Wednesday, June 22, 2005
Solar Sail Sinks
Yesterday, the Planetary Society, a private group interested in fostering space travel, attempted to launch a $4 million solar sail called "Cosmos 1" from a Russian submarine. Unfortunately the booster rocket failed, and the satellite never had a chance. So what is a solar sail? The idea is to use sunlight as a "wind" to push a spaceship through the solar system. Light, like wind, exerts pressure and pushes on objects. For us on Earth, this pressure is much, much, much smaller than the forces of gravity and friction that control our movement, so we don't notice it. But in space, this pressure can push objects around. (Just note that this is not the solar wind that causes aurora here on Earth.) A solar sail is a very large piece of light-weight material (just like a boat sail) that has a large area for sunlight to push on. The sunlight will slowly accelerate the spacecraft, allowing it to move around the solar system without the need for a rocket engine. Changes in the spacecraft's speed are slow, but they add up over time. And spacecraft can be made lightweight, since most of the weight of any spacecraft is its engine and fuel. This launch was an experiment to see if a solar sail can really work, and it is a shame that the sail never even had a chance to unfurl. I suspect that the Planetary Society will try again before too much longer to prove this fanciful technology!