Editing Solar sail (section)

{{about|spacecraft propulsion by radiation pressure from sunlight|propulsion by means of the solar wind| electric sail |and| magnetic sail|The Planetary Society spacecraft|LightSail}}
{{redirect-distinguish|laser sail|Laser (dinghy)}}
{{short description|Space propulsion method using Sun radiation}}

[[File:IKAROS solar sail.jpg|thumb|[[IKAROS]], the first space-probe with a solar sail in flight (artist's depiction), featuring a typical square sail configuration of almost 200 m<sup>2</sup>]]

'''Solar sails''' (also known as '''lightsails''', '''light sails''', and '''[[photon]] sails''') are a method of [[spacecraft propulsion]] using [[radiation pressure]] exerted by [[sunlight]] on large surfaces. A number of spaceflight missions to test solar propulsion and navigation have been proposed since the 1980s. The two spacecraft to successfully use the technology for propulsion were [[IKAROS]], launched in 2010, and [[LightSail-2]], launched in 2019.<ref>{{cite web|url=https://www.space.com/25800-ikaros-solar-sail.html|title=Ikaros: First Successful Solar Sail |last=Howell|first=Elizabeth |date=7 May 2014|access-date=13 January 2025|website=space.com}}</ref>

A useful analogy to solar sailing may be a [[sailboat|sailing boat]]; the light exerting a [[force]] on the large surface is akin to a sail being blown by the wind. High-energy [[Laser propulsion|laser beams]] could be used as an alternative light source to exert much greater force than would be possible using sunlight, a concept known as beam sailing. Solar sail craft offer the possibility of low-cost operations combined with high speeds (relative to [[chemical rocket]]s) and long operating lifetimes. Since they have few moving parts and use no propellant, they can potentially be used numerous times for the delivery of payloads.

Solar sails use a phenomenon that has a proven, measured effect on [[astrodynamics]]. Solar pressure affects all spacecraft, whether in [[Interplanetary spaceflight|interplanetary space]] or in orbit around a planet or small body. A typical spacecraft going to Mars, for example, will be displaced thousands of kilometers by solar pressure, so the effects must be accounted for in trajectory planning, which has been done since the time of the earliest interplanetary spacecraft of the 1960s. Solar pressure also affects the [[Spacecraft attitude|orientation]] of a spacecraft, a factor that must be included in [[spacecraft design]].<ref>Georgevic, R. M. (1973) "The Solar Radiation Pressure Forces and Torques Model", ''The Journal of the Astronautical Sciences'', Vol. 27, No. 1, Jan–Feb. First known publication describing how solar radiation pressure creates forces and torques that affect spacecraft.</ref>

The total force exerted on an {{convert|800 by 800|m}} solar sail, for example, is about {{cvt|5|N|lbf|lk=on}} at Earth's distance from the Sun,<ref name="Wright ">{{citation| author = Jerome Wright| year = 1992| title = Space Sailing| publisher = Gordon and Breach Science Publishers}}</ref> making it a low-thrust [[spacecraft propulsion|propulsion]] system, similar to spacecraft propelled by [[Electrically powered spacecraft propulsion|electric engines]], but as it uses no propellant, that force is exerted almost constantly and the collective effect over time is great enough to be considered a potential manner of propelling spacecraft.