Yesterday, a satellite smaller than a shoebox unfurled a solar sail making it the first spacecraft to orbit the Earth powered by sunlight. LightSail2 is a project of the Planetary Society, a fantastic nonprofit organization co-founded by astronomer and science educator Carl Sagan. From the New York Times:
For centuries, it was only a dream: traveling through space propelled by the sun's photons. It was first imagined in the 1600s by Johannes Kepler, the German astronomer who described the laws of the planets' orbits. In 1964, Arthur C. Clarke moved it into the realm of science fiction in "Sunjammer," a short story. Carl Sagan, the cosmologist, believed it could be more than a speculative fantasy, and in the 1970s began promoting the building of solar sails for space exploration.
After 10 years of planning and over 40,000 private donations worth $7 million, that idea took flight on Tuesday, as LightSail 2, a spacecraft built for the Planetary Society, co-founded by Mr. Sagan, began what its creators hope will be a year of sailing around Earth.
"This is still one of the most feasible pathways to have real interstellar space travel in the future," said Sasha Sagan, a writer as well as the daughter of the astronomer.
If it succeeds in its mission, it will contribute to overcoming one of the greatest limitations on the outer bounds of space travel — that the power that steers spacecraft, usually hydrazine fuel, eventually runs out.