Pre-pulsar spaceship (or PPS for short) is any of three different period-30c/5 orthogonalspaceships in which a pre-pulsar is pushed by a pair of spiders. The back sparks of these spaceships can be used to perturb gliders in many different ways, allowing the easy construction of c/5 puffers.
The first pre-pulsar spaceship, the symmetric pre-pulsar spaceship (or SPPS for short, shown to the right) was found by David Bell in May 1998[1] and was based on the p15 pre-pulsar spaceship found by Noam Elkies in December 1997.
The asymmetric pre-pulsar spaceship (or APPS, shown below) was found by Alan Hensel, also in May 1998, based on a skewed version of the pre-pulsar.
The glide symmetric pre-pulsar spaceship (or GPPS, shown below) was also found by David Bell in May 1998. It is similar to the symmetric pre-pulsar spaceship but contains an extra T-tetromino between the spiders and is glide symmetric.
Martin Grant's 601-glider spider synthesis resulted in a 1212-glider synthesis for the symmetric pre-pulsar spaceship on March 8, 2019.[2]
In June 1998, David Bell found reactions to convert between the symmetric and glide-symmetric forms of the p30 pre-pulsar spaceship.[citation needed]