Yonada was a 10,000-year-old asteroid-ship, built by the Fabrini when they realized that their home sun was about to go supernova and destroy all life on their planet. Yonada was constructed to look like an asteroid and was sent on a computer-controlled course to a habitable colony world. The ship measured two hundred miles (320 km) in diameter, about the size of the plutino Ixion in the solar system. Chemically, it was a typical asteroid; however, it was self-propelled by atomic power and could correct for gravitational stresses. The engines left behind a trail of debris and hard radiation. The ship could defend itself with chemically-fueled missiles.
The Enterprise crew discovered that Yonada was on a collision course with the populated planet Daran V. The inhabitants of Yonada had been in space for so long that they had forgotten that they were on a ship. They called the ship's computer the Oracle and had developed a sophisticated religion around it and its purpose to bring them to "the new world".
Central to this faith was the Oracle Room, which contained the physical representation of the Oracle, a kneeling position for use by the high priestess when conversing with the Oracle, and a plinth containing the Book of the People. The Oracle Room also contained a number of defensive mechanisms under the control of the Oracle, including a means of incapacitating intruders using an electric shock, and a means of heating the room to very high temperatures very quickly and kill the victims in heat strokes or burn them alive. It also contained the concealed entrance to Yonada's control room.
The Enterprise crew helped Natira, the leader of the Yonada colonists, to understand that their world was a ship, and corrected the worldship's course to its intended destination for a safe course. (TOS: "For the World is Hollow and I Have Touched the Sky")