|Last Updated: Mon Jan 27 11:18:09 UTC 2014|
Naval Air Defence
Editor's Note 2005: while
dated technologically, the issues raised in 1983 analysis not only
remain, but have become more pronounced with the regional and global
proliferation of advanced Russian weapons like the Moskit, Yakhont,
Uran, Ovod and Krypton. The advent of X-band active array anti-missile
radars such as the APAR and the SPY-3 will for the first time introduce
a credible capability to deal with saturation missile attacks.
Roma, Eilat, Sheffield - all of these warships have something in common. The Roma was sunk in 1943, by a remotely guided glidebomb launched from a Luftwaffe bomber. The Eilat fell victim to an SS-N-2 Styx turbojet radar guided antiship missile in 1967. The Sheffield was gutted, after being hit by an air launched AM.39 Exocet missile, in 1982.
History repeats itself, again and again, but navies often seem oblivious to the very real threat presented by the anti-shipping missile. Absurd as it may seem, only few of the warships despatched by the Royal Navy to the Falklands were equipped to cope with anti-shipping missiles.
Then one may look at the Soviet Navy, its ships bristling with SAM systems and gatling guns, yet devoid of the air-cover which can so effectively protect them.
Modern antishipping weapons are sophisticated systems, often fitted with devious microcomputer brains to evade defensive gunfire or SAMs. This means that elaborate measures, usually costly, must be adopted to counter them. In this sense, they are a powerful deterrent, on the other hand, they are equally effective as an offensive weapon, dealing crippling blows with single strikes.
The range of weapons which may be used in the antishipping role is enormous. Whether one looks at the near sinking of an Argentine corvette by a couple of marines, armed with an antitank rocket launcher, or the crippling of the USS Worden, in the Gulf of Tonkin, by a runaway Shrike antiradiation missile, it is apparent that ships are extremely vulnerable targets.
They are slow, they have radar cross-sections of a great size, large infrared signatures and to make things worse, usually radiate lots of energy throughout the electromagnetic spectrum. Take the worst attributes imaginable, for making a survivable weapon, combine them - and presto, you have a modern warship.
Easily detectable, incapable of any evasive manoeuvring worth speaking of, ships can only rely on the effectiveness of their defensive systems and the cover provided by aircraft, to protect them.
Due to their large signatures, they can be detected with virtually any form of guidance imaginable, this reflects in the incredible number of weapons used in the role.
One could start with the lightweights, for instance wire guided rockets (the author declines to use the term missile) as the AS.12. These weapons are steered onto the target by an operator, the projectile unwinds a wire pair from a spool, as it flies to the target (this form of guidance is important, in the historical sense, as the guided, rocket boosted glidebombs and piggyback Ju-88 Mistels of the Luftwaffe used it, quite successfully, during WW II).
A more sophisticated approach to the problem does exist, for a short range, lightweight weapon, that being semiactive radar guidance. British Aerospace Sea Skua represents such a weapon. Meant to disable its target (tell that to the Argentine patrol boat, which sank after a hit), it is a light and simple weapon, launched from the Lynx ASW helo, it homes in on targets illuminated by the Lynx's Seaspray radar (see TE, June 1982), the objective of a hit being the damaging of radar and communication antennae and arrays. Without these, the target is blind and defenceless, it must withdraw or become easy prey for the helo's mother vessel: With a range below 8 nm and only 35 kg of warhead, the four rounds carried by the Lynx hardly represent a major threat to large vessels, however, the system should keep an opponent on its toes.
Taking things one step further, we can look at shorter range missiles with the capability to seriously damage or sink a vessel.
The somewhat obsolete AGM-12 Bullpup fits in this class. These missiles employ radio command link guidance, a radio receiver is fitted inside the missile, incoming commands are fed into a control computer. This computer monitors the weapon's pitch/roll/yaw rate, via a set of gyroscopes, and will cancel out any errors, which it sees as deviations from commanded rates. The pilot (or weapon systems officer) of the launch aircraft merely steers the weapon into the target, with a short joystick. The obvious limitation lies in the necessity of being within visual range of the target, which also limits operation to clear weather.
An improvement on this would be the AGM-65 Maverick. This missile was initially developed for the anti-armour/fortification role, versions being fitted with modular TV (A), magnifying TV (B), laser (C) and Imaging Infra-Red (IIR-D) guidance kits. The TV/IIR guidance provides the weapon with fire and forget capability.
Prior to launch, the pilot will slew the missile's nose mounted camera onto the target, observing the scene on a CRT in the cockpit. Placing the missile's crosshairs onto the target, an electronic contrast lock engages, and the weapon may be fired. The missile's guidance will then fly it directly into the region tracked by the contrast lock. With 60 kg of shaped charge, tanks are doomed (Maverick has apparently demonstrated an 88% kill rate), just as patrol boats or hovercraft are. Vessels such as destroyers could be disabled, possibly even gutted, if they were to sustain more than one hit.
The IIR D model offers a night capability, aside from the ability to see through camouflage or smoke screens, coupled with its fire and forget capability, and 14 nm range, the AGM-65D is a potent weapon for close-in attacks on shipping. The disadvantage of the AGM-65 is the necessity to close to visual range, which may render launch aircraft vulnerable to SAMs.
The British Aerospace AJ168 Martel avoids this problem, via the use of TV/command link guidance. After launch, the missile is steered from the launch aircraft, via a radio command link, the crew observing a scene transmitted from the missile's nose camera, via a datalink. With a range of 30 nm, the weapon may be launched from a standoff position; once within close enough range of the target, the operator engages an on-board contrast lock, much like the AGM-65, and the missile enters its terminal homing phase, hitting the target at Mach 2, its impact fused 150 kg warhead inflicting maximum damage.
Optimised for the antishipping role, Martel is a more dangerous weapon than the Maverick, but its more complicated guidance places greater demand on the launch aircraft.
The newly developed British Aerospace Sea Eagle Anti-Ship Missile will give aircraft such as the Sea Harrier (pictured) a quantum improvement in the maritime strike role. Sea Eagle is said to be longer ranging than its American equivalent, the Harpoon, and also to have the ability to analyse and disseminate false information being given out by the defending target in an effort to break the lock that the missile's guidance and acquisition unit has on the intended target. In this way the Sea Eagle becomes a truly 'smart' anti-ship sea skimmer whereas its market competitors rely largely on attacking the most obvious radar return available.
At this stage we can allow ourselves a digression, to take a peek at anti-radiation missiles. These weapons employ passive radar homing, diving onto a selected source of microwave radiation. In essence developed to counter air-defence systems and obliterate SAM launch and guidance systems, ARMs have a significant -(and little publicised) role in antiship warfare. If a vessel is to protect itself from the whole spectrum of airborne threats, it is nearly always forced to employ radar to locate and track the enemy. Doing so, it is a perfect target for an ARM, the USN learning this the hard way, when the destroyer USS Worden was disabled by a Shrike ARM, during the Vietnam war.
The proximity fused missile detonated 30 m above the vessel and crippled its control centre; it was most likely launched by an A-7, with the intention of wiping out a North Vietnamese radar site.
The defensive measure commonly employed is the powering down of the radar, after the launch of an ARM. Attacking aircraft may approach at high speed, launch an ARM and wait to see if the radar powers down. If it doesn't, the fast (better than Mach 2) ARM will most likely penetrate the SAM/gun screen and disable the vessel; if the radar goes down, the aircraft may penetrate close enough to press home an attack with missiles such as IIR Maverick, and the vessel has severe problems, countering say a four round salvo. The advantage offered by ARMs is large lock on range, the ability to choose a specific target and high speed, aside from a small radar cross-section, head-on, and a lack of radar emissions to alert the victim.
The established ARM in US service is the Texas Instruments AGM-45 Shrike, a Mach 2 weapon with a 66 kg fragmentation warhead and circa 10 nm of range. The Shrike airframe is a development of the AIM-7 Sparrow AAM. The successor to the Shrike is the Texas Instruments AGM-88A HARM (High-speed ARM); this weapon may be launched by aircraft not fitted with complicated warning receivers (e.g. APR-38 as on F-4G), it is intended to arm the F/A-18A, A-6E and F-4G. The F-18 may carry up to four rounds, which maybe launched in a Self-protect, Target-of-opportunity or Pre-briefed mode.
Other notable ARMs are the GD Standard and the Matra AS.37 Martel. ARMs can vastly complicate the life of most navies, particularly those which lack air cover, as this allows attackers to get in close enough for launch.
Another class of weapons which deserves attention at this stage, are laser guided bombs (see TE, Sept. 1981). The TI GBU-10, 12, 16 Paveway family represents the most wide spread weapon currently in service. LGBs are difficult to use, where the opponent has decent SAMs; however, if the vessel under attack has to rely on guns or short range/low altitude SAMs, the LGB may be quite effective (the limits of its launch envelope lie at 30,000 ft/7.5 nm). A direct hit by a 2000 lb demolition bomb will sink most modern, soft-skinned vessels.
In this sense, the LGB is an effective means of taking out defenceless tankers, freighters, troopships or anything else devoid of effective air cover.
The F-111 C/Pave Tack combination offers a very effective means of delivering this class of weapons (one should never underrate the free fall demolition bomb, where it can be used, it is devastating; consider the Battle of Midway, or count RN losses in the Falklands, as a recent reminder).
Another newer member of the Pave series is the Rockwell/Hughes GBU-15 Cruciform Wing Weapon, a modular glide bomb built around the Mk 84 2000 lb demolition bomb.
Currently in the process of being integrated with the RAAF F-111C, the GBU-15 allows for low altitude release (toss bombing) between 200 and 1000 ft at ranges up to 5 nm. After release, the bomb is steered via command link, the F-111C navigator viewing the scene from the bomb's nose camera on a cockpit CRT. Once in visual range, the seeker may be locked on to the target, like the AGM-65, and the bomb glides into its victim. The GBU-15 does have range limitations, but it packs a lot of punch and has no IR signature worth mentioning. Later versions of the CWW may carry the IIR seeker developed for the AGM-65D, enabling night/adverse weather operation.
Having exhausted our options among general purpose weapons, we can now turn to dedicated, sea skimming anti shipping missiles. Up to recently, this class of weapon was used only by the more advanced powers, but the late seventies saw the proliferation of sea skimmers among Third world countries.
The author declines to categorise the SS-N-2 Styx, and its air launched cousins, among true sea skimmers, as these weapons seem to follow shallow, low altitude, diving trajectories, obliterating the target with massive 2000 lb warheads.
The various members of the Aerospatiale Exocet family are becoming very popular with developing countries, as they are very simple to operate; delivered as packaged rounds, they require little support. This places further incentive on the major powers, to deploy naval air power, as air power is the most effective and failsafe means of stopping Exocet, by destroying the missile's launch platform before it may launch the weapon.
Harpoon! The illustration depicts the low level run-in phase of the AGM-84A's flightpath. Harpoon is smokeless, with a low infra-red and radar signature, which makes it difficult to detect and even harder to destroy. Upon reaching the target vessel the missile will drop to an extremely low height above the waves, punching through the side, penetrating deep inside before the delayed fuse detonates the warhead. Smaller vessels such as destroyers or frigates seldom survive the effects of the 227 kg warhead. Harpoon is in the inventory of the RAAF for use from P-3 Orion aircraft and will soon be available for the F-111 C in addition to the F-18A when that aircraft becomes operational through the mid-eighties. Harpoon is also used by the RAN aboard the FFG frigates, the DDG destroyers and the Oberon class submarines.
The AM.39 Exocet is a 4.69 m missile, weighing in at 660 kg (165 kg blast/fragmentation warhead). Powered by a solid propellant rocket, the missile cruises at Mach 0.93 to a range of up to 40 nm. Released at medium to low altitude, with range/bearing information supplied by the launch vehicle (generally the Super Etendard fitted with the Thomson-CSF Agave X-band monopulse radar; this aircraft is a light strike fighter, which would easily fall prey to any modern fighter), the missile descends to a cruise altitude of 10-15 m, under the control of its twin gyro inertial navigator coupled with a radar altimeter. The missile activates its active radar seeker when 6-8 nm from the target; once locked on, it descends to 5 m, just prior to impact, Exocet drops to 2 m. Fusing is impact and backup proximity. Though Exocet is an earlier generation sea skimmer, with limited range and large IR signature, it does have home on jam modes and is a quite lethal weapon, as evidenced by the fate of the Sheffield and Atlantic Conveyor. Even an unsophisticated (i.e. incapable of correctly fusing iron bombs) service as the Fuerza Aerea Argentina could operate the weapon, which proved to be a real pain in the neck for the RN, with no AEW and limited fighter cover.
Another weapon in the class of Exocet is the slightly smaller Messerschmitt-Bolkow-Blohm Kormoran, carried by F-104Gs and Tornadoes of the West German Navy.
A superior class of sea skimmers are the newer, turbojet powered weapons, offering greater range, lower IR signature, smokeless operation, at the cost of slightly lower speed. The dominant weapon in this class is, currently, the McDonnell Douglas AGM-84A Harpoon, used by most advanced Western nations. Harpoon is carried by the RAN's Oberon class attack subs and FFG frigates, the air-launched version by the P-3C Orion. The weapon is being integrated with the fire control of the F-111C and will be a standard fit on the F/A-18.
The air-launched AGM-84A Harpoon is slightly smaller and lighter than Exocet, weighing 527 kg; the missile is 3.84 m long.
Harpoon may be physically divided into four sections. The nose of the weapon, covered by a dielectric radome, contains the guidance section. This comprises a Texas Instruments PR53/DSQ-28 two-axis, frequency agile, active radar seeker for terminal homing, and a midcourse guidance unit consisting of a Lear-Siegler or Northrop three axis strapdown inertial reference system, an IBM 47piSP-OA general purpose digital computer and a Honeywell AN/APN-194 radar altimeter. The ordnance section follows, being comprised of a Naval Weapons Center 227 kg penetration blast warhead. The missile is fitted with a delayed impact fuse and proximity fuses, to ensure detonation. The sustainer section begins just fore of the main wings and runs to the tail of the missile. A one shot Silver-Zinc battery, the power source for on-board systems, is situated between the wings, inside the sealed, non-vented fuel tank which carries the JP type fuel. The semiflush, fixed inlet for the engine lies between the ventral pair of wings.
The engine is a Teledyne CAE J402-CA-400 single spool turbojet, delivering 600 lb of thrust at sea level. The final section of the missile is wrapped around the tailpipe of the engine; it contains four electromechanical control actuators, which move the four control surfaces on the tail of the missile. Harpoon is supplied as a complete round, the fitting of its wings and fins is the only major operation required to upload the weapon on to the launch aircraft.
Harpoon may be launched with the aircraft at various attitudes and speeds. Immediately after release attitude control activates, stabilising in roll and maintaining a constant 33 degree dive angle, until the radar altimeter commands pullout. During the dive, the weapon begins to steer toward the target and the turbojet is activated. Harpoon then levels off at its cruise altitude, under control of the midcourse guidance unit. Once a specified distance is reached from the target, the radar seeker activates and commences its search pattern. The missile has two main modes, Range and Bearing Launch, where the target range and bearing are roughly known, or Bearing Only Launch, though the missile may also be launched without initial data, by pointing the aircraft in the direction of the target for 40 seconds prior to launch or casualty (Line-Of-Sight mode). Initial target information is derived from sensors on the launch aircraft, say radar or electronic surveillance equipment, and may be entered automatically or manually.
RBL mode has three search patterns, Large, Medium and Small. The Large pattern is used at maximum range; it searches a small area and then expands the pattern until a target is detected. The Small pattern offers good discrimination between closely spaced targets, but need not work at maximum range.
BOL mode will attack the first target detected, activating the seeker during the initial dive.
The active radar seeker is frequency agile, this allows it to circumvent jamming and avoid interfering with other Harpoons, aimed at close or identical targets. After the target has been detected, Harpoon locks on and commences its low level run-in, the altitude depending on the wave size. At a specified range, the terminal phase manoeuvre commences. Harpoon may be preprogrammed to a number of trajectories, ranging from an ultra low sea skimming attack, for vessels with defensive SAMs or guns, in order to confuse the fire control with clutter from the surface, to medium and high apogee pop-up attacks, ideal for small, fast manoeuvring targets as missile/torpedo boats, the weapon diving down and punching through the deck. The missile employs proportional guidance in the azimuthal plane.
Harpoon represents a flexible and effective all weather antishipping missile. One of its greatest assets is flexibility in targeting, as the launch aircraft may gain bearing information on its target via the use of radar warning receivers and launch Harpoon without even being detected. Alternately, it may provoke a vessel into an ECM battle, to ascertain its bearing, and then launch. Finally, it may use information supplied by other aircraft or vessels. Combined with high performance launch platforms as the F-111C or F/A-18A, Harpoon becomes a serious threat to any navy not equipped with the best in lookdown shootdown air cover, capable of stopping these aircraft at least 60 nm from the defended vessels.
The Lynx helo-mounted BAe Sea Skua is a short range (15 km) weapon intended for use against small maritime targets such as patrol boats, light freighters and landing and support craft. Sea Skua more than proved itself in the Falklands where it was used successfully while still not being fully cleared for operational deployment. Lynx typically carries four such missiles and is one of the helicopters short-listed for eventual use aboard the RAN's new FFG frigates.
Having entered service in the late seventies, Harpoon is, by no means, the last word in standoff anti-shipping weapons. The General Dynamics MRASM (Medium Range Anti-Ship Missile) is a derivative of the AGM-109 Tomahawk cruise missile airframe, with a conventional warhead and Harpoon guidance system, offering a range of several hundred miles. This weapon would equip USN aircraft and vessels; it may also be fitted to long range maritime bombers (a possible pre-retirement role for the B-52).
A supersonic successor to the Exocet is under development and the British Aerospace Sea Eagle is likely to enter the scene very shortly.
What one could expect to see in future anti-shipping missiles is a separation into two major classes. Short range weapons, in the 30 nm class, will become smaller and faster, being launched by agile, high performance fighter bombers. Long range weapons will remain slow, but are likely to increase in range, and acquire much more devious guidance, combining say radar with IR systems possessing the capability to recognise and select specific targets from their shape/thermal signature.
These weapons would employ stealth measures and follow complicated terminal homing trajectories to confuse the target's point defence SAMs and guns. Either way, unhealthy systems to tangle with. The question arises, what are the defensive measures and how effective are they, in the face of such weapons?
That will become the subject of Part 2.
Once Australia's F-111 force completes its avionics update, is fully operational with the Pave Tack acquisition system and is armed with Harpoon and Paveway laser guided bomb then these 1000 nautical mile plus radius of action strike aircraft will present an enormous deterrent to any likely maritime aggressor.
Even quite sophisticated systems, such as the GWS-25 Seawolf, may have problems, finding it necessary to revert to optical tracking, under some conditions. Though it is often acknowledged that the best means of countering these weapons is destroying the launch vehicle, only the US Navy has taken appropriate measures to that effect, while still sensibly fitting its vessels with point defence weapons.
The seriousness of the problem is aggravated by the arms supply policies of both the US and France, as high performance weapons such as Harpoon have been supplied to Iran (one can question how long it will take for a carbon copy Harpoonski to appear), and countries such as Saudi Arabia, which need hot remain stable. The Aerospatiale Exocet has become one of France's hottest selling export items, since the 1982 Falklands war.
Countering the various anti-shipping missiles in the inventory of the Voenno-Morskiy Flot, the Soviet Navy, the Aviatsia Voenno Morskovo Flota, Naval Aviation and finally the Dal'naya Aviatsia, the Long Range Aviation command of Soviet Military Aviation (Voenno-Vozdushnye Sily - VVS), is enough of a task on its own, but Western naval forces will have to contend with their own weapons, aircraft and missiles, as was demonstrated in the South Atlantic.
The structure of naval air defence systems differs from service to service. The United States' Navy has the world's most effective air defence system in use, the system itself has gradually evolved since World War II and it reflects the great importance the United States place on the ability to deploy air power anywhere and any time.
USN deployments are usually structured around a carrier battle group, generally comprised of one or two conventional carriers, one or more missile equipped cruisers and an array of destroyers, tankers and supply vessels, the battle group will often operate in conjunction with nuclear attack subs.
The key element in the air defence system is the Grumman E-2C Hawkeye AEW (Airborne Early Warning) aircraft. The E-2C can detect targets up to 220 nm and track them at low level. The first line of defence are the Grumman F-14A Tomcat fighters, which receive direct datalink information on the targets from the E-2C (for detailed account see Carriers in the Indian, March 1982).
The fleet usually has two to four Tomcats on ForCAP (task force CAP); usually a pair will engage targets at the limit of the defensive zone, with the 100 nm AIM-54 Phoenix or 50 nm AIM-7F Sparrow radar guided missiles, head-on. Aircraft which penetrate this screen are then mopped up by Tomcats armed with Sparrow or AIM-9L Sidewinder IR missiles; in the future this close-in role is to be assumed by the F-18A.
Given that an intruder escapes the fighters, it must tackle the CG-47 Aegis air defence cruiser, with its massive RCA SPY-1A phased array radar system. The cruiser will fire the 60 nm range RIM-66C Standard 2 SAM. Assuming the enemy has eluded the Standard, it must face the RIM-7M Sea Sparrow SAM and the carrier's last ditch defence, the GD Vulcan Phalanx radar directed gatling gun.
As capable as the system may appear to be, it has its opponents, who generally claim that any aircraft which penetrates the outer defences need not do any more than launch a small standoff missile with a 1 Megaton+ nuclear warhead which need not hit anything, but will definitely make a mess if it goes off anywhere within 5 to 10 nm of the carrier.
One may assume that only the USSR would possess that capability, otherwise it is unlikely that conventional aircraft following conventional attack profiles would be successful.
The Royal Navy had structured its air defence system into the US system, up to the Falklands events, intending to rely on US AEW capability when operating in range of hostile land-based aircraft. As a consequence, the RN assumed it would carry out independent operations only in the North Atlantic, where it would have to deal with long range maritime patrol aircraft, such as the Tu-20 Bears and Tu-16 Badgers, later perhaps the reported turbofan successor to these ex-bombers.
The primary line of defence is the subsonic Sea Harrier FRS. Mk 1, armed with Sidewinder AAMs and 2 x 30 mm cannon. Its radar has very limited range and does not possess lookdown-shootdown capability, a serious deficiency in the air defence role. The Harrier is backed up by the 45 nm GWS-30 Sea Dart area defence SAM, launched primarily from the type 42 destroyer or Invincible class carrier.
Point air defence was to be provided by the GWS-25 Seawolf SAM, carried by some frigates, though many vessels carry the Short Seacat. As the events of May and June 1982 were to prove, this system was inadequate, as the RN lost three warships and two landing ships to direct bombing attacks and a destroyer and transport to Exocet sea skimmers. The principal cause was the lack of AEW, though the Harrier's limited CAP payload range (in spite of which 30 Argentines were downed with no losses) and deficiencies in and/or lack of adequate close range SAM cover share the blame.
As a countermeasure the RN is fitting Phalanx to its Invincible class carriers and after 11 weeks of development, deployed an AEW Sea King helo, fitted with a modified EMI Searchwater radar set, adapted from Nimrod MR.2. This AEW helo is a very basic substitute for the E-2C and is limited in range and capability. It is unlikely anything will be achieved with the Harrier's payload/range, though its radar is to receive an update. In its current form, the RN air defence system cannot deal with any high performance strike aircraft and has limited capability against standoff sea skimmers.
The Soviet Navy, or Voenno-Morskiy Flot, has limited, if any, air cover, that being provided by the rather mediocre Yakovlev Yak-36 Forger, armed with AA-8 Aphid IR AAMs, embarked on Moskva and Kiev class helo carriers. The principal area defence weapons are the 20 nm SA-N-1 Goa SAM, carried by Kresta I and Kynda cruisers and destroyers, and the newer 30 nm SA-N-3 Goblet SAM, which arms the Kiev, Moskva and Kresta II classes.
Signaal, of the Netherlands, have produced an effective anti-missile, anti aircraft close-in weapons system in their Goalkeeper. Basically Goalkeeper is similar to the General Dynamics Phalanx except that it uses the slower fire rate but higher projectile force 30 mm Hughes chain gun from the Fairchild A-10 Thunderbolt ll ground attack aircraft. Like Phalanx, Goalkeeper is fully self contained and can literally be 'bolted' onto the clear deck space of almost any ship above patrol boat size.
Intruders penetrating the SAM screen must face the SA-N-4 close-in SAM system and radar directed guns (presumably derivatives of the 23 mm gatling used in strike aircraft), these weapons carried by the Kiev, Kirov classes aside from smaller vessels.
A new vertical launch area defence weapon, the SA-N-6, is entering service on the Kirov class battlecruisers and Sovryemmeniy class destroyers. As the V-MF operates without viable air cover, this reflects in their in-depth SAM and gun defences, a modern battlecruiser being armed with two classes of SAM backed up by guns.
The question is, of course, how effective are these systems against small, fast, low flying targets (it appears nobody is willing to try them out). The lack of AEW, some degree of which may be provided by the Ka-25 Hormone B helo otherwise tasked with missile targeting, would be a major weakness - the low performance of the Forger does little to offset that weakness.
Changes are likely to occur when the reported 80,000 ton conventional carrier enters service, but that may be some time in the future. At this stage, Soviet surface vessels would appear to be vulnerable to some sea skimmers and standoff weapons, given there is adequate standoff jamming (ECM) to degrade their detection capability.
As the Russians do not have reasonable AEW, their vessels must employ radar constantly (unlike US carrier battle groups, which often operate under radio/radar silence), leading to the option of using anti radiation missiles - attackers may employ ECM to penetrate the relatively small 30 nm defensive perimeter and then launch ARMs. The limited radar horizon would make strikes far easier for F-111 class aircraft.
Having examined the air defence systems, briefly, we may now look at each class of weapon.
The most effective class of weapon, in terms of lethality, range and flexibility, are fighter aircraft. In order to be successful in this role, they must have the following attributes -- lookdown shootdown radar, track-while-scan capability against multiple targets, all weather radar guided missiles and short range dogfight missiles, good climb rate, top speed and dash capability and maximum endurance for combat air patrol (CAP). Only the F-14 and the F-18 meet these requirements, being tailored for the role.
The Sea Harrier cannot satisfy the role and it is unlikely the AV-8B or future Sea Harrier versions will satisfy anything but basic defence against lower performance aircraft - high performance platforms (F-111 class) with standoff missiles will penetrate (The author points out that an Amraam fitted Sea Harrier will lack radar range, dash speed and CAP endurance to cope with a threat such as the Tu-26 Backfire, though it could obviously handle anything put up by Third World countries.)
The outlook for the future may focus on supersonic V/STOL or STOVL fighters, however at this stage, the USN has too much invested in conventional carriers and Britain cannot afford anything more than improving than the Sea Harrier. The situation will change when the survivability of a conventional carrier degrades to a level unacceptable to the USN, then some spending will occur.
Area Defence Weapons are an important part of any air defence structure, filling the gaps in the fighter screen and stopping intruders which found their way through. Probably the most lethal weapon in this class is the vertical launch SA-N-6, supposedly derived from the SA-10. This 1500 kg missile is fitted with active radar guidance (see TE, June 1982), and has a cruise velocity close to Mach 6; its limitation lies in its 27 nm range.
Long range, on the other hand, is the strength of the British Aerospace Dynamics Sea Dart, which can hit targets beyond 45 nm (classified). The Sea Dart employs a rocket booster for launch and initial acceleration to Mach 2; after burn-out, a variable thrust Rolls-Royce Odin ramjet powers the missile during its Mach 3.5 cruise. Illumination for the semi-active radar guidance is provided by the Marconi type 1022 and 909 surveillance and tracking radars, operating in the E/F and G/H bands respectively (two 909 sets provide illumination).
The GD RIM-66C Standard 2 ER is an improved, extended range version of the Standard missile replacing Terrier on cruisers and destroyers. It is the primary weapon of the CG-47 Aegis cruiser, which launches the missile from the Martin Marietta EX-41 Vertical Launching System. Unlike versions of the Standard launched by other vessels, RIM-66A/67A, Standard 2 does not require continuous target illumination, thus reducing time available for the target to take defensive measures.
RIM-66C employs the same airframe as earlier models, including the Mk 30 Mod 2 sustain engine and Mk 12 Mod 1 booster, allowing a Mach 2.5 cruise, but the guidance has been altered. The missile employs an inertial reference unit for midcourse guidance and receives target position updates from the massive SPY-1A E/F band phased array surveillance/tracking radar. The SPY-1A employs four fixed, flat, electronically phased arrays, each tilted slightly upward, providing continuous 360 degree radar coverage from the horizon up. The phased array has no moving parts, the shape and direction of the search or tracking beam being controlled very rapidly by electronic means; this allows the system very short reaction time and the ability to track targets as soon as detected. The SPY-1A operates in conjunction with a set of Mk 99 fire control systems. Target illumination is carried out only for the terminal homing phase of the Standard, which has an I/J band monopulse seeker installed instead of the usual conical scanning unit. CG-47 has four SPG-62 illuminators, all slaved to the SPY-1A, which provides all tracking information. The missile is fitted with impact and proximity fusing.
The Standard/Aegis weapon system is being retrofitted to some DD-963 destroyers converting them to the CG-47 cruiser, also raising the cost to a staggering $1400 million apiece; the question is, whether the system will perform. The SPY-1A can apparently track hundreds of targets at once and has a search range of the order of 200 nm, rather excessive for the 60 nm SAM it operates with. On the other hand, an immensely powerful radar of this kind would be near impossible to jam at missile launch range.
Whatever arguments one may raise for or against the system, its excessive cost (the USN wants 16) will confine it solely to the USN inventory.
If an aircraft or missile penetrates the area defence missile screen, it must be stopped by a close-in Point Defence Weapon. These come in various types, whether missiles or guns currently, or lasers and particle beams in the future. The missiles in use employ a number of guidance systems, as follows:
Maritime air defence system supreme. Grumman's massive F-14A Tomcat fighter can deal with multiple targets up to a range of 100 nm, at high, low and medium altitudes. The primary sensor is the huge AWG-9 radar and fire control system which detects targets at ranges in excess of 100 nm. Target identification capability will be improved with the fitting of Northrop TCS (Television Camera System), a derivative of the TISEO stabilised TV telescope, In ACEVAL/AIMVAL tests, a TCS equipped F-14A identified an F-111 at 40 nm and an F-5 at more than 10 nm. With its three classes of AAM, gun and automated fire control, the F-14A represents the ultimate in naval air defence weapons. (Dave Erickson, USN)
Seacat employs Command-to-line-of-sight (CLOS) in one of its various forms. When optically tracked, the operator steers the missile onto the target with pitch/yaw commands via a radio command link; the missile has a flare on its tail which allows the operator to clearly identify it as it flies to the target. In spite of its clear weather limitation and demands on operator skill, Seacat managed to down six Argentine aircraft during the Falklands war; while operated in confined spaces (San Carlos) it was not confused or affected by land mass, as are radar guided weapons.
This class of weapon cannot effectively cope with sea skimmers, as its ability to track a target depends on operator skill, which is inadequate for the manoeuvring trajectories of modern weapons.
An improvement is offered by the GWS-25 Seawolf, which employs fully automatic CLOS or semi-automatic CLOS guidance. In the fully automatic mode the type 967/968 search radars detect and track all targets in range. If a trajectory indicates a hostile target, the monopulse type 910 tracking radar locks on, after missile launch tracking the target and up to two missiles. The system calculates course corrections for the missile from track information and steers it into the target. The missile flies at Mach 2+ and is fitted with a proximity/impact fused 13.4 kg warhead. Given that the radar has difficulty tracking the target, TV tracking is employed for the target, radar tracking missile only, steering it to the LOS. Seawolf was the only missile system the RN deployed in the Falklands with the capability to stop sea skimmers (during its trials, Seawolf apparently downed a six inch cannon shell in flight), it also took its toll of aircraft, in one instance decimating an incoming wave of A-4s by downing two and ditching one of four Its disadvantage is its lack of fire and forget capability, only two missiles may be handled at a time, which suffices for self defence, but won't really help other vessels to be covered.
A further weakness, in this sense, lies with current (perhaps by time of reading changed) threat assessment software which apparently looks for trajectories aimed at the launch vessel only, i.e. a passing Exocet aimed for someone else could be ignored.
The Soviet SA-N-4 appears to employ similar guidance, using a low light TV system for backup target tracking; one could assume that the Soviet weapon would force more operator control over threat assessment (less automation).
Another commonly used weapon is the Raytheon RIM-7 Sea Sparrow, a modified version of the early AIM-7 AAM. Sea Sparrow is currently being replaced by two newer weapon systems, the RAM and Phalanx.
General Dynamics RIM-116A RAM is a specialised weapon tailored to the task of stopping sea skimmers. The RAM (Rolling Airframe Missile) employs a Sidewinder engine (this implying a velocity around Mach 2.5), warhead and fusing, Stinger IR seeker, and is launched from a rifled tube; this imparts rotation during launch.
The standard launcher is derived from Phalanx, with 24 launch tubes, and would be aimed in the direction of the incoming missile during the several seconds after detection. RAM is then launched, employing twin aerials on its nose to passively home in on the sea skimmer's radar transmissions. Once within adequate range, the IR seeker, resistant to most common counter-measures, engages and initiates terminal homing. The GaAs laser optical proximity fuse then detonates the 11.4 kg fragmentation warhead.
RAM is to enter production this year, to arm USN, West German and other (NATO) vessels. Ram offers the advantage of being a fire and forget multishot weapon; the only serious weakness it may have could prove to be an inability to find small turbojet missiles with a lot of IR background radiation; rocket propelled weapons have hotter and larger exhaust plumes (e.g. Exocet) and should be readily detected.
General Dynamics' Phalanx is a system based on the proven M-61A1 six barrel gatling gun. The M-61 fires 20 mm ammunition at the rate of 6000 rounds/minute (100 rounds/second) and is the standard cannon fitted to US fighter aircraft. Phalanx uses an M-61 which is coupled to a tracking radar and computer, all mounted on a rotating platform. The system employs closed loop tracking, where the radar tracks the incoming missile and the fired stream of ammunition. Shells fired by the system have flat rear faces, to reflect the radar energy, the nose of each shell is configured to convey a maximum ability to penetrate surfaces with small radii of curvature. The position of the stream of gunfire is thus monitored and the computer steers it onto the target, constantly attempting to zero the position error between the target and the end of the stream. Phalanx does an impressive job of chewing drones to pieces in mid air. The weapon should work effectively on most current sea skimmers. The advantage of the system is its suitability for retrofits, as it is a self contained weapon requiring little more than electrical power hookups.
Phalanx is being fitted to all USN carriers, replacing Sparrow launchers, in most instances. Most surface vessels will be fitted, including the FFG-7, which is being supplied to the RAN. At the time of writing, HMAS Adelaide was not fitted, but her sister ships were scheduled to receive the system.
HMS Illustrious sailed for the South Atlantic, in mid-1982, after a rushed fitting and testing of the system, as it was obviously reasoned that a sneak Exocet attack by the Argentines could not be ruled out.
The future outlook for point defence systems is bright (it has to be, looking at some of the sweet little missiles being cooked up worldwide), it appears a lot of research is being focused on beam weapons (see TE, December 1981), particularly lasers.
A US Navy F-18A takes on fuel from a KA-3 tanker. The USN will use its multirole F-18s to replace F-4 Phantoms in the inner circle air defence role and early model A-7s in the attack role. From the late eighties the F-18A Hornet will be equipped with both ASRAAM and AMRAAM advanced missile systems. (USN)
Lasers offer the advantages of agility and multishot capability, sizzling the target to a crisp in 1-3 seconds, but their weakness lies in the requirement of clean optics, something a trifle difficult to guarantee in a maritime environment. Further problems revolve about the tracking systems, which should be accurate to 10-5 rad^-5 at least, this is rather difficult to achieve. The teething problems are not insurmountable; but they will take time and cost a lot of money. A practical laser weapon will not enter service in the next few years. High energy electron beams and particle beams are being experimented with, but they are far behind lasers and would suffer the same difficulties with tracking.
Naval air defence philosophies will remain a battleground for various factions throughout the world, as all sides try to counter the opposition's, and their own, antishipping weapons, generation after generation. As effective as some systems are, they always seem to appear too late and in too little numbers. In this sense, defence planners should carefully consider their choice of weapon, to avoid rapid obsolescence.
Sea skimmers are here to stay and the RAN should take decisive measures, if it wishes to stay afloat. The future will tell how appropriate current decisions are.
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