‘Prahaar’ NLOS-BSM Explained

The maiden test-firing of the Prahaar (to strike) quick-reaction, vertically launched surface-to-surface non-line-of-sight battlefield support missile (NLOS-BSM)—developed by the Defence Research & Development Organisation’s (DRDO) Advanced Systems Laboratory (ASL) on July 21, 2011--formally kicked off Phase 2 of the Indian Army’s on-going transformational efforts aimed at acquiring precision-guided munitions (PGM) that would provide responsive, long-range lateral supporting fire-assaults as well as shape the theatre-based battlespace for ensuring the conditions for decisive victories. The Prahaar, which has been under development since 2008, has a length of 7.3 metres (23.95 feet) and diameter of 420mm (1.38 feet), weighs 1,280kg, is armed with a 200kg warhead, has a circular error probable (CEP) of less than 10 metres, and is powered by a single-stage solid-propellant rocket that takes the missile to a height of 35km (114,829 feet) before reaching its target in a depressed ballistic trajectory out to a range of 150km in about 250 seconds. Its airframe is derived from the Mach 4 AAD-1 endo-atmospheric ballistic missile interceptor, which has been under development by the ASL since late 1998. Carried inside a hermetically sealed cannister with a 10-year shelf-life, the Prahaar will come packed in a six-unit pod configuration on board a high-mobility 8 x 8 BEML-TATRA wheeled vehicle housing both a command-and-control shelter as well as a transporter-erector-launcher (TEL) mechanism designed by Larsen & Toubro. The solid-fuelled Prahaar is, in essence, a product that overcomes all the deficiencies displayed by the DRDO-developed Prithvi family of battlefield support missiles (the SS-150, SS-250, SS-350 and Dhanush), which makes uses of liquid fuel and is cumbersome both in terms of transportation and launch readiness procedures.

The Indian Army’s search for a precision-guided NLOS-BSM dates back to late 2002, when it began examining options like the 280km-range 9K720 Iskander-E from Russia’s KB Mashynostroyeniya, and the 300km-range LORA from Israel Aerospace Industries’ MLM Division. The decision to import such weapons was, however, abandoned two years later in favour of an indigenous solution by leveraging those core technological competencies that had already been achieved by both the ASL and the DRDO’s Research Centre Imarat (RCI) while in the process of developing the Agni family of nuclear-capable intermediate-/medium-range ballistic missiles and the BrahMos supersonic multi-role/multi-platform cruise missile. Thus, just like in the case of LORA, it was decided that the Prahaar would follow a relatively simple three-element design, comprising a warhead in the fore section, propulsion unit, including the solid-fuel rocket motor with a nozzle. The nozzle would be encircled by the navigation, flight control and guidance unit, which includes the integrated avionic guidance and flight control section, cruciform tail control surfaces, actuators, related antennas and connectors. The ring-laser gyro-based inertial navigation system (RLG-INS), along with its miniaturised GLONASS-K GPS receiver incorporating a 12-channel selective availability anti-spoofing module (SAASM) GPS receiver and using digital RS-422/485 databus interfaces, plus the inertial measurement unit (IMU) utilising an RS-485 digital databus interface, and on-board digital computer, were all designed and built by RCI. For the road-mobile TEL, RCI developed a lightweight land navigation system called FINGS (for providing position and north-pointing information) that makes use of three fibre-optic gyroscopes (weighing less than 1kg), three micro-machined silicon accelerometers and a microprocessor. The system senses acceleration and rotation about three orthogonal axes and outputs temperature compensated incremental angles and incremental velocities. For ensuring the Prahaar’s in-flight manoeuvrability a cooperative dual-control system using divert thrusters was developed for actuating forward and aft control devices simultaneously to significantly improve the missile’s dynamic capability. Thus, to effect the desired manoeuvre, the missile’s aft fins will initially be deflected to generate a force opposite that of the force being used conventionally (thereby pushing the missile’s tail in the direction of the commanded manoeuvre), while simultaneously actuating the forward thrusters to also push the missile’s nose in the direction of the commanded manoeuvre, but at a faster rate than the tail section. This causes the missile body to simultaneously rotate and translate in the direction of the commanded manoeuvre. Once a sufficient amount of aerodynamic force develops due to body rotation, the aft fins are deflected to generate a force that opposes the commanded manoeuvre to maintain a moment on the missile body and complete the commanded manoeuvre. An important benefit of this dual-control strategy is that the missile begins to translate in the direction of the commanded manoeuvre immediately. It is believed that the Prahaar’s warhead section options will include unitary high-explosive blast fragmentation payloads, and sensor-fuzed anti-personnel/anti-materiel (APAM) munitions. While design and fabrication expertise for the former is available with the DRDO, for the latter foreign R & D expertise has been sought from Israel Military Industries (IMI).

Deployment Plans

Under Phase 1 of the Army’s efforts to acquire the requisite fire-assault capabilities for decisively influencing both the contact and deep battles, the BrahMos Block 2 supersonic PGM (with its range and cruise altitude capped at 290km and 13km, respectively, in order for Russia to adhere to the missile technology control regime guidelines) is presently being acquired to equip three missile artillery regiments that form part of the ORBATs of the Indian Army’s three dedicated Artillery Divisions—40, 41 and 42. On December 22, 2004 the first production version of the land-based, quick-reaction BrahMos Block 2 was successfully test-fired from the Pokhran Firing Range. Each BrahMos Block 2 Regiment comprises three Batteries each with four mobile autonomous launchers or MAL (each with three vertically-launched missiles), three mobile command posts (MCP), one fixed command centre, nine missile replenishment vehicles, and three maintenance support vehicles. Each Regiment can fire 36 BrahMos Block 2 missiles against different targets (like interior and exterior lines of communication and transportation nodes) within seconds over a frontage of 600km.

The Army has mandated the bulk procurement of both the BrahMos Block 2 (and the projected Block 3) and Prahaar PGMs for four principal reasons: First, there’s the need to replace the existing stocks of liquid-fuelled Prithvi-1 SS-150 BSMs that have far outlived their utility. Second, during a future round of all-out hostilities (which are likely to be of limited duration, not lasting more than two weeks), the Army wants to reduce as much as possible its traditional reliance on the Indian Air Force (IAF) for close air support and tactical battlespace interdiction during the first 72 hours and wants to acquire its own integral ground-launched firepower assets that are available on demand under all weather conditions. This in turn will free the IAF to realise its larger objective of shaping the multi-theatre battlespace by decapitating the enemy’s tactical airpower through relentless offensive air superiority and counter-base air campaigns. Third, the Army wants to compensate for its debilitating present-day lack of new-generation tube artillery assets (like 155mm/52-cal howitzers of the towed, tracked and motorised varieties) by acquiring precision-guided BSMs that are easily transportable by road and railways, have minimal visual and electromagnetic signatures and a small deployment footprint, and are therefore easily moved and hidden. Fourth, post-OP Parakram (the 10-month eyeball-to-eyeball standoff with Pakistan starting December 2001), Army HQ, while in the process of conceptualising its future warfighting doctrines, plus the strategies and tactics required for waging ‘hyperwar’ or multi-dimensional parallel warfare, had projected a requirement for quick-reaction NLOS-PGMs that will be employed for both the tactical and operational levels of war, meaning such weapons will no longer will be solely a Corps-level deep (operational) fire-assault asset, but they will also be employed by combined arms brigade-sized battle groups at the close combat (tactical) level. The need therefore was for PGMs with increased range and accuracy for providing destructive, protective/suppressive and special-purpose fire-assaults, thereby maximising lethality and minimising collateral damage all along the close, deep and rear operational spectrums of the non-linear and non-contiguous AirLand battlespace. In other words, what the Army wanted was adoption of a warfighting posture in which tactical- and operational-level fire-assaults and manoeuvre warfare would be complementary elements, thereby enabling the ground forces commander to rapidly suppress and destroy hostile forces and restrict the enemy’s ability to counter friendly actions by mobilising and marshalling its operational reserves, thereby, setting the stage for successful manoeuvre warfare operations. Friendly formations could thus use manoeuvre to dislocate or isolate enemy units, while rocket artillery-based fire-assaults fires could achieve maximum effectiveness and efficiency. While one without the other would lessen the chances of success, combined, they would make destroying larger enemy forces feasible and enhance the protection of friendly forces. In addition, asymmetric threats in built-up areas would dictate the use of immediately responsive and continuously available fire-assaults in all types of terrain and weather against time-sensitive targets without fear of collateral damage.

At this stage it must be clarified, though,  that the Indian Army has yet to articulate the optimum pro-active warfighting strategy (mistakenly referred to as the non-existent Cold Start Doctrine by both Indian and foreign think-tanks) that is designed to both reduce the mobilisation time of its offensive formations and their break-out into enemy territory (within a 72-hour period) in a series of shallow thrusts going no deeper than 30km into enemy territory (therefore those who contend that very early in the war the Indian Army will make deep armoured thrusts inside Pakistan are either being ignorant at best, or mischievous at worst). Given the fact that the next round of all-out war between the two countries will be short, swift and intense, the Army believes that instead of making multiple Corps-level thrusts deep into enemy territory, the objective should be to force the Pakistan Army to commit its operational reserves into battle at the very early stages of the war by making a series of shallow thrusts into enemy territory with Brigade-sized combined arms battle groups, following which the Indian Army would employ superior operational art backed up by network-centric knowledge-based war-waging technologies and tactics to envelop and overwhelm the hostile forces by waging effects-based ‘parallel’ or ‘hyper’ war, thereby destroying the enemy’s war-waging assets in detail.

Also to be noted is that the deployment of NLOS-BSMs like the Prahaar, will constitute only one element of the Army’s transformational knowledge-based warfighting strategy. Needless to say, the deployment of Prahaar will make no sense unless and until the Army succeeds in acquiring the required level of battlespace transparency through the induction of the requisite type of situational awareness/common operating picture acquisition tools that will optimally compress the observe, orient, decide, act (OODA) loop. Such tools, like the Tac-C3I, are still years away from deployment, as are its components like the battlespace surveillance system, the battlespace management system, the futuristic combat net radio network, and the F-INSAS system.

 

Another critical factor likely to affect the Prahaar’s battlespace performance (especially its accuracy) will be the status of the projected Indian Regional Navigational Satellite System (IRNSS)--an autonomous regional GPS-based satellite navigation system being developed by the Indian Space Research Organisation (ISRO) since May 2006 with a project funding of Rs16 billion. Though the project was originally due for completion by 2012, the scheduled deployment milestones to be attained have slipped by a few more years. Though both the Prahaar and BrahMos presently have access to high-accuracy MILSPEC PY-standard codes relayed by Russia’s GLONASS-K GPS satellite constellation, the plan for the long-run is to discard this option in favour of the IRNSS, which will eventually comprise a constellation of seven GPS navigation satellites placed in geostationary orbit that will provide an absolute position accuracy of better than 10 metres throughout India and within a region extending approximately 2,000km around India.

Prithvi BSM Now A Dead Dog

Even though the 4.4-tonne, liquid-fuelled SS-150 Prithvi-1 ground-launched BSM was under development since 1983 under the DRDO’s Integrated Guided Missiles Development Programme, the Indian Army was never interested in procuring any such weapon system and therefore it neither submitted its General Staff Qualitative Requirements (GSQR) for any BSM, nor was it asked to submit one by the Ministry of Defence (MoD). However, after coming under enormous pressure from then Indian Prime Minister Rajiv Gandhi in 1988, Army HQ reluctantly agreed to induct into service a version of the SS-150 armed with a 1-tonne high-explosive (HE) unitary warhead and offering a circular error probability (CEP--a measure of accuracy and consistency) of 100 metres (and not 25 metres as claimed by the DRDO) at maximum range.  Despite the DRDO’s protestations, the Army chose not to induct any SS-150s armed with blast pre-fragmented warheads, cluster munitions-carrying payloads, incendiary warheads and fuel-air explosive warheads, since the poor CEP of the SS-150 (due to its dry-tuned gyro-based strap-down inertial navigation system) ensured that any damage caused to the enemy would be only of a collateral nature. Thus, deliveries of the SS-150s got underway from 1993 and lasted till early 2009, with about 180 being built by the MoD-owned, Hyderabad-based Bharat Dynamics Ltd. These missiles presently equip the 333 (raised in June 1993 in Panchmarhi and commissioned in October 1995 under the Ambala-based 40 Artillery Division of the Mathura-based I Corps), 444 (raised in October 2001 under the Pune-based 41 Artillery Division of the Jodhpur-based XII Corps) and 555 Missile Groups (operational by January 2005 under the 42 Artillery Division of the Ambala-based II Corps), with each Group being equipped with 60 liquid-fuelled SS-150s. Each Prithvi Missile Group was made up of two Sub-Groups that in turn are made up of two Troops. Each Troop has six SS-150 mobile autonomous launchers (MAL). Thus, each Group has 24 MALs and almost 72 support vehicles (including the four command-and-control vehicles, plus fuel carriers, missile transporters, oxidizer carriers, and warhead carriers). However, in times of hostilities, the missiles will be pre-fuelled (the shelf-life of the liquid propellant is 10 years) before being deployed to their launch sites where only three vehicles—the MAL, power supply vehicle and one Mobile Command Post (MCP)—would be employed. The SS-150 is fuelled by a liquid propellant (a 50:50 combination of isomeric xylidine and trimethlyamine), with the oxidizer being inhibited red fuming nitric acid (IRFNA). The propellant has a 260 specific impulse and was specified by the Army, which required a range fluctuation between 40km and 150km and this could only have been achieved by a variable total impulse best generated by liquid propellants. Following its launch, the SS-150’s semi-ballistic trajectory takes it to an altitude of 30km following which it adopts either a steep ballistic trajectory at nearly 80 degrees, or a lift-augmented descent trajectory. As far as the latter option goes, there are six flight-path variations available, which are pre-programmed prior to launch.

The Indian Army has always found the SS-150 deficient in five critical areas. Firstly, a Prithvi pre-filled with its highly skin-corrosive liquid propellant has shelf-life limitations, while fuelling the missile under battlefield conditions requires large preparatory time. Secondly, as explained earlier, the missile’s field deployment footprint is characterised by a large number of support vehicles, which can easily be detected by the enemy’s airborne/space-based overhead reconnaissance assets. Thirdly, since the missile’s terminal velocity is low, its unitary HE warhead will not be able to penetrate the hardened fortifications on the international border between India and Pakistan. Fourthly, given its poor terminal accuracy, it never did qualify as a reliable BSM when equipped with any kind of conventional warhead. And lastly, the SS-150 takes time to accelerate as it rises upon firing, making it an easily observable target both by visual means and radar, which in turn will lead to swift counter-bombardment by the enemy. Even though the DRDO now claims that the follow-on 350km-range Prithvi-2 SS-250 variant (under development since 1996 and being proposed to replace those SS-150s whose shelf-lives have either already expired or will expire by 2014) has a CEP of less than 10 metres (this being achieved by doing away with the strap-down inertial navigation system and using a new ring-laser gyro-based INS coupled to a GLONASS-K GPS receiver developed by the DRDO’s Vignyanakancha-based Research Centre Imarat), the Prithvi-2 still suffers from the very same four remaining shortcomings of the SS-150, and therefore, contrary to what the DRDO has been claiming, the Prithvi-2 will never enter service with either the Indian Army or the Strategic Forces Command, a fact already confirmed by the MoD, which has decreed that the existing SS-150s under the Strategic Forces Command will be replaced in future by the 2,500km-range Agni-2A Prime. Thus, the Prithvi in all its manifestations is a dead dog that continues to be flogged by the DRDO for meaningless glory. The Prithvi-2 was first test-fired on January 27, 1996 and this was followed by further test-firings conducted on March 31, 2001, on October 12, 2009 (when two Prithvi-2s were fired), on March 27 and June 18, 2010, on September 24, 2010, on December 22, 2010 (when two missiles were fired), and finally on June 9, 2011. It has so far demonstrated a flight duration of 483 seconds and a peak altitude of 43.5km, but unlike the BrahMos, has never been test-fired over a land-based firing range.—Prasun K. Sengupta