Prithvi

Section: Ballistic Missiles; Updated on: October 12, 2009;  

The Prithvi (Earth) is a single stage, dual engine, liquid fuel (red fuming nitric acid as an oxidiser, with a 50/50 mix of xylidiene and triethylamine as fuel), road-mobile, short-range ballistic missile which began design in 1983 and was first tested in 1988. The missile has a length of 9 metres, a diameter of 1.1 metres and a weight of 4000 kg. It has a unique appearance, with four delta-shaped wings midway down the fuselage. The missile’s volatile liquid fuel launch mode must be loaded immediately prior to launch, which might prove to be a disadvantage in the field. However liquid fuel gives better accuracy and the missile crews who operate them undergo intense training in three general phases; missile sub-system, handling & maintenance. An advanced simulator has been developed to train the missile crews in it’s operation. Liquid fuel also provides the capability, for in-flight manoeuvring; the missile is capable of being manoeuvred up to 15º in flight.

Prithvi has a distinctive design, using a particular gyro system with a uniquely configured software. When the flight is in progress, the drift can be monitored through the on-board computer. It has other innovations as well; the type of thrust termination is so innovatively configured that for a multiple payload, multiple ranges can be achieved. The strap-down inertial guidance system has a twin microprocessor-based computer integrated with interrupt-driven, real time software. Its navigation system guides it to the target within a CEP (Circular Error Probable) equal to .01% of its range. During one test, the missile reportedly achieved a high accuracy rate, which suggests that guidance system may include the capability of feeding GPS inputs into its inertial navigation system.

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Test flight of the Prithvi SS-250
Some of Prithvi’s warheads

Initially two variants were developed at DRDO, one for the Army and the other for the Air Force, but presently the SS-250 is only variant being produced at Bharat Dynamics Limited (BDL), Hyderabad. The Army version, designated as the SS-150 had a range of 150 km and could carry up to a maximum of a 1000 kg as its payload. The Air Force version, designated as the SS-250 had a range of 250 km and could carry up to a maximum of a 500 kg as its payload. By using boosted liquid propellant to generate more thrust-to-weight ratio, DRDO has increased the payload of the SS-250 to 1000 kg. The Prithvi reportedly has the highest warhead-weight to overall-weight of any missile in its class.

The missile can carry a variety of conventional warheads such as pre-fragmented explosives, bomblets, incendiary, cluster munitions, sub-munitions, fuel-air explosives and high-explosives. The nuclear tests conducted in May 1998 proved that miniaturized nuclear warheads of various yields can also be fitted and Dr. APJ Abdul Kalam, the then-incumbent Scientific Advisor to the Government and DRDO Chief, stated that a few days after the Shakti-98 n-tests. However, after the Agni-I MRBM test in January 2002, K. Santhanam - former RAW officer, DRDO technical advisor, nuclear scientist and presently IDSA Director - stated that the Prithvi missile was never meant to carry nuclear warheads under normal circumstances. This indicates that the solid-fuelled Agni has completely taken over the ‘nuclear’ role from the liquid-fuelled Prithvi.

The missile is strengthened against ABM defences with a guidance system that can be programmed to follow up to six different trajectories so as to avoid interception. Another defence the missile has, is the application of a special type of radar absorbing paint to reduce radar signature. For field operations, the missile will be transported on an all-terrain, eight wheel Kolos Tatra 4×4 truck. The missile is deployed from the vehicle and fired from a simple launcher. Each battery of four Prithvi carrier vehicles will be accompanied by a missile re-supply & loading vehicle, a propellant tanker and also a command post to provide target data to the missile’s guidance system before launch. It also has an integrated surveillance & mission support capability and other support vehicles & equipment.

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The Prithvi’s support vehicles
Prithvi SS-150 at the Republic Day

By October 1995, 20 pre-production Prithvi SS-150s were delivered to the Army to form the 333rd Missile Group based in Secunderabad. Two more have been formed since, 444 and 555. The former has been raised and trained and should receive its equipment soon, while the latter exists only on paper and is yet to be raised. Each group will have 12 launchers, with possibly another three more acting as reserves. Around 120 Prithvis (both variants) have been produced to date, at BDL, with 40-50% of them being the SS-250 and is now the only production version at BDL. Various technical tests of the SS-250 variant have been carried out and a recent one on 31 March 2001, reportedly carried multiple payloads over 250 km and was solid-fuelled. On 18 April 2001 in Parliament, then-incumbent Defence Minister Jaswant Singh stated that the SS-250 was being inducted into the IAF, but apparently the IAF plans to use it only for familiarisation training.

The last Prithvi test occurred on 12 December 2001 and was reportedly liquid-fuelled. The test was flawless and the missile impacted at the intended target point accurately. This Prithvi was provided with a homing facility and was a more advanced version than the one tested in March 2001. Significantly in December 1998, the Army deployed the SS-150 in a major military exercise for the first time since its induction. Code-named Shiv-Shakti, the military exercise signified that the Prithvi had been further inducted into the military doctrine. If the missile is deployed in states like Kashmir, Punjab and Gujrat which border Pakistan, it would place the cities of Islamabad, Lahore, Karachi, Hyderabad and many of Pakistan’s strategic military installations within its range. An unspecified number of Prithvis are rumoured to be based near Jalandhar, northern Punjab, for use as a tactical battlefield missile against Pakistan.

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Prithvi SS-150 on a Tatra 4×4
Prithvi SS-150, at Aero India ‘98

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