Space sunshade

The possibility that global warming will trigger abrupt climate change is something people might not want to think about. But University of Arizona astronomer Roger Angel thinks about it. Angel is now publishing a first detailed, scholarly paper, "Feasibility of cooling the Earth with a cloud of small spacecraft near L1," in the Proceedings of the National Academy of Sciences. The plan would be to launch a constellation of trillions of small free-flying spacecraft a million miles above Earth into an orbit aligned with the sun, called the L-1 orbit. The spacecraft would form a long, cylindrical cloud with a diameter about half that of Earth, and about 10 times longer. About 10 percent of the sunlight passing through the 60,000-mile length of the cloud, pointing lengthwise between the Earth and the sun, would be diverted away from our planet. The effect would be to uniformly reduce sunlight by about 2 percent over the entire planet, enough to balance the heating of a doubling of atmospheric carbon dioxide in Earth's atmosphere.It would use "MEMS" technology mirrors as tiny sails that tilt to hold the flyers position in the orbiting constellation. The flyer's transparency and steering mechanism prevent it from being blown away by radiation pressure. Radiation pressure is the pressure from the sun's light itself. The sunshade could be deployed by a total 20 electromagnetic launchers launching a stack of flyers every 5 minutes for 10 years. The electromagnetic launchers would ideally run on hydroelectric power, but even in the worst-case environmental scenario with coal-generated electricity, each ton of carbon used to make electricity would mitigate the effect of 1000 tons of atmospheric carbon.

Source: eurekalert.orgAdded: 26 February 2007