Speed Demonoid
Speed Demonoid  
View static image  
Pattern type  Spaceship  

Number of cells  1021124  
Bounding box  872867×1839173  
Direction  Diagonal  
Period  17833792  
Mod  8916896  
Speed  1746011c/8916896  
Speed (unsimplified)  3492022c/17833792  
Heat  Unknown  
Discovered by  Pavel Grankovskiy Dave Greene  
Year of discovery  2020  
 

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Speed Demonoid is a selfconstructing adjustable spaceship constructed by Pavel Grankovskiy with the help of Dave Greene and completed on September 18, 2020.^{[1]}
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 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.^{[2]} Speed Demonoid v2 can be trivially adjusted to move at any speed that is a rational fraction lower 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.^{[3]}
On the Conwaylife.com forums, the Speed Demonoid was voted Pattern of the Year 2020, tying for the top spot with the Bandersnatch.^{[4]}
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 constructionarm and reflector circuitry to be constructed.
Both TRIGGER1 and TRIGGER2 are precisely synchronized so that they exactly keep up with the recipe gliders, despite being on different lanes and using onetime turners to move instead of conventional reflectors. Besides igniting the second crabstretcher wick, the TRIGGER2 signal also triggers selfdestruct circuitry associated with the Scorbie Splitter and Snark.
The bait still lifes in the selfdestruct circuitry were found by Simon Ekström's GoLdestroy 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.
References
 ↑ Pavel Grankovskiy (September 18, 2020). Re: Speed Demonoid (completed) (discussion thread) at the ConwayLife.com forums
 ↑ Pavel Grankovskiy (September 26, 2020). Re: Speed Demonoid (discussion thread) at the ConwayLife.com forums
 ↑ Dave Greene (November 1, 2020). Re: Speed Demonoid (discussion thread) at the ConwayLife.com forums
 ↑ MathAndCode (March 18, 2021). Re: Speed Demonoid (discussion thread) at the ConwayLife.com forums
 Patterns
 Periodic objects with minimum population between 1,000,000 and 9,999,999
 Patterns with between 1,000,000 and 9,999,999 cells
 Patterns found by Pavel Grankovskiy
 Patterns found by Dave Greene
 Patterns found in 2020
 Outertotalistically endemic patterns
 Spaceships
 Spaceships with period 17833792
 Diagonal spaceships
 Spaceships with speed 1746011c/8916896
 Spaceships with unsimplified speed 3492022c/17833792
 Spaceships with mod 8916896
 Glide symmetric spaceships
 Nonmonotonic spaceships