Missing the point - solar sails use solar wind (Score 1)

I've been working on a NASA solar sails project, and our solar sails (still in the design and simulation phase, to be sure) have nothing to do with reflecting light, as this paper suggests.

The sun gives off not only light, but also spits off extremely fast moving plasma, called the solar wind. The wind, though not very dense, typically moves as a speed of several hundred miles per second. That's around a million miles an hour. (You can check current contitions here). The idea is to use the momentum from the solar wind, which is mostly ionized hydrogen, not the light from the sun, to propel the spacecraft. (There are some very good images on the website.)

The most interesting approach was suggested by Robert Winglee of the University of Washington. He suggest using a giant magnetosphere (essentially a magnetic field stretched out by a plasma) as a sail. The magnetophere deflects the solar wind, transferring momentum into the spacecraft. There is also another advantage - the magnetosphere works as a shield to keep the wind from damaging the spacecraft itself.

The "sail" is made from an ionized gas trapped in a magnetic field. It's easy to let the sail out and take it in, and if the sail ever "breaks," you can just make a new one using more plasma.

So, despite what the paper has to say, solar sail research is alive and well. It's just that the most promising designs work a little differently than the author thought.