The lightweight spaceship (or LWSS for short or small fish) is the smallest orthogonally moving spaceship, and the second most common spaceship (after the glider). Random soups will emit one LWSS for approximately every 615 gliders. It moves orthogonally at c/2 and has period 4. It was found by John Conway in 1970.
In April 1992, David Bell found a tagalong for two lightweight spaceships (or two middleweight spaceships or two heavyweight spaceships). It can be extended indefinitely by attaching it to the back of itself.
Interestingly, a hivenudger with symmetric rear (that is, both rear spaceships being of same "weight") can pull this tagalong.