Setting Sail in the Sun
By rigging large pieces of cloth atop boats, early explorers harnessed the wind to voyage across oceans. Now, modern space explorers want to use sails to send spacecraft to the far reaches of the solar system and beyond. These sails will be made of large, ultra-thin gossamer plastic sheets that, instead of wind, will be propelled using sunlight.
Light particles, or photons, exert a small pressure when they bounce off a reflective surface. Ever since James Maxwell proved that light exerts pressure in the 1860s, space exploration visionaries have talked about solar sailing. Exciting new developments this year are making their vision a reality.
In May, the Japanese Space Exploration Agency successfully launched IKAROS, the first-ever spacecraft to use solar sail for propulsion in space. The spacecraft finished unfurling its sail in June and is now accelerating toward Venus under solar pressure. Two more solar sail launches are on the horizon: NASA plans to launch a sail this fall, while the Planetary Society is aiming for a launch in 2011.