The 17c/45 reaction is a reaction in which a pi-heptomino moves forward 17 cells in the course of 45 generations while the blinker moves back 6 cells and is rephased. This reaction has been known for many years, but it was only in September 2002 that David Bell suggested that it could be used to build a 17c/45 spaceship, based on a reaction he had found in which pis crawling along two lines of blinkers interact to emit a glider every 45 generations. Gabriel Nivasch explicitly constructed the first 17c/45 spaceship using this reaction on December 31, 2004.
Similar glider-emitting interactions were later found by Gabriel Nivasch and Jason Summers. The basic idea of the design is that streams of gliders created in this way can be used to construct fleets of standard spaceships which are used to carry gliders to the front of the blinker trails, where they can be used to build more blinkers.