The DY-500 class was an Earth interplanetary and colony ship type of the early 22nd century, a successor to the DY-100, represented by the SS Mariposa.
The type is first mentioned in the original series episode Space Seed. On meeting the drifting Botany Bay, Kirk takes it for a DY-500, and Spock corrects him: the older DY-100 design is much the same in outline.
The class comes to the fore in the Next Generation episode Up the Long Ladder. Records show that the SS Mariposa, a DY-500, left Earth in 2123 with two very different groups of settlers, one technological and one devoted to a simple rural life, and an odd cargo that included spinning wheels and livestock.
The Enterprise-D finds their descendants on two worlds in the Ficus sector, the farming Bringloidi and the Mariposans, a society of clones grown from the five survivors of the ship's crash.