c/3 orthogonal is an orthogonal speed that is equivalent to one third of the speed of light.
Dean Hickerson discovered the first c/3 orthogonal spaceship, 25P3H1V0.2, in August 1989 using an automated search program for finding spaceships. This was the first spaceship that traveled at a speed other than the standard speeds of c/4 diagonal and c/2 orthogonal. These early searches also found the turtle, which provides a useful domino spark at its trailing edge, to which various tagalongs can be attached. Hickerson also found a grammar for constructing arbitrarily large c/3 spaceships.
After these early searches, no new c/3 technology was discovered until David Bell began searching in March 1992. These searches found various spaceships, including the dart and brain. Among these new spaceships was one that appeared to have a loosely attached component. By removing this component the spaceship did no self destruct, but rather became a period 9 spaceship, 117P9H3V0, which was the first c/3 spaceship with a period other than 3. Bell noticed that the back of this spaceship was essentially like that of the turtle, except that it was wider; based on this he performed searches for spaceships with similar back ends, producing the first period 15 spaceship, as well as a period 3 ship that produces a single cell spark at its back. This one-bit sparker was used by Stephen Silver to create the first period 6 c/3 spaceship in February 1999, which contained a period-6, glide-symmetric component supported at both the front and the back by period 3 components.
Many c/3 spaceships with interesting properties have been discovered. Of particular interest are edge sparkers, which can be used to perturb objects, especially gliders; period 3, however, tends to be too low to produce sparks far from the side of the spaceship. Despite this some c/3 ships with useful, but weak, edge sparks have been discovered. An important sparker used for perturbing objects is the wasp, which, although it does not have a true edge spark, can perturb objects such as gliders. Other important c/3 sparkers produce sparks at their trailing edges, and can often be used to perturb the standard spaceships. Another important spaceship property for making perturbations is the edge repairing ability of a small c/3 component. This property was first noticed by David Bell in his two smallest spaceships, the early edge repair spaceships. These spaceships can be used for various perturbations and can even eat a few objects, most notably, a block can be eaten by two edge repair spaceships. Of a less useful nature is the first non-monotonic c/3 spaceship, 233P3H1V0, discovered by Hartmut Holzwart in April 1994. In 1995 Holzwart also found several methods of constructing extensible c/3 greyships.
David Bell discovered the first c/3 orthogonal puffer in April 1996, which produced one blinker and two blocks every 54 generations. This puffer was found by searching for an incomplete spaceship with a long orthogonal line of live cells at its trailing edge, much like the c/2 line puffers. After finding reactions that did not destroy the line after a number of generations, he searched for arms that could support the front of the puffer. This method turned up several other puffers with different periods, as well as some higher period spaceships. Different period puffers could also be produced by placing debris behind already known puffers, and this was used to create the second puffer, a period 24 block puffer using Bell's earlier period 54 puffer. Several puffers of smaller periods have been found, including a period 9 blockstacker found by Jason Summers in December 2000 and a period 15 beehive puffer found by Paul Tooke in October 2002. Several puffer engines can also be formed by perturbing the output of unstable puffers which would otherwise destroy themselves.
The first c/3 orthogonal rake was based on a period 45 puffer and was found in May 1996. At the time of its construction the edge repair property of many c/3 spaceships was still unknown, and so the rake is bulky due to the heavy use of side sparkers to perturb and clean up reactions. Bell also used this period 45 puffer as the basis of the first period 45 rake. Several higher period rakes could be constructed which were also based on this puffer. The next rake technology to be found was based on a period 114 blinker puffer that provided a large spark that could be easily perturbed. Rakes of lower periods have also been constructed, the lowest being period 27. There is a construction method known for rakes of period 144 + 3N, but the method of construction is complex and these rakes would necessarily be quite large, and so no period 144 + 3N rake has yet been constructed.
There are currently no known c/3 orthogonal wickstretchers.
- David Bell's article, "Spaceships in Conway's Life (Part 3)"
- David Bell's article, "Speed c/3 Technology in Conway's Life"
- David Bell's archive of c/3 ships and puffers in Life
- Jason Summers "Game of Life Status page