A superstring is an infinite orthogonal row of cells stabilized on one side so that it moves at the speed of light, often leaving debris behind. The first examples were found in 1971 by Edward Fitzgerald and Robert Wainwright. Superstrings were studied extensively by Peter Rott during between 1992 and 1994, and he found examples with many different periods. In August 1998, Stephen Silver proved that odd-period superstrings are impossible.
Sometimes a finite section of a superstring can be made to run between two tracks, known as waveguide. This gives a fuse that can be made as wide as desired. The first example was found by Tony Smithurst and uses tubs. Shortly after seeing this example, in March 1997 Peter Rott found another superstring track consisting of boats. At present these are the only two waveguides known. Both are destroyed by the superstring as it moves along -- it would be interesting to find one that remains intact.