SS (registry)
SS was a identifying prefix before a starship name for some vessels in the Earth and Federation registries. 

Prior to Dr. Zefram Cochrane's discovery of warp drive, it was used to signify sleeper ships and space modules. (; ) The earliest warp-capable "space ships" used this registry. (; ) The prefix was then seen on survey ships and colonization starships. ()

Within a hundred years, freighters and transports were given SS prefixes. (; ) By the mid-24th century, some  science ships were given the prefix as well. ()

List of SS ships by date

Background information
The registry "SS" is used by the United States Navy as a  for submarines. For s, SS is used as a naming prefix for a steam ship. SS was first used in a Star Trek production as early as  (for the SS Valiant), but was actually referenced in Gene Roddenberry's Star Trek pitch for the main ship, the SS Yorktown, which ultimately became the .

ja:SS（レジストリ）
Prefixes