2c/7 orthogonal is a speed that is equivalent to two sevenths of the speed of light.
The first 2c/7 spaceship discovered was the weekender, which was found by David Eppstein on January 12, 2000 using his search program, gfind. On April 27, 2000, Stephen Silver discovered a tagalong that can be pulled by two weekenders. Attaching these tagalongs to weekenders was the only known method of constructing other 2c/7 spaceships, besides building self-sustaining loops of weekender conduits (see Rakes).
On December 26, 2013, Ivan Fomichev built a period-8974 2c/7 puffer by perturbing a lightweight spaceship with several weekenders. The next day, he built a smaller period-6622 puffer after Hartmut Holzwart pointed out a simpler design Jason Summers used in his 2c/5 puffer. 
- Jason Summers' jslife pattern collection.
- Andrew J. Wade (December 30, 2019). Re: Spaceship Discussion Thread (discussion thread) at the ConwayLife.com forums
- Ivan Fomichev (December 26, 2013). "Re: Weekender Reactions: Building a 2c/7 Puffer". Retrieved on December 27, 2013.
- Ivan Fomichev (May 22, 2014). "Re: Weekender Reactions: Building a 2c/7 Puffer". Retrieved on May 26, 2014.
- Chris Cain (September 26, 2015). "Re: Small Spaceship Syntheses". Retrieved on November 17, 2015.