An ancient Warship found on Taranis. John Sheppard renamed the warship Orion after finding its original name, Hippaforalkus, to be a mouthful.
Initially damaged, presumably from a Wraith attack, it lay in the Taranian bay, however, when the Atlantis expedition visited the planet, the Taranians showed them the ship. Unable to fly, the ship was, however, repairable, but unfortunately the surface of the planet was in the process of erupting, and time was short.
Dr. McKay began work on the the ship's engine, being able to bring power onto the ship, as well as the internal communications, however time was running short. When they realized that the Orion is the only way that they can evacuate the people of the planet, they moved those remaining on the planet surface onto the Orion in the hopes that McKay could fix the ship.
Unable to fix the sublight engines, McKay managed to repair the hyperdrive and shields, and formulated a plan. Knowing that the shields would only last 4.1 seconds when the planet's surface erupted, he used his skill to jump to hyperspace before the 4.1 seconds were up, whilst the super-volcano below erupted. Saving the life of the Taranians, Chancellor Lycus agreed to let the Atlantis expedition use the craft in need, for much needed help in relocating the planet.
After almost three weeks of repairs, the Orion was ready to stand along side the Daedalus to defend Atlantis from the on-coming Wraith hive ship.