The class J starship was a small, antiquated starship design used by the Federation and independent traders alike well into the mid-23rd century.
In 2266, Harcourt Fenton Mudd possessed an unregistered small class J cargo ship which he utilized as a transport vessel. While attempting to outrun the Enterprise, Mudd piloted the ship into an asteroid belt, in the process causing his engines to overheat. Disabled, the ship was ultimately destroyed by an asteroid collision, but not before the Enterprise was able to beam off all of the ship's inhabitants. 
The same year, Starfleet maintained an old class J starship for use as a cadet training vessel. During an inspection by Fleet Captain Pike, a baffle plate ruptured, exposing the crew to harmful delta rays. Pike received an extremely high dose which ultimately left him an invalid, as he went in to rescue the cadets. 
The Deneva colony also had a class J starship at their disposal, described as a one-man vessel of Denevan configuration. The USS Enterprise was unable to intercept it, after it came into sensor range, even at warp 8 before it was destroyed by the heat of the Denevan sun. 
In 2269, the Federation operated the space cruiser Aurora. The ship was stolen by Dr. Sevrin and five of his followers in search for the mythical planet Eden. The ship was destroyed when attempting to pull free from a tractor beam. 
- ↑ Roddenberry, G. (story); Kandel, S. (teleplay); Hart, H. (director) (1966). "Mudd's Women". Star Trek: The Original Series. Season 1. Episode 6. NBC.
- ↑ Roddenberry, G. (writer); Daniels, M. (director) (1966). "The Menagerie, Part I". Star Trek: The Original Series. Season 1. Episode 11. NBC.
- ↑ Carabatsos, S. (writer); Daugherty, H. (director) (1967). "Operation -- Annihilate!". Star Trek: The Original Series. Season 1. Episode 29. NBC.
- ↑ Heinemann, A. (story/teleplay); Richards, M. (story); Alexander, D. (director) (1969). "The Way to Eden". Star Trek: The Original Series. Season 3. Episode 20. NBC.