The following is classified level Iota. Unauthorized access is punishable under the IJN Security Act, PTEI convention, section 22.3.6.
Among the abilities of shipgirls is the production capabilities of their internal factories. When provided with resources, fairies are able to utilize them to produce a multitude of items. While all shipgirls carry internal factories regardless of class, their production capability varies widely; due to the skills of the crew and the nature of the shipgirls themselves.
While most shipgirls have equipment tailored specifically for them after construction, most are refitted with additional equipment such as armament, radar, planes, and such to enhance their abilities. However, this introduces several issues, as the shipgirl's systems are not configured to use, produce, and maintain the new equipment. In order to deal with these issues, the shipgirl can undergo remodeling, but that is a significant investment in time and resources. A simpler alternative is to give the shipgirl a blueprint.
Blueprints are a set of protocols which interface with a shipgirl's internals that allow the equipped shipgirl to produce, equip, and maintain a specific item. For example, a torpedo array blueprint allows a shipgirl to create the mount, maintain the array, interface with the array, store torpedoes, create torpedoes, and launch torpedoes. An aircraft blueprint allows a shipgirl to manufacture, maintain, refuel, reload, and create the proper hangar space for that aircraft.
Blueprints usage is limited by the capabilities of the shipgirl. The systems of an aircraft carrier, for example, will outright reject most armament blueprints and refuse to function. Whereas the systems of a light cruiser can accept some types of aircraft blueprints, but may be unable to produce them due to incomplete or malformed subsystems. Attempting to equip a blueprint that is incompatible with a shipgirl's systems may have detrimental or downright bizarre consequences. One recorded incident involved a heavy cruiser that began laying eggs after being equipped with aircraft blueprints. For more information, see: Shipgirl or the Egg Theory
The number of available "slots" for blueprint usage depends on the ability for a shipgirl's body to maintain them. Equipping more blueprints than a shipgirl is capable of maintaining is severely detrimental to a shipgirl's health.
If a blueprint is removed or otherwise lost, the shipgirl is unable to maintain or use the equipment created by the blueprint. In those cases, a shipgirl's body will usually cannibalize all related systems after a short amount of time. Whether this is a natural conservative measure or an immune response is unknown.
The physical form of blueprints varies widely, though they tend to take a form similar to the item they represent. Blueprints are created through the process of Equipment Construction. For more information, see: Equipment Construction.
As with all shipgirl internals, internal factories exist within compressed space. For more information, see: Compressed Space