The propulsion mechanism for the spacecraft is photons striking the structure of the ship, which is a very large aluminized Mylar surface area made up of four triangles forming a giant kite-like body. When photons strike the sail-like surfaces they will transmit momentum to the ship, and propel it. Because the spacecraft is powered by sunlight, it will require no onboard fuel.
This was designed by the Planetary Society. Japan plans a launch of a similar spacecraft in 2010.
At that rate, we would reach Jupiter in about 162 days. It would only take us 28,300 years to reach Proxima Centauri. We also need Solar-powered Wormholes!
Those who have read the book Planet of the Apes will find the design familiar.
There’s one issue with such a design: It’s a one-way trip. You can go AWAY from the sun, not towards it. Great for the trip out, uses no fuel. But if you want to come back, you need fuel to get back… This would be great for unmanned probes and like, assuming it can later detach the sails when they become more of a hindrance than a help.