Pekka Janhumen, a researcher at the Finnish Meteorological Institute, and a consortium of European scientists have developed an electric solar wind sail that could fundamentally change space travel as we know it. The sail relies on the solar wind, a continuous plasma stream that emanates from the sun, to act as its principal thrust source by applying continuous pressure to its metallic tethers. A large, solar-powered electron gun keeps the tethers positively charged.
According to Janhumen, the electric sail could make possible the mining of resources from asteroids -- to produce rocket fuel in orbit, for example (but don't hold your breath). It could even be incorporated into large, orbiting solar power satellites that would transmit a continuous stream of solar energy by microwaves to stations on Earth (doesn't that sound a bit like JAXA's SSPS project?) .
Lest you think this is all a big joke, the first international "electric sail meeting" will be held in Noordwijk, The Netherlands on May 19, 2008 at the European Space Agency's (ESA) European Space Research and Technology Center (ESTEC).