Editing Interplanetary spaceflight (section)

===Solar sails===
{{main|Solar sail}}
[[File:Solarsail msfc.jpg|left|thumb|NASA illustration of a solar-sail propelled spacecraft]]
Solar sails rely on the fact that light reflected from a surface exerts pressure on the surface. The [[radiation pressure]] is small and decreases by the square of the distance from the Sun, but unlike rockets, solar sails require no fuel. Although the thrust is small, it continues as long as the Sun shines and the sail is deployed.<ref>{{cite web | url=http://www.ugcs.caltech.edu/~diedrich/cgi/search.cgi?solar+sail | title=Abstracts of NASA articles on solar sails | url-status=dead | archive-url=https://web.archive.org/web/20080311000832/http://www.ugcs.caltech.edu/~diedrich/cgi/search.cgi?solar+sail | archive-date=2008-03-11 }}</ref>

The original concept relied only on radiation from the Sun – for example in [[Arthur C. Clarke]]'s 1965 story "[[Sunjammer]]". More recent light sail designs propose to boost the thrust by aiming ground-based [[laser]]s or [[maser]]s at the sail. Ground-based [[laser]]s or [[maser]]s can also help a light-sail spacecraft to ''decelerate'': the sail splits into an outer and inner section, the outer section is pushed forward and its shape is changed mechanically to focus reflected radiation on the inner portion, and the radiation focused on the inner section acts as a brake.

Although most articles about light sails focus on [[interstellar travel]], there have been several proposals for their use within the Solar System.

Currently, the only spacecraft to use a solar sail as the main method of propulsion is [[IKAROS]] which was launched by [[JAXA]] on May 21, 2010. It has since been successfully deployed, and shown to be producing acceleration as expected.  Many ordinary spacecraft and satellites also use solar collectors, temperature-control panels and Sun shades as light sails, to make minor corrections to their attitude and orbit without using fuel. A few have even had small purpose-built solar sails for this use (for example Eurostar E3000 [[geostationary]] communications satellites built by [[EADS Astrium]]).