Red Giants and Solar Sails

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G.L. Matloff (2010), JBIS, 63, 74-77

Refcode: 2010.63.74
Keywords: Interstellar migration, solar sail, giant star

Our Sun will eventually leave the main sequence and expand in size and luminosity to become a giant star. For much of its ~108 year career as a giant, the Sun will reside on the horizontal branch of the Hertzsprung-Russell diagram, with a surface temperature of ~5000 K, a radius about 10x its present-day radius, and about 50x its current luminosity. A space-manufactured beryllium solar-photon sail could be used for emigration from the solar system during this solar phase. Space environmental effects limit the closest approach distance to the giant star to around 0.5 AU, assuming the quiet phase of the stellar activity cycle. Beryllium spectral reflectivity values are used to calculate a wavelength averaged sail spectral reflectivity. This parameter and a reasonable value of spacecraft areal mass thickness (8.87 x 10-5 kg/m2) are used to estimate the interstellar cruise velocity for a sail fully unfurled at a 0.5-1 AU perihelion from an initially parabolic orbit that is always oriented normal to the star. These will be 2-3x greater than those possible for the same craft launched from today's Sun.

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