Planetary Society Resurrects Plan to Launch Solar Sail

The quest to fly the first solar sail spacecraft is back on, with scientists once again hoping they can harness the energy of light to power a ship through space despite earlier failures.

The Planetary Society recently announced plans to build a solar sail craft by the end of 2010, thanks to a $1 million anonymous donation made to the Pasadena, Calif.-based organization to reignite the project.

"This was an enabling donation, there's no doubt," said Bruce Betts, Planetary Society director of projects. "We've been continuing to think and do studies, but we didn?t have the funding in place to embark on this project. Now we do."

The Planetary Society aims to launch a spacecraft called LightSail-1 to an orbit of about 500 miles (800 km) above Earth to demonstrate that energy from sunlight alone can propel a ship through space. The push of photons against the spacecraft's mirror-bright sails should provide enough energy to keep the craft's orbit from decaying, scientists think.

The recent donation reinvigorates the Society's solar sail hopes, which were dashed in 2005 when the Russian Volna rocket carrying its first solar sail prototype, Cosmos 1, failed to reach orbit.

Betts said the donation provided about half the necessary funds to build LightSail-1, but the project would take about $2 million total. The Planetary Society is soliciting contributions from other supporters to make up the difference.

The 2010 goal does not leave much time to achieve a launch, but the Society says it's already made some progress toward designing and building the new craft. It plans to capitalize on knowledge gained during the Cosmos 1 project to accelerate plans.

"It is a very short turnaround with a tight schedule," Betts conceded. "We definitely have a head start because we've been thinking about this for a very long time."

Even so, the design of LightSail-1 is significantly different from the previous attempt, and is intended to be much smaller and easier to launch. Engineers plan to use Cubesat technology, which helps miniaturize satellite components to save launch weight and volume. One Cubesat is a box about the size of a 1-liter container and 10 centimeters on a side.

LightSail-1 will use one Cubesat box for its central electronics and control module, and two additional ones to house the solar sail, which will be made from 344 square feet (32 square meters) of mylar fabric.

LightSail-1 is intended to be followed in a few years by two sister craft on missions that will travel farther out in the solar system.

The solar sailing concept was proposed in the 1920s, but no one has yet succeeded in demonstrating that it works for a controlled flight in space. In addition to the Cosmos 1 disappointment, NASA's NanoSail-D attempt was lost in the third failed flight of SpaceX's Falcon 1 rocket in 2008.

Many are hoping this new vehicle will work, including Ann Druyan, artist and widow of famed astronomer Carl Sagan, a Planetary Society co-founder. Druyan is serving as Chief Advisor to the current project.

"Carl and I once wrote, 'We have lingered too long on the shores of the cosmic ocean. It?s time to set sail for the stars,'" she said. "We are celebrating his birthday by announcing the maiden voyages of a fleet of ships conceived to fulfill that mythic imperative. I think I know what this would have meant to him."

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