For decades, scientists and science fiction writers alike have floated the idea of using solar sails to propel spacecraft across vast distances. One of those advocates was the late astronomer Carl Sagan. In honor of Sagan's 75th birthday, the Planetary Society, which Sagan co-founded in 1980, announced a series of forthcoming solar sail experiments. Funded by a wealthy, and anonymous, donor, the group will launch their LightSail system three times over the next few years. The first two missions will be in Earth orbit, and the target of the third is about 900,000 miles away, in a popular "hang out" zone for traditional satellites collecting scientific data. From the New York Times:
The (actual sail) is made of aluminized Mylar about one-quarter the thickness of a trash bag. The body of the spacecraft will consist of three miniature satellites known as CubeSats, four inches on a side, which were first developed by students at Stanford and now can be bought on the Web, among other places. One of the cubes will hold electronics and the other two will carry folded-up sails, (Planetary Society co-founder Louis) Friedman said.
Assembled like blocks, the whole thing weighs less than five kilograms, or about 11 pounds. "The hardware is the smallest part," Dr. Friedman said. "You can't spend a lot on a five-kilogram system."
The LightSail missions will be spread about a year apart, starting around the end of 2010, with the exact timing depending on what rockets are available. The idea, Dr. Friedman said, is to piggyback on the launching of a regular satellite. Various American and Russian rockets are all possibilities for a ride, he said.
Dr. Friedman said the first flight, LightSail-1, would be a success if the sail could be controlled for even a small part of an orbit and it showed any sign of being accelerated by sunlight.