In­dia’s Anti-sub­ma­rine War­fare Ca­pa­bil­ity on the Brink

At present the force level of sub­marines with the in­dian navy is just 13 which in­cludes nine of Sind­hughosh class and four of Shishu­mar class


At present the force level of sub­marines with the In­dian Navy is just 13 which in­cludes nine of Sind­hughosh class and four of Shishu­mar class. Lt Gen­eral Naresh Chand (Retd)

anti-SuB­Ma­rine War­fare (aSW) iS de­fined as a branch of un­der­wa­ter war­fare that em­ploys sur­face war­ships, air­craft or sub­marines to find, track and de­ter, dam­age or de­stroy en­emy sub­marines. the first step is to de­tect, track and iden­tify fol­lowed by de­struc­tion/ degra­da­tion of the sub­ma­rine.

De­tec­tion Tech­nol­ogy and Sys­tems

the doc­trine of sub­ma­rine op­er­a­tions is based on to­tal se­crecy and stealth while on an op­er­a­tional mis­sion, own sub­marineÕs de­tec­tion by the en­emy could prove fa­tal. thus hav­ing ef­fec­tive sen­sor sys­tems for de­tec­tion of en­emy’s sub­marines first, pro­vide a great ad­van­tage to own sub­marines and sur­face ships. De­tails of sen­sors in use are given in suc­ceed­ing para­graphs.

Vis­ual. ear­lier method of mak­ing vis­ual de­tec­tion is not that ef­fec­tive with modern sub­marines due to their low Ôindis­cre­tion rateÕ. Mo­dem con­ven­tional sub­marines are gen­er­ally pow­ered by diesel-elec­tric propul­sion sys­tems. Diesel en­gines are used on the sur­face or with a snorkel to charge bat­ter­ies which are used to power elec­tric mo­tors for propul­sion. While un­der­wa­ter, oxy­gen is stored in high pres­sure tanks and re­leased slowly to sus­tain the crew. The ‘in­dis­cre­tion ra­tio’ is thus de­fined as the ra­tio of the time spent charg­ing the sub­ma­rine bat­ter­ies, to the time elapsed for the com­plete dis­charge/charge cy­cle of the bat­ter­ies. in a typ­i­cal diesel-elec­tric sub­ma­rine, the in­dis­cre­tion ra­tio is about 10 per cent, which in­creases rapidly with in­creas­ing speed.

Ra­dio in­ter­cep­tion. ra­dio in­ter­cep­tion was pos­si­ble dur­ing the two ear­lier World Wars as the Ger­man sub­marines op­er­ated in a pack and the en­cryp­tion tech­niques were not that so­phis­ti­cated. Modern sub­marines trans­mit through meth­ods that make the trans­mis­sion dif­fi­cult to de­tect.

Radar. this was an ef­fec­tive sen­sor dur­ing World War ii for de­tect­ing sur­faced sub­marines. With the de­vel­op­ment of the snorkel and the ad­vent of nu­clear-pow­ered sub­marines; sub­marines rarely sur­faced out­side their home port thus it was not pos­si­ble to de­tect them with radar.


Sonar (sound nav­i­ga­tion and rang­ing) has emerged as the pri­mary means of de­tect­ing submerged sub­marines. it has mul­ti­ple uses for un­der­wa­ter de­tec­tion as sound waves can ef­fec­tively move un­der­wa­ter. Sonar can be pas­sive or ac­tive.

Pas­sive sonar. Pas­sive sonar sys­tems do not emit any sig­nal and are used to de­tect noise em­a­nat­ing from a sub­ma­rine. Being silent thus it is stealthy and can­not be de­tected. Pas­sive sonar can­not mea­sure the range of an ob­ject un­less it is used with mul­ti­ple pas­sive lis­ten­ing de­vices.

Ac­tive sonar. ac­tive sonar has trans­duc­ers which emit an acous­tic sig­nal which get re­flected when they meet an ob­ject. The re­flected sig­nal is then picked up, which al­lows mea­sure­ment of range and az­imuth, sim­i­lar to a radar. as ac­tive sonar will re­veal the source of emis­sion which will give out the po­si­tion of the op­er­a­tor thus it is used by fast mov­ing plat­forms like air­craft and he­li­copters, and by noisy plat­forms like sur­face ships but rarely by sub­marines. in all cases ac­tive sonar is ac­ti­vated in short bursts to avoid de­tec­tion. Due to the lim­i­ta­tion of not hav­ing stealth features, ac­tive sonar is nor­mally con­sid­ered a backup to pas­sive sonar.

Towed Sonar. Be­cause of the prob­lems of ship noise, towed sonars are also used. th­ese also have the ad­van­tage of being able to be placed deeper in the wa­ter but have a prob­lem in shal­lower waters. they can be towed ar­rays (lin­ear) or vari­able depth sonars (VDS) with 2/3D ar­rays. they re­quire a winch to de­ploy and re­cover, which is large and ex­pen­sive. VDS sets are pri­mar­ily ac­tive in op­er­a­tion while towed ar­rays are pas­sive. an ex­am­ple of a modern ac­tive/pas­sive ship towed sonar is Sonar 2087 made by thales un­der­wa­ter Sys­tems. Sonar 2087 is de­signed to pro­vide a man­age­able source of high qual­ity sonar data. it is high source level, low com­plex­ity, om­ni­di­rec­tional acous­tic pro­jec­tor de­ployed in a hy­dro­dy­namic towed sin­gle ping con­tact bear­ing am­bi­gu­ity res­o­lu­tion; sin­gle re­ceive towed ar­ray and very low fre­quency pas­sive de­tec­tion and track­ing. ac­tive/pas­sive mode de­pends upon the coun­ter­mea­sures taken by the sub­ma­rine.

Vari­able Depth Sonar. in the re­cent past sonar ar­rays were hull mounted on the ship but it was found out that they re­quired means of re­duc­ing flow noise. This was done by a can­vas cover dome which was later on made of steel and then of re­in­forced plas­tic or pres­surised rub­ber. Such sonars are pri­mar­ily ac­tive in op­er­a­tion. an ex­am­ple of this is the modern hull-mounted sonar an/ SqS-56, which features dig­i­tal im­ple­men­ta­tion, sys­tem con­trol by a built-in mini­com­puter, and an ad­vanced dis­play sys­tem. the sonar is an ac­tive/pas­sive, dig­i­tal sonar pro­vid­ing panoramic echo rang­ing and panoramic pas­sive sur­veil­lance.

Sonar on Aerial Plat­forms

Sonobuoy. ac­tive sonar is also dropped from aerial plat­forms in the form of dis­pos­able sonobuoys for de­tec­tion in the zone of in­ter­est. the term Sonobuoy is formed from Sonar and buoy. it is a small equip­ment which can be dropped or ejected from an aerial plat­form or sur­face ship to de­tect a sub­ma­rine and trans­mit the re­ceived sig­nal by ra­dio to a des­ig­nated re­ceiver.

Dip­ping sonar. Wide area, un­der­wa­ter bat­tlespace sur­veil­lance, us­ing the ac­tive and pas­sive func­tions of Sonar 2087 is com­ple­mented by air­borne acous­tics suite which in­cludes the Sonar 2189 low fre­quency dip­ping sonar (based on flash) and a sonobuoy de­tec­tion sys­tem. for closer range sur­veil­lance and self-pro­tec­tion the type 23 also op­er­ates the hull mounted Sonar 2050. all of this sonar equip­ment has been sup­plied by thales un­der­wa­ter Sys­tems. the royal navy em­ploys the sonar from their Mar­itime force Pro­tec­tion and air­borne anti-sub­ma­rine war­fare Mer­lin he­li­copter. another ex­am­ple is the aqS-13 se­ries sys­tems used by the uS navy. this was man­u­fac­tured by a di­vi­sion of Bendix cor­po­ra­tion which went through mul­ti­ple own­er­ships and name changes over the years and is cur­rently L-3 com­mu­ni­ca­tions ocean Sys­tems.

Some de­vel­op­ments. Syn­thetic aper­ture Sonar mea­sures the slight dif­fer­ences in a bunch of acous­tic ÔpingsÕoff the same lo­ca­tion to ac­quire de­tails of the sub­sur­face ob­ject. another new tech­nique uses low-fre­quency sonar (less than 1,000 hz) to in­crease the sys­temÕs range but which re­duces ac­cu­racy.

Mag­netic anom­aly de­tec­tion (MAD). MaD is sim­ply an elec­tronic mag­ne­tome­ter which can mea­sure mag­netic field vari­a­tions due to large metal ob­jects, such as the steel hull of a sub­ma­rine. Be­fore the de­vel­op­ment of sonar buoys, MaD sys­tem was com­monly in­stalled on aerial plat­forms to pick up shal­low-submerged sub­marines.

Ac­tive sonar is also dropped from aerial plat­forms in the form of dis­pos­able sonobuoys for de­tec­tion in the zone of in­ter­est

Anti-sub­ma­rine weapons

they can be guided, un­guided and rocket/ mor­tar weapons.

Guided ASW weapons. the modern tor­pedo can be loosely called the sea ver­sion of a mis­sile as it is self-pro­pelled, car­ries a war­head, nav­i­gates it­self to the tar­get with its own sen­sors or from the launch­ing plat­for­mÕs sen­sors and det­o­nates on con­tact

with the tar­get or in close prox­im­ity to it. they can also be launched from aerial plat­forms. tor­pedo is the most ef­fec­tive weapon for aSW and also against sur­face ships. there are many types of tor­pe­does in ser­vice with the navies of the world. Mark 48 and its im­proved ad­vanced ca­pa­bil­ity vari­ant are uS heavy­weight sub­ma­rine-launched tor­pe­does. Mark 46 aerial tor­pedo is the back­bone of the uS navyÕs light­weight anti-sub­ma­rine war­fare tor­pedo in­ven­tory. in­di­aÕs taL is a light­weight tor­pedo (LWt) which was in­di­aÕs first pro­duc­tion grade tor­pedo. Ad­vanced LWt is suc­ces­sor pro­gramme of taL which has some mi­nor changes and ma­jor im­prove­ments and is likely go for tri­als this year. the Black Shark is a heavy­weight tor­pedo de­vel­oped by WaSS of italy and is spe­cially meant for Scorp•ne diesel-elec­tric sub­marines pro­duced by france. Non- guided ASW weapons. th­ese are mines and depth charges. Mines are laid in crit­i­cal sea lanes and har­bours to de­ter in­trud­ers. Depth charges are fired in the close prox­im­ity of sub­marines to dam­age them. Rock­ets and mor­tar. anti-sub­ma­rine grenades and anti-sub­ma­rine rock­ets have a short re­sponse time as they are fired through the air onto the tar­get. an im­prove­ment in the re­sponse time is achieved by launch­ing a tor­pedo via a rocket which gives the sub­ma­rine less time to take coun­ter­mea­sures. Scor­pene un­der Project 75. at present the force level of sub­marines with the in­dian navy (in) is just 13 which in­cludes nine of Sind­hughosh class and four of Shishu­mar class. the in had for­mu­lated a 30-year Sub­ma­rine Per­spec­tive Plan in 1999 which en­vis­aged 12 sub­marines by 2012 and the num­ber was ex­pected to dou­ble by 2029. the de­liv­ery sched­ule of the new sub­marines was to be dove­tailed with the phas­ing out of the ex­ist­ing Shishu­mar and Sind­hughosh classes of sub­marines. the two dis­tinct sub­ma­rine de­signs were named as Project 75 and Project 75(i). for Project 75, a con­tract with DcnS was signed for six french sub­marines Scor­pene to be made in the Mazagon Dock Lim­ited, and to be de­liv­ered be­tween 2012 and 2016. there has been a de­lay of about four years and the first Scor­pene sub­ma­rine, named inS Kal­vari, was un­docked in april 2015 for start­ing sea tri­als. it is hoped that the de­liv­ery starts this year and the re­main­ing five de­liv­ered by 2020.

Project 75(I). this was to fol­low-up of Project 75 and ac­cord­ingly a re­quest for in­for­ma­tion (rfi) was is­sued in 2008 for procur­ing of six aiP equipped sub­marines with high de­gree of stealth and land-at­tack ca­pa­bil­ity. the pro­jected cost then was $10 bil­lion (`50,000 crore). now it is ` 64,000 crore but this is just an in­dica­tive cost and ac­tual cost will only be known when the con­tract is signed. th­ese were also to be built at an in­dian ship­yard, pub­lic or pri­vate, with special em­pha­sis on full trans­fer of tech­nol­ogy. now th­ese have come un­der the ÔMake in in­di­aÕpro­gramme of the nDa Gov­ern­ment but there seems no progress.

Nu­clear Sub­marines

in­dia has am­bi­tious plans to ac­quire sea com­po­nent of the nu­clear triad. to­wards this aim it has leased inS chakra from rus­sia which is nu­clear-pow­ered at­tack sub­ma­rine. in­di­aÕs own nu­clear-pow­ered bal­lis­tic mis­sile sub­ma­rine project is pro­gress­ing well and the first sub­ma­rine INS Ari­hant is ex­pected to be com­mis­sioned soon.

ASW He­li­copters

he­li­copters with aSW sys­tems are nor­mally de­ployed by all naval forces to de­stroy sub­marines at long ranges. there are many type of aSW he­li­copters in ser­vice and a few ex­am­ples are as fol­lows: ation aSW and aSuW he­li­copter pro­duced by Siko­rsky air­craft cor­po­ra­tion. it is cur­rently one of the most ad­vanced naval he­li­copters avail­able.

NH90. nh90 nfh, of­fered by nhin­dus­tries, is an ad­vanced aSW he­li­copter built by thales.

Ka- 27 or Ka-28 (ex­port des­ig­na­tion). this is a rus­sian aSW and aSuW he­li­copter which is in ser­vice in in­dia. the Ka-27 he­li­copter is equipped with VGS-3 dip­ping sonar and sonobuoys to track and de­tect sub­marines. it can fire tor­pe­does, anti-sub­ma­rine mis­siles PLaB-250-120 anti-sub­ma­rine bombs and oMaB bombs. S-70B Sea­hawk. the S-70B Sea­hawk is an aSW and aSuW he­li­copter de­vel­oped by Siko­rsky air­craft cor­po­ra­tion. the S-70B he­li­copter is fit­ted with sen­sors like search radar, sonobuoy launcher, he­li­copter Lon­grange ac­tive Sonar Dip­ping Sonar, towed MaD and is suit­ably armed.

Gaps on In­dia’s ASW Ca­pa­bil­ity

Sub­marines. at present in­dia has only 13 sub­marines which is no where near the force lev­els pro­jected in the 30-year Sub- ma­rine Per­spec­tive Plan of the in­dian navy. Six Scor­penes are likely to be in­ducted by 2020 pro­vided no hitch comes up due to the leak in the de­sign doc­u­ments. Project 75(i) has yet to crys­talise. Go­ing by the ex­pe­ri­ence of Scor­pene, it may take about two decades be­fore the in­duc­tion starts. Mean­while, the cur­rent sub­marines will get ob­so­les­cent, leav­ing a wide gap in the sub­sur­face op­er­a­tional readi­ness.

ASW He­li­copters. in­dian navyÕs Ka-28 fleet has been re­duced to just four op­er­a­tional he­li­copters thus in­dia has signed a deal with rus­sia to mod­ernise ten Ka-28 naval he­li­copters at a cost of $294 mil­lion. The Sea King he­li­copter fleet has been re­duced to just 16-17 up­graded machines with a few ca­pa­ble of fly­ing at any one time. the navy has doubts of the aSW ca­pa­bil­ity of in­dige­nous Dhruv he­li­copter. the in­dian navy had orig­i­nally planned to ac­quire 54 multi-role he­li­copters and 16 of th­ese should have come in 2007 or so as re­place­ment for the first lot of Sea Kings but noth­ing has hap­pened. Siko­rskyÕs S-70BtM Sea­hawk aSW/aSuW was short­listed for ac­quir­ing 16 as an in­terim ar­range­ment but that project has not moved for­ward. all naval ships have multi-role he­li­copters on­board, e.g., all de­stroy­ers will have two each and inS Vikra­ma­ditya air­craft car­rier can-carry 12 he­li­copters. it was re­ported ear­lier in the me­dia that only one-fifth of he­li­copters are avail­able for the high-end ships thus leav­ing a big gap in their aSW ca­pa­bil­ity.

Sonar. the naval Phys­i­cal & oceano­graphic Lab­o­ra­tory has de­vel­oped a va­ri­ety of in­dige­nous sonars for sur­face ships na­gan was a towed ar­ray sonar sys­tem that was con­verted into demon­stara­tor and the project closed in 2012. other sys­tem for sur­face ships is the hull Mounted Sonar ad­vancedÐnG (huMSa) which is an ac­tive-cum pas­sive sys­tem. huMSa uG is an up­graded ver­sion of huMSa with new re­ceiver elec­tron­ics and an ul­tra-cool power am­pli­fier sys­tem. Ad­vance Light Towed ar­ray Sonar (aL­taS) is a sonar sys­tem for the de­tec­tion, lo­cal­i­sa­tion and clas­si­fi­ca­tion of sub­marines op­er­at­ing es­pe­cially the be­low sonic layer. it is use­ful in aSW op­er­a­tions and is the apt sen­sor for war­ships to lo­cate silent sub­marines. for eKM class of sub­marines it has de­vel­oped uShuS sonar suite. Mihir was a first-gen­er­a­tion he­li­copter sonar sys­tem, com­pris­ing of dunk­ing sonar and a four chan­nel sonobuoy pro­ces­sor. it was de­signed for ad­vanced light he­li­copter type plat­form. Low fre­quency dunk­ing sonar is an ad­vanced ver­sion of Mihir.

Mean­while it is re­ported that in­dia has im­ported six of at­las elek­tron­ikÕs ac­tive towed ar­ray Sonar (ac­taS) which is a lowfre­quency aSW sonar sys­tem that op­er­ates si­mul­ta­ne­ously in ac­tive and pas­sive modes and pro­vides high-res­o­lu­tion tar­get de­tec­tion. ac­taS pro­vides ex­cel­lent per­for­mance up to very long ranges, which in­cludes over-the-hori­zon sur­veil­lance. it is de­signed to de­tect, track and clas­sify sub­marines, tor­pe­does, sur­face ves­sels, in­clud­ing fast boats. as per me­dia re­ports th­ese were im­ported for Kamorta class of ASW corvettes but three have been fit­ted on tal­war class frigates and three on Delhi class de­stroy­ers. the ad­di­tional re­quire­ments will be met by the Bharat elec­tron­ics Lim­ited man­u­fac­tur­ing un­der trans­fer of tech­nol­ogy from Ger­many.

Black Shark tor­pe­doe. the Black Shark is a heavy­weight tor­pedo de­vel­oped by WaSS of italy and is spe­cially meant for Scorp•ne diesel-elec­tric sub­marines which are being made in in­dia. it has an ef­fec­tive range of 50 km (27 nM) and speed of 50 kt (about 90km/h). Black Shark was to be fit­ted on in­di­aÕs Scor­pene Sub­marines but is wait­ing for a go-ahead from the in­dian Min­istry of De­fence. in case Black Shark is not cleared, in­dia will have to look for another tor­pe­doe which could re­place it with­out any de­sign changes.

It was re­ported ear­lier in the me­dia that only one-fifth of he­li­copters are avail­able for the high-end ships thus leav­ing a big gap in their ASW ca­pa­bil­ity

(Top) Kal­vari sub­ma­rine at sea; (above) Mk 46 light­weight tor­pedo

PHO­TO­GRAPHS: In­dian Navy, US Navy

(Top to bot­tom) Siko­rsky’s S-70B Sea­hawk he­li­copter; NH90 NFH ad­vanced ASW he­li­copter and Rus­sian Ka-27 he­li­copter.

PHO­TO­GRAPHS: Siko­rsky, NH In­dus­tries, US Navy

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