AGNI - STRATEGIC BALLISTIC MISSILE

AGNI - STRATEGIC BALLISTIC MISSILE
Agni-TD, Agni-I, Agni-II, Agni-IIAT, Agni-3, Agni-3++
© Arun Vishwakarma
Agni is a Sanskrit/Hindi word meaning Fire, given that it is a strategic ballistic missile. The Agni missile family is envisaged to be the mainstay of the Indian missile-based strategic nuclear deterrence. The Agni family will continue to grow its stable, providing a breadth of payload and range capabilities. The Agni-I is a short range ballistic missile (SRBM) with a single stage engine. While the Agni-II is an intermediate range ballistic missile (IRBM) with two solid fuel stages and a Post Boost Vehicle (PBV) integrated into the missile's Re-entry Vehicle (RV). The Agni's manoeuvring RV is made of a carbon-carbon composite material that is light and able to sustain high thermal stresses of re-entry, in a variety of trajectories. The Agni-IIAT is a more advanced version of Agni-II, albeit with more sophisticated and lighter materials, providing better range and wider operating regime. Agni-III is a compact long range missile in test phase. Agni-3SL is a compact version of Agni-3 suitable for submarine launch.
Variants
Chronologically Agni-TD was first developed to quickly prove critical technologies, followed by the Agni-II IRBM, and then a short range version missile called Agni-I. In defense literature/publications this numbering system jumble, leading to the Agni-I name, often confuses readers. Indian reports mention development of the Agni-III-TD and Agni-III missiles with greater range and payload capability, albeit with great obfuscation of actual configuration and specification. Recently video images of Agni-III were released by DRDO. Based on technical viability and data from news fragments, the Agni family of missiles can be referred to the following likely configurations with what is believed to be the saner nomenclature.

Development
India launched the Integrated Guided Missile Development Program (IGMDP) in 1983 to concurrently develop and produce a wide range of missiles for surface-to-surface and surface-to-air roles. The IGMDP mandated development of the Agni, Prithvi, Trishul, Akash, Nag and Astra missile systems is managed by the DRDO. After successfully delivering all missiles except Trishul IGDMP program will conclude by Dec 2008. Bharat Dynamics Limited (BDL) manufactures Agni missiles and has the capacity to manufacture 18 missiles per year. A small number (less than five) of Agni-II missiles were believed to be operational in late 2000, and a production rate of 15 to 20 missiles per year has been suggested.
The Agni missile series consist of following missiles (in chronological order):
· Agni-TD/TTB (Technology Demonstrator / Technology Test Bed)
· Agni-II - IRBM (3300 km range, 1000 kg payload)
· Agni-I - SRBM (850 km range, 1000 kg payload)
· Agni-III - ICBM (5500 Km @ 1500Kg, 12,000 km @ 450 kg)
Agni variants under development (estimated performance):
· Agni-IIAT - ICBM (4,000 km range, 1500 kg payload)
· Agni-III++ - ICBM (10,000+ km range, 1000 kg payload)
Warhead Options
India's nuclear warhead options are still relatively limited, though adequate. Since the first Peaceful Nuclear Explosion (PNE) in 1974 (PoK-I), India adopted the recessed deterrence posture initially consisting of fission weapons (~15 KT yield) followed by boosted fission weapons of 200 KT yield, suitable for the Agni-TD/TTB. The PoK-II 1998 'Shakti' series of nuclear tests in Pokhran were reportedly done to validate multiple weapon designs, of 1995 vintage. Interestingly the 200 KT boosted fission design of 1980 was not tested in PoK-II, evidently its core components and technologies were validated in newer designs, and giving way to a lighter and more efficient S1 design. It is interesting to note that India has access to large quantities[135] of Tritium - produced at an extremely low cost - which lends flexibility to Indian weapon design options, an option that is not available or viable to prior nuclear weapon states.
The primary warhead for the Agni family would be a 200-300 Kt fusion weapon based on the Shakti-1 (Pokhran-II) test in 1998. The weapons yield is adjustable from 45-300Kt by changing the amount and quality of tertiary fuel. Yield of 45-200Kt range using natural Uranium and 45-300Kt range using moderately enriched fuel (U235 or Pu).
The fusion weapon based on the S-1 design reportedly weighs less than 450 Kg, however other sources indicate a mass of between 300 to 200 Kg[137A]. The 45kT S1 device reportedly weighed 450 kg and used an inert mantle to ensure third stage did not generate any yield[141]. It has also emerged that by 1982, the BARC/DRDO team had produced a design for a (pure) fission device that weighed between 170 and 200 kg for a yield of 15 KT - a huge change from the 1000 kg monster tested in 1974[142]. This would mean that a missile warhead based on this 1982 vintage design would weigh some 250 - 350 kg. On the eve of Agni-III D1 test flight on 12 April 2007, Union Minister of State for Defence MM Pallam Raju confirmed that "the strategic payload of the missile is between 100 kg to 250 kg"[142a]. One can conservatively deduce that the 250 kg mentioned by the minister corresponded to Indian Thermo-nuclear weapon, and 100Kg correspond to either 20Kt medium yield boosted fission weapon because low yield sub-KT weapon are tactical & not considered as strategic weapons. Therefore, when considering the range and payload parameters of the Agni and Prithvi missiles, these figures must be borne in mind.