A shuttle is an oscillator in which an unstable object moves back and forth between stabilizing objects. The most well-known and first discovered examples are the queen bee shuttle (which is sometimes referred to as the shuttle) and the twin bees shuttle. A large number of T-tetromino and pre-pulsar shuttles are known, including the p30 Eureka. Reflectors can be used to construct glider shuttles (see relay).
Simple shuttles commonly have a period that is a multiple of 2, but asymmetric shuttles are also known, in which one end is stabilized by a different period mechanism from the other.
Glider shuttle
A glider shuttle is a shuttle in which one or more gliders circulate in a repetitive pattern.