The Yoyodyne Division (also known as Yoyodyne Propulsion Systems or YPS) was a shipbuilding entity. In the 22nd century the YPS pulse fusion was utilized in DY-500-class colony ships. (TNG: "Up The Long Ladder" ) In the 24th century the Division built starships for the United Federation of Planets at various shipyards including 40 Eridani A Starfleet Construction Yards, Copernicus Ship Yards, and San Francisco Fleet Yards. The firm had an office on Deep Space 9's Promenade. (Star Trek: Deep Space Nine)