Caterpillar

This article is about the 17c/45 crawler ship. For the adjustable spaceship, see Caterloopillar.

Caterpillar
View static image
Pattern type	Spaceship
Number of cells	11880063
Bounding box	4195 × 330721
Direction	Orthogonal
Period	270
Mod	270
Speed	17c/45
Speed (unsimplified)	102c/270
Heat	12114897.5
Discovered by	Gabriel Nivasch David Bell Jason Summers
Year of discovery	2004
Rules Outer-totalistic rules B3/S23 only # of rules 20 = 1
Pattern files Macrocell caterpillar.mc Zip archive caterpillar.zip
Identifiers Eppstein ID 1

The Caterpillar is the first 17c/45 orthogonal spaceship to be constructed, and is the first engineered spaceship based on a crawler with a 17c/45 reaction. It was the only known (barring minor modifications described below) 17c/45 orthogonal spaceship until the construction of the Speed Orthogonoid in 2022. It was created via a combination of manually-constructed parts put together by David Bell, Jason Summers and Gabriel Nivasch and a computer-aided construction coded by Nivasch. The Caterpillar's construction cost lots of time before completion on December 31, 2004.

Full view of caterpillar, 40 cells/pixel (click to view)

Click to load content Various zoom levels of caterpillar demonstrating its size

Caterpillar has 11,880,063 cells which can be reduced to 11,880,039 cells trivially. In terms of population, it was one of the largest patterns constructed in Game of Life up to that point; in terms of spaceships, it was perhaps the largest interesting spaceship until June 2023, which saw it surpassed by a currently unnamed (34,7)c/156 construction by Luka Okanishi of more than double the minimum population. The image of the caterpillar shown to the right is zoomed out to a scale of 32 cells per pixel, showing only the top 3% of it. Encoded as an RLE file, it is over 29MB in size.

The spaceship moves at the speed of 17c/45, the fourth fastest known orthogonal speed (excluding those achievable by some adjustable spaceships), which may initially seem counterintuitive due to its size. However, this speed is ingrained into the fundamental crawler reaction and is entirely unrelated to the length of the spaceship. After each of the longest-lived LWSSes is created near the back of the spaceship, it takes almost 2,688,000 ticks for that LWSS to travel to the front of the spaceship and be used in the helix burning reaction. However, every 270 ticks the entire configuration returns to its previous state, but shifted forward by 102 cells.

Since at least 2013, some effort has been invested into constructing a smaller 17c/45 spaceship based on the same reaction, which has yet to come to fruition.

See also

• Centipede
• HBK caterpillar

External links

• Caterpillar at the Life Lexicon
• "The 17c/45 Caterpillar spaceship". Gabriel Nivasch's Life page (January 2005). A "brief overview" of how the Caterpillar works (with illustrations and RLE files of parts), the pattern in RLE format, plus complete C++ & RLE sources for assembling it.
• "17c/45 "Caterpillar" spaceship". Jason Summer's Life page. A short summary of what the Caterpillar is with a few pictures, plus the pattern in RLE and .mc (macrocell) formats. Golly loads the macrocell file much more quickly than the RLE.
• Life (B3/S23) at David Eppstein's Glider Database
• New 17c/45 Spaceship: The Caterpillar at Game of Life News. Posted by Heinrich Koenig on December 31, 2004.