Good ol' magnetic flux pinning could be the solution to holding modules of a spacecraft together without tethers or retrorockets. I was all psyched when I saw the article title, but though it starts off by talking about Luke Skywalker, the actual discussion centers around slightly more practical goals. Hey, one step at a time, right?

"The cold of space is enough to make the superconductors work--although for spacecraft inside the orbit of Mars, the superconductors will have to be shaded from direct sunlight in order to maintain their grip."