For ships it's similar between the two; sub-light speeds are handled by engines that shoves stuff out the back to propel the ship forward and light speeds handl

For ships it's similar between the two; sub-light speeds are handled by engines that shoves stuff out the back to propel the ship forward and light speeds handled by magical technology that plays with space/time. From conversations in the movies I'm led to believe the Death Stars followed the same premise. For that amount of mass it has to be impressive technology though.