From Prithvi To Pralay

Although precision-guided, conventionally-armed surface-to-surface battlefield support missiles (SS-BSM) first developed by the US began to surface in the late 1980s and were subsequently combat-proven throughout the following decade in the Middle East, it was in the late 1970s  that precision-guided SS-BSM solutions first emerged from the USSR, and were followed by those from China and Israel. The first precision-guided BSMs to enter service were the 70km-range 9K79 Tochka and the 400km-range 9K714 Oka built by KB Mashynostroyeniya’s (KBM) Votkinsk Machine Building Plant.

These were followed in the late 1980s by China’s 600km-range DF-15/M-9 ballistic BSMs developed and built by the China Aerospace Science and Technology Corp’s (previously known as the 5th Aerospace Academy) Academy of Rocket Motor Technology (also known as the 4th Academy), and the ballistic 290km-range DF-11/M-11 Hatf-3/Ghaznavi BSM, developed and produced by the Sanjiang Missile Corp (also known as the 066 Base).

However, the most widely employed and fielded precision-guided SS-BSM to date remains the Lockheed Martin-built MGM-140 Army Tactical Missile System (ATacMS), which weighs 1,670kg (3,690lb), is 13 feet (3.96 metres) high, has a diameter of 24 inches (2 feet, or 610mm), finspan of 1.4 metres, and has a weapons payload of either 560kg (1,240lb) or a 227kg (500lb) unitary warhead. Service ceiling is 50km, while the range is up to 300km. The powerplant is an Atlantic Research-built 40,000lb (18,144kg) static thrust solid-propellant rocket. Inertial guidance is provided by a Honeywell H700-3A ring-laser gyroscope coupled to a GPS receiver using secure, high-accuracy PY-code navigational updates from the US’ Navstar constellation of GPS satellites.

The M74 warhead dispenses 950 M42 anti-personnel/anti-materiel (APAM) sub-munitions that are cast forward at a 45-degree angle over the target area, producing a 33,000 square-metre (360,000 square feet) footprint. Another type of sensor-fuzed munitions, once dispensed, glide to their pre-programmed target area, and each selects a target within its assigned acoustic segment of the formation. Once a target has been acquired by the terminal infra-red seeker, the weapon guides to terminal impact and uses a tandem shaped-charge warhead to destroy the selected armoured vehicle. Effectively, 18 ATacMS equals the impact of 792 155mm artillery rounds. ATacMS’ launch can be as much as 30 degrees off axis, and the missile is steered aerodynamically by electrically-actuated control-fins during the descent phase, modifying the flight path from a ballistic parabola. Offsetting the launch angle and descending semi-ballistically complicates the enemy’s ability to trace trajectory back to the launch vehicle.

Russia’s answer to the ATacMS was the 9K720 Iskander-E SS-BSM. Built by KBM, it is a 3.8-tonne solid-fuelled, single-stage BSM with a range of 280km and capable of carrying a payload of up to 480kg, which includes cluster sub-munitions, high-explosive fragmentation or penetrating charge unitary warheads, plus thermobaric (fuel-air explosive) and electro-magnetic pulse detonation warheads. Claimed to have a CEP of 7 metres, the Iskander-E comes equipped with dynamic gas thrusters and aerodynamic fins for controlling the missile in flight. A ring-laser gyro-based inertial navigation system (RLG-INS) brings the missile into the target area, where an optronic sensor scans terrain around a target and compares it to the image downloaded into its on-board computer before launch. This makes the missile independent of GPS navigation and resistant to jamming. The missile has a 10-year shelf-life.

In India, the Indian Army (IA), which had closely followed the development and employment of the 9K79 Tochka and the 9K714 Oka precision-guided SS-BSMs, also keenly desired such a rocket-artillery capability, since they could be swiftly employed for causing heavy attrition losses of dug-in, multi-echelon enemy land forces formations in the plains that stood in the way of an advancing IA Strike Corps over a frontage of up to 70km in depth and 120km wide. This consequently gave rise to the requirement for SS-BSMs like the liquid-fuelled Prithvi-1 in the 1990s and the solid-fuelled Pralay for the future battlefields.

The first Prithvi-1-equipped Missile Group was 333 (raised in June 1993 and commissioned in October 1995), followed by the 444 (raised in October 2003) and ultimately the 555 (operational by January 2005), each equipped with a total of 75 liquid-fuelled, conventional warhead-armed, 150km-range SS-BSMs, including reserve rounds). The three Prithvi Missile Groups formed part of the ORBATs of the Indian Army’s three dedicated Artillery Divisions—40, 41 and 42.

Each Prithvi Missile Group is made up of two Sub-Groups that in turn are made up of two Troops. Each Troop has two mobile autonomous launchers (MAL). Thus, each Group has 8 launchers and almost 24 support vehicles (including the Fuel Carrier, Missile Transporter, Oxidiser Carrier, Warhead Carrier). 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 Prithvi SS-150—officially described by the DRDO as a tactical surface-to-surface missile and by the Army as a battlefield support missile--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 as specified by the IA, which required a range fluctuation between 40km (with a CEP of 110 metres) and 150km (with a CEP of 220 metres) when using dry-tuned gyros for inertial navigation and this could only have been achieved by a variable total impulse best generated by liquid propellants.

Following its launch, the SS-150’s ascending trajectory takes it to an altitude of 30km following which it adopts either a steep downward 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) in order to defeat or confuse anti-ballistic missile defences. All Prithvi-1/SS-150 SS-BSMs carry up to five types of conventional warheads. It is evident from all this that the SS-150 will, during, hostilities, be employed for massed but effects-based fire assaults against largely static targets like troop concentrations and POL storage sites, this being done in order to severely degrade the hostile force’s theatre-level and strategic reserves before they could become effective in the forward tactical battle areas.

Although the DRDO had in the previous decade developed a solid-fuelled Prithvi-3 Precision-guided SS-BSM with a CEP of 30 metres at its maximum range of 600km (through the adoption of RLG-INS units imported from the TAMAM Division of Israel Aerospace Industries), the IA was dissatisfied with its solid-propellant’s low burn rate of 10 millimetres per second and instead had specified a solid-propellant with a burn rate of minimum 70 millimetres per second. This became available only in 2015 from the DRDO’s Nashik-based Advanced Centre for Energetic Materials (ACEM), following which it was decided to develop the Pralay precision-guided SS-BSM as a derivative of the cannister-encased, land-mobile Shaurya SS-BSM, which can carry a 1-tonne nuclear warhead over a distance of 750km, weighs 6 tonnes, has a diameter of 0.74 metres and is 10 metres long.

The Shaurya’s solid-fuel, two-stage solid-fuelled rocket accelerates the missile to six times the speed of sound before it reaches an altitude of 40km (125,000 feet), after which it levels out and cruises towards the target, powered by its on-board fuel. The Shaurya has already demonstrated a CEP of 30 metres out to a range of 750km.

The Pralay on the other hand has been designed to have a maximum strike range of 500km and weighs 5 tonnes. With a 1,000kg all-conventional payload (five types of warheads are available), it can travel a distance of 350km and if the payload is halved, then the Pralay will be able to go as far as 500km. In both cases, the CEP attained will be 30 metres. The time taken from missile-launch till warhead detonation over-target will be considerably lesser than that attained by either the Prithvi-3 or Shaurya, primarily due to the usage of higher energetic solid-propellants with high burn-rate.

But it needs to be noted that the Pralay will NOT be used by the IA to hit targets located 500km or 350km inside hostile territory. Rather, the Pralay’s MALs will be located in the IA’s rear-areas—typically located 150km inside friendly territory—and will be used over a frontage of up to 70km in depth and 120km wide inside enemy territory, with the width and depth of the frontage being determined by the integral ISTR capabilities of the IA Strike Corps’ Battlefield Surveillance System (BSS) network, comprising both land-based optronic sensors and MALE-UAV assets using land-mobile SATCOM-based VSATs for battlespace network connectivity.

And shown below is the LRDE-developed Aslesha Mk.2 man-portable S-band active phased-array low-level air-defence alert radar that is now undergoing user-trials at some of the ALGs located in Arunachal Pradesh and Uttarakhand.