SM-2 for the FFGs

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The SM-2 missile, which has been ordered for the FFG Upgrade project, provides something approaching an area air defence capability; this weapon will also arm the new AWDs.
Although the SM-1 missile is being replaced in the FFGs, mainly because it has long been out of production and is unsustainable, equipping the Adelaide class frigates with the SM-2 missile will provide a significant lift to their anti-air warfare capability.

First developed in the 1960s, SM-1 has a range of some 50km whereas anti-ship missiles in regional inventories can now be fired from aircraft well outside that range (in excess of 120km) and many can out-manoeuvre the SM-1 missile. Additionally, the FFG is able to only engage two air targets simultaneously, whereas a number of countries in our region of interest are able to program multiple missiles, fired with impunity from outside SM-1 range, to arrive simultaneously and swamp a ship's defences.

Another drawback to the SM-1 missile is that it relies on a dedicated Fire Control radar to illuminate the target throughout its flight, which effectively alerts the aircraft, so that it can take timely evasive action, whereas SM-2 relies on an R/F uplink for guidance and the target is illuminated only in the final phase. And as we have noted, besides these technical limitations, the SM-1 missile is no longer in production and cannot be supported for much longer.

In its operational modes SM-2 is a much more capable missile than SM-1 in terms of both range and improved warhead, and assuming the FFG's sensors are up to the task (and aren't outrun by the missile) the SM-2 equipped FFG will have the potential for a true area air defence capability. The version being acquired, the Block IIIA, is the last version of SM-2, which can be fired from the FFG's rail launch system. SM-2 Block III introduced an improved Target Detecting Device for better performance against low-altitude targets while Block IIIA came with a new warhead with heavier grain explosive.

Subsequent versions (Block IIIB onwards) are designed for vertical launch systems. The forward-mounted Mk 41 vertical launch system that is being installed as part of the FFG upgrade, has been designed to accommodate ESSM not SM-2, hence the need to modify the Mk 13 'one-arm-bandit' rail launcher, until now used for Harpoon and SM-1.

So where are we now with the SM-2 program? The decision to acquire SM-2 for the FFGs followed a study into the replacement of the SM-1 missile as Phase 3 of Sea 1390 the FFG Upgrade project. Under Phase 4A approval was given to the FMS procurement of the Mk 698 Test Set and its installation at the ADF Guided Weapons maintenance facility at Defence Area Orchard Hills, Sydney to coincide with the introduction of SM-2.

On 12 July 2004 the Government agreed Second Pass approval to upgrade four FFGs, with lives beyond 2006, to fire SM-2 missiles. The approved budget was $582m (2004 prices). A year later the US Defense Security Cooperation Agency notified Congress of a possible Foreign Military Sale to Australia of up to 175 SM-2 Block IIIA Standard missiles as well as associated equipment and services.

According to the statement Australia had requested up to 175 SM-2 Block IIIA
Standard missiles, up to 30 Telemetry missiles, up to two SM-2 Block IIIA Inert Operational missiles, together with canisters, containers, spare and repair parts, supply support, personnel training and training equipment. Also included were publications and technical data, US Government and contractor technical assistance, and other related elements of logistics support. The total value, if all options are exercised, could be as high as $US315 million ($424m).

But while the SM-2 program is being progressed under Sea 1390, the missile's integration and installation is being arranged not with prime contractor ADI Limited, but with the rail launcher OEM (BAE Systems Land & Armaments) for its modification, the Mk 92 OEM (Lockheed Martin Corporation), with the USN SM-2 Integration Agent (BAE Systems North America) for overall integration with the FFG's modernised Mk 92 fire control system and various others.

The rail launcher, or more correctly the Mk 13 Mod 4 Guided Missile Launching System (GMLS), is an interesting - if now somewhat outmoded - system for storing, retrieving and launching a variety of missiles. Since 1962, when it was first introduced into service, more than 100 Mk 13s have been installed aboard cruisers, destroyers and frigates of the US Navy and those of eight allied forces. The RAN had three systems on the DDGs and another six on the FFGs. Like the Mk 41 VLS, the Mk 13 is a compact system that can be assembled dockside and installed aboard as a single entity. At Garden Island ADI has the only MK 13 GMLS complete repair facility outside the United States.

The Mk 13 system comprises the familiar 'one armed bandit' launcher above deck and the cylindrical magazine immediately beneath. This last has a rotating structure comprising and inner and outer ring, which can store up to 40 missiles ready for service. A hoist raises a missile from either inner or outer magazine rings to the launcher guide arm (or lowers it from launcher to magazine as necessary). The magazine ring rotates in either direction corresponding to the shortest distance from the selected missile to the hoist position, thus speeding up response times when under attack.

Control of the Mk 13 rail launcher normally occurs remotely from the Mk 92 fire control system (FCS) and all AAW and normal SSW firing is ordered from the FCS. But local loading and pointing of the missile from the adjacent control console is possible for jettisoning (of defective missiles), strikedown exercises and on-loading, off-loading and casualty operation. Harpoon missiles can be fired from the control console if a major casualty occurs to the FCS and Harpoon firing must be continued.

In response to a missile select order from the Mk 92 FCS or local order from the control console, the magazine ring indexes to bring a missile of the ordered type to the hoist position for loading to the guide arm. When the missile is in proper position on the guide arm, it is secured and contact established with the internal missile circuits. The launcher then trains and elevates in response to the FCS pointing orders. When the FCS initiates missile firing a fin opener cranks open the folded missile fins, the missile is armed and the forward motion latch is unlocked. With these actions complete the missile rocket motor ignites and the missile is fired.

While its predecessor, the SM-1, is strictly a home-all-the-way missile relying solely on illumination of the target for its acquisition, the SM-2 IIIA missile's primary mode of target engagement uses mid-course guidance via an R/F link with radar illumination of the target for missile homing during the terminal phase. (Mid-course guidance with relevant modification of the Mk 92 FCS has been acquired as part of the SM-2 FMS procurement.)

The Fire Control System (FCS), Mk 92 is the US Navy's version of the Signaal M20 series FCS and is widely deployed on board FFG 7 ships in conjunction with the Mk75 3-inch (76mm) Gun and the Mk 13 GMLS. The MK 92 FCS integrates target detection with multi-channel anti-air and anti-surface missile and gun systems control, engaging up to four targets simultaneously. The MK 92 track-while-scan radar employs the Combined Antenna System (CAS), which houses both search antenna and tracker antenna inside a single egg-shaped radome. A separate Target Illumination Radar (STIR) designed for the FFG-7 Mk 92 FCS application provides a large diameter antenna for target illumination at ranges beyond CAS capabilities.

The Mk 92 FCS has been upgraded to Mod 12 under the FFG upgrade program. According to prime contractor ADI, the Mod 12 system includes improved signal processing and further use of solid state electronics. To support both SM-1 and ESSM missile engagements new CWI transmitters were designed and built providing a growth path to SM-2. The upgraded FCS provides improved performance against very small RCS sea skimming missiles in high clutter conditions and greater reliability and maintainability. The existing functionality in Surface Warfare has been maintained including integration with the Harpoon weapon system.

The introduction of the SM-2 capability requires the updating of the technology and accuracy of the inertial navigation system (INS). The current gyrocompass needs replacing so that more precise own-ship movement parameters (eg pitch, roll, etc) together with additional data, such as movement rates (horizontal and vertical rates of motion) can be supplied to the Weapons Control Systems (WCS) software.

This accurate information regarding the launching platform is necessary so that the SM-2 missile can be correctly initialised for flight to the Predicted Interception Point. The intended replacement unit is the AN/WSN-7B INS, a standard US Navy MOTS item which is form, fit and function compatible with the current FFG AN/WSN-2 gyro-compass. Procurement is again through FMS to gain access to economies of scale from US Navy ordering.

It is anticipated that Ordnance Alteration (ORDALT) instructions for the modification of the Mod 12 FCS to provide full SM-2 capability will be undertaken by a US consortium comprising NAVSEA and BAE Systems NA and its Land & Armaments group, with kits presumably then provided for installation by ADI or BAES employees.

Modifications to the Mk 13 GMLS are relatively minor with the provision and laying of ablative insulation at the base of the magazine and the launcher arm deck surrounds to minimise blast effects from the more powerful rocket motors. Again ORDALT instructions are being prepared by the OEM (BAES A&L) for these and other tasks on the GMLS including changes to magazine components and the control console circuitry to suit the new missile.

By Tom Muir, Canberra
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