Lightweight spaceship
Lightweight spaceship  
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Pattern type  Spaceship  

Family  XWSS  
Number of cells  9  
Bounding box  5 × 4  
Frequency class  11.2  
Direction  Orthogonal  
Period  4  
Mod  2  
Speed  c/2  
Speed (unsimplified)  2c/4  
Heat  11  
Discovered by  John Conway  
Year of discovery  1970  
 
 
 

The lightweight spaceship (commonly abbreviated to LWSS) or (rarely) small fish^{[1]} is the smallest orthogonal spaceship, and the second most common spaceship after the glider. It moves at speed c/2 and has period 4 (and is therefore often referred to as 2c/4). It was found by John Conway in 1970.
Tagalong
In April 1992, David Bell found a tagalong for two lightweight spaceships (or two middleweight spaceships or two heavyweight spaceships). It can be extended indefinitely by attaching it to the back of itself. Interestingly, a hivenudger with symmetric rear (that is, both rear spaceships being of same "weight") can pull this tagalong.
Tagalong for two lightweight spaceships (click above to open LifeViewer) RLE: here Plaintext: here 
Construction
Four 3G syntheses for the LWSS (click above to open LifeViewer) 
A number of different ways to construct a LWSS can be found in Mark Niemiec's glider synthesis database;^{[2]} above are shown threeglider syntheses.
A threeobject oneglider seed for the lightweight spaceship, consisting of two blocks and a beehive, is used in the pattern Patterns/Life/Breeders/switchenginebreederMR.rle included in Golly's pattern collection. The seed constellation itself can be constructed with four gliders,^{[3]} leading to a way of constructing the LWSS using 5 gliders.
A different oneglider seed that fits inside a 12 × 12 square can be found in the octohash database;^{[4]} it is a constellation of a blinker and an eater 1, itself constructible with four gliders.^{[5]} There are 60 matches in the octo3obj database which are clean oneglider seeds for the LWSS.^{[6]}


Occurrence
 See also: List of common spaceships
Random soups investigated by Achim Flammenkamp emitted one LWSS for approximately every 615 gliders.^{[7]} The LWSS is also the eighteenth most common object on Adam P. Goucher's Catagolue.^{[8]}
There are 731 results in the octohash database,^{[note 1]} 6563 results in the octo3obj database,^{[note 2]} and 1009 results in the octo3g database^{[note 3]} with at least one escaping LWSS.
See also
 Fake xWSS
 Middleweight spaceship, Heavyweight spaceship, LWSS on MWSS 1, LWSS on HWSS 1
 Lightweight emulator
 Toaster
 Infinite LWSS hotel
 GtoLWSS
Notes
 ↑ There are two collisions, each with two escaping LWSSes. One collision (headerless RLE 8b2o$9bo$b2o6bobo$obo2b2o3b2o$2o2b2o$6bo!) has final population 158. The other collision (b2o$obo$2o6b2o$9bo$9bobo$10b2o2$12bo$11b2o$11bobo!) has final population alternating between 367 and 373.
 ↑ There are 28 results where two lightweight spaceships escape.
 ↑ There is one collision (headerless RLE obo$b2o$bo75$75bo$76b2o$75b2o$80bo$79b2o$79bobo!) with two escaping lightweight spaceships. The final population is 377.
References
 ↑ "Small fish". The Life Lexicon. Stephen Silver. Retrieved on June 10, 2009.
 ↑ The 1 ninebit spaceship at Mark D. Niemiec's Life Page (download pattern file: ss/9lw.rle)
 ↑ xs14_696y6oozy5cc at Adam P. Goucher's Catagolue (pseudoobject)
 ↑ Repository on GitHub
 ↑ xp2_354cxs at Adam P. Goucher's Catagolue (pseudoobject)
 ↑ Dave Greene (October 21, 2022). Re: Octohash fingerprints (discussion thread) at the ConwayLife.com forums
 ↑ "Spontaneous appeared Spaceships out of Random Dust". Achim Flammenkamp (December 9, 1995). Retrieved on August 18, 2011.
 ↑ Adam P. Goucher. "Statistics". Catagolue. Retrieved on June 24, 2016.
External links
 LWSS at the Life Lexicon
 Lightweight spaceship at Adam P. Goucher's Catagolue
 Lightweight Spaceship at Heinrich Koenig's Game of Life Object Catalogs
 Life (B3/S23) at David Eppstein's Glider Database
 LWSS on LWSS at Adam P. Goucher's Catagolue (pseudoobject)
 xWSS Tagalong at Adam P. Goucher's Catagolue
 Patterns
 Patterns with Catagolue frequency class 11
 Natural periodic objects
 Spaceships with 9 cells
 Periodic objects with minimum population 9
 Patterns with 9 cells
 Patterns found by John Conway
 Patterns found in 1970
 Patterns that can be constructed with 3 gliders
 Spaceships
 Spaceships with period 4
 Orthogonal spaceships
 Spaceships with speed c/2
 Spaceships with unsimplified speed 2c/4
 Spaceships with heat 11
 XWSS variants
 Spaceships with mod 2
 Polyominoes
 Glide symmetric spaceships