Trekipedia

J Class

The J class freighter was somewhat smaller than the Y class, but otherwise similar.^[2] Unlike the Y class, however, J class freighters could readily separate from their cargo containers, making the vessel a much smaller, more maneuverable ship.^[3] Such freighters were usually armed only with low-yield plasma cannons for meteor defense, but most crews upgraded as soon as they could. Enterprise NX-01 helmsman Travis Mayweather, who grew up on the J class freighter E.C.S. Horizon, acknowledged that “running freight is dangerous … you’re a dozen light-years from home with 20 kilotons of dilithium ore in your hold, armed with nothing but a popgun for shooting oncoming meteors. What would you do?”^[2] In 2265, Harry Mudd’s J class ship was destroyed in an asteroid field, though he was rescued by the U.S.S. Enterprise NCC-1701.^[1]