Battleships are massive warships that are a rack above Cruiser and a tier below dreadnoughts. They are usually at a midpoint between bombardment capabilities and ship-ship combat; making them ideal for lange-scale invasions and fleet engagements.
Earth Human battleships are no exception to this, being about 1 500m long (making them the third-largest Non-Capital ships in the Earth navy, after carriers and dreadnoughts), and 400m wide. They have a crew of 500, a MEGA-level mainframe, are plated with 4m of Composite Alloy; and are powered by a 5 Gigawatt reactor. They are propelled by a PHASE drive; and normally don't have an AI. Despite being so large, they only have five decks.
The first deck is engineering; the second is storage (food, ammo, etc.) and has one of the point-defence systems. Third is the MAC gun, seven 175mm howitzers on each side, and the crew quarters. Fourth is ten rail turrets (on each side), and the servers. Fifth is the bridge, the other point-defence system, and two (one on each side, both facing forwards) PHASE missile launchers.
They are unable to carry any extra passengers, and have four dropship bays. Battleships are the smallest ships in the navy to have as many dropships on-board as they do dropship bays. Also, the howitzers CAN be used against ground targets; although the ship must remain (fairly) stationary to use them reliably against something on the ground; and since most of the shell burn up in-transit through the atmosphere, it only has the effect of a 100mm shell (MUCH less dangerous).
Bombardier Variant: The same chassis, but with two Ionic cannons (one per side) instead of the howitzers. However, this variant is slower than the standard battleship, limiting it's use.
Missile Ship Variant: Same chassis, but replace the howitzers with SPARROW pods and the rail turrets with NOVA launchers.
Laser Battleship: Replace all the broadside weapons with plasma cannons (NOT Ionic guns. Plasma guns are more effective at ship-ship combat, but can't be used against ground targets, require extra magnetic-field-creation equipment that slows the ship down; and generally costs an arseload of money).