Livescience is reporting an electrically charged 'solar sail' could be ready for testing in as few as three years. A team from Finland believes it has made a breakthrough with the concept, which traditionally has involved a lightweight 'sail' which would receive thrust form the Sun's solar winds of charged particles. The Finnish team's concept includes an electron gun (charged from solar panels) which would create a self sustaining flow of particles to generate thrust in the sail.
"Two solar panels would power an electron gun that keeps the spacecraft tethers charged, creating propulsion from the similarly charged solar wind pushing against the sail. Researchers are looking into aluminum or copper alloy wires for the tethers. The maiden mission would also test a concept to increase the thrust from the solar wind, called radio frequency electron heating. "turbo" charge. The subscale mission would also test a "turbo" charge for the solar sail. Radio-frequency waves could excite the solar wind particles through electron heating, which might boost the thrust created."
The solar sail concept has proven to be difficult to test, with two Russian attempts failing in 1999 & 2001, and a joint US-Russian mission failing 2005 due to a launch failure. A small scale a Japanese space test in 2004 proved successful, however. The payoff, of course, would be for the technology to allow much cheaper deep space exploration missions and lowering the cost of transport within the solar system. A fleet of such vehicles could retrieve resources from asteroids allowing the production of rocket fuel in either low Earth orbit or a planned Lunar base.