Interstellar travel is a mainstay of science fiction, but the distances involved are prohibitively large. The closest star system to Earth, Alpha Centauri, is 4.2 light-years away—an almost incomprehensible 26,000,000,000,000 miles away. Using today’s propulsion technology, it would take us tens of thousands of years to travel that far. If humans are serious about wanting to explore other star or planetary systems, new kinds of propulsion that push spaceships close to the speed of light must be developed.

People have been dreaming of ways to do this for a very long time. One of the earliest references to faster-than-light travel in fiction appeared in 1928 in The Skylark of Space by E.E. “Doc” Smith. Since then, warp drives, wormholes, hyperspace and other such notions have fueled the imagination of entire generations. But can science build the craft that could take us to the stars in less than a human lifetime?

The answer is “maybe.” Physicists, mathematicians and engineers have published wild designs, including hypothetical space ramjets and black-hole-powered spacecraft. None of them are close to being built, but some of the more feasible ideas are already in space, or could be soon. Photon-powered sails went to space last year, and a type of high-thrust ion engine is scheduled to launch in 2014.

Here, we round up the proposals that might someday take us to the stars.