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Cylon War-era basestars
The Cylons had deployed three different variants of Basestars during the First Cylon War.
Much like its modern counterpart, this model utilized chemically-propelled missiles (with both nuclear and conventional warheads) as the main form of offensive weaponry. Raiders were deployed from access points (totaling 8 in number) throughout a basestar's hull to provide defense. This design, as with later iterations, was capable of operating within an atmosphere (Blood and Chrome).
The origins of the initial basestars are unclear. However, as Cylons were a creation of man in the early days before the war, it is probable that man himself (through the efforts of various colonies) designed the various ships and weapons used by the Cylons for the use in intra-colonial wars prior to the Articles of Colonization.
This configuration features two y-shaped hulls in tandem alignment, with a 1st variant-like top and bottom hull. Missile launchers are located in between the arms of the ship, along the central axis ("Blood and Chrome").
Third "Guardian" Variant
Towards the end of the first Cylon War, the Cylons built a prototype basestar that had roughly the same shape as the modern basestar. The first hybrids were developed for use with this model.
It is explained by Athena that a group of Centurions calling themselves Guardians fractured from the Cylon majority with such a basestar. The belief is that they escaped to the far reaches of space to avoid being shut-down in favor of their modernized, non-sentient successors (TRS: "Razor"). The only basestar of this type known to exist was destroyed by Colonial forces shortly after its discovery.
Modern basestars, built sometime before the Fall of the Twelve Colonies, are the same size as a Colonial battlestar, but are considered by the Cylons to be weaker than battleships in the Colonial Fleet. The shape of the newer basestar reflects its name, with two offset Y-shaped hulls attached at their centers by a single pylon, the warship has a distinctive "star" shape, which can rotate into a tandem-Y configuration for entry into a planetary atmosphere (TRS: "The Plan").
The most unique aspect of a modern baseship is its organic nature. Composed of organic resin, and a large flesh-like interior, the baseship could be considered an individual organism in itself, and just like any other "injured" organism, the basestar is able to heal its wounds (battle damage) over time (TRS: "Guess What's Coming to Dinner?"). The organics are all connected the the ship's "brain", known as a Hybrid, which can control the ship's functions from firing weapons, down to performing an FTL jump.
They are equipped with a superior jump system and no visible means of sublight propulsion, lacking any engine pods or nacelles, but remain capable of chasing down a battlestar (TRS: "Exodus, Part II").
Baseships possess several conventional rooms and hallways, which are sleek but generally bland. Lighting plays a large role in the aesthetics and some rooms are furnished with clearly human objects, such as beds and couches. Humanoid Cylons project different surroundings to navigate ship corridors more easily, and to provide them with an individually pleasing environment (such as a lush forest). Data and other functions (such as analyzing visual information) are handled within a liquid computer interface that resembles a stream of water flowing over a luminous glass surface. Cylons can interact with the main computer by placing their hands in these basins (TRS: "Torn").
Command and Control
A basestar is operated by many humanoid Cylons. Up to all seven models of them issue commands for the basestar from a central command and control center. Consensus amongst models is the typical procedure, as such the process of deliberation and voting on decisions may cause the basestar to react more slowly than a battlestar's command and control in a CIC.
A basestar has a datastream, or computer network, which interfaces with the Hybrid and all aspects of the basestar's operation.
A typical Cylon basestar is moderately armed, and relies on unconventional means for military strength. Generally, a basestar is armed with 220 missile launchers located on the central spire, and on the arms of the vessel, which are capable of carrying nuclear or conventional tipped ship to ship, or long-range ballistic (with Multiple Independently Targetable Reentry Vehicle payloads) missiles to their targets. Ballistic missiles are able to strike planetary targets from high orbit ("The Plan"). Ship to ship missiles are easily defended against by Colonial electronic countermeasures, which lends the Cylons to rely more on the basestar's Raider compliment for for both offensive and defensive purposes.
A basestar can carry up to (and maybe even more) 434 Raiders, launched from storage bays located on each arm of the ship. Upon launch, they set out to swarm the enemy target (almost like insects), while the basestar covers them with an opening salvo of ship to ship missiles. This tactic, suggests a reliance on overwhelming force to destroy a foe, since a basestar does not appear to have point-defense batteries, or heavy armoring. Cylon basestars appear quite vulnerable to Colonial battlestars in close-range combat when fighter support is not prominent (TRS: "Resurrection Ship, Part II"). From this, it can be theorized that basestars are designed primarily as carriers for the massive fleet of Raiders they carry, rather than as a front-line main battleship. Their reliance on long-distance attacks with missiles and their complement of Raiders, as well as their overall fragility seem to support this (TRS: "Miniseries", "33", "Razor", "The Plan").