ANTI SHIP MISSILES(ASM/AShM)
The advent of the anti-ship missile has increased the vulnerability of naval ships.this article aims to provide a brief idea of anti ship missile system and related details.
ASMs can be launched from OTH (over-the-horizon) distances, at sea skimming altitudes just above the top of waves and have sufficient ECCM by which they can counter at least some of the countermeasures applied by the ship. eg HARPOON, EXOCET, URAN etc
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In addition to the sea-skimming altitudes, their high transonic speed makes early detection hard which translates into a very short response time for the appropriate countermeasure.
the response time is further reduced by the advent of anti-ship missiles with maneuvering capability at supersonic speeds. eg brahmos,moskit
The threat is even worse if a number of these missiles are launched from different platforms
simultaneously ie coordinated attack to saturate the air defenses of the target ship.(WOLF PACK MODE)
Some of the ASMs are capable of locking on to the radar emissions of a ship. most modern missiles have anti-jam capabilities and either shut off their seekers and continue on the previous path or lock/home on to the jammer (Home On Jam) if jammed. also many missiles are capable of locking on to the IR signature of a ship making them even more dangerous.newer ASMs are capable of differentiating between the chaff and the ship by using pulse doppler radars in their seekers.
u must understand that radar can act as a homing beacon for some ASMs and thus cannot be relied upon totally as it may have to be shut down in case the missile locks on to the radar emissions.
the other method of detecting the ASM is the ESM on board the ship. using the forward scatter of the missile radar, it should be detected at long ranges. although most sea skimming missiles do not go active until they are fairly close to the target they do have to operate their radar altimeters all the time. a part of this signal is reflected by the waves in the forward direction and could be picked up by a ships ESM systems if they are sensitive enough to detect this forward scatter . this opens up the possibility of jamming the altimeter frequency.
Also a missile not using the altimeter continuously would have to operate at higher altitudes and thus become vurnerable to the anti air missiles.
However, if the missile uses passive HOJ or locks on to the IR signature of the ship it would not be detected by conventional ESM. also the use of spread spectrum techniques in the missile radars makes them much harder to detect by ESM. the problem of stealth used by some missiles nowdays can be overcomed by looking for them in the IR region due to that fact that they cannot reduce their IR signature especially if they go to higher operating speeds. thus the IR detection systems will allow us to detect the ASMs.
Also missile like NSM use stealth technology to reduce the RCS and thus reduce the reaction time of the defender. these advance missiles have various ECCM techniques incorporated and thus the ships ECM is rendered useless.
There are 4 stages involved in a missile attack by a ASM
1. the first phase depends on first detecting the target ship. one has to locate and identify where the enemy ships are. this is the surveillance phase. radar is one type of sensor which is used for surveillance. the surveillance radars may in some cases be land based but can also be mounted on satellites, aircrafts uavs etc.
2. the 2nd stage is the deployment of attacking launch platforms and selection of specific targets for missiles or gun fire. this is called the targeting phase. the radars employed in targeting are usually aboard the ships or aircraft that launch the Anti-Ship Missiles.
3. in the third phase, i.e the mid course guidance phase occurs after the missile launch. the midcourse portion of the guidance phase may or may not use radar sensors. some anti- ship missiles use inertial guidance untill they approach the target, then turn on their radar and acquire the target.
4. the fourth phase is the terminal guidance phase, in which the missile radar/IR seeker is actively
tracking the target ship, and attempts to home on the radar echo/heat signature.
thus for a anti ship missile to be successful it is necessary for each of the stages to be successfully negotiated.
In order to effectively engage the missile, detection and tracking of the missile has
to be maintained by means of active and the passive sensors.
1. active detection includes radar and laser.
2. passive detection includes detecting the missiles active radar, electronics, acoustic, thermal IR emissions and other power sources from the target.
Passive detection ranges are much greater than the active detection ranges due to the one way propagation of the electromagnetic wave in the propagation medium. after initial detection and identification is gained, a targeting solution is obtained by employing specific location of the target. once the targeting solution is obtained the anti-missile weapons can be launched. active detection and targeting sensors are in turn subjected to passive detection by the enemy defence providing alert and warning. the best solution is of course to destroy the missile launch platform. however, this is not always possible.
One way of putting the enemy at serious disdvantage is to make them shoot at nothing i.e use decoys, electronic warfare, and even hack the enemy network to create illusory targets. 3 layered defence envelope is necessary to shoot/seduce the incoming missile with
1.anti-missile missiles eg RIM-162 ESSM , Barak 1 & 8 etc
2.close-In Weapon System eg Phalanx , AK-630M , Type 1130, OTO Melara- medium calibre guns etc
3.decoy systems (chaff, flares or active decoys are employed to seduce attacking anti ship missiles by creating false targets.)
eg MASS (Multi Ammunition Soft Kill System) shipborne decoy launcher system: MASS is a compact, reactive and fully automatic soft-kill launcher system deploying programmable multi-spectral Omni-Trap decoy rounds with radar, IR, laser, EO and ultraviolet payload, thus providing protection against against anti-ship missiles employing radio frequency (RF) microwave, infrared (IR) and/or electro-optical (EO) seekers.
also Off-board Corner Reflector (OCR) decoys can be utilize to provide an improved capability against anti-ship RF seekers.
however in a fast paced sea battle u can run out of anti missile interceptors, since they are carried only in small numbers.another option is to use laser weapons or electromagnetic rail guns, which are kind of unhindered by the no of reloads.
also modern ASMs capable of turning around and searching for the ship again if it has been decoyed by a chaff,IR decoys etc and has not hit anything. Thus we can see that ASMs are getting more and more intelligent and becoming very dangerous adversary to deal with.
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