# Types of spaceships

There are many different **types of spaceships** in Conway's Game of Life and related automata. The following are the terminology that are in common use. This page contains only very general terminology that applies to wide varieties of spaceships.

## Contents

## Edge-repair spaceship

An **edge-repair spaceship** is a spaceship that has an edge that possesses no spark and yet is able to perturb things because of its ability to repair certain types of damage to itself. The most useful example is edge-repair spaceship 1, which can destroy Herschels as it travels. Another well-known example is edge-repair spaceship 2, which can destroy beehives.

## Flipper

A **flipper** is a spaceship (or oscillator) that forms its mirror image halfway through its period. All flipper spaceships are glide symmetric and conversely all glide symmetric spaceships are flippers. The most common examples are the glider, lightweight spaceship, middleweight spaceship, and heavyweight spaceship.

## Flotilla

A **flotilla** is a spaceship composed of a number of smaller interacting spaceships. Often one or more of these is not a true spaceship and could not survive without the support of the others. Flotilla 1 is the most common example, and it contains an overweight spaceship escorted by two heavyweight spaceships.

## Frothing spaceship

A **frothing spaceship** is a spaceship whose back end appears to be unstable and breaking apart, but which nonetheless survives (compare with frothing puffer). The exhaust festers and clings to the back of the spaceship before breaking off.

## Glide symmetric spaceship

A spaceship is said to be **glide symmetric** if it undergoes reflection and translation simultaneously. It is not difficult to show that a spaceship is glide symmetric if and only if it is a flipper.

## Knightship

A **knightship** is a spaceship of type (2m,m)/n (that is, a spaceship that moves two cells horizontally for every one cell it moves vertically). Knightships must be asymmetric and their period must be at least 6, which makes searching for them using programs like lifesrc very difficult. An "almost knightship" was found by Eugene Langvagen on March 23, 2004, which would be a period-6 knightship if it weren't for two cells that are incorrect in its sixth generation.^{[1]}

By analogy with the corresponding fairy chess pieces, spaceships of types (3m,m)/n, (3m,2m)/n and (4m,m)/n would presumably be called camelships, zebraships and giraffeships, respectively.

Alternatively, 'knightship' may refer to any spaceship that travels in an oblique direction (not diagonally or orthogonally). The first oblique spaceship to be discovered, Gemini, was found in May, 2010 with a velocity of (5120,1024)c/33699586. In June, 2010 Dave Greene constructed the first true knightship in Life, which is based on Gemini and travels at a velocity of (4096,8192)/c35567490.^{[2]}

## Non-monotonic spaceship

A spaceship is said to be **non-monotonic** if its leading edge falls back in some generations. The first non-monotonic spaceship to be found was the diagonal 13-engine Cordership, by Dean Hickerson in April 1991. The first orthogonal example was found by Hartmut Holzwart in August 1992, which has period 4 and travels at speed c/4. In April 1994, Holzwart found examples of period 3 spaceships with this property, and this is clearly the smallest possible period. Another well-known non-monotonic spaceship is the weekender.

## Smoking ship

A **smoking ship** is a spaceship that produces smoke. If the smoke extends past the edge of the rest of the spaceship, then it can be used to perturb other objects as the spaceship passes by. Running gliders into the smoke is often a good way to turn or duplicate them, or convert them into other objects. Sometimes the smoke from a smoking ship may itself be perturbed by accompanying spaceships in order to form a puffer. A simple example of a smoking ship is the Schick engine.

## Standard spaceship

A **standard spaceship** is a glider, lightweight spaceship, middleweight spaceship, or heavyweight spaceship. That is, it is one of the original spaceships that have been known since 1970. A **non-standard spaceship** is any other spaceship.

## See also

- List of glide symmetric spaceships
- List of non-monotonic spaceships
- List of smoking ships
- Spaceship terminology
- Tagalong

## References

- ↑ "PLife Home Page". Retrieved on May 22, 2009.
- ↑ post on the conwaylife.com forums