three-nine (space train)
The eponymous fictional space craft of the Ginga Tetsudou 999 science fiction series from the 70s created by Matsumoto Leiji.
The Special Limited Express Three-Nine (銀河超特急 999号) is actually a very advanced and sophisticated long range interstellar transport spacecraft. It is shaped like an old steam train so its passengers are more comfortable and feel more at home, becoming less nostalgic of Earth as the ship travels to planets and places located very far away in the far reaches of the Milky Way galaxy.
It is operated by an alien called Conductor.
The basic design is based in a Japanese National Railways Steam Locomotive C-62 Model.