It begins with the period-20 spaceship that consists of a p20 puffer stabilized by a third lwss; this is the basis for the standard p20 forward and backward rakes. 1994 December 7, Paul Callahan, “Program to search for collisions in Conway's Life (C code)”, in comp.theory.cell-automata (Usenet):
the simple "gliders" work perfectly fine, but the LWSS spaceship works great until the 15th generation when a singular pixel gets misplaced and the entire structure collapses. 1992 August 23, Albert Schnezer, “Programming Life in Tpascal”, in comp.theory.cell-automata (Usenet):
For example, two gliders can produce another glider, and three gliders can produce a LWSS or MWSS or a HWSS. 1992 August 13, David Bell, “Spaceships in Conway's Life (Part 1)”, in comp.theory.cell-automata (Usenet):