Speed Demonoid

Speed Demonoid
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Pattern type	Spaceship
Number of cells	1021124
Bounding box	872867 × 1839173
Direction	Diagonal
Period	17833792
Mod	8916896
Speed	1746011c/8916896 | 3492022c/17833792
Heat	Unknown
Discovered by	Pavel Grankovskiy Dave Greene
Year of discovery	2020
Rules Outer-totalistic rules B3/S23 only # of rules 20 = 1
Glider synthesis Fewest gliders 31822† †Can be constructed with 15 gliders using the reverse caber tosser universal constructor.
Pattern files Macrocell speeddemonoid.mc

Speed Demonoid is a self-constructing adjustable spaceship constructed by Pavel Grankovskiy with the help of Dave Greene and completed on September 18, 2020.

Due to a limitation in the design, this initial version of the Speed Demonoid design has an upper limit speed of 2c/9 diagonally, rather than the theoretical maximum of c/4. A redesign of the circuitry was required to correct this limitation.

Below the 2c/9 upper limit, the Speed Demonoid can be adjusted to move at any rational diagonal speed, by moving the trailing TRIGGER1 and TRIGGER2 gliders to the correct locations.

On September 26, a new Speed Demonoid variant was constructed to be smoother to simulate in HashLife, and to improve on the 2c/9 upper speed limit mentioned above. This new Speed Demonoid can be trivially adjusted to move at any rational diagonal speed slower than c/4. A Golly 3.x/4.0 script is available that will set up a glider recipe to construct a Speed Demonoid for any chosen speed, within certain practical size limitations.

The Speed Demonoid was voted Pattern of the Year for 2020 on the ConwayLife.com forums, tied with Bandersnatch.

Details

The Speed Demonoid achieves its speed by building a crab spaceship and turning it into a double wickstretcher. The two wicks are ignited at different times specified by the locations of the TRIGGER1 and TRIGGER2 gliders. With the help of "guard gliders" traveling near the crab spaceship, when the burning wicks reach the crab, they produce target objects at the right location to allow the next copy of the construction-arm and reflector circuitry to be constructed. The TRIGGER1 guard glider allows the fuse to stop burning while the crab spaceship continues onward, and continues stretching the second wick. By contrast, the TRIGGER2 guard glider enables the destruction and eventual complete cleanup of the crab spaceship.

Both TRIGGER1 and TRIGGER2 are precisely synchronized so that they exactly keep up with the recipe gliders, despite being on different lanes and using one-time turners to move instead of conventional reflectors. Besides igniting the second crabstretcher wick, the TRIGGER2 signal also triggers self-destruct circuitry associated with the Scorbie Splitter and Snark.

The bait still lifes in the self-destruct circuitry were found by Simon Ekström's GoL-destroy search program. A similar design was used in the 10hd and 0hd Demonoids, but has been seen very rarely since then. Other recent Demonoids have used "destruction arms" similar to the one in the original Gemini spaceship, which incrementally shoot down parent constructor circuitry once it is no longer in use.