The BC-304, also known as the Daedalus-class warship, is a class of deep space carrier built by the Tau'ri, and the most advanced series of vessels in the Tau'ri fleet capable of rivaling even the most powerful alien spaceships. As of 2010, six Daedalus-class warships have been built. These 304s are the Daedalus, Odyssey, Korolev, Apollo, Sun Tzu, and George Hammond. Five are known to be in active service. All but two are operated by the United States Air Force. One 304, the Korolev, was given to the Russian Federation, and subsequently lost in a battle with the Ori, while another 304, the Sun Tzu, is operated by the Chinese Government.
Although referred to as "sister ships" to the BC-303 Prometheus, the 304s differ significantly in their design and technology. While the Prometheus was originally built with reverse-engineered Goa'uld technology and salvaged equipment such as the Transportation rings, the 304s incorporated Asgard technology in their original design. All 304 class ships are equipped with Asgard shields, sensors, transporters, as well as intergalactic hyperdrivetechnology that allow the ships to carry supplies to Atlantis in the Pegasus galaxy.
However, the Asgard initially refused to install any of their weapons on the 304s, changing their minds only when faced with their extinction as a species. In 2007, they equipped Earth's flagship, the Odyssey, with their most advanced technology, including plasma beam weapons. Later, the Daedalus and Apollo were also updated with these weapons. It is assumed that all future ships will be provided with these weapons as well.
Originally, the Prometheus proved itself to be a capable warship, with several more ships of the BC-303-classplanned for construction. However, in a show of gratitude for the Tau'ri's help in battling the Replicators, the Asgardprovided a technological retrofit for the Prometheus.
With the Asgard upgrades, and whatever knowledge and fine-tuning that the Prometheus went through during her shakedown, the current BC-303 class became obsolete. Therefore, a new spaceship, intended to be built from the ground up with these upgrades, was designed. It immediately became one of Stargate Command's most important projects. Currently, seventy percent of the SGC's operating budget has been transferred to the construction of Daedalus-class vessels. The first vessel of the class was the Daedalus, which was introduced in 2005. Upon its completion, the ship was immediately assigned to the Pegasus galaxy to assist the Atlantis expedition in the Tau'ri-Wraith war.
The following year, in 2006, the second Daedalus-class ship, the Odyssey, was constructed. The ship's initial mission was to deal with the Lucian Alliance and, foremost, the forces of the Ori, which had invaded the galaxy.
The first two Daedalus-class ships were commanded by the United States Air Force. However, when the Ori invaded the Milky Way a third Daedalus-class ship was near completion. The Korolev was given to the Russians as a "trade agreement" for the United States of America to continue running the SGC with the Alpha Gate, which was on lease from Russia. The Korolev was destroyed during the Battle of P3Y-229 soon after being rushed into service.
In 2007, when faced with the extinction of their race, the Asgard gave the Tau'ritheir complete knowledge base in the form of the Asgard computer core. They also gave the Tau'ri vessel, Odyssey, a mass-upgrade. Since that historic event all Daedalus-class warships have been outfitted with Asgard advancements, in the form of Asgard plasma beam weapons. These weapons have given the Tau'ri a military superiority over most other known races in the universe.
Another Daedalus-class ship, the Apollo was constructed later in 2007. It was stationed around Earth in defense against a potential Ori attack. The attack never took place however, and it was subsequently assigned to the Pegasus galaxy to fight the Asurans in the Asuran-Tau'ri-Wraith war.
The next 304 in line, the Sun Tzu, was put into service by China in early 2009. In its first mission, the Sun Tzu and the Apollo jointly engaged the Super-hive, which had found the location of Earth. The attack was a failure and both the ships were crippled in battle. The Hive ship was subsequently destroyed over Earth.
Additionally, Earth's sixth 304, the George Hammond (introduced in an alternate timeline as the "Phoenix"), was completed in 2009 and is placed under the command of Colonel Samantha Carter. It later took part in the defenseof Icarus Base and other Lucian Alliance conflicts.
While talking with Sheppard and Teyla, Carter tells them that while the George Hammond brings the number of 304's available to Earth up to four, there are no more hulls being laid out for other members of the class currently. Carter explains that building the ships costs seven billion dollars and with the economy, there simply isn't the money to build anymore. The Russians are also not attempting to replace the Korolev given how a short a period it lasted and the Sun Tzu still has to be recovered if its even possible to salvage it after all the damage the ship took against the super-hive.
Following the appearance of Queen Death, both the Daedalus and the George Hammond are dispatched to the Pegasus galaxy. However, after a battle that results in severe damage to both ships, the Daedalus returns to Earth as Atlantis no longer has a ZPM to contact home. The Hammond is left to defend Atlantis alone and participates in several battles with the Wraith, including the final battle with Queen Death. While its considered to recall the Daedalus, its determined to be pointless as the Daedalus is simply too far away to make it to the battle. The Hammond survives the battles it engages in in the Pegasus galaxy and later returns to Earth to help battle the Lucian Alliance.