The second generation of interstellar space craft developed by the United States military and its allies, and the pioneer in the Daedalus-class battlecruiser (BC-304 class). Commanded by Colonel Steven Caldwell, her original mission was to render aid to the Atlantis expedition trapped in the Pegasus Galaxy and defeat a convoy of Wraith hive ships bent on destroying the Ancient city.
The Daedalus is armed with rail guns, Mark XIII tactical warheads and a bay of F-302 fighters. It also possesses Asgard shielding and transporter technology, but initially none of their weapons. Prior to the Asgard's mass extinction an Asgard scientist, Hermiod, was assigned to the ship in order to assure that their technologies are not abused. Following the Asgard's extinction the ship, along with the rest of Earth's cruisers, was outfitted with the advanced beam weapon.
Propulsion consists of standard thrusters as well as an Asgard hyperdrive engine, capable of traveling one-way between Earth and Atlantis in 18 days. The ship's primary mission is now to ferry personnel and supplies from Earth to Atlantis, and then to travel back again, but the Daedalus often stays in the vicinity of Atlantis for some time before making another loop.
The Siege, Part 3 - The Daedalus, commanded by Colonel Steven Caldwell, arrives over Atlantis to fight off their seige of the city.
The Intruder - On its way back from Earth the Daedalus is taken over by a Wraith virus that has been dormant in the system.
The Hive - Daedalus comes to the aid of Sheppard's team, helping to rescue them from a Wraith hive.
Enemies - The Daedalus plays a crucial role in a fragile alliance with a Wraith hive, working to undermine and attack its enemies.
No Man's Land - Daedalus's crew successfully evacuates Atlantis's people and allies from a Wraith ship headed for Earth before the enemy vessel is destroyed.
McKay and Mrs. Miller - Rodney McKay's sister Jeannie is introduced to the Stargate Program on board the Daedalus, which ferries her to the Pegasus Galaxy to assist the Atlantis team.
The Return, Part 1 - During a test of the inter-galactic gate bridge Caldwell's crew flags down an Ancient ship traveling at near light speed.
Be All My Sins Remember'd - Daedalus participates in a massive coalition of Earth, Wraith, and Traveler ships in an attack on the planet Asuras, resulting in the destruction of the Replicator homeworld.
The Kindred, Part 1 - The ship takes Atlantis personnel to one of Michael's secret facilities in the hopes of rescuing Teyla -- only to find a clone of Carson Beckett instead.
Search and Rescue - Daedalus engages in a pitched battle with Michael's hive, rescuing Atlantis personnel from the enemy ship.
The Daedalus Variations - Another Daedalus from a parallel reality shows up over Atlantis, and when Sheppard's team investigates they find themselves skipping from one reality to another.
First Contact - The ship hosts Todd and a delegation of Wraith for Dr. Keller's gene therapy trials.
The Lost Tribe - Todd seizes control of the ship after he suspects that the humans have betrayed his trust, taking it in search of an Ancient weapon that is being used against the Wraith.
Enemy at the Gate - Daeadlus engages a powerful new Wraith super-hive, which proves more than a match for Earth's ship and leaves it crippled.