Cruise missiles have become weapons of choice at sea because of their ability to fly close to the sea surface at very high speeds (sub-sonic/supersonic), formidable wave point programming, and lethal explosive capabilities
Blue water navies defend and attack with a variety platforms utilising a wide range of weapons. The three-dimensional operations of a formidable navy involve aircrafts, surface ships and submarines. Each of these platforms has weapons designed for its specific role. A naval force far away from its homeport is thus fully capable of meeting threats arising from the air, surface or under water. A warship’s weapon outfit includes missiles for anti-air and antiship warfare; torpedoes, depth charges and rockets for anti-submarine warfare; and guns for anti-surface, anti-air, anti-missile and naval gunfire support roles. Among the missiles, a warship’s outfit generally comprises of surface-to-surface missiles (SSM) and surface-to-air-missiles (SAM). The SSM capability has rapidly advanced to the realm of the cruise missiles.
The cruise missile owes it origins to the German V1/V2 rockets and mainly to the fact that manned aircraft missions had proved to be very expensive during the wars (loss of trained fighter pilots as well as expensive aircraft). Unfortunately, the cruise missile development until the 1970s resulted only in unreliable and inaccurate outcomes, which were not acceptable to the armed forces. Cruise missiles overcame their inherent technical difficulties and owe their tremendous success and popularity to notable technological advances in the fields of propulsion (small turbofan jet engines resulted in smaller and lighter airframes); miniaturisation of electronic components (smaller onboard computers led to much better guidance and control abilities); and high-density fuels, much better explosives, and smaller warheads. Cruise missiles have become weapons of choice at sea because of their ability to fly close to the sea surface at very high speeds (subsonic/supersonic), formidable wave point programming, and lethal explosive capabilities. These make the missiles very difficult to detect and counter at sea.
A survey of some of the most powerful weapon platforms at sea would confirm that the surface-to-surface missile is one of the most potent armaments onboard. The significant surface-to-surface missiles include the Tomahawk, the Exocet, the Uran, the YJ-18, the RBS15, the BrahMos, and the under development LRASM.
The Tomahawk Land Attack Missile (TLAM) has proved its versatility by successfully carrying out attacks on various types of land targets under hostile environments. The land attack Tomahawk is equipped with inertial and terrain contour matching radar guidance. The missile constantly matches its database with the actual terrain to update its position. For terminal guidance, it uses the optical Digital Scene Matching Area Correlation (DSMAC) system for comparing the actual target image with the stored one. In TERCOM a digital characterisation of an area of terrain is mapped based on digital terrain elevation data or stereo imagery and loaded in the missile. During flight, the missile compares the stored map data with radar altimeter data, missile’s inertial navigation system is updated, and the missile can correct its course if required. In DSMAC, a digitized image of an area is mapped and then embedded into a TLAM mission. While in flight the missile compares the stored images with the actual image for updating its inertial navigation system to enable course corrections.
The BrahMos is a supersonic ramjet cruise missile being produced under a joint venture between the Indian Defence Research and Development Organisation and the Russian NPO Mashinostroeyenia. It is the fastest cruise missile in the world with a range of 290 km.
The Tomahawk Weapon System comprises of four major components; Tomahawk Missile, Theatre Mission Planning Centre, Afloat Planning System , Tomahawk Weapon Control System for surface ships, and Combat Control System for submarines. Systems of the missile include GPS receiver; an upgrade of the optical DSMAC system; time of arrival (TOA) control, and improved 402 turbo engines. The missile is provided to ships as an ‘all-up-round’. It includes the missile, the booster, and a transportation container which itself acts as a launch tube. TLAM-C has a conventional unitary warhead for attacking hardened targets, and TLAM-D has a conventional submunitions (dispense bomblets) warhead for use against softer targets.
TLAM Block III system upgrade had included jamming-resistant GPS system receivers, TOA and improved accuracy for low contrast matching of DSMAC, extended range, and a lighter warhead. The warhead for Block IV, the WDU-36, has an insensitive PBXN-107 explosive, the FMU-148 fuse, and the BBU-47 fuse booster.
Tactical Tomahawk has the capability to reprogramme the missile during flight to attack any of 15 preprogrammed alternate targets or the warship can redirect the missile to any new GPS designated target. It is also able to loiter over a target area for some hours, and with its onboard TV camera, enable battle damage assessment and if required redirection of the missile to any other target. Addition of network-centric warfare-capabilities is a major improvement to the Tomahawk where in it can use data from multiple sensors (ships, satellites, aircraft UAVs, etc.) to find its target as well as share its own sensor data.
The new features in Block IV modifications include a new multi-mode passive seeker. As far as warhead is concerned, it is understood that Joint Multi-Effects Warhead System, bunker busting feature as well as Advanced Anti-Radiation Guided Missile technology is being incorporated for increasing the warhead versatility. The TLAM-D contains 166 submunitions in 24 canisters; 22 canisters of seven each, and 2 canisters of six each of Combined Effects Munition bomblet used with the CBU-87 Combined Effects Munition of the US Air Force. Developments are also underway to use scramjet technology and make TLAM a supersonic missile with a speed of Mach 3.
The MBDA’s Exocet
The variant Block 3 MM40 is the shiplaunched version of the Exocet. The basic body design of the Exocet is based upon the Nord AS30 air-to-ground tactical missile. It has a solid-propellant booster and with a turbojet sustainer motor providing it a range of more than 180 km. It is a missile, which flies 1-2 m above the sea level and remains very difficult to detect until about 6 km from the target. It is guided inertially and has an active radar terminal guidance. The Exocet MM40 has three main versions Block 1, Block 2 and Block 3 for deployment from ships as well as coastal batteries. The Block 3 version can attack targets from different angles through GPSbased waypoint commands. It weighs 670 kg, with a warhead weight of 165 kg.
The Russian Uran missile is a subsonic anti-ship missile with active radar terminal guidance. It is the booster launch version of the Kh-35U missile. Target designation and flight mission details are fed to missile prior to the launch. The missile is guided through inertial navigation system until it reaches the target zone. There after the radar is switched on for locating and tracking the target, once target has been acquired the missile traverses at very low altitude until it hits the target. It is said that it can be launched in sea states up to six. The acquisition range of the radar is 20 km. The ARGS-35E radar is being replaced by SPE radar MMS built Gran-KE seeker. The Uran is highly secure even in a hostile counter-measure environment. It has a weight of 610 kg with a shaped charge warhead of 145 kg.
The YJ-18 is a Chinese anti-ship cruise missile with a NATO designation of CH-SSNX-13. It is said to be a copy of the Russian 3M-54E that is subsonic during the cruise phase and turns supersonic in the terminal phase. It has a range of 540 km. It may be having a BeiDou based inertial guidance with a warhead (explosive/anti-radiation) of 300 kg. It is said to be deployed from the Type 052D destroyers.
The RBS15 is potent long-range surface-tosurface missile developed and manufactured by Saab Bofors Dynamics. It weighs 800 kg with a blast/pre-fragmentation warhead of 200 kg. It has inertial, GPS guidance with active radar terminal homing. It has range of 250 km and cruises at subsonic speeds. The RBS15 Mk3 missile system is claimed to have extremely flexible trajectory, an advanced target seeker with all-weather capability and high defence penetration capability. Saab claims that it will support the missile system throughout its 30-year service life and offer in-country maintenance and other flexible maintenance solutions for its customers.
The BrahMos is a supersonic ramjet cruise missile being produced under a joint venture between the Indian Defence Research and Development Organisation and the Russian NPO Mashinostroeyenia. It is the fastest cruise missile in the world with a range of 290 km. Because of its high speed (close to Mach 3), it can penetrate current anti-missile defences. It has a wingspan of 1.7 m, diameter of 70 cm with a warhead of 200 kg. Its Block III version can carry out land attack also. It is understood that it has been tested in supersonic dive mode, without any seeker; against hidden land, targets with G3OM based navigation system, which can use GPS, GLONAS, as well as the Indian GAGAN satellite systems. BrahMos-II (K) is a hypersonic missile under development with a range of 290 km and a speed of Mach 7. It is likely to be propelled with scramjet air breathing jet engine.
Missiles of the Future (LRASM)
DARPA is developing an anti-ship cruise missile with advanced stealth features as a replacement for the Harpoon missile for the US Navy. Lockheed Martin has been given a limited production contract for 90 missiles to meet US Navy’s urgent requirements. In August this year, the US Navy has officially designated the air-launched LRASM as the AGM-158C. LRASM will be fitted with a modified Mk 114 jettison-able rocket booster for launch from ships using the existing Mk 41 Vertical Launch System. LRASM is likely to herald autonomous targeting capabilities by utilising onboard targeting systems. The LRASM would not require GPS, data links or any prior intelligence, it would be able to carry out positive identification of its target and track and attack it on its own. It will have advanced counter-countermeasures to penetrate the enemy defences under highly adverse conditions.
The basic design of LRASM is derived from the AGM-158B JASM-ER with addition of a new weapon data link, radio frequency sensor (multi-mode), altimeter, and better power system. It is a sea skimmer with a range of 370 km, which can be guided to target, given midcourse corrections, or function in stand-alone mode for selection of the target. The guidance system and the homing head have been designed by BAE Systems. These comprise, imaging infrared homing with automatic scene/target matching recognition, jamming resistant GPS/INS, passive RF and threat warning, ESM, radar warning sensors, and data link. Data link enables the missile to collate real time digital picture of the target zone from friendly assets. The emission data is autonomously classified, and acquired for generation of the missile’s attack trajectory. The LRASM can search and attack the target on its own using the active radar, the multimode homing head enables the missile to avoid being decoyed and hitting the incorrect target. It is claimed that the missile can also operate in swarms and has land attack capability.
Cruise missiles are very expensive weapons costing millions of dollars per piece. Therefore, selection of the target becomes a difficult task, as cost-benefit analysis has to be carried out prior to launching the cruise missile on its mission. However, with their minimal signatures in the visual, infrared and radar spectrums they become weapons of choice in mission of high priority and stealth.
It appears that the trend towards developments of supersonic/hypersonic scramjet cruise missiles will continue to gather momentum and such missiles could be in the naval inventories by 2020. Coupled with hypersonic missiles, would be real time target data updating and guidance by extremely fast onboard computers and satellite-based systems. The kinetic energy of hypersonic cruise missiles would be a lethality multiplier against targets at sea and therefore such a missile would be a formidable weapon without a credible countermeasure as on date. The costs continue to increase with new developments; however, maintenance requirements appear to be reducing with canisterised missiles. The proliferation of precision guided missiles would continue to increase with reductions in cost of components, electronics and software.
The author is former DGNAI and Senior Fellow, New Westminster College, Canada