The USA's two designs of Littoral Combat Ship (LCS) look very different. The Freedom class is a monohull ship, whereas the Independence class. is a trimaran (designed by Australian shipbuilder Austral). The ships were in a competition from which one was to be selected, but the US Government decided to acquire both types. The Freedom is smaller and more suited to short missions, whereas the Independence is larger with longer range. The cost and complexity of acquiring two different ship types is lessened by using a common set of interchangeable Mission Modules.
The modules are shipping container sized units, with standard electrical, cooling and data interfaces, holding anti-submarine, mine warfare or other equipment. Also accommodation modules can be used for extra personnel. There is an "Interface Control Document" (ICD) defining the hardware interface between the ship and module (such as how much 440VAC 60Hz 3 phase electrical power is available) and a "Interface Design Specification" (IDS) defining the data communications interface (including use of CORBA).
In theory, much of the cost and complexity of the ships is thus in the modules. Also it would be possible to change the ships for different missions, but this is proving problematic in practice.
One interesting aspect of the mission modules is their use of Linux software. This opens the possibility of creating new modules with commercial off the shelf equipment. The modules could also be used in other ships, including civilian vessels pressed into service for military use. Rather than use the exact specification of the USA's LCS mission modules, a more flexible approach could be used with a blend of commercial and military interfaces. As an example, the same interfaces used for networking separate military platforms, such as ships, aircraft and vehicles, could be used to interface the mission modules. The fact that the modules where physically next to each other within a ship would not stop the use of the same networked interfaces as would be used if the modules where on independent ships, aircraft or vehicles. The ship would simply act as a way to house and transport the modules.
Australia has acquired and on order several amphibious transport ships with generous space for ISO sized modules. In his 2006 thesis for the US Naval Postgraduate School, Aykut Kertmen carried out an "EVALUATION OF THE LITTORAL COMBAT SHIP (LCS) POTENTIAL FOR THE TURKISH NAVY", including likening the mission modules to Lego.
The company Sea Bos, offer a "Mission Module Container", which is essentially a standard ISO shipping container modified for military use. In place of the usual double doors on the end of the container, it has two bi fold doors, making access easier on board ship. There is also a side door for personnel and an additional door opposite the cargo doors. The container has raceways in each top corner for cabling. The container is also fitted with insulated walls and air-conditioning. The walls, ceiling and floor are fitted with a rail system for installing equipment racks. Lastly teh container is painted standard military grey.
Integral refrigerated ("reefer") ISO containers have a standard power connection defined by ISO 1496-2 and can have a microprocessor for controlling temperature and communicate with the ship via a data sent over the power line using the ISO 10368 Standard. As these standards are in widespread civillain use, they may be of value for adoption for military modules.