Orthogonal loopship

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Orthogonal loopship
Orthogonal loopship image
Pattern type Spaceship
Number of cells 267672
Bounding box 2948889×3875385
Direction Orthogonal
Period 40007022
Mod 20003511
Speed 1000130c/40007022
Speed (unsimplified) 2000260c/40007022
Heat Unknown
Discovered by Dave Greene
Year of discovery 2018

The orthogonal loopship is a self-constructing adjustable spaceship built by Dave Greene on October 31, 2018.[1]

Overview

Like other loopships, the orthogonal loopship consists of a signal storage loop that moves by sending out two copies of a glider construction recipe. The first copy of the recipe is used to construct a new signal storage loop some distance from the original. The second copy is then directed into the new signal storage loop to allow the cycle to repeat. The previous loop circuitry self-destructs cleanly after it has emitted two copies of its contents. A more detailed description of the loopship's structure can be found in this blog article.

This was the first loopship that runs at a reasonable speed in HashLife-enabled simulation software such as Golly. For several years the only other spaceship pattern that could be considered to be a loopship would have been a properly programmed 0E0P metacell, but this would have required months or years to simulate a full cycle. The next example, the self-synthesizing oblique loopship, appeared in 2021.

Design

The orthogonal loopship was constructed before crabstretcher technology became available, so it uses Cordership-based elbow pushes in a glide-reflecting design to allow for re-use of some of the corners of its signal storage loops.

This was necessary because Corderships travel slowly enough to make it more difficult to store a recipe for a simple diamond-shaped memory loop inside that same loop. Too much empty space is needed in the recipe, due to the need to wait until each Cordership gets far enough away before shooting it down to produce a target elbow; with a naive design, no matter how big the loop is made, the required wait times require such large gaps that there's no room left to store the actual construction recipe.

A key trick used in the orthogonal loopship is an overlapping set of Cordership push recipes. Cordership seeds are created, then triggered to produce Corderships traveling in opposite directions, which are later shot down to produce target blocks at new corner locations where further construction can take place. To make it possible for the construction recipe small enough to fit inside the signal loop once it's constructed, the two Cordership seeds are triggered nearly simultaneously -- in parallel rather than in series. This requires some customization.

Infinite family of related spaceships

It is relatively easy to adjust the orthogonal loopship's recipe to produce variants that travel at slightly different speeds. The required adjustments involve making coordinated changes to the distances between segments of the recipe. The key gaps in the construction recipe that control how long the Corderships are allowed to travel, are overlapped with each other, so an adjustment to both dimensions of the diamond-shaped signal loop can be completed with a single coordinated change in the base pattern, or a fairly small set of adjustments to the orthogonal loopship's glider synthesis recipe[2].

Image gallery

Path followed by the orthogonal loopship's recipe gliders

References

  1. Dave Greene (October 31, 2018). Self-Constructing Spaceship Challenges (discussion thread) at the ConwayLife.com forums
  2. Dave Greene (May 4, 2019). Re: Self-Constructing Spaceship Challenges (discussion thread) at the ConwayLife.com forums