Aphelion is an old Lombax ship that was left behind on Fastoon years ago during Tachyon's attack in the Lombax's home world. It was not functioning but very much kept together. Ratchet and Clank discovered it after they landed on the planet, with Ratchet becoming very adamant about repairing it. After he did, it became his ship.
Aphelion comes with an AI, giving it the ability to speak and think, making it a character in the series other than a vehicle. During Tools of Destruction and A Crack in Time, it was heard talking. However, in later games, it was mute. Aphelion speaks with a computerized, female british accent, making Aphelion possibly a she.