Sunday, January 01, 2006

What is a Solar Sail?

NASA and The Planetary Society are about to launch spacecraft driven by solar sail technology, but what is a solar sail and how does it work?

The idea is far from new. Johannes Kepler first observed the natural phenomenon we call "solar wind" in the 17th century, when he noticed the wild curlings on a comet tail through his telescope.
Scientists now understand this is not wind, but a flow of various charged particles emanating from the sun, streaming outward from our Solar System. Solar Sails capture the photons from this "wind", actual particles of light which lack mass but can transfer momentum. And since they are traveling at the speed of light, harnessing their momentum provides an incredible speed boost.

When harnessing the light of our Sun a spacecraft could travel about 10 times faster than the orbital speed of the shuttle, and it can use the same force to move around the Solar System, without any other fuel, and return to Earth upon completion of a mission.
Using a different photon source--like a laser or magnetic beam transmitter--could result in speeds of up to 18,000 miles per second, or one-tenth light speed.

Different materials have been tested as sails, along with different types of deployment methods. Most spacecraft being designed right now are to be launched by conventional rocket and unfurl sails in space, but much effort is being made to design a revolutionary propulsion system that could be launched from the ground, perhaps using a microwave beam system.

With all the current testing and development it seems very likely mankind will once again experience an Age of Sail...

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