Allows for the construction of capital ships such as Dreadnoughts, Carriers, Supercarriers, Titans. However, they are generally only used for the construction of Supercarriers and Titans as Carriers/Dreads can be constructed using the much less expensive X-Large Ship Assembly Array.
Anchoring one of these arrays will ensure negative attention from larger alliances who will suspect that you are building super-caps or titans. Very expensive to construct using Planetary Interaction (the BPO alone is 500M ISK). Note that in order to move these around, you must have a ship with an 850k m3 cargo bay.