Of Lightsails, Ramjets, and Fusion Runways

  • Paul Gilster


Terminology is always treacherous—one field’s jargon contradicts another’s unstated assumptions—but we must now make a distinction between solar sails and lightsails. The solar sail is pushed by photons from the Sun, while the lightsail is usually much larger and driven by man-made light, microwaves, or perhaps some kind of particle beam. This distinction isn’t exclusive, though, because even before we’ve launched the first free-flying solar sail, the mission planners for The Planetary Society’s Cosmos i have plans to demonstrate both photon and microwave propulsion on the same sail. Nor is size an absolute criterion, for solar sails can be vast in their own right. The early solar sail designs NASA studied for the Halley’s Comet rendezvous reached 640,000 square meters, fully a half-mile to the side.


Solar Wind Particle Beam Diamond Film Solar Sail Fresnel Lens 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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    “while centrifugal force holds the spinning, web-slung mirror taut and flat in the void.”— Eric K. Drexler, “The Canvas of the Night,” in Arthur C. Clarke, ed. Project Solar Sail (New York: Roc, 1990), 44–45.Google Scholar
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© Springer Science+Business Media New York 2004

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  • Paul Gilster

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