Light Sails and Laser Beams

Planetary Society

The history of solar sailing is basically the story of Charlie Brown and the football. It remains a great concept, a technology that could theoretically take us to the stars. But for all their promise, actual solar sail missions tend to end in failure, usually before they even begin, and often through no fault of their own.

Notable disappointments include the Planetary Society's Cosmos 1, which in 2005 got dumped into the ocean by an errant Volna rocket immediately after launch. Ditto NASA's Nanosail-D in 2008, except that this time it was a Falcon 1 rocket that failed.

Now, thanks to a $1 million anonymous donation, the Planetary Society is ready to try again with a spacecraft called LightSail, the first of which is due to reach orbit late next year (assuming the Society can raise the rest of the project's estimated cost of "under $2 million").

I wish them the best of luck. And I hope when they do fly, they'll include a nifty experiment that was planned for Cosmos 1, but never got the chance to be tested. Back then physicist Gregory Benford, who's probably better known as a science fiction writer, along with his brother James, president of Microwave Sciences near San Francisco, proposed hitting Cosmos-1 with a ground-based microwave beam to see if it could impart a modicum of acceleration.

Microwave or laser beam propulsion has been proposed as a way to push sail-equipped starships to fantastic speeds. We're a long way from building such vehicles, but the Benfords' experiment was at least a way to get started by testing the basic physics.

Louis Friedman of the Planetary Society, arguably the world's foremost champion of solar sailing and director of the LightSail program, says it's too early to say whether a beaming experiment will be included. "I would like to do it, but we have not addressed it yet," he writes by email.

Let's hope it works out. And best of luck, too, to the Japanese space agency JAXA, which is planning its own solar sail mission in 2010, called IKAROS.

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