retract an antenna out of the way.

Both those efforts were aimed at testing "space reflectors" for ground illumination, and not for space propulsion.

In 2001, Friedman’s group staged a space deployment test flight analogous to last year's Japanese mission. The flight plan called for a quick up-and-down hop with a brief unfurling to test the mechanism. The payload was fired on cue from the submarine, but Russian engineers failed to build a workable deployment system — and the sail, still packed in its canister, never detached from the rocket in flight. The insurance payoff from that failure helped fund this week's flight.

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