Photo courtesy NASA
Solar sails use the sun's energy to propel spacecraft across the cosmos.  See more pictures of solar sails.
Hundreds of space missions have been launched since the last lunar mission, including several deep space probes that have been sent to the edges of our solar system. However, our journeys to space have been limited by the power of chemical rocket engines and the amount of rocket fuel that a spacecraft can carry. Today, the weight of a space shuttle at launch is approximately 95 percent fuel. What could we accomplish if we could reduce our need for so much fuel and the tanks that hold it?

International space agencies and some private corporations have proposed many methods of transportation that would allow us to go farther, but a manned space mission has yet to go beyond the moon. The most realistic of these space transportation options calls for the elimination of both rocket fuel and rocket engines -- replacing them with sails. Yes, that's right, sails.

NASA is one of the organizations that has been studying this amazing technology called solar sails that will use the sun's power to send us into deep space. In this article, HowStuffWorks shows you how the idea of solar sailing developed, where NASA and others are in testing this technology and how far and fast solar sails might take us in the universe.