The Arks were colonization ships that carried the colonists from Earth to the 'Verse. There is very little information about them, what little we see in the RPG basic book suggests they were approximately 30 million tons, which gives them an approximate dimension of 6,000 feet long by 2,000 feet wide and 1,000 feet high. We do not know anything about how the colonists were transported (awake, in cold sleep, in virtual reality suspended animation, etc) but some sources suggest the cultures of the colonists intermingled on the ships. There is no information about the technology used, since the ship systems used in the game would not support sustained flight over interstellar distances. The basic book also says there is an Ark on display on Bernadette, open as a museum, and I did mention that in a game session (Seek the Seeker).

But once I thought about it, I realized that is unlikely. The Arks would have been cannibalized to provide materials for the early colonies. A mile long ship designed for space would probably not have the structure to support its weight planetside, and if it did, that would be a very poor design.

So, here's my view on the Arks. The Arks were fitted with a reactionless gravitic drive which, either due to size requirements or efficiency problems, is not used by modern spacecraft in the 'Verse. The Arks were built using a modular system which was designed to be broken down once the ship arrived. Some modules became space stations, others were deployed planetside as prefabricated living facilities and factories. The main engineering sections containing the drives and a bridge module were used as super tugs to move asteroids and comets for mining and terraforming purposes.

The museum on Bernadette might look like a scale model of an Ark on the outside, and sections of it replicate or are sections from the original Ark, but it is not a whole Ark.