Japan's Institute of Space and Astronautical Science has successfully completed the first in-space deployment of an experimental solar sail. A solar sail uses the pressure of photons streaming from the sun to slowly accelerate, allowing for travel within the solar system without the need to carry on-board fuel. Although the acceleration is gradual, it's also relentless; a fully functional solar sail should be able to achieve speeds far greater than any current rocket system.
The experimental deployment did not test the ability of the sail material to catch sunlight for propulsion, only the ability to unfurl a large, thin, sheet in orbit. (None of the articles I found on this, including the project's English-language homepage at ISAS, indicated the area of the sails, only the thickness (0.0075 mm). If anyone finds a reference to the square meter area of the sails, drop me a note and I'll update this post.)
