Naval Tactical or Combat Management Systems

5. Naval tactical or Combat Management Systems were originally conceived to support immediate actions, particularly against air targets. Thus, the emphasis was on maintaining a plot as close as possible to the evolving tactical situation. Experiments shortly after the World War II showed that manual plots could not keep up with more than a few ac at a time, because of the time delays inherent in a radar operator's detection of a target and his report, between that report and the moment the report was plotted and also between entry and deduction of the target motion. Importantly, those in the Operations Room observing the evolving plot could not appreciate the latency of target information. Hence, Combat Management System design initially laid emphasis on limiting delays in reporting and in displaying information.

6. The forerunners in digital tactical data systems (such as American NTDS, the British ADAWS, the French SENIT and the Italian SADOC) initially began as Air Defence systems to control interceptor aircraft. They therefore emphasised upon the ability to keep track of numerous relatively distant airborne targets and could tolerate some imprecision in tracking (since the pilot, usually assisted by the aircraft's radar, could make up for inaccuracies of a few miles). A separate line of development came out of the requirements needed for gun (and then missile) fire control. The imprecision acceptable for fighter direction was far less acceptable for gunfire control. This line of development has manifested itself in systems like the American Aegis system.

Early NTDS

CMS Architecture

7. Systems such as the American NTDS were conceived before the advent of inexpensive micro computers. These systems supplied video to all the balance system consoles. Consoles, weapons and sensors were connected directly to the central computer in a star architecture. Any change in architecture or components required a combination of rewiring and reprogramming.

8. The next major change in system architecture was the placing of computers and other elements on one or more data buses. This did not necessarily change the functional aspects of the system, but it did make repair and replacement simpler. On the other hand, it demanded more elements in the system. As the data bus capacity was finite, the computer could not be expected to provide every monitor in the system with its video. Instead, it provided limited commands to the relevant consoles, to provide the necessary video by means of their own computing power. As the consoles gained computing power, they took up some of the tasks formerly resident in the main computers.

9. Combat Management Systems thereafter developed on either of two primary forms of architecture ie Centralised architecture or Federated system. The Federated system further developed into the Distributed System. The salient features s of these primary forms are outlined in the succeeding paragraphs.

10. Centralised Architecture. In centralised systems, the single central computer conducts calculations in addition to maintaining a coherent current tactical picture. In the American NTDS system, one computer maintains the tactical picture (including accepting and integrating data from the digital link) and analyses it. A second computer, a weapon direction system, generates maintains and analyses the a set of potential targets, from among which engagements are may be ordered. The two main computers are interchangeable and they provide some insurance against failure, as either can run the entire system. Actual fire control is the province of a separate fire control computer which could function even if the automated combat system collapsed. The British ADAWS series adopted a similar approach, the main difference being that missile and gun fire control functions were merged in a single computer.

11. Federated Architecture. Any central computer is limited partly by the number of different functions between which it must shift, which is a direct function of its computing power. One solution is to unload functions onto peripheral computers, ultimately leaving only the vital one of picture compilation to the central computer itself. This shift to federated processing initially exploited mini-computers introduced in the late 1960s and early 1970s. In theory, each console can be independently programmed, so new systems and new functions are relatively easy to fit into the system. Only the channel between the console and the central picture-keeping computer is firmly specified. The consoles can be separately wired to the sensors feeding them and to the systems they control. Existing systems generally require considerable integration between the programs in different computers, so that they can act together and one machine can take on additional duties in the event of a failure. The French TAVITAC and Italian IPN series used federated architecture. The two types of federated architecture are as follows: -

(a) Star. The picture-keeper connects to a series of secondary machines, each of which connects to a particular sensor and / or weapon. CAAIS is an example of Federated Star architecture.

(b) Ring. In this architecture, each computer is assigned a specific role, and all are wired together through a Data Bus.