Interstellar solar sail effort

The first Starship Congress conference session was devoted to solar sails, leading off with Jim Benford’s keynote, followed by Les Johnson, who described current and near-term work. Right now the only propulsion method that will get us to interstellar velocities is the sail, and even then we’re talking no more than a couple of hundred kilometers per second.

Carbon fiber is ideal for sail work because when you put a microwave beam on the sail the material absorbs energy and begins to heat. A sail made of aluminum would begin to melt as you reach about 900 K, limiting possible accelerations, but carbon fiber has a low areal density (about 8 grams per square meter in the material the Benfords used) and a microwave reflectivity approaching 90 percent.

The material is actually a carbon-carbon microtruss, meaning a core of carbon fibers is fused to a textured outer surface. With carbon nanotubes woven into the material, this microtruss is capable of temperatures up to 3000 K, at which point it doesn’t melt but sublimes, going from solid to gas with no intervening liquid state.

http://nextbigfuture.com/2013/08/interstellar-solar-sail-effort.html