|
Dusty Plasma Solar Sails by
Robert B. Sheldon
15 August 2003 Sunlight, according to Einstein, carries momentum, and should therefore provide thrust to a sail that reflects it. Naturally the thrust is small, and requires a lightweight material to generate any acceleration. In the search for thinner and lighter sail materials, there have been repeated efforts at developing colloidal materials such as aerogels that have some of the lowest densities of any rigid materials because of their open, 3-D structure. We present a colloidal sail made of material with lower density than smoke--a dusty plasma. The charged dust grains are held together electrostatically by a plasma "glue" whose properties are only now being studied. We have traded a mechanical sail design, however, for a plasma confinement design. Since the 1950's, plasma confinement has usually been accomplished with external magnetic fields generated by heavy magnets. Recently Robert Winglee at UWash has suggested that the plasma can be induced to carry current and provide some of its own confinement, sort of bootstrap approach, that may allow a spacecraft to create a 30km magnetic bubble in the solar wind. Such a large bubble, he argues, could extract momentum directly from the solar wind rather than the photon flux, despite the fact that the photons carry 1000 times more momentum than particles. If such a large bubble were seeded with dust, we reasoned, it might provide the sort of performance solar sail enthusiasts have dreamed about. We discuss the dusty plasma confinement problem and try to get some ballpark estimates of the performance expected.
Questions? - Email the author Questions? - Email the author |