A Cordership is any spaceship that is based on switch engines. They necessarily have speed c/12 and period that is a multiple of 96. Corderships were the slowest known spaceships before discovery of Gemini in 2010, although arbitrarily slow spaceships had been known to exist (see universal constructor). They are named after Charles Corderman, who discovered the switch engine in 1971.
The first Cordership, which used 13 switch engines, was found by Dean Hickerson in April 1991. He soon thereafter found a smaller 10-engine Cordership, and in August 1993 a 7-engine Cordership. In July 1998 he found the first 6-engine Cordership. Many Corderships are now known that use 8, 5, 4, 3, or 2 switch engines.