SMCS, the Submarine Command System, was first created for the Royal Navy of the United Kingdom's Vanguard-class submarines as a tactical information system and a torpedo weapon control system. Versions have now also been installed on all active Royal Navy submarine classes.
Initial Phase: SMCS for Vanguard class With the decision in 1983 to build a new class of submarine to carry the Trident missile system, the UK Ministry of Defence (MoD) ran an open competition for the command system. Up to that point all Royal Navy (RN) ships and submarines had command systems built by Ferranti using custom-built electronics and specialised proprietary processors. In a departure from previous practice, which had favoured 'preferred contractor' policies, the competition was won by a new company called Gresham-CAP, leading a consortium of Gresham-Lion (now part of Ultra Electronics plc) and CAP Scientific. The consortium proposed a novel distributed processing system based on commercial off-the-shelf (COTS) processors, with a modular software architecture largely written in the Ada programming language. Each set of Initial Phase SMCS equipment has multiple computer nodes. At the centre of the system there is an Input/Output Node (which provides interfaces to weapons and sensors) and a Central Services Node (which holds fast numeric processors). Each central node is duplicated to create a fault-tolerant system which is dual modular redundant. The Human-Computer Interface (HCI) is provided by multifunction consoles and some additional terminals. The dual redundant central nodes are linked to each other and to the consoles via a dual redundant fibre optic LAN. In the initial phase equipment fitted to the Vanguard-class submarines most processing is done by Intel 80386 single-board computers, each with its own Ada run-time environment. CAP Scientific created a complex layer of middleware to link the many processors together. At its time SMCS was the largest Ada project so far seen. As a pioneering user of Ada, the SMCS project encountered many teething problems with the large-scale use of Ada compilers, Ada development tools, and the special characteristics of the early dialect of the Ada programming language, later known as Ada 83.
Second Phase: SMCS for Swiftsure and Trafalgar class By 1991, CAP Scientific was part of Sema Group and the SMCS project was owned by BAeSEMA, a joint venture between Sema Group and British Aerospace. Once SMCS was proven to work on Vanguard boats, it was proposed in the early 1990s to extend its use to the Swiftsure-class submarines and the Trafalgar-class submarines, as part of an improvement programme for these vessels. There was a commercial desire for yet further adoption of COTS technology. The consensus was to port SMCS to some form of UNIX. Sema Group, with considerable experience both of real-time systems and of commercial UNIX, had concerns about the technological feasibility of this port. The essence of the problem was the need to map the Ada tasking environment to the run-time model of UNIX processes in a way which preserved SMCS' real-time characteristics enough to maintain dependability. A team from BAeSEMA, led by Ray Foulkes, conducted thorough research into possible alternatives to the distributed Ada architecture used in the Initial phase. After extensive investigation of the run-time behaviour of different UNIX variants, and of the code generated by different Ada compilers, the project selected the Solaris operating system running on SPARC computers, which could now be procured as COTS single-board computers. To limit risk, only the consoles were converted to Solaris on SPARC in this phase. The central nodes were kept in the same form as the Initial Phase equipment. The benefit was that there was no need to implement the dual modular redundancy scheme on Solaris at this stage. However, the project had to manage some additional issues arising from mixed intel/SPARC working, such as endianism (since intel architecture is little-endian and SPARC is big-endian). A detailed and generally accurate independent analysis of these stages in the development of SMCS was made in 1998.
Third Phase: ACMS for Astute class After being successfully deployed on the Swiftsure and Trafalgar submarines in the mixed Intel/SPARC configuration, the architecture was further revised for the UK's new attack boats, the Astute-class submarines. The Astute Combat Management System (ACMS) combines SMCS with several other sub-systems. For ACMS, the Central Nodes have also been converted to SPARC computers. The dual redundant architecture, both of central nodes and of LAN connections, remains a key feature. There are about twice as many consoles as provided in earlier versions of SMCS. This phase of SMCS is an all-UNIX solution running Solaris on multiple SPARC nodes, with built-in dual redundancy.
Submarine Command System Next Generation
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