The Planetary Society has teamed up with an international team of scientists and engineers to build and fly Cosmos 1, the very first solar sail. This is the first space mission of a public interest organization and it is being done without government funding. The Babakin Space Center in Russia is developing the spacecraft, and the Makeev Rocket Design Bureau has built the Volna launch vehicle. The force is controlled by the angle of the sail with respect to the Sun, adding to or subtracting from the orbital velocity. The reaction here causes a change in momentum, pushing the sail and giving the spacecraft thrust.
Light pressure is the force transferred by sunlight onto the sails.
The solar wind is made up of ionized particles ejected by the Sun. These particles move much slower than light. A solar sail does not stop or reflect them, although they also may impart some of their momentum to the solar sail. However, the force from the solar wind is less than one percent of that from light pressure. Solar sails can be used to boost or decrease the orbits of spacecraft, travel between the planets within our solar system, and someday take us to worlds around other stars.