The lightweight spaceship (commonly abbreviated to LWSS) or (rarely) small fish is the smallest orthogonal spaceship, and the second most common spaceship after the glider. It moves at speed c/2 and has period 4 (and is therefore often referred to as 2c/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.
- Main article: List of common spaceships
Random soups investigated by Achim Flammenkamp emitted one LWSS for approximately every 615 gliders. The LWSS is also the eighteenth most common object on Adam P. Goucher's Catagolue.
All strict still lifes with a population of 20 or fewer cells, as well as all oscillators and spaceships with 16 or fewer cells, are known to be glider-constructible. A glider synthesis of this object can be found in the infobox to the right.