Fu­ture Trends in Army Air De­fence Sys­tems

Air de­fence has evolved due to the rise of air power which ini­tially started with fighter/bomber air­craft. Over a pe­riod of time at­tack he­li­copters, un­manned aerial ve­hi­cles, cruise and bal­lis­tic mis­siles be­came part of the air threat.

SP's LandForces - - FRONT PAGE - Lt Gen­eral (Retd) Naresh Chand

Air de­fence has evolved due to the rise of air power which ini­tially started with fighter/bomber air­craft.

ARMY AIR DE­FENCE (AAD) is a sys­tem which in­cludes sur­veil­lance sen­sors, fire con­trol de­vises, kill weapons like guns, mis­siles and di­rected en­ergy weapons, and a bat­tle man­age­ment sys­tem to in­te­grate all th­ese sub­sys­tems. Air de­fence has evolved due to the rise of air power which ini­tially started with fighter/bomber air­craft. Over a pe­riod of time at­tack he­li­copters, un­manned aerial ve­hi­cles (UAVs), cruise and bal­lis­tic mis­siles be­came part of the air threat. Thus the race be­tween ‘air threat’ and ‘counter-to-air threat’ con­tin­ues with both di­men­sions ex­plor­ing new tech­nolo­gies to outdo each other. The over­lay of un­con­ven­tional war­fare has added to the com­plex­ity of so­lu­tions.

Fu­ture Trends in Air Threat

In­creased re­liance on stealth by fighter/ bomber air­craft. Ex­am­ple of F-22 Rap­tor and F-35 Light­ning II of the US are there.

Im­proved avion­ics pro­vid­ing bet­ter be­yond vis­ual range (BVR) ca­pa­bil­ity to fighter air­craft. In­creased use of UAVs, armed UAVs and mi­cro/mini-UAVs.

In­creased mis­sile threat.

Pro­lif­er­a­tion of pre­ci­sion guided mu­ni­tions (PGMs).

Threat from rock­ets, ar­tillery and mor­tars, all us­ing PGMs.

Bet­ter elec­tronic war­fare ca­pa­bil­ity for jam­ming air de­fence sys­tems. All this re­sults in multi-plat­form, silent and stand­off threat.

Fu­ture Trends in AD Guns

Con­ven­tional Guns: Guns in­clud­ing ma­chine guns were first used to counter air threat. Th­ese weapons were not de­signed for air de­fence role. Dur­ing World War II, air de­fence guns started get­ting evolved. The most pop­u­lar gun used by the Al­lies was 40mmL/60 of Swe­den ori­gin which was a purely me­chan­i­cal gun with high rate of fire. This gun was suc­ceeded by 40mmL/70 which was radar con­trolled. This gun is still in ser­vice in In­dia for al­most 50 years. Other coun­tries pro­duced many types of air de­fence guns with vary­ing ranges, cal­i­bre and fire con­trol sys­tem. Er­rors in fir­ing due to a mov­ing tar­get in all three di­men­sions si­mul­ta­ne­ously like the fighter air­craft, grav­ity and ef­fect of at­mo­spheric con­di­tions was made up by pro­vid­ing bet­ter fire con­trol sys­tems and a high rate of fire. High rate of fire lim­ited the cal­i­bre of the gun or else the gun would be­come very heavy and thus im­ped­ing mo­bil­ity. Con­ven­tional guns have reached a plateau in de­vel­op­ment, thus the fo­cus for de­vel­op­ment is on fire con­trol sys­tems and am­mu­ni­tion. Some fu­ture trends are:

Un­manned and re­motely-con­trolled tur­ret with in­te­grated am­mu­ni­tion feed will en­sure bet­ter re­ac­tion time and re­duc­tion in crew.

Multi-weapon plat­forms with guns and mis­siles on the same plat­form to pro­vide multi-lay­ered de­fence and im­proved kill ca­pa­bil­ity. Co-lo­cat­ing fire con­trol sys­tems on the weapon plat­form for shorter re­ac­tion time and re­duc­tion in crew.

Pro­vide mo­bil­ity with high mo­bil­ity ve­hi­cles.

High rate of fire with multi-bar­rel guns hav­ing in­de­pen­dent breech blocks. Al­ter­na­tively those have very high ac­cu­racy which en­ables re­duc­tion in the rate of fire and have higher cal­i­bre for bet­ter kill and longer range.

Elec­tro-mag­netic (EM) gun: The muz­zle ve­loc­ity is pro­vided by EM forces and not by the ex­pan­sion of pro­pel­lant guns. EM gun can pro­pel a three kg pro­jec­tile at speed of more than 3000m/s. It is still un­der de­vel­op­ment.

Di­rected en­ergy weapons (DEW): Th­ese weapons are right out of Star Wars. DEW weapons use their en­ergy to dis­able/de­stroy tar­gets and have a high re­quire­ment of power. They can be based on high power mi­crowave, charge par­ti­cle beam or laser. DEW weapons are un­der de­vel­op­ment in many coun­tries in­clud­ing In­dia. They are the clas­sic PGMs.

The race be­tween ‘air threat’ and ‘counter-toair threat’ con­tin­ues with both di­men­sions ex­plor­ing new tech­nolo­gies to outdo each other

Am­mu­ni­tion

Air de­fence guns have a lim­i­ta­tion of cal­i­bre (nor­mally max­i­mum of 40mm) and so the shell is very small. The re­sult was that it was dif­fi­cult to fit an air­burst or a prox­im­ity fuse in the nose. The cal­i­bre also lim­ited the high ex­plo­sive con­tent of the shell. This has been over­come with de­vel­op­ments in elec­tron­ics and kill con­tent. Air­burst or prox­im­ity fuse bursts close to the tar­get, and thus in­creases the kill zone. Some ex­am­ples are:

Ad­vanced Hit Ef­fi­ciency and De­struc

tion (AHEAD): This is pro­duced by Rhein­metall. AHEAD has a cone of 100-150 tung­sten al­loy pel­lets as the kill con­tent. The muz­zle ve­loc­ity is cal­cu­lated for each round and time to the tar­get is fed in the pre­ci­sion fuse re­sult­ing in the shell ex­plod­ing at op­ti­mum range to cre­ate a sub pro­jec­tile cloud. The pel­lets are hurled at great speed to de­stroy the tar­get.

Pen­e­tra­tor with En­hanced Lat­eral

Ef­fect (PELE): PELE is also man­u­fac­tured by Rhein­metall. This is a very unique con­cept where frag­men­ta­tion of the shell is caused with­out ex­plo­sive and fuse but has high pen­e­tra­tive power and lethal­ity. The outer shell and its in­ner fill­ing are made of ma­te­rial with dif­fer­ent den­si­ties which cause rise in pres­sure on im­pact and frag­men­ta­tion.

Driven Am­mu­ni­tion Re­duced Time of

Flight (DART): DART pro­jec­tile is guided by a beam, has ca­nard con­trol with a range of five-km and a prox­im­ity fuse which bursts be­tween 5 me­tres and 10 me­tres.

Sur­face-to-Air Mis­sile (SAM) Sys­tems

SAM sys­tems were de­vel­oped to over­come the short­com­ings of the air de­fence guns like lim­ited range and ac­cu­racy. Se­ri­ous at­tempts to de­velop SAM sys­tems started dur­ing World War II but none were made op­er­a­tional. Dur­ing the Cold War­era, known sys­tems de­ployed were the US’s Nike Ajax and the Soviet Union’s S-75 Dv­ina. Dv­ina was very pop­u­lar and was de­ployed in many coun­tries. The In­dian Air Force was the first ser­vice to de­ploy mis­siles in In­dia. Later on, both the Army and the Navy ac­quired SAMs. There were a large va­ri­ety of SAMs de­vel­oped world over rang­ing from radar con­trolled larger sys­tems like HAWK of the US and Kvadrat of Rus­sia. Ranges also varied from long-range to medi­u­mand short-range. There were many con­fig­u­ra­tions from static plat­forms to mo­bile plat­forms and man-por­ta­ble air de­fence sys­tems (Manpads). A guided mis­sile has a pro­pel­lant en­gine, guid­ance sys­tem, steer­ing sys­tem and a war­head to de­stroy the tar­get. Guid­ance sys­tems can be radar or many other sys­tems like ra­dio-con­trolled, in­frared, laser and us­ing mil­lime­tre radar. The cur­rent de­vel­op­ments are pro­vid­ing hy­per ve­loc­ity, bet­ter war­head and ac­tive seeker for a guid­ance sys­tem. The SAMs must cater for mul­ti­ple long-range threat to very short-range threat with a very short re­ac­tion time. The mis­sile should have twoway data link with high ca­pac­ity and in­de­pen­dent of the radar for very short re­ac­tion time and ac­cu­racy.

The Army needs highly mo­bile sys­tems to de­ploy and re­de­ploy very fast with a very short re­ac­tion time. It should also take care of short-range bal­lis­tic mis­siles (SRBMs), at­tack he­li­copters, cruise mis­siles and UAVs. Cur­rent sys­tems like Pa­triot Ad­vance Ca­pa­bil­ity 3 (PAC3) and lat­est ver­sion of Barak 8 claim to have all th­ese at­tributes. PAC3

war­head is a unique “hit-to-kill” (ki­netic kill ve­hi­cle) ca­pa­bil­ity that com­pletely elim­i­nates the need for a prox­im­ity-fused war­head. How­ever, the mis­sile has lethal­ity enhancer (a small ex­plo­sive di­rec­tional war­head) which launches a stream of lowspeed steel frag­ments in the di­rec­tion of the tar­get in or­der to make the mis­sile crosssec­tion greater to en­hance the kill prob­a­bil­ity. Barak 8 is a short- to long-range, pro­vid­ing point and area de­fence on land and sea. The mis­sile is based on ad­vanced mis­sile state-of-the-art phased ar­ray, mul­ti­mis­sion radar, multi-lay­ers com­mu­ni­ca­tion and flex­i­ble com­mand and con­trol sys­tem. There are many more ad­vanced sys­tems be­ing de­vel­oped in­clud­ing for Manpads. The aim is to counter mul­ti­ple air threat with a sin­gle mis­sile sys­tem with speed and ac­cu­racy, in all-weather con­di­tions.

Fire Con­trol Sys­tems

A sur­veil­lance and fire con­trol sys­tem is in­te­gral part of a SAM sys­tem. Ear­lier there were sep­a­rate radars for sur­veil­lance and fire con­trol. Such a con­fig­u­ra­tion is still re­quired for long-range mis­siles al­though such in­for­ma­tion can also be pro­vided by UAVs as well through satel­lites. Radar’s ef­fec­tive range de­pends upon its an­tenna height and hence this is a lim­i­ta­tion for low fly­ing tar­gets. For short-range quick re­ac­tion mis­siles, the func­tion of sur­veil­lance and fire con­trol is com­bined in sin­gle radar.

The other chal­lenge is to de­tect stealth ob­jects. Some de­vel­op­ments:

Phase Ar­ray Tech­nol­ogy: It uses ac­tive elec­tron­i­cally switched ar­ray (AESA) in which trans­mit­ter and re­ceiver func­tions are com­posed of nu­mer­ous small solid-state trans­mit/ re­ceive mod­ules (TRMs) which emit sep­a­rate ra­dio beams that in­ter­fere con­struc­tively to pro­duce a beam. It is pos­si­ble to change the op­er­at­ing fre­quency with ev­ery pulse. AESA

The Army needs highly mo­bile sys­tems to de­ploy and re­de­ploy very fast with a very short re­ac­tion time

radar can also pro­duce mul­ti­ple beams for mul­ti­ple tar­get track­ing. In­dia has in­dige­nous AESA radar with its Akash SAM sys­tem.

Varied Band Spec­trum: Op­er­at­ing in VHF band is dif­fi­cult to jam and can de­tect tar­gets with low radar cross sec­tion.

Over the Hori­zon Radar (OTH): The OTH uses bounce ef­fect of HF waves with a de­tec­tion ca­pa­bil­ity of thou­sands of kilo­me­tres. It is pri­mar­ily used for sur­veil­lance and anti-stealth.

Multi-band Spec­trum: It func­tions si­mul­ta­ne­ously in mul­ti­ple fre­quency bands with the help of AESA. Search and track­ing is car­ried out in dif­fer­ent bands. It has very ef­fec­tive elec­tronic counter coun­ter­mea­sure (ECCM) sys­tem.

Elec­tro-op­tics Fire Con­trol Sys­tems

(EOFCS): EOFCS is a pas­sive sys­tem which uses EO sys­tems like for­ward look­ing in­frared (FLIR), IR search and track­ing (IRST), ther­mal im­agers and CCD cam­era for fire con­trol, is gyro-sta­bilised with an in­de­pen­dent sight­ing sys­tem.

Counter Stealth: Many de­vel­op­ments are go­ing on to de­tect stealth plat­forms like multi-band, pas­sive sys­tems, pas­sive co­her­ent lo­ca­tion (PCL) mode. EADS has dis­played a pas­sive radar sys­tem that can de­tect re­flec­tions from three dif­fer­ent bands, namely FM, dig­i­tal au­dio broad­cast­ing and dig­i­tal video broad­cast­ing-ter­res­trial bands. Laser tech­nol­ogy is also be­ing ex­plored to de­tect stealth.

PHO­TO­GRAPH: Lock­heed Martin

Lock­heed Martin’s Pa­triot Ad­vanced Ca­pa­bil­ity 3 mis­sile

PHO­TO­GRAPH: IAI

Barak 8 Indo-Is­raeli sur­face-to-air mis­sile

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