- "...the Apollo and the Daedalus have been retrofitted with the new Asgard plasma beam weapon which—given—are very, very powerful..."
- ―Dr. Rodney McKay
Plasma beam weapons are a newly developed technology created by the Asgard shortly before their extinction and gifted to the Tau'ri as part of their legacy.
Overview
Instead of firing pulses of energy like most energy weapons, even much of their own, Asgard plasma beam weapons release a narrow, high-intensity beam of super-heated plasma. Just one of these beams is capable of overloading and penetrating even the most advanced shields and burning through the hulls and internal structures of an enemy vessel with comparative ease, causing heavy damage to the target; if the beam hits a critical area ships can be destroyed with only 2 to 3 shots. (SG1: "Unending") (SGA: "Be All My Sins Remember'd")
While there are energy weapons that can discharge more raw power at once, capable of splitting ships in half with just one shot and cutting through offending barriers with frightening efficiency, they require an extended period of time and significant power to charge. The advantage of plasma beam weapons lies in their ability to come online and charge at an incredibly rapid rate (using up relatively little power in the process) and deliver several consecutive shots in only a few seconds, overwhelming enemy defenses while they are still recovering from the previous hits. (SG1: "Unending") (SGA: "The Siege, Part 1", "First Strike", "Be All My Sins Remember'd")
Even warships as powerful as Ori motherships and the Aurora-class have yet to mount an effective defense against these weapons, and they have also proven capable of destroying Wraith hive-ships, powerful ships in their own right, with just three well-placed shots. Hive-ships equipped with ZPMs are virtually immune to these weapons, due to the far greater density of their hull. (SG1: "Unending") (SGA: "Be All My Sins Remember'd", "The Last Man", "Search and Rescue", "Enemy at the Gate")
It appears that the amount of power these weapons discharge is adjustable, in cases where disabling a vessel instead of destroying it is necessary, but this could just be a case of precision aiming. (SGA: "Search and Rescue")
History
The Odyssey destroys an Ori mothership
These weapons were placed on the Odyssey as a gift to the Tau'ri in a mass upgrade, providing the ship with a means to effectively fight the Ori warships that had been invading the Milky Way galaxy. These weapons were eventually equipped on both the Daedalus and the Apollo, which put them to good use almost immediately when they used them to rapidly destroy the Aurora-class warships that the Asurans were deploying in the Pegasus galaxy. Since then, all Daedalus-class warships have been outfitted with these weapons. (SG1: "Unending") (SGA: "Be All My Sins Remember'd")
These weapons saw action in the Battle of M2S-445, where they first disabled then later destroyed Michael's cruiser. They were later used in the Battle of the ZPM powered Hive Ship, but were completly ineffective against the upgraded hive due to its denser hull. (SGA: "Search and Rescue", "Enemy at the Gate")
In an alternate timeline, these weapons were also equipped to the Phoenix, and used to destroy Wraith hive-ships in even fewer hits than Ori motherships and Aurora-class warships, as hive-ships possess no shields (allowing even easier penetration). (SGA: "The Last Man")
