Survivability of a CBG in combat

Issues Details: 
Vol 11 Issue 1 Mar - Apr 2017
Page No.: 
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An enriching exposition of operations against a CBG post detection
Vice Admiral Pradeep Chauhan, AVSM**, VSM, IN (Retd)
Wednesday, March 15, 2017



The Jan-Feb 2017 issue of this magazine (Vol 10, Issue 6) presented readers with a review of the cost-effectiveness of the Carrier Battle Group (CBG) as the embodiment of maritime air power. It also invited them to appraise the ‘survivability (defensibility)’ of the CBG in terms of combat-surveillance and resultant detection. These, it would be recalled, are the opening stages of the standard combat cycle involving sequential ‘Surveillance, Detection, Classification, Identification, Localisation, Tracking, Attack-Criteria (i.e. Evasion/Engagement), and Damage Assessment’. This piece dwells upon the post-detection stages.

If detection has, indeed, been achieved by the adversary, he has now to overcome the ‘classification’ challenge.  In terms of traffic density, the Indian Ocean is the busiest of all the world’s oceans, with over 120,000 ships transiting the International Shipping Lanes (ISLs) of this ocean every year.  On our western seaboard, the Strait of Ba-el-Mandeb (connecting the Gulf of Aden and the Red Sea) accounts for some 22,000 ships annually, while the Strait of Malacca on the country’s eastern seaboard accounts for a staggering 70,000 ships every year.  Amongst these numbers are several large, fast ships, many of which are of a comparable size and speed to that of an aircraft carrier, but are not warships at all.  Examples include Ultra Large Crude Carriers (ULCCs) such as those operated by the shipping company ‘TI’ (Tankers International), Very Large Crude Carriers (VLCCs), the five 19,100-TEU cellular container carriers that are owned and operated by the China Shipping Container Lines (CSCL), a number of cruise-ferries and cruise-liners, several ‘car-and-truck’ carriers, and, a large variety of ‘Roll-on-Roll-off’ [Ro-Ro] ships.  Moreover, heavy-lift warships as also those designed for amphibious operations (such as the French Navy’s Mistral Class) and a number of Classes of LPDs [Landing Platforms Dock]), can also be quite easily mistaken for aircraft carriers.  The latter of course, may be expected to routinely employ AIS-spoofing techniques to negate the ability of the mandatory fitment aboard merchantmen of IMO-approved AIS (Automatic Identification System) to distinguish a warship from a fast merchantman. Thus, the process of correct classification requires Long-Range Maritime-Patrol (LRMP) aircraft and is by no means as simple as it might initially appear.  Despite enjoying its reputation as a ‘hunter’, every LRMP aircraft is acutely aware that when ‘hunting’ for a CBG, it is simultaneously the ‘hunted’ and is extremely vulnerable to attrition by the Combat Air Patrols (CAP) that are routinely mounted by Carrier-based fighters such as the MiG-29K.  As such, every time the LRMP aircraft makes a detection of what it thinks might be an aircraft carrier — but which might well turn out to be a carrier-sized merchantman or a ‘non-carrier’ warship such as a fast LPD — it has no choice but to assume that every such contact is, indeed, the enemy aircraft-carrier.  Consequently, it is forced to immediately adopt a series of gambit tactics designed to promote its own survival against interception by carrier-based aircraft.  These departures from its mathematically-designed search-pattern seriously degrade the ‘probability-of-detection’.  This, as any experienced LRMP crew knows, is a very serious limitation and plays havoc with the entire process of executing a planned ‘Search’ by airborne scouts. 

The foregoing challenges notwithstanding, let us assume that a contact that has been detected is classified as an aircraft carrier.  The next problem is that of ‘identification’: whose aircraft carrier, is it?  This question is germane because extra-regional aircraft carriers (especially those of US and French navies) are regularly deployed in both, the Arabian Sea and the Bay of Bengal.  Were one of these to be engaged by a trigger-happy LRMP Pakistani or Chinese aircraft searching for the Indian Navy’s CBG, the consequences are likely to be catastrophic.  Although it is possible for an LRMP aircraft to affect a ‘search mission’ while using only passive means such as ESM (Electronic Support Measures), acoustic devices (sonobuoys, for example) and electro-optics, such a ‘search’ would yield a low ‘probability-of-detection’. As such, more often than not, a ‘search’ mission seeking to confirm the presence or absence of a CBG in the area being searched, would be undertaken at least partially by active transmissions on the airborne radar of the LRMP aircraft. The constituent ships of the CBG, being far more capacious than an LRMP aircraft, carry a far greater variety of Electronic Warfare suites of far greater sophistication than an aircraft can.  As such, an LRMP aircraft transmitting on its radar is very vulnerable — first to detection by any or all of the excellently data-linked constituents of the CBG and thereafter to interception by carrier-based aircraft data-linked to highly-qualified aircraft-direction teams and equipped with state-of-the-art Beyond Missile Range (BVR) well before it can reach its own ‘weapon-release-line’ (WRL). 

Next assume that the CBG has indeed been detected, correctly classified and correctly identified. The attacker must now make a series of command decisions leading to the launch of weapons, and these weapons must now transit the space between their point of origin and the carrier. While all this is occurring, the carrier is moving.  For instance, during a 30-minute period, a carrier doing 22 knots could have manoeuvred anywhere within a circle measuring 1,304 km2 (380 nm2).  In just a little over 90 minutes, this area grows to 11,736 km2 (3,500 nm2)!  Thus, if the CBG is not ‘tracked’ continuously — or at least continually, — positional errors could easily become very significant.   And yet, the requirement of continual/continuous tracking increases the probability of destruction of even a missile-equipped LRMP aircraft by carrier-based interception manifold. LRMP aircraft-holdings in the inventories of our potential adversaries are severely limited and every loss of an LRMP aircraft imposes a very severe penalty on the adversary’s overall capability in terms of maritime operations. This is because it is these very LRMP aircraft that are required to ‘trigger’ the launch of shore-based aircraft of the enemy air force that have been earmarked for ‘Maritime Air Operations’ (MAO). Without this trigger, the MAO Commander does not know when exactly he should launch his own Fighter Ground Attack (FGA) aircraft to attack the carrier. This is a critical input to him because in attacking the CBG at large distances from the coast, his aircraft will need to operate with a number of limitations.  They will consume a significant amount of fuel in the transit to and from their weapon-release line. As a result, their time-on-target will be limited.  If a tanker-aircraft is deployed near the seaward limit of the autonomous radius-of-action of the FGA, the refueller itself will become a strategically important (and hence hugely attractive) target for the carrier-borne aircraft and, as a further consequence, additional resources will have to be committed by way of air-defence fighter-aircraft so as to ensure its safety.  The enemy’s shore-based strike-aircraft would, perforce, be operating well outside the cover of their land-based radars and hence be bereft of direction by their Fighter Controllers.  On the other hand, the Carrier’s own fighters, operating in the ‘interceptor’ role, would have relatively more fuel and hence greater combat-time (time-on-task). They would be operating within the radar cover of the CBG as a whole, and, with their contemporary armament of BVR air-to-air missiles, would have the advantage of being directed by ship-borne fighter-controllers (known in the Indian Navy as ‘Direction Officers’). It is clear that the MAO Commander ashore cannot afford to fritter away the fuel-endurance of his aircraft by launching them too early and, yet, he certainly cannot afford to launch them too late. Consequently, the timeliness and accuracy of the ‘launch-trigger’ provided to him by his LRMP aircraft is a sine qua non for his operations. Similarly, where enemy conventionally-powered submarines are concerned, they will need to be redeployed in order to intercept the highly mobile and comparatively speedy CBG.  This redeployment is achieved through what is known as ‘MR-Sub Cooperation’ (‘MR’ = ‘Maritime Reconnaissance’ aircraft, and is just another term for an LRMP aircraft). The aircraft typically remotely triggers a shore-based Very Low Frequency (VLF) station and provides the information required for one or more submerged diesel-electric submarines to undertake ‘Contact-Motion Analysis’ (CMA) and accordingly redeploy for an interception.  Without the LRMP aircraft, the dreadfully slow speed of conventionally-powered submarines makes this whole business of redeployment a non-starter. 

Hence, as the CBG attains sequential or simultaneous destruction of the enemy’s LRMP aircraft, it incrementally cripples the ability of the adversary to sensibly deploy either shore-based FGA or submarines against it. This, then, allows the CBG to close the enemy coast, should that be its operational intent. This brings us to the critically important question of whether closing the enemy coast to attack targets ashore (military power-projection) is, indeed, what we want our CBG to do. 

In determining the concept of naval operations in times of conflict, the Indian Navy will, in certain scenarios, need to close a defended coast in order to address enemy warships and other assets.  To do so, what we will need is not merely a ‘Fleet Aircraft Carrier’ with a displacement of some 45,000 tonnes or so, but a larger one, of at least 65,000 tonnes displacement that is designed for limited strikes on targets ashore.  The differences between one and another sort of aircraft carrier may be readily gleaned from the following diagram:

Speculation is rife that this will be the minimum size of India’s second Indigenously-built Aircraft Carrier (frequently referred-to as IAC-2). That it will be a CATOBAR carrier is very likely, as this will enable it to embark carrier-borne COD (carrier on board delivery) aircraft and, far more significantly, AWACS aircraft such as modernised variants of the American ‘E-2D Hawkeye’ or perhaps some variant of the Russian ‘Yak-44’. With the latter’s development remaining somewhat ‘iffy’ at this point in time, a modernised variant of the ‘E-2D Hawkeye’ is probably the only serious choice.  Shore-strike capability is not, however, without its pitfalls.  As Professor Robert C. Rubel of the US Naval War College cautions, “Do not become decisively engaged with land forces unless decisively superior…. the requirement to feed aircraft continuously into a land fight essentially robs the aircraft carrier of its manoeuvrability… do not tie a mobile fleet to a piece of ground”.  

What about the survivability of the CBG against sub-surface threats? This is a more complex matter than the CBG’s ability to deal with aircraft threats. The ubiquitous ‘negative-gradient’ acoustic profile of the Arabian Sea makes early detection of submarines difficult, particularly with hull-mounted sonars. If towed-array sonars are used, there is a significant penalty to be paid in terms of manoeuvrability and speed-of-advance. On the other hand, traditional deployments of conventional submarine concentrate upon ‘choke-points’ — whether created ‘geographically’ or ‘operationally’.  To be even marginally effective, mid-ocean deployments by conventionally-propelled submarines need very accurate and timely tactical-intelligence with regard to the ‘Mean Line of Advance’ (MLA) of the CBG. Thus, a conventionally-propelled submarine can be effectively redeployed for a mid-ocean interception of the CBG only through some form of MR-Sub Cooperation.  If the LRMP aircraft suffer significant attrition from carrier-based fighter-interceptors, MR-Sub cooperation is a non-starter. In any case, quite apart from its ‘blue-water’ positioning, the high speed-of-advance of the CBG is, in itself, an effective submarine-evasion measure, especially when it is overlaid by tactical manoeuvring involving course-variations. 

However, once a nuclear-propelled attack submarine (what NATO refers to as an ‘SSN’) is introduced, the threat-equation changes sharply. On the one hand, SSNs are significantly noisier than contemporary diesel-electric submarines.  On the other, their endurance limits are dictated by crew-fatigue and not by battery-life. As such, they have no ‘indiscrete’ periods dictated by the need to recharge batteries.  Of course, this is also true (albeit to a limited extent) of diesel-electric submarines that are equipped with one or another form of ‘Air-Independent Propulsion’ (AIP). Where the SSN really scores over the AIP-equipped diesel-electric boat (submarines are traditionally referred to as ‘boats’) is in its high underwater speed.  This, coupled with the fact that SSNs routinely carry a combination of torpedoes (both ‘anti-ship’ and ‘anti-submarine’) and anti-surface missiles, means that there are no ‘Limiting Lines of Approach’ (LLAs) for an SSN and the CBG faces an all-round threat, rather than solely one from the van as is the case with the threat posed by conventionally-propelled boats. Thus, against an SSN, the ability of the CBG to use high transit speeds as an effective submarine-evasion tactic is nullified.  Unable to ‘evade’ the threat, the CBG is forced to address it through the adoption of anti-submarine attack methods.  On the other hand, the threat has metamorphosed into an all-round one, involving both, torpedoes and subsurface-launched missiles. Of course, the submarine must still be able to obtain an accurate fire-control solution through Contact Motion Analysis (CMA) and reach its launch position without being detected and hence prosecuted. As in all forms of Anti-Submarine Warfare (ASW), earliest detection is vital.  Although there certainly are technical means available to the CBG to achieve long-range detection, tactical means would invariably have to be superimposed upon technical ones.  Yet, for all that, there is no gainsaying the fact that howsoever efficient, ASW measures taken by surface-ships against an SSN-threat are seldom going to be adequate.  Airborne ASW, on the other hand, is much more promising and this is where rotary-wing ASW aircraft (helicopters) become ever so critical.  The need to maximise the number of medium-range and long-range ASW-capable helicopters once again points to the IAC-2 displacing at least 65,000 tonnes. Almost every Indian frontline surface combatant that might form part of a CBG is capable of embarking and deploying two specialised medium/heavy ASW helicopters and the maximum utilisation of this deck-capacity is crucial. The deployment of one’s own SSN — in an anti-submarine (hunter-killer) role against another SSN (or an SSBN) — as an intrinsic element within one’s CBG is an option that has been extensively validated by the US Navy and, amongst several other advantages, holds out much promise in dealing with the enemy-SSN threat. 

Irrespective of the launch-platform, the threat of the anti-ship cruise missile has been greatly diminished by the anti-missile capability provided by the Barak in its standard as well as extended-range variants.  Today, there is a palpable sense of confidence that every ship of the CBG (including the aircraft-carrier itself) has the proven ability to ‘take-on’ a first-launch of an incoming anti-ship sea-skimming missile by the enemy and to thereafter ‘take-out’ the launch-platform (whether surface, sub-surface or airborne) using aircraft or BrahMos or other surface-to-surface missiles. This sense of self-assurance and the resultant rise in Fleet morale is no small thing and has contributed significantly to a resurgence of bold and imaginative operational planning.  

However, there is much debate over the issue of what has come to be known as the ‘anti-ship ballistic missile’.  The Chinese-made ‘Dong Feng 21-D’ (DF-21D [CSS-5 Mod-4]) is widely touted by some as being a ‘Carrier-Killer’.  The actual state of development of this capability is far less clear than these Cassandran prophecies of doom might have us believe.  As the veteran analyst, Commander Otto Kreisher, USNR (Retd), points out, “…For a ballistic missile to hit a target at 1,000 miles or more, it has to know where that target is located, with a high degree of accuracy. That’s complicated when the target — such as a carrier strike group — is moving at up to 30 knots (55.5 kmph).  For the weapon to be effective, such a geographic fix must be updated constantly.  To locate a carrier initially, China could use its over-the-horizon radars, which can search out more than a thousand miles. But the geographic accuracy of OTH radars at long range can be off by scores of miles. China is known to have at least three reconnaissance satellites in orbit over the Pacific — with SAR or optical sensors — that could be used to more accurately fix a carrier’s position. Long-range Chinese reconnaissance aircraft or attack submarines could also pinpoint a carrier, if they were operating in the right area.  But in a time of conflict, a patrol airplane or submarine attempting to get close to a carrier — shielded by its E-2C early warning airplanes, F/A-18 interceptors, and an anti-submarine screen of subs and destroyers — might not succeed.  If the Chinese could get an accurate fix on the carrier, the data would have to be processed, and the missile prepared, programmed, and launched — a complicated command and control procedure that has to be routinely tested and practiced to ensure it works. The missile, its homing sensors, and guidance system would also have to function properly to reach and hit the moving carrier.” 

Those integrated steps — to find, fix, target, and hit — are crucial links in what the military calls the ‘kill chain’ of a successful weapons system. The complexity of this kill chain led Jan van Tol, a retired US Navy captain and senior fellow on strategic planning at the US Centre for Strategic and Budgetary Assessment, to wonder…. in an interview, “I have seen no stories of any kind that China has successfully tested the system, first, against any mobile targets; … secondly, mobile targets at sea; and thirdly, mobile targets at sea amid clutter,” meaning the various support ships in a carrier battle group.  Such a demonstration “is what’s really important to show that the weapon had actually reached operational capability,” and these are “very difficult things.”   Although China has no ability to target a carrier operating within the Indian Ocean and although this threat is not an immediate one, it needs to be prepared-for assiduously in terms of Ant-Ballistic Missile systems — whether an imported system or some indigenous one.

Given the foregoing arguments, all indicators are that while the Vikramaditya and the new Vikrant will essentially be ‘Fleet Carriers’, the ‘IAC-2’ (Vishal? Viraat?) will be a much larger one — 65,000 tonnes or more.  Building her will need a shipyard such as the Cochin Shipyard or Pipapav Shipyard (or both) and should this be the case, the sky is the limit for public-private partnerships that ‘Make in India’.

Military Affairs