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Submarine Command Systems.

The command system is the logical development of the more traditional combat system in older submarines. Today's nuclear-powered and conventional submarines (SSN, SSBN, SSK) have no problems in acquiring data from sensors. In fact, there is a high risk of data overload affecting the command team's ability to initiate the best response to a threat, but the command system's task is to use the most advanced information technology (IT) techniques to present the data in a form that aids decision-making.

In one important respect submarine command systems differ from those designed for surface warships: older-generation combat direction systems (CDS) generally deal with bearings-only and frequency data, and these cannot provide the operator with a full tactical picture. In other respects, however, they are similar to those systems found on surface ships, and must also maintain and process track information to support command decisions. Compiling a geographical picture is very complex because water is a hostile medium; although sound travels great distances, it follows irregular paths, depending on temperature and salinity, and a surprising range of marine noises makes identification of genuine targets very difficult. As a result, submarine command systems generate and store only a fraction of the number of tracks held by a surface system, but they must often be stored for long periods for comparison.

The modern submarine, Whether conventionally- or nuclear-powered, has a remarkable range of sensors providing inputs to the command system. The most important of these is the bow sonar (either cylindrical, spherical or `wrap-around' conformal), which tracks the target, usually in a passive mode, and uses digital processing. Flank arrays provide range-triangulation, while mine-avoidance and under-ice sonar provide a measure of self-protection. The towed array, originally a clip-on type but reelable in the latest large submarines, is used for long-range passive detection and surveillance. Add to these the inputs from the mast-mounted electronic support measures (ESM) and the visual data acquired through the periscope, and the need for a coherent and rational means of presenting this to a team of operators becomes obvious. A modern command system may even integrate self-protection decoys. What submarines have lacked is not inputs but a means of creating a tactical picture for the command team.

The command system addresses that problem, and uses computers to create an underwater tactical picture, known by the unglamorous term `situational awareness'. A typical command system forms the picture passively from the digital sonar feeding a series of automatic target-followers (ATF). Although it is theoretically possible to obtain Target-motion Analysis (TMA) automatically, in practice operators periodically submit targets to computer-aided manual TMA (known as Mate in the US Navy). If the target is not manoeuvring, the TMA solution can be projected ahead. In theory, a series of TMA solutions builds up into a tactical picture as the computer projects the movement of each target. But in practice targets manoeuvre, so a single operator can probably evaluate up to ten targets before it becomes necessary to re-evaluate the first target. It then becomes clear that the number of aided TMA stations in a submarine's CDS determines the number of targets it can handle.

The closer a submarine operates inshore, the less such limitations are acceptable, but the only alternative seems to be automation, which many submariners dislike. One way to achieve a solution to the problem is to merge multiple sensors, and it seems that references to new and powerful TMA algorithms generally indicate a mixing of available data from passive sensors. Another way is to use simple forms of analysis to eliminate the greater majority of targets as irrelevant, and leave the others to the semi-automatic TMA.

Automated submarine CDSs were attractive because they could accept a surface picture via a datalink, solving the age-old problem of submarines cooperating with surface forces.

The US Navy's Undersea Warfare Advanced System Technology Office has developed a software library aptly named the Submarine Force Mission Planning Library (SFMPL). This contains a wide variety of tactical aids, some vital to fire control (including new TMA algorithms). A typical submarine outfit has two Tac-series computers running SFMPL software, one for acoustics and the other for combat management.


IBM's Submarine Advanced Combat System (Subacs) was designed to replace the BQQ-5 sonar and Mk 117 fire control system in the later Los Angeles (SSN-688) class attack submarines. It seems to have been conceived as a submarine equivalent of the SQQ-89, a system that would detect targets automatically on a variety of arrays and combine the data into a single usable tactical picture. Compared to the BQQ-5, major sonar improvements were incorporated into the Subacs: the Submarine Active Detection System (Sads) digital transmitter, the BQG-5 Wide Aperture Array and a thin-line towed array. The Sads gives much greater beam-agility and more flexible waveforms, while the fire control and picture-compilation functions are carried out by a modified Combat Control System Mk 1. The main improvement is that several weapons-control elements are merged into a single Weapons Launch System (WLS) and own-ship data-collection is merged into an Own Ship's Data System (OSDS).

The first system, BSY-1, was delivered in July 1987, for installation in the submarine San Juan (SSN-751), and from the Scranton (SSN-756) onwards, all were completed with the full BSY-1 suite. Lockheed Martin was awarded the prime contract for the BSY-2 when it was split from the BSY-1 after the earlier system developed software problems in the mid-1980s. The BSY-2 strives to achieve the same goal as the BSY-1, largely distributed processing, multi-purpose consoles, combat system display consoles and a number of other improved displays. The first system cost about $ 280 million, and the others cost about $ 250 million each. The total programme cost is estimated at $ 7.4 billion, and was to have been amortised over 29 Seawolf (SSN-21) class, but the cutback to only three units makes the BSY-2 the most expensive submarine command system in the world.

The prototype BSY-2 system was delivered in December 1993 for the Seawolf, a second system has been supplied for the Connecticut (SSN-22) and another is on order for the Jimmy Carter (SSN-23).

Little has been released on the command system for the Virginia (SSN-774) class, and it is not certain that it will be designated BSY-3. The Virginia class' smaller hull size forces some compromises on the designers of the so-called New Attack Submarine Network, but on the other hand many sub-systems are now also lighter and smaller.

Over the Horizon

The German Submarine Consortium has broken all records in exporting submarines, both the conventional diesel-electric drive versions and two new designs with air-independent propulsion. The current Isus-90 (Integrated Sensor Underwater System) command system is a development of the STN Atlas Isus-83, built around the core of the CSU-90 sonar. The Isus-83 was developed for the modernisation of the Type 206 submarines, associated with the digital CSU-83 sonar.

The Isus-90 is an open architecture system, with all operational software written in ADA. MPR 2300-B processors are used throughout, with an STN Atlas RT 6400 chip. A typical system uses five multi-function two-screen colour consoles, three for sonar inputs and two for tactical displays. There is also a separate contact evaluation plot. The first export application was the Isus-90-1 supplied for the Israeli Dolphin class, while the Italian Navy bought the Isus-90-20 for its upgraded Nazario Sauro class boats. The Isus-90 will also be supplied to the Hellenic Navy for its new Type 214 boats, to the South African Navy for its new Type 209/1400 boats, and will probably be selected by the Republic of Korea Navy for its Type 214s.

The Royal Navy issued its Staff Requirement (Sea) 7566 in the early 1980s, to develop a command system for its planned Vanguard class strategic submarines (SSBN) and for an upgrade for the Swiftsure and Trafalgar class SSNs. In 1984, BAeSEMA and Ferranti (both now absorbed into BAE Systems) were awarded project-definition contracts for a SubMarine Command System (SMCS), leading to a contract for fourteen systems to BAeSEMA in April 1986, following-up six years later with another nine.
The Rest of the World

Modern Submarine Command and Combat Systems

Denmark Tactis Terma system for the Tumleren and
 Narhvalen classes
 Isaacs Export version of Tactics
Netherlands Sinbads Signaal system for export
 Gipsy Designed for Walrus class (Sewaco VIII)
Norway MSI-90U Kongsberg system designed for Ula class
 and German Type 212
Russia Uzel System in Project 877 `Kilo' type
South Africa Orca Indigenous Altech system for upgraded
 Spear class (Daphne type)
Sweden 9SCS Mk 3 Celsius system for Gotland class
UK Kafs RN DCC system used by Brazil
USA SFCS Mk 1 system used by Australia, Canada, India
 SFCS Mk 2 Used by Israel
 Subics 900 Offered to Egypt
 ACS Rockwell Collins system used in Australian
 Collins class [2000]

The system was based on the Submarine/Surface Ship Command & Control Evolutionary System for Successive Operational Requirements (Successor) family of hardware/software modules. Four variants were projected: SMCS-V for the Vanguard class, SMCS-S for the Swiftsure class, SMCS-T for the Trafalgar class, and SMCS-U for the second batch of the Upholder class SSKs. The SMCS-V entered service in 1993, and SMCS-S and SMCS-T followed a year later, but the SMCS-U was cancelled when the Upholder class was terminated at four boats. A fifth variant is under development for the new Astute class SSNs, formerly known as the Batch 2 Trafalgar Class (B2TC), presumably designated SMCS-A. The Swiftsure and Trafalgar classes are undergoing a major upgrade as well, based on the 2076 integrated sonar suite.

The usual SMCS layout includes four full multi-function consoles and three similar but less capable displays. These displays include a main tactical display and two remote terminals, one in the control room and one in the sonar compartment. The main consoles include touch-sensitive panels, two plasma displays, two fire control buttons and a graphics tablet. Under software releases 6 and 7 the Swiftsures and Trafalgars integrate the 2076 sonar suite and a new fibre-optic Tactical Weapon System Highway, allowing data fusion and de-fusion. Release 7 was scheduled for 2000.

The first French integrated submarine combat system was the UDS International/DCN International Systeme d'Armes Tactiques (Sat), which employed the Tit digital data-handling system integrated with a DLA-series fire control system. It entered service in 1985 in the Redoutable class SSBNs, and was followed by the derivative Sade system in the Rubis class SSNs. The next class of SSNs, the Amethyste class and the upgraded Rubis class, had the Thomson (now Thales) Subics (no relation of an American system using the same acronym), which was built around the Titac tactical data-handling system. The Systeme d'Armes Defensive (Sad) is part of the command system for the newer Triomphant class SSBNs, integrated with the Sytac tactical data-handling system.

The Submarine Tactical Integrated Combat System (Subtics) is a Thales system tailored to the export market, and was sold to Pakistan for the Khalid class SSKs. It is an open architecture system bearing a close relationship to Subics II, but using elements developed for the Triomphant class system. All sensors feed a dual-redundant databus though four processors. One manages broadband low-frequency inputs from the active sonar and the cylindrical bow array, a second handles broadband inputs from the ranging and intercept arrays, a third processes the narrow-band inputs from the flank and towed arrays and the fourth receives the inputs from the electronic support measures, optronic periscopes and radar. The system controls the F 17 wire-guided torpedoes and SM-39 anti-ship missiles through a torpedo/missile control processor. Each of six twin-screen Colibri multi-function colour consoles using 68040 processors is separately connected to the main system databus; there is no local area network.

Software is written in C and there are several major software modules:

* Classification/identification (audio and Lofar/Demon analysis, with generation of interactive hypotheses)

* Track management (automatic and interactive association and fusion, sorting of best representative acoustic tracks)

* Contact motion and analysis (automatic and interactive)

* Situation elaboration (refinement of the tactical picture by associating and fusing acoustic and non-acoustic data, conducting interactive TMA, and track management to select tracks of particular interest)

* Command and decision, threat-evaluation of localised and classified tracks, and attack and escape planning tools

* Engagement and launching modules, based on DLA-4A and DLT software, to launch two torpedoes and two missiles simultaneously.

The Subtics has been selected for the three Pakistani Khalid class SSKs, but it seems possible that more may be built at Karachi in the future. It is rumoured to also equip the modernised ex-Swedish Challenger class in the Republic of Singapore Navy, and will be the obvious choice if Thales wins the contract to build the Project 75 SSKs for the Indian Navy. The Subtics system is soon to be found on the new Chilean O'Higgins class (Scorpene type) subs as well.

Space does not permit full descriptions of every combat system afloat, but to recapitulate, they are growing more complex in their functionality, while paradoxically reducing the workload on the submariners.

In short

* "Paradox One: the ever-growing demand for information is gradually being satisfied by modern sensors, but in parallel, the flow of information is becoming difficult, not to say impossible, to manage"

* "The solution: while smart displays come to the rescue up to a certain degree, automation (though disliked) appears to be a sine qua non"

* "Paradox Two: combat systems are growing in complexity while reducing submariner workload."
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Author:Preston, Anthony
Publication:Armada International
Date:Aug 1, 2001
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