The Hyperion Class Heavy Cruiser, is 990 meters long, and is one of the oldest types of Earth Alliance
ships still in service. They were all built before the Earth-Minbari war
The vast majority of them were destroyed in the war, but many of them survived and are still in active service. The Hyperion Class has also recently been upgraded, so that it now can carry beam weapons and otherwise improved weaponry. There is neither artificial gravity nor a rotating section on board, so the crew works in micro-gravity. This makes these ships only suitable for shorter missions, while the crews on the much larger Omega Class Destroyers with rotating sections can stay out for longer patrols. The Heavy Cruiser also carries a few Starfuries on board, and it is the smallest Earth Alliance ship than can open their own jump-point.
The Hyperion Crusiers have had their share of notoriety in Earth Alliance history, the Prometheus was the ship involved in the failed First Contact with a the Minbari and their powerful Sharlin Class Warcruiser. The failed meeting ended with the death of the Minbari spiritual leader Dukhat, and the start of the deadly Earth-Minbari War. (cf. "A Late Delivery from Avalon", "In the Beginning")
EAS Hyperion - (A Voice in the Wilderness, Part II)
(2 Unnamed vessels) - (Severed Dreams)
EAS Prometheus - (A Late Delivery From Avalon)
The Class of ship was named after the first appearance of the vessel, the EAS Hyperion.
This, in turn, was named after the Babylon 5 Internet archive (and home of The Lurker's Guide to Babylon 5) originally located at Hyperion.COM.