Yesterday, NASA made another breakthrough in the future of spaceflight when one of its satellites successfully deployed a solar sail. The hundred foot sail works by catching solar energy, and using it to move. Since this system is fueled by the Sun itself, instead of by traditional fuel, it can theoretically last forever without costing taxpayers billions of dollars in rocket fuel. This is the first time that a solar sail has been deployed in a low earth orbit, but the technology has been developing for decades.
The sail is built primarily out of Mylar, which is the same basic compound found in common plastic wrap. These sails use the electro-magnetic radiation in light to push them forward. Some scientists speculate that the force of the light from our own sun may be enough to push solar powered spacecraft into neighboring solar systems. Up until now, interstellar flight has been looked at as impossible, both because of the enormous amount of fuel that traditional spacecraft would have to carry, and because of the sheer distance. The nearest star, Proxima Centauri, is 4.2 light years from the Earth. This means that it would take the Voyager spacecraft, which travel at 35,000 miles an hour, 40,000 years to reach this star. Scientists are now speculating that solar-sail powered vehicles might be fast enough to complete this journey in a much more reasonable time frame, although the exact numbers are still pure speculation.